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AN EXPERIMENTAL STUDY OF PREHEATED LIQUID FUEL INJECTION IN A PORT INJECTED ENGINE

Michael B. Hebbes

A thesis submitted in conformity with the requirements for the degree of Master of Applied Science

Graduate Department of Mechanical and Industrial Engineering University of Toronto

@Copyright by Michael B. Hebbes, 1998.

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Abstract

An experimentai investigation was perfcrmed in order to determine the effects of

pre-heating liquid fuel during injection in a multi-port hie1 injected engine configuration.

Iso-octane, a pure research grade hiel. has been injected through a modified fuel injector

at upstream temperatures ranging from 20°C to 220°C. An increase in fuel spray cone

angle and the amount of fuel atomization was observed to occur with increasing fuel

preheats. A rapid transition was observed in measured cone angle at a reduced

temperature of 0.73.

Acknowledgements

1 would like to thank Professor McCahan and Professor Wallace for keeping me

on track and providinp helpful advice over the past two years. 1 would like to thank

Richard Ancimer and Eric Brombacher for a great deal of help during the experimental

setup phase of the thesis. A special thanks to Hannu Jaaskelainen and Paul Salanki for

crucial advice, without which, this research would not have been possible. Finally, I

would like to thank my parents for their support throrighout my studies.

Table of Contents

Abstract

Acknowledgements

Table of Contents

List of Tables

List of Figures

List of Appendices xi

. . . Nomenclature xlll

1. Introduction 1

1 . l . Overview of the Problem ... ..... . ............... . .. . ............... ............ .... 1

1 2. Thesis Organization ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3

2. Theory 5

2.1. Thermodynamics.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5

2.2. Intake Port Phenomena.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2

22.1. Fuel Transport Phenomena.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 13

2.3. Hydrocarbon Emissions.. . . . . . .. . . . ... .... ... . . - . . . .. . . . .. . . . . . . .. . . . . . 16

3. Previous Work 18

3.1. History of Fuel Metering Systems ... . .. . .. . . . . . . . . . . . . .. . . . . . . . . .. . . . . . . . . . . . . . . . 18

3.2. Previous Research.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 19

. . 3.2.1. Fuel Vaponzing Systems.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . 19

3.2.2. Heat Transfer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. - 2 1

3.3.6. Fuel Sprays.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22

4 . Preliminary Experimental Work

........................................................... 4.1. Experimental Apparatus -26

....................................................................... 4.2. Data Acquisition 27

............................................................ 4.3. Experimental Procedure 28

............................................................ 4.4. Results and Conclusions 29

5 . Experimental Apparatus and Equipment 33

.............................................................. 5.1. Engine Specifications -33

........................................................................ 5.2. Nitrogen Flow 34

......................................................................... 5.3. Fuel Injectors 35

............................................. 5.4. Fuel Delivery and Measurïng System 37

................................................ 5.5. Ford Injector Fuel Supply System 40

......................................... 5.6. Stanadyne Injector Fuel Supply System -42

................................................................ 5.7. Fuel Heating System 44

.............................................................. 5.8. Exhaust Management -47

......................................................... 5.9. Data Acquisition Hardware 48

............................................................................... 5.10. Sensors 50

........................................................ 5.1 1 . Data Acquisition Software 54

........................................................ 5.12. Data Acquisition Triggers -55

..................................................................... 5.1 3 . Optical Access - 5 5

.......................................................... 5.14. Photographie Equipment 56

6 . Experimental Procedures 58

.............................................................. 6.1. Cali bration Procedures 58

........................................ 6.1.1. Stanadyne Fuel Injector Calibration 58

........................................................... 6.2. Experimental Procedure -60

....................................... 6.2.1. Ford Fuel Injector Expenmentation -61

62 .2 . Stanadyne Fuel Inject~

7 . Results and Discussion

................ 7.1. Overview

................................ Experimentation -62

64

..................................................... 64

................................................... 7.2. Ford Injector Experïmental Data 66

............................................ 7.3. S tanadyne Injector Experimental Data 66

....................................... 7.4. Examining Experimental Test Conditions -68

............................................. 7.4.1. Fuel-to-Air Equivalence Ratios 69

............................................... 7.4.2. Nitrogen Volumetric Flowrate 71

........................................ 7.4.3. Examining Fuel Injection Pressures -72

.......... 7.4.4. Stanadyne Injector Fuei Deiivery at Elevated Temperatures 74

........... 7.4.5. Exarnining Manifold Pressure and Secondary Temperatures 76

................................................. 7.5. Examining the Acquired Images -78

.......................................................... 7.6. Liquid to Liquid Injections 87

7.7. Preheated Fuel Flow through the Stanadyne Injector ........................... 58

8 . Conclusions and Recomrnendations 94

Refèrences 96

Appendices 99

List of Tables

.................................................. Table 5.1 Engine component dimensions 34

.......................................... Table 5.2 Data acquisition channel information 49

............................................... Table 5.3 Sensor locations and noise levels 50

......................................... Table 7.1 Mean data corresponding to figure 7.6 82

....................................................... . Table A 1 Listing of fuel properties -99

................................................................... Table D . 1 Calibration data I l l

....................................................... Table D.2 Calibration summary data 112

.......... Table H . 1 Temperatures and corresponding Jakob numbers for iso-octane 123

............................................. Table 1.1 Stanadyne injector calibration data 127

............................................. Table L2 Stanadyne injector calibration data 127


............................................. Table 1.4 Stanadyne injector calibntion data 128


........................... Table J . 1 Ford injector bottom view-port experimental data 130

................................ Table J.2 Ford injector top view-port experimental data 131

.......................................... Table J.3 Stanadyne injector experimental data 132

.......................................... Table 5.4 Stanadyne injector experimental data 133



.......................................... Table 5.7 Stanadyne injector experimental data 135

.......................................... Table J.8 S tanadyne injector experimental data 136

vii


......................................... Table J . 1 O Stanadyne injector experimental data 137

........................................ Table J . 1 1 Stanadyne injector experimental data 137

Table 5.12 Stanadyne injector experimental pressure data . Matching pressure data for ........................................................... the data listed in tables 5.3 to J . 1 1 138

List of Figures

Figure 2 .1 Pressure vs . specific volume for iso-octane .................................. 6

Figure 2.2 Pressure vs . enthalpy for iso-octane ........................................... 8

Figure 2.3 Possible fuel travel paths into the cylinder ................................... 13

Figure 3.4 Liquid fuel evolution through intake system ................................. 14

Figure 4.1 Apparatus schematic diagram .................................................. 27

Figure 4.2 Injections of iso-octane through the converging nozzle at 3.77bar and increasing upstream teniperatures: a) 30°C (0.56Tc) and b) 1 60°C (O.SOT,-). ........ 31

Figure 4.3 Injections of iso-octane through the converging nozzle at 10.00bar and ....... increasing upstream temperatures: a) 135°C (0.75 Tc) and b) 2 10°C (0.89Tcj 33

Figure 5.1 Ford Injector fuel supply system ............................................... 40

Figure 5.2 Ford fuel injector setup .......................................................... 42

Figure 5.3 Stanadyne Injector fuel supply system ....................................... .44

Figure 5.4 Heater control system ........................................................... 46

............................................................... Figure 5.5 Condenser system -48

Figure 5.6 Data acquisition signal connections ........................................... 54

Figure 7.1 Fuel line pressure as a function of time ....................................... 68

Figure 7.2 Mass fiowrate as a function of temperature .................... ,.. ........... 76

Figure 7.3 Ford injector fuel injections at room temperature shown frorn: a) the top view port. b) the bottom view-port ..................................................... 80

Figure 7.4 Schematic diagram illustrating a fuel spray capnired in the top view port ............................................................................................... 81

Figure 7.5 Schematic diagram illustrating a fuel spray captured in the bottom view .................................................... port .. ......................................... 81

Figure 7.6 Fuel injection through the Stanadyne injector shown from the bottomview port location at increasing upstream . temperature: a) 25OC (0.55 Tc). b) 80°C (0.65

Tc). c ) 135°C (0.73 Tc). d) 142OC (0.76 Tc). e) 173.g°C (0.8 1 Tc) and f) 306.9OC (0.88 Tc) ................................................................................................ 83

Figure 7.7 Schematic diagram illustratinp a fuel spray captured in the bottorn view port ............................................................................................... 86

Figure 7.8 Cone angle as a function of reduced temperature . + Iso-octane fuel injection data through the Stanadyne injecotor . O Iso-octane fuel injection data from the prelirninary experiments . SIoss dodecane fuel injection data .............................................................................................. - 9 1

Figure B . 1 Ford fuel injector calibration program front panel .......................... 100

Figure B.2 Ford fuel injector calibration program back panel.. ........ .. ............. IO1

Figure B.3 Stanadyne fuel injector calibration program front panel ................... 102

Figure B.4 Stanadyne fuel injector calibration program bclck panel ................... 102

Figure B.5 Fuel line pressure front panel ................................................. 102

Figure B.6 Fuel line pressure back panel .................................................. 103

Figure B.7 Experimental data acquisition front panel ................................... 104

Figure C . 1 Stanadyne injector modification ............................................... 107

Figure D . 1 Characteristic injector Flow curve ............................................ - 1 10

Figure E . 1 Nitrogen flowrate vs . voltage .................................................. 114

Figure E.2 Schaevitz tranducer pressure vs . voltage ..................................... 117

List of Appendices

A. Fuel Data 99

B. LabView Virtual Instruments 100

B. 1. Ford Fuel Injector Calibration Program ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 100

B.2. Stanadyne Fuel Injector Calibration Programs ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 1

8.3. Experirnental Data Acquisition Programs ... . . . . . . . . . . . . .. .. . .. . . . . . . .. . . . . . . . ... 103

C. Stanadyne Injector iklodifications 105

D. Ford Fuel Injector Calibration 1 08

D. 1. Ford Fuel Injector Calibration Procedure.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 108

D.2. Ford Injector Calibration Data .... . . .. ...... . . . . .. . . .. . .. . . ... . ... . . . . . . . -. . . . . . -.. 1 1 1

E. Transducer Calibration Procedures and Curves 113

F. Data Sheets 118

F. 1. Ford Injector Calibration Sheet ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 18

F.2. Stanadyne Injector Calibration S heet.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 19

F.3. Experimental Data Sheet.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 20

G. Calculations 121

G. 1. Volumetric Flowrate ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - . . . . . . . . . . .. 12 1

G.2. Ford Injector Pulse Width Calculation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12 1

H. Jakob Number Data 123

1. Stanadyne Injector Calibration Data 127

J . Expenmental Data 130

J . I . Ford Injector Experimental Data ................................................... 130

5.2. Stanadyne Injector Experimental Data ............................................ 132

xii

Ab breviations

cm

D AQ

EOS

EVC

EVO

FIA

FI

HC

IVC

IV0

MPFI

MAP

PTC

P D

SBR

slpm

SSR

TTL

VI

computational fluid dynarnics

data acquisition

equation of state

exhaust valve open

exhaust valve closed

fuel-to-air ratio

fuel injection

h ydrocarbons

intake valve close

intake valve open

muhipoint fuel injection

manifold absolute pressure

positive temperature coefficient

proportional, in tegral, differential

Simonet-Behar-Rauzy

standard liters per minute

solid state relay

transistor-transistor logic

virtual instrument

Symbols

CP liquid specific heat evaluated at the bulk fluid pressure

duty cycle

heat of vaporization evaluated at the bulk fluid pressure

Jakob nurnber

cycle number

critical pressure

system free surface pressure

liquid vapour pressure at a given tempenture

normal boiling temperature

critical temperature

reduced temperature

specific volume

liquid superheat

volumetric et'ficiency

equivalence ratio

liquid surface tension

rotational speed

xiv

1. Introduction

1.1. Overview of the Problem

In a typical gasoline engine, liquid fuel is injected into a relatively low pressure

environment of approximately 1 atm absolute pressure or less. After injection, the fuel

will break up into liquid droplets. The liquid fuel would ideally vaporize and mix with

the airstream into which it is injected. As there is normally not enough energy available

in either the fuel or the air to facilitate complete vaporization, a more realistic picture is

that the liquid fuel impacts on the valve stem and cylinder head wall surfaces and

evaporates. The high temperature impaction surfaces help to vaporize the liquid fuel,

preparing it for the combustion process to follow.

Under a variety of engine operating conditions, it has been found that the injected

fuel undergoes a process quite different from the ideal situation. Specifically, and most

irnportantly, during cold engine start up conditions, the impaction surfaces are not hot

enough to vaporize the liquid fuel Stream. This leads to the formation of a liquid fuel

film on the valve and cylinder head surface. The liquid fuel film can then proceed to flow

into the engine cylinder. Ideally, al1 the fuel entering the cylinder would be in vapor form

for efficient combustion but when liquid fuel is present this leads to problems including

non-homogeneous mixtures and the need for fuel enrichment. In extreme cases, the flame

can pass over the liquid fuel in the cylinder. The film then evaporates into the hot

product gases resulting in the exhaust of raw hydrocarbons (HC). In fact, engine cold

start conditions have been shown to be important in HC emissions production, with

approximately 80 percent of automotive tailpipe HC ernissions in the Federai Test

Procedure occumng in the first five minutes of engine operation [ I l . In recent yenrs a

number of experimental investigations have been carried out in order to study this

phenornenon and these Xe discussed in more detail in the Previous Work chapter of this

document.

The problem of wall wetting or fuel film formation is just now being thoroughly

investigated. To reduce or eliminate wall wetting, we atternpt to take advantage of the

thermodynamic properties of the fuel. Fuel injectors are designed to atomize the fuel

during the injection process. Preheating the liquid fuel prior to injection is anticipated to

superimpose therrnodynarnic vaporization effects ont0 the mechanical atomization

process. Superheating of a liquid, in the context of fuel sprays, occurs when a single-

phase liquid exits the nozzle of an injector at a temperature higher than the saturation

temperature at the bulk liquid pressure. When a liquid is superheated, it enters a non-

equilibrium metastable state, from which some or al1 of the liquid wilI undergo a phase

change to vapour. This is commonly referred to as flashing.

Heated fuel injectors have been utilized in the past as a means of fuel preparation

in direct injection compression ignition engines. In the present research, using a

preheating fuel system in a port injected spark ignition engine is the ultimate intended

goal. In the present study the spray performance was evaluated in an isolated, controlled

research environment using comrnercially available automotive injectors.

1.2. Thesis Organization

This work involves an experimental investigation of preheated liquid fuel

injection. A 1990 Ford Escort 1.9 L, four cylinder, port fuel injected engine was

converted to a single cylinder research engine. Due to the complexities involved with a

fully functional firing engine the investigation was first simplified to a steady state

problern in order to isolate and uncouple the fuel injection process from the effects of any

pulsed intake port flows. The experimental apparatus has been designed and büilt to

cIosely approxirnate a cold engine w m - u p condition at 1000 rpm. Three sets of

experiments were carried out; one using a standard Ford pintle-type injector at ambient

temperatures for base line tests, a second using a modified Stanadyne pencil-type diesel

injector at ambient fuel temperature and a third using the same modified injector at high

fuel temperatures. The primary objective of this study was to obtain photographie images

in order to both characterize the injection event and illustrate the effects of fuel

preheatinp. In addition to image acquisition, the experiments involved acquiring

numerical data in the f o m of injection and intake gas pressures, temperatures and flow

rates in order to fully characterize the injection event.

A detailed discussion including thermodynamics, heat transfer, phase change and

other relevant fuel spray topics are discussed in the Theory chapter of this document. A

summary of the previous work carried out in this field is presented in chapter 3. Section

4 provides a proof of concept obtained from a preliminary set of experirnents. Th3 details

of the expenmental apparatus and experimental procedure are provided in chapter 5 and

6, from which the results of chapter 7 were obtained. A discussion of these results and

the conclusions that can be made are covered in chapters 7 and 8 respectively.

2. Theory

Before dealing with specific examples concerning the developrnent of fuel spray

technology in MPFI engines, a more fundamental discussion dealing with the relevant

thermodynamics of fuel sprays is a necessary first step. Following an explanation of the

fundamentals, characterization of the intake port environment and how the fuel delivery

into this environmznt affects hydrocarbon emissions are discussed.

2.1. Thermodynamics

To understand a preheated liquid spray, a description of the thermodynamics

involved is necessary. A pressure versus specific volume diagram is shown in figure 2.1.

The important features in the diagram are the liquid and vapour saturation boundaries, the

liquid and vapour spinodal lines, the critical point and a metastable isotherm. These lines

are generated using an equation of state (EOS). Liquid and vapour spinodal lines are

essentially the limit of intrïnsic stability and represent the absolute themodynamic limit

of stability for a single-phase fluid. The spinodal curve is composed of the locus of

spinodal limit points and the equation that describes these points takes the following

form:

cntical point

, < saturation boundary \

1 <-- iso thern- \

\ -..

/ Iiauid sr

1 O 1 O 1 O 10 Log volume [rnA3/kg]

Figure S. 1 Pressure versus specific volume for iso-octane.

As shown in figure 2.1, the liquid spinoda1 is constmcted from the metastable isothem

local minima and the vapour spinodal is constmcted from the metastable isotherm local

maxima. The States on a metastable isothem between the liquid spinodal and the vapour

spinodal are non-physical. In this region the fluid can only exist as a two-phase mixture.

A fluid that is fully liquid and exists between the liquid saturation boundary and the

liquid spinodal is in a metastable state and is generaily referred to as a superheated Iiquid.

An important characteristic of a metastable state is that it is a non-equilibrium state. An

ideal equilibrium phase change is considered to be a spontaneous process but in actual

fact some degree of liquid superheating or vapour subcooling will occur before phase

transition. A superheated Iiquid, if pertwbed, will undergo a phase change to a liquid-

vapour mixture or a vapour depending on the conditions [2].

The thermodynarnics of superheated fuel sprays are most readily described with

the aid of a pressure versus enthalpy diagram, as shown in fipure 2.2. Labels included on

the diagrarn are the liquid saturation boundary, the liquid spinodal, the critical point and

two injection events. The liquid saturation boundary was extrapolated up to the critical

point. A thinner line than the computed saturation boundary represents the extrapolation.

The expansion processes during a conventional fuel injection and of a heated injection

have been approximately placed on figure 2.2. The conventional injection process simply

expands the fuel from point 1' to 2', al1 of which occurs in the liquid region. This is often

referred to as a liquid-to-liquid injection.

In a preheated injection, the fuel starts as a subcooled liquid at 1 , expands below

the equilibrium saturation pressure at 2, remains as a superheated Iiquid while expanding

down to approximately point 3 and then liquid and vapor coexist from 3 to 4. The figure

as shown is based on a nearly isobaric phase transition. From position 2 to 3 the liquid is

said to exist in a metastable state. A liquid can exist for a limited time as a superheated

liquid without phase transition depending on the injection conditions. Vapor bubbles wil l

begin to nucleate and expand in size if the time the fluid remains at state 3 is sufficient

and nucleation sites are available. This growth will continue until ail equilibrium vapor

fraction is achieved [3]. Realistically, a critical nuclei must form as the kinetic limit at

state 3 is approached.

2-50 t conventional <- liquid fuel

injection

. 1 critical point

<-- flash boiling fie1 injection

liquid spinodal >

liquid saturation boundary

Figure 2.2 Pressure versus enthaipy for iso-octane.

The degree of superheat is defined in terms of the location of a particular

metastable state between the liquid saturation boundary and spinodal. The maximum

superheat occurs at the liquid spinodal, where the liquid is completely unstable and must

undergo a phase change. The minimum superheat value occurs at the liquid saturation

boundary and is equal to zero at that point. The degree of superheat at a given metastable

state can be described by the Jakob number which is defined as:

In equation 2.2, c, is the liquid specific heat evaluated at the bulk fluid pressure, hl,, is the

heat of vaporization evaluated at the bulk fluid pressure and AT is the superheat.

Superheat is defined as:

TI is the bulk liquid temperature of the metastable liquid and T, is the saturation

temperature at the bulk liquid pressure. The Jakob number is physically described as the

ratio of energy avaiIable for vaporization in a metastable liquid relative to the latent heat

of vaporization of the fhid at a given pressure. A Jakob number equal to or greater than

1.0 indicates that the metastable Iiquid theoretically has enough energy to undergo

complete adiabatic isobaric phase change. A Jakob number of l e s than 1 .O corresponds

to metastable States where the Iiquid contains an inadequate amount of energy to undergo

complete evaporation. In this case the liquid will transition to a liquid/vapuur

equili brium mixture.

Nucleation or vapor formation, which is the onset of the flashing event, does not

necessarily have to occur on the surface of the liquid phase. The transition of a

metastable liquid to a liquid/vapour mixture is initiated by a nucleation event. Nucleation

is the formation of a critical sized vapour bubble in the liquid, which can be initiated by

either a heterogeneous or homogeneous event. Heterogeneous nucleation occurs at low

Ievels of superheat where an interface perturbation acts to initiate the transition from

Iiquid to vapour. Heterogeneous nucleation sites exist at the interface between the

metastable phase and another phase, either liquid or solid. With a sufficient degree of

superheat, and in the absence of heterogeneous nucleation sites, the random rnolecular

fluctuation in the bulk fluid can create a local vapour bubble greater than the critical

nuclei size. This type of bubble formation is known as homogeneous nucleation. Once

homogeneous nucleation is initiated, conversion of liquid to vapour can proceed very

rapidl y.

Brown and York carried out one of the most widely referenced liquid spray

studies in 1962 at the University of Michigan [4]. The study includes a description of the

thermociynamic processes involved in liquid spray analysis and some important

conclusions that can be made with respect to flashinp sprays. Brown and York point out

that this process is comrnon in many applications but has received Little attention as a

topic for research. Brown and York looked at sprays composed of water and Freon- 1 1.

lets were analyzed for drop size, drop velocities and spray patterns. A critical superheat

was found, above which the jet liquid is shattered by rapid bubble growth within the jet

itself. The bubble growth rate was correlated with the Weber number and degree of

superheat of the liquid. Three different spray nozzles with different surface roughness

charactenstics were used to investigate the effect of orifice roughness on jet break-up.

With water it was found that a substantial increase above the saturation temperature was

necessary in order to induce significant shattering. The nozzle with the roughest surface

was able to disintegrate a water jet even when unheated. A sharp-edged orifice delayed

the onset of jet break-up due to the limited liquid-to-nozzle contact surface. Ln the longer

nozzle, without a s h q edged exit, the fuel contacts the nozzle for an extended penod,

which was hypothesized to induce eddies. These eddies produced low pressure regions in

the flow field that Ied to bubble nucleation [43.

Further research into flash boiling of liquid fuel was carried out at General Motors

by R.D. Oza [5] . Oza was able to build on the previous findings presented by Plesset and

Zwick [6]. Plesset and Zwick found that a bubble in a Iiquid with a low degree of

superheat will have a longer idle time and a sIower growth rate than that for a bubble in a

liquid with a high degree of superheat. Idle time is interpreted to mean the time period

before bubble growth occurs. A iiquid with a lower degree of superheat will take ionger

to shatter after emerging from the nozzle [6 ] . Such a liquid jet, with a small degree of

superheat, would not be suited for a practical engine due to the presence of relatively

high-speed intake airfiows. The intake airflow wouid disturb the spray before flashing

could occur and for that reason Oza focused on higher degrees of superheat. Oza used a

speciaily developed injector to deliver propane, indolene and methanol into a constant

volume vessei at a relatively high degree of superheat. Two flash boiling injection

regimes were concluded to exist from the images obtained; the first regime was

characterized as flashing with constant spray cone angle and the second regime was

characterized as flashing with external expansion. The first regirne was attributed to flash

boiling inside the nozzle due to a local pressure drop beIow the fuel saturation pressure

leading to bubble nucleation and a two-phase flow. For the external expansion regirne,

the spray cone angle increased with pressure ratio (ratio of upstream to downstream

pressure across the injector) indicating an expansion of a two-phase flow. There are a

number of benefits that corne with flash boiling injection including enhanced

atomization, increased initial spray-cone angle for faster fuel-air mixing and reduced

spray penetration [3].

Flash boiIing phenomena may have applicability to both current and future engine

technologies. The present MPR study is an attempt to reduce the flash boiling injection

problem to a manageable state for investigation. In sirnplifying the experirnent to a

steady state problem, the intake port environment must be analyzed to determine which

phenornena are significant.

2.2. Intake Port Phenornena

To characterize the injection event for the purpose of experimental design and to

determine the effects of reducing the injection environment to a steady state system it is

necessary to discuss the nature of the flows within the intake port. In a MPFI engine

there is a fueI injector in each engine intake port. In MPFI spark ignition engines three

major intake-port flow processes can be established [7].

1. Overlap backflow is the reverse flow blowdown period just after the inlet valve has

opened when the cylinder pressure is higher than the intake manifold pressure.

2. Mixing between the backflow and fresh charge occurs in the intake. so these two gas

mixtures do not rernain segregated. This is often referred to as a forward induction

flow.

3. It is normal design practice to have the intake valve closed well after bottom center to

take advantage of the air's inertia. At lower speeds, however, the intake air velocity is

low and inertia effects are small. As the piston moves up from bottom center, it

displaces some of the cytinder contents back into the intake port producing a

displacement backflow.

Al1 of these processes have an influence on the intake environment and therefore have

relevance to the present study. The thermal environment produced by the factors listed

above and the engine operating conditions will have a strong effect on what f o m the fuel

transport will take. In schematic fom, the possible paths of the injected fuel tbrough the

inlet port may be represented as follows:

vapour and smaiiest droplets entrained in gas flow l

impinges on port walls

impinges on inlet valve

and/or back flow andor backflow

Figure 2.3 Possible fuel travel paths through into the cylinder 171.

The focus of the present study is to observe the fuel sprays thernselves rather than looking

at the port walls and the valve surface. The air flow and backflow through the port

effects the fueI that impinges on the port and valve surfaces but would have a lesser effect

on the fuel spray itself.

2.2.1. Fuel Transport Phenornena

Research at a number of institutions has Ied to the development of theories on fuel

transport phenomena. The fuel transport phenomena described here is based on ectual

engine operation [8]. Fuel behaviour rnechanisms include:

1. Strip-atomization of film fuel by the intake flow.

2. Squeezing of the fuel film between the intake vdve and valve seat surface as the

valve closes, to form large droplets.

3. Deposition of liquid fuel as films distributed on the intake vdve and head region.

In this study it was found that injection geometry, injection timing, fuel-to-air ratio and

port surface temperature d l influence the fuel behaviour [8]. The following flow diagram

shows the sequence of events that determine the liquid fuel evolution through the intake

systern to the cylinder.

1 intake valve open j

entq of visible dropIet j Stream md liquid film

intake valve closed : film squeezing droplets splashing

liquid film deposits on walls

combustion I I

1 survival of films

I 1

into next cycle 1 - --

Figure 2.4 Liquid fuel evolution through intake system [8].

When the intake valve opens (NO), the cylinder pressure is initially higher than the

intake manifold pressure leading to a backflow into th3 intake manifold. When the

pressure differential between the cylinder and the intake manifold reaches equilibrium,

the backflow stops. When the piston starts to move down, the induction phase of the

cycle begins and a high-speed airfiow into the cylinder is produced. A visible Stream of

liquid fuel droplets and liquid film wall flow has been observed to enter the cylinder

before the intake valve closed [8]. The closing of the intake valve was found to produce

an interesting flow pattern in the cylinder. When the valve closed, any fuel film present

on the valve seat was squeezed out and produced a splashing effect that introduced

relatively large droplets into the cylinder. Some of the liquid fuel that reaches the

cylinder can f o m isolated puddles that are not cornbusted [8]. Further investigation in a

transparent research engine again showed the three distinct phases of fiel droplets p s t

the intake vdve as descnbed in figure 2.4 tg].

The most significant fuel atomization process was concluded to be strip-

atomization. The fuel injection event produces fuel films on the port, intake valve stem

and the back of the intake valve surfaces. Strip-atomization is the hydrodynamic

stripping of droplets frorn these fuel films by the shear stress of the intake flow. This

process was found to be dominant for both closed and open intake valve injections.

Furthermore, the reverse blowdown process has been identified as an important factor in

the mixture preparation process at part load and has a direct link to stnp-atomization [IO].

The reverse blow-down process significantly strip-atomizes the liquid fuel in the vicinity

of the intake valve and changes the thermal environment of the intake port, which aids in

liquid fuel evaporation [a]. The fuel deposited on the valve and the port surfaces was

found to be pushed towards the cylinder by the shear stress applied by the intake airflow

and by gravity. Large quantities of liquid fuel reaching the cyIinder can cause increases in

hydrocarbon emissions. This illusrrates a need for improvement of port fuel injection

technology under warm up conditions.

2.3. Hydrocarbon Emissions

Although the preliminary phase of this project did not involve fired engine

conditions, the ultimate goal is to fire an engine and acquire HC emissions information.

HC emissions are at the greatest concentration during the starting, warm-up and transient

processes in spark ignition engines [ I l . The main reasons for these increased HC

emissions are:

1. Fuel enrichment is used to achieve desired driveability and performance levels.

2. It takes a finite amount of time to warm up a catalytic converter rendering it

inefficient for the first few minutes of operation.

3. Crevice volumes are largest when the engine is cold.

4. Mixture non-uniformity and quenching is more pronounced in a cold engine which

can lead to incomplete combustion.

5. Liquid fuel effects - liquid fuel can reach the cylinder as described in the previous

section.

It is hypothesized that HC emissions levels would drop with the implernentation

of the fuel preheating systern developed for the present work. The mechanisms for HC

formation due strictly to the evohtion of liquid fuel through intake port are described in

the paragraphs to follow.

In port-fuel injected engines, the injector wil1 normalIy direct the liquid fuel

towards the back of the intake valve and the surrounding port surfaces [ I l ] . Most of the

injected fuel will impinge on a surface, while a small arnount may evaporate from the fuel

droplets formed in the atomization process. Fuel vaporization that occurs when droplets

impinge on cylinder head waIls is strongly effected by the wall temperature. When the

fuel is injected on a closed intake valve, the fuel vaporization process is aided by a rapid

backflow of burned gases from the cylinder when the intake valve opens. If the fueI is

injected on an open intake valve, the vaporization of fuel off impaction surfaces is

decreased and a greater amount of liquid fuel can enter the cyIinder in the f o m of

entrained droplets or rivers. A large part of the liquid would evaporate and mix with the

in cylinder air, fuel vapor and residual gas to form a normal combustible mixture during

intake and compression. Any liquid remaining, particuIarIy less volatile components,

may be stored in deposits, oil Iayers or crevices and corne out into the bulk gases during

expansion and exhaust increasing HC emissions.

A number of studies have been carried out to investigate the possibility of

irnproving the fuel injection process in a port injected engine. Most studies focus on

vaporizing liquid fuel after injection, whereas the focus of this study was to preheat the

liquid fuel prior to injection in order to induce improvernents in vaporization.

3. Previous Work

Automotive fuel metenng systems have undergone numerous modifications over

the last LOO years. From carburetion to fuel injection, many of these modifications have

been necessary due to ever increasing engine performance standards including exhaust

emissions level regulations and power requirements. The history of fuel metering

methods are discussed bnefly as an introduction to the previous work done in the field of

fuel delivery.

3.1. History of Fuel Metering Systems

One of the original methods of fuel preparation was the surface carburetor

designed by KarI Benz. The carburetor was used extensively but it was soon discovered

that a tight control of fuel-to-air (F/A) ratio could not be achieved. In 1898, the Deutz

engine factory developed a fuel injection pump. As early as 1903, the Wright Brothers

used port injection in a four-cylinder engine to power their first flight. In 1930 the

German Aviation Research Institute initiated a direct injection development program due

to the introduction of a diesel fuel pump. The possibility of fillinp the cylinders more

completely with air without the hindrance of a throttIe plate provided increased power

gains. Even with port injection there is a gain in air induction over carburetors. In the

late 1950's Daimler Benz switched from direct injection to port injection for the first time

in a production vehicIe, the Mercedes-Benz 300. In the 1950's Bendix published its

electronic fuel injection systern and Bnsch developed technical solutions to the electronic

systern. In 1967 the D-Jetronic unit was introduced and many automotive manufacturers

implemented the system. This well adapted system couId simply replace the carburetor

without a lot of other add-ons. When ernission control legislation became more stnngent,

exhaust gas recirculation (EGR) and new control systems became necessary. This Ied to

the mechanically controlled continuous injection K-Jetronic system and the electronically

controlled intermittent injection L-Jetronic system that are still used today in rnany

engines. Single point and multipoint injection systems in various configurations have

been under development since their originai introduction over one hundred years ago

[ E l .

3.2. Previous Research

3.2.1. Fuel Vaporizing Systems

Vaporizing fuel just after injection has been studied as a means of reducing engine

HC emissions. This process has been referred to as pre-vaporization meaning that the

fuel is subjected to a vaporizing technique prior to induction into the cylinder. It has been

shown that pre-vaporization effectively decreases fuel droplet size or eliminates droplets

altogether which can irnprove the mixture preparation process and decrease the need for

over-fueling during engine start up and transient operation. Decreased fuel droplet size

has also been shown to reduce HC emissions during steady state engine operation [13].

Pre-vaponzation is essentially a post injection technique to reduce HC emissions while

the proposed preheating method is carried out prior to injection.

The effect of heating a fuel impaction surface prier to fuel and air entry into the

manifold was investigated at Ford Motor Company [14]. Heating the manifold in an

atternpt to preheat the intake air was investigated experimentally and analytically. It was

found that heating the intake air is not the best method for improving fuel air mixture

preparation because the heat of vaporization rnust transfer from the air to the fuel in a

Iimited time period. In order to achieve this, there rnust be an excessively high

temperature gradient between the air and the fuel. It was found that only 5 to 40 % of the

fuel was evaporated depending on engine operating conditions used and the mode1

assumptions. To investigate the possibility of using this locd heating method a test

fixture was designed. The fixture included a standard Bosch injector placed upstream of

a throttle plate. A coil-heated section was placed just downstream from the throttle plate.

It was found that local heating vaporizes the fuel before it enters the intake manifold and

eiiminates most of the fuel delivery problems in a Iaboratory situation [14].

Unfortunately, system response times, w m - u p time and efficiencies were nci included

in this study but would prove to be important in determining if the system is feasible in

practice.

A study by Heywood used a single cylinder research engine and a pre-vaporizing

system with a set of test variables including fuel injection schedule, inlet pressure, engine

speed and enrichment [l] . The system used a separate injector in order to carry out fuel

vaporization. Just downstream of the secondary pre-vaporizing injector a heating coi1

was wrapped around a tube and used to quickly heat the fuel. Compressed air was used

to create swirl and displacement flows within the tube and thereby entrain vaporized fuel

into the engine cylinder. When the pre-vaporization system was used, the port injector

was deactivated. The most significant conclusion made with respect to pre-vaponzation

fuel injection was that stable engine firing was achieved at the first engine cycle of

injection without enrichment and with reduced HC emissions [l].

ln a third study of fuel pre-vaporization, some preliminary computer modeling

work was cited as a proof of concept for experimental investigation [I5]. The computer

model showed that the light constituents of hydrocarbon fuels are the main components

that evaporate during cold start conditions. It was found that as little as 20 % of the

metered fuel is evaporated before reaching the inlet valves.

Other methods have been investigated as a means of improving the fuel delivery

process. Attempts have been made to study the effects of heat transfer, specifically

heating the injector body, as a means of improving fuel delivzry characteristics.

3-2.2. Heat Transfer

In recent years a number of investigations were carried out in the area of heat

transfer as it relates to fuel preparation in a port injected engine. Positive temperature

coefficient (PTC) heaters were investigated as a method of fuel injector heating. These

self-regulating cerarnic heater devices have been used in the past for the purpose of

preventing wax formation in diesel fuel filters [Io]. The PTC heater was tested using a

CFD approach to investigate heat transfer characteristics to a pintle type injector [17].

The model included two heaters, one at the injector inlet and one at the outlet and

assumed a wide-open injector for maximum flow rate and therefore maximum required

heat transfer. It was found that heat transfer rates were significantly lowered when the

injector body temperature was increased with the PTC heaters. When a layer of fuel

vapour formed between the liquid fuel and the injector it acted as an insulator and

prevented the necessary heat transfer [17]. The main problem with such a system for the

purposes of this research is that the upper temperature limits of PTC heaters do not

appear to be high enough so a more advanced control strategy was designed for fuel

heating purposes.

3.2.3. Fuel Sprays

The quality of a given fuel spray is controlled by a variety of factors including fuel

injector nozzle type and geometry, the injected liquid fuel properties and the gas

properties into which the liquid fuel is injected. Two injectors have been used in the

present study. Obtaining an understanding of the fuel sprays each injector develops with

a certain fuel is important before comments on any changes that arise due to preheating of

the fuel can be made.

It has been shown that the combination of liquid properties suc11 as density,

viscosity and surface tension influence the ability of a given fuel injector to produce an

atomized spray under low manifold pressure conditions [Ml. In some cases, with pump

grade gasoline as the injected liquid, the injector will achially produce a pencil-jet spray.

In a pencil-jet spray the fuel is not well atomized but instead it is in the fom of a thin

liquid stream that breaks down into large irregular liquid droplets. It was found that

pump grade gasoline was more likely to forrn a pencil-jet than a pure fuel. In this study

no real concIusions were made as to why this was the case but it rnay be due to the

heavier HC components present in the gasoline. In addition, gasoline may have other

additives that could influence the fuel spray break-up 1181. This evidence indicates that

choosing a pure hydrocarbon test fuel may be beneficial in tems of fuel spray

repeatability.

Fuel injectors that are used in MPFI applications are known to produce sprays that

are not very welI atomized. In fact, the first step in the present study was to look at the

spray developed by a Ford fuel injector in order to show the possible room for

improvement in a qualitative sense.

Saito et al. developed a method for observing fuel behaviour in the intake

manifold [19]. A section of the lower intake runner was replaced with a transparent

acrylic material for observation purposes. It was found that droplets with a diameter of

approximately 30 pm or less were transported by intake air into the combustion chamber.

Droplets larger than this threshold value impacted on port and valve surfaces. Port wall

wetting has been established as a major cause of start-up and transient HC emissions

increases.

A wide range of liquid fuel spray patterns can be achieved depending on the

injector used. One study in particular investigated the effects of droplet size, intake valve

lift (open or ciosed valve injection) and coolant temperature on engine HC ernissions

[20]. Three different fuel injectors were used in order to Vary the fuel droplet sizes.

Yang et al. concluded that, in generaI, decreased Fuel spray droplet size Ieads to a

decrease in HC emissions. Similar resuits were obtained in another experimental study

done by Shayler et al. [21] where it was found that HC and CO emissions are influenced

by both injector type and fuel composition.

A third study looked at the intake fuel preparation system from an analytical

perspective [22]. The simulation model treated the process as a multiphase flow

phenomenon with a gaseous (air and fuel vapor) phase, a dispersed phase (droplet

population) and a continuous phase (liquid film flowing on the wall). In accordance with

experimental studies carried out in the past, the multi-component fuel-droplet model

indicated that droplet size is the most important factor related to fuel vaporization. As the

droplet size decreases the vapor fraction increase was found to be exponential [22].

These trends illustrate a need for improved injector performance in the form of

improved fuel atomization. Specifically, improvement is required dunng engine w a m up

conditions and might be achieved with the aid of a fuel preheating technique.

4. Preliminary Experimental Work

A previous experimental investigation looked at improving residential oil furnace

burner operation [23] . In oil furnace burner applications, emphasis is typically placed on

providing a mechanical break-up mechanism of liquid sprays. In the study camed out by

Sloss. the possibility of exploiting themodynamic properties as a means of enhanced fuel

spray atomization and evaporation was investigated. The main objective of this research

was to carry out a photographic study on the phenornenon of flashing injection and rapid

evaporation of heavy hydrocarbon fuel sprays. A method was devised to control the

pressure drop across the nozzle and the temperature upstream of the nozzle and thereby

set the thermodynamic state of the fuel spray. This technique of superheating the fuel

prior to injection is quite similar to the methods proposed in the present study. In fact.

with the steady fuel spray and the use of a simple converging nozzle the problem was

simplified as much as possible. In a port injected engine, the fuel spray is a pulsed flow

through a nozzle with a more complex geometry. For that reason i t was decided to begin

the present study with a set of preliminary experirnents utilizing the apparatus designed

and construcred by Sloss. The SBR (Simonet-Behar-Rauzy) equation of state

[24,25,26,27] was used to develop a pressure versus volume and a pressure versus

temperature plot and to calculate Jakob numbers for iso-octane. A list of data for iso-

octane has been included in Appendix A. The plots and Jakob numbers were used to

Iocate a given fuel state dunng experimentation. It was anticipated that these

experiments would provide a proof of concept for the present study as well as aid in the

development of a functional preheating port injection system in order to expand this line

of research.

4.1. Experimental Apparatus

A basic schematic diagram of the system used is shown in figure 4.1. The details

of the apparatus and the hardware used can be found in reference [33]. The nozzle was

mounted at the top of an injection chamber facing downward. A 1.0 bar nitrogen

environment was maintained within the injection chamber to prevent the formation of

combustible mixtures. Two sides of the injection chamber were equipped with view

ports for optical access and lighting of the nozzle exit and the fuel spray. A single shot

photography system acquired images of the spray event. The f~irnace section, constmcted

of refractory brick, heated the fuel line to the desired temperatures. A 1450 W finned

heater was the primary heating method and a 150 W band heater the secondary heating

method. The nozzle was a simpIe conical body converging nozzle with an exit diameter

of 0.2 1 mm with a converging half angle of 45 degrees.

fuel in

capillary tube

injection - chamber

4 drain

Figure 4.1

J- accumulator

Apparatus schematic diaoram f251.

fuel reservoir

4.2. Data Acquisition

A number of important parameters were monitored during the experirnents.

National Instruments hardware and software were used to acquired data for the

experiment. A detailed discussion of the LabView programs, tnggering methods and

event coordination techniques can be found in reference [23]. Thermocouple

measurements of furnace temperature and nozzle fuel temperature were acquired.

Injection pressure was measured with a strain gauge pressure transducer. The

corresponding data and photographs for each experiment were saved and recorded after

each run for later development and analysis.

4.3. Experimental Procedure

The detailed procedure carried out for each experiment is laid out in reference

[23]. A brief description is included for clarity. Although the experiment was originally

constructed for relatively heavy hydrocarbon fuel sprays, no hardware modifications

were necessary to produce an iso-octane spray. Iso-octane is a relatively light

hydrocarbon and was the research fuel used for a11 experiments camied out in this thesis.

A general description of the experimental procedure used is as foIlows:

1. The fuel supply systern was flushed clean of any previous experimental fuel.

2. The computer data acquisition system, camera, microflash and sensors were powered

up and prepared.

3. The upstream pressure was set and verified. (Note: Only one upstream pressure was

used for any given experiment. In other words, upstream temperature was the

variable that was incremented dunng an experimental run.)

4. The heaters were powered up and aIlowed a significant arnount of soak time

(approximately 1 hour or more) to reach the desired steady state upstream fuel

temperature.

5. A nitrogen environment within the spray chamber was maintained for safety reasons.

6 . A control valve was then opened producing a steady fuel spray. The upstream fuel

line pressure provided a threshold triggering signai to the data acquisition system.

7. A single photograph and the corresponding temperature and pressure data were

acquired with the aid of the data acquisition software.

The experirnental test matrix for the steady spray experiments included at least ten fuel

temperatures at each of the two pressures. Two sets of data, including a photopraph,

were acquired at each ternperature to ensure that a good quality image was obtained.

4.4. Results and Conclusions

Figure 4.2 shows the developrnent of the spray as the upstream ternperature is

increased. The normal boiling point for iso-octane is 99OC. In this case the upstream

pressure is 3.77 bar which is a typical value for the pressure in the fuel rail of a port

injected engine. The Jakob numbers corresponding to figure 4.2 are 0.00 and 0.59

respective 1 y. The Jako b nurnbers are calculated using upstream temperature and a

downstream pressure of 1 atm to characterize a given fuel spray. In figure 4.2, the first

image shows a thin fuel Stream at an upstream temperature of 30°C while the second

image shows a finely atornized spray with a large cone angle at an upstream fuel

ternperature of 160°C. The Jakob numbers corresponding to figure 4.3 are 0.33 and 1.14

respeciively. Figure 4.3 shows a similar development trend at an upstream pressure of

1 Obar with an upstream fuel temperature range of 135°C to 2 10°C-

Both of the figures illustrate a transition or a chznge in the fuel spray appearance.

Figure 4.2(a) shows a thin Stream of liquid fuel issuing from the nozzle while the

rernaining pictures illustrate different flashing flows. In figure 4.2(a) the jet appears to be

slightly larger in diameter in the upper section of the image. Surface instabilities become

visible just after the fuel exits frorn the nozzIe. The jet appears to be quite unstable

further downstream from the nozzle and break up into individual droplets is beginning to

occur. Preheating of the fuel to 160°C changes the fueI properties and causes the jet to

break up just downstream from the nozzle exit. Vapour bubbles nucleate and grow

within the superheated liquid, expanding the jet. Relatively large liquid droplets stiil

appear visible in the spray.

Figure 4.3 illustrates fuel sprays at different upstream fuel iemperatures chan

figure 4.2 at an upstream pressure of loba . A photograph of the coid liquid jet was not

included at this upstream pressure because there was little difference between this jet at

the two test pressures. Figure 4.3(a) shows a coherent fiashing spray at 135°C while an

increase in temperature to 2 10°C in figure 4.3(b) shows an increase in the jet cone angle

and a decrease in the coherent jet spray penetration distance. Both sprays appear to be

finely atomized at the elevated temperatures and liquid droplet size appears to decrease

from figure 4.3(a) to figure 4.3(b).

After preliminary results were obtained, it was hypothesized that a sirnilar result

would to be beneficial in a port injected engine configuration. In order to prove the

beneficial effects of preheating liquid fuel prior to injection it was first necessary to

observe similar fuel spray characteristics in a functional intake manifold.

Figure 4.2 Injections of iso-octane through the converging nozzle at 3.8 bar and increasing upstrearn temperatures: a) 30°C (0.56 Tc) and b) 160°C (0.80 Tc).

Figure 4.3 Injections of iso-octane through the converging nozzle at 10.0 bar and increasing upstream temperatures: a) 135OC (0.75 T c ) and b) 2 10°C (0.89 Tc).

5. Experimental Apparatus and Equipment

A port fuel injection system was designed to deliver fuel with variable liquid

temperatures upstream of the injector. The experimental setup was developed to simulate

a variety of engine operating conditions with a focus on a cold engine start condition at

1000 rpm. In order to simulate the desired engine test conditions a number of parameters

were set and monitored. These parameters inciude; cylinder head temperature, fuel

supply temperature upstream of the injector, fuel pressure upstream of the injector,

throttle position, the gas flowrate through the intake port and the delivered fuel mass

flowrate. For the purposes of this research, the engine was not motored or fired, the

engine airflow was sirnulated with steady nitrogen flow through the single cylinder intake

system. Two injectors were used for the experiments; a computer controlled injector for

low temperature injections and a modified mechanically actuated injector for both low

and high temperature injections. A modular approach was taken with the fuel injectors

and fuel delivery systems in order to allow for simple changes between systems.

5.1. Engine Specifications

A 1.9 L four cylinder MPFI Ford spark ignition engine has been converted to a

single cylinder steady flow research engine. This engine was chosen because it was a

four cylinder, single overhead Cam, port injected engine with an aluminum cross flow

cylinder head and alurninum upper and Iower intake manifolds. An engine with a single

overhead Cam was appropriate because with this configuration push rods are eliminated

leaving more room for instrument accessibility around the periphery of the cylinder head.

An in-line cylinder configuration with aluminum accessory parts allowed for easier

machining modifications and opticai access. The engine specifications are as follows:

Table 5.1 Engine cornponent dimensions.

Engine Component Dimension (mm)

cylinder bore

- - - - - -- 1 intake valve head diameter

stroke

intake valve Iift 11.0 1

87.9 l

intake valve stem diameter 8 .O

The Ford cylinder head was mounted to a custom made block plate that was matched to

the engine cylinder diameter. The engine was used in a single cylinder configuration so

the block plate mated with the cylinder deck to simulate an engine cylinder. The

remaining cylinders were not in use so the plate covered cylinders 2, 3, and 4. The

exhaust and intake systems are discussed in a later section.

5.2. Nitrogen Flow

Under normal operating conditions, atmospheric air is the working fluid for an

engine. Achieving combustion was not a goal for this research and since nitrogen closely

approximates air it was the best choice as the working fluid. The experiment was set up

in an engine test ce11 that was previously equipped with a high flowrate hydrogen fuel

supply system. This hydrogen systern was equipped with nitrogen purge capabilities and

was ideal for producing the needed flowrates of up to approximately 1000 slpm. A gas

rail with a single, high flowrate regulator was capable of adapting to six bottles of

compressed nitrogen sirnultaneously. The compressed gas was located extemal to the

building with a 45 psia pressure relief valve on the gas rail to prevent over-pressure. The

nitropen supply line was equipped with a gas filter and three gas solenoid valves. The

solenoid valves were actuated by a 12 VDC relay that was controlled with a simple off/on

toggle switch. Once the test ce11 power supply was turned on, the nitrogen flow started

when the toggle switch was set to on. The nitrogen flow was metered with a 12.7 mm

Nupro baIl valve.

5.3. Fuel Injectors

The low temperature injection experiments were camed out using a Ford

~Motorcraft CM-4488 EF6FZ-9F593-A fuel injector. The injector nozzle was a pintle type

with a converging geometry at the tip. Custom made injection control circuitry was

assembled. The circuitry used a 17 VDC battery input and T ï L pulses from the LabView

software and the data acquisition board to produce peak and hold injection pulses at the

injector input. Electronic control of the injector allowed for accurate pulse width and

frequency settings. The Ford injector was not suitable for delivering high temperature

fuel because of the method of injector actuation. A soIenoid-actuated injector would not

function in an elevated temperature environment because the heat could damage the

electronics and alter the induced magnetic field. It was necessary to develop a high

temperature mechanical injector to deliver fuel over a large temperature range.

The high temperature injection experiments were carried out with a custom

modified Stanadyne pencil type injector (mode1 9.5). This injector is nomally used in

compression ignition engines with direct cylinder injection. The injector was a pintle

type with a converging geometry at the tip. Injector control parameters such as lift

pressure, injection frequency and pulse width are independently set with this particular

injector which allows for the approximation of port injection conditions. The injector

was chosen for this research because its structure and method of actuation alIowed for

modifications and operation at elevated temperatures. It was composed entirely of

metallic compounds that allowed fuel delivery in the desired temperature range without

risk of interna1 component damage. Using a mechanically actuated injector, however,

increased the control problems discussed earlier. A Bosch fuel purnp was used to

develop the necessary injector cracking pressure. Lift pressure was set with the threaded

compression screw at the end of the injector. The screw compresses the spring inside the

injector, which changes the force holding the needle against the seat. As the spring is

compressed, a higher fuel line pressure is developed by the fuel pump in order to produce

a fuel spray. Three modifications were made to the injector in order to meet the operation

requirements and are described in Appendix C. One negative aspect that came with using

this mechanical injector was loss of precision control. Unlike the Ford injector, pulse

width and frequency were difficult to accurately control when using the Stanadyne

injector and Bosch fuel pümp. A second compromise that had to be made with the

Stanadyne injector was that it had an opening pressure lower limit of approximately 500

psig which is on the order of ten times Iarger than the upstream pressure of the Ford

injector.

5.4. Fuel Delivery and Measuring System

A versatile fuel delivery system was needed in order to carry out a nurnber of

important functions during experimentation. The system was required to pressurize the

fuel rail for the Bosch fuel injector, supply fuel to a mechanical fuel pump for the

Stanadyne fuel injector and act as a mass flow calibration device for the two injectors.

Schematic diagrarns for the fuel delivery systems are depicted in figure 5.1 for the

Bosch injector setup and figure 5.3 for the Stanadyne injector semp. The fuel delivery

system components are described in the following sections. The procedures used for

experimentation and fuel injector calibration are described in the next chapter.

The electric fuel pump was a 1/20 hp, 120 VAC, 60 Hz pump with a maximum

speed of 3000 rpm (Universal Electnc Company, senal # 4RA1105R, model #

ABlS076N). The pump was a thermally protected model for use with combustible

materials. The pump is actuated with an off/on toggle switch. Two fuel supply tanks or

reservoirs were used in this system as shown in figure 5.1. The stainIess steel supply

tanks each have a capacity of approximately 10 L. Each of the tanks had manual valves

on the supply end and threaded caps on the top for filling purposes. The recirculation line

from the fuel rail couId be connected to either of the tanks depending on the experiment

being conducted. The recirculation cap was equipped with a 3 psig relief valve to avoid

any reservoir pressurization. Two tanks were used in this system for versatility reasons.

Under standard opersiting conditions, both tanks contained a research grade fuel. When

two fuels were used, supply tank #1 contained pump grade fuel and supply tank #2

contained research grade fuel. This allowed for the use of a variety of research fuels

some of which could be corrosive to the fuel injector. After the system was run with the

corrosive fuel the pump grade fuel could be used to rinse the injector and thus prevent any

injector damage. A second reason for having two fuel reservoirs was to allow a

separation of the mass measuring side of the system from the bulk fuel supply side. This

spread the components out and provided roorn for the mass scale enclosure.

Most of the fuel lines shown in figure 5.1 were 6.4 mm stainless steel lines joined

with Swagelok fittings. Rubber fuel Iine, 7.9 mm in diameter, was used for the line from

the pump to the fuel rail and the recirculation line from the fuel rail pressure replator to

the reservoir to alIow far easy mobility.

A number of valves were used in the system. All of the valves that are not shaded

are manually controlled open/close valves that were positioned in various locations to

provide a range of system configurations and to allow for simple disassembly. The

mechanical valves are labeled 1, 2 ,3 and 4. The three shaded valves numbered 1, 2 and 3

are electronicall y controlled, 120 VAC, 60 Hz solenoid valves (Asco solenoids)

controlled with solid state relays (Crydom SSR, 120 V, 10 A, 3-32 VAC control). Valves

1 and 2 are two way valves, meaning that there are two States of operation. The fueI flow

input side is always the same but the fuel flow output can be changed between two

possible paths depending on the solenoid state. The non-energized state for these two

valves is depicted schematically as straight through in figure 5.1. The energized state is a

90 degree angle in schematic form. Valves 1 and 2 are controlled by a relay, which is in

tum computer controlled. Valve 3 is a one way solenoid valve, meaning that it is either

open or closed. The non-energized state is closed. This valve is controlled with a simple

hand operated toggle switch. The purpose of these valves will become clear when the

overall system operation is explained in the next chapter.

Two fuel filters were added to the fuel line. One of the filters uses a second fluid

to filter the fuel. The second filter is a meshed barrier to remove any particulate matter in

the fuel flow. The fuel measuring side of the fuel delivery system was mainly used for

injector calibration. The mass measurïng part of the fuel delivery system was made up of

a digital scale, two enclosures and a fuel reservoir. The small reservoir was composed of

stainless steel and had a fuel level indicator made of clear tubing fitted on the side. A

Sartorius (model# 1404MP8) digital scale was used to make mass measurements. The

scale limit was 2.0 kg and it was accurate down to hundredths of a gram. The scale was

also equipped with a leveling bubble to ensure that the mass measurements would be

accurate and consistent. The small reservoir and the digital scale were completely

enclosed in Plexiglas. The purpose of this enclosure was to obtain mass measurements

that were not affected by any air currents in the laboratory. The digital scale used was

very sensitive to any disturbances and for that reason was completely isolated. A rubber

boot was used to seai tne top of the small reservoir with the roof of the Plexiglas box in

order to capture any fuel vapor and improve systern accuracy.

fuel reservoirs pressure relief valve

fuel rail pressure

m füel rail temperature

pressure 1 I regulator

1

i ipj 1

fiel i level fiiel return Iine u-

i .w , isolated tùel injectors

Figure 5.1 Ford Injector fuel supply system.

5.5. Ford Injector Fuel Supply System

The fuel rail was mounted to the Iower intake manifold (not shown) as per the

stock Ford layout for the experiments and for fuel injector calibration. The fuel delivery

system utilized the standard Ford fuel rail and Ford injector. The fuel rail is designed to

accommodate four fuel injectors, one for each engine cylinder, however only one injector

is shown in figure 5.2. The other three injectors were present to seal the fuel rail properly

but they were not pulsed and were therefore inactive. Leaving the three inactive injectors

in place was the easiest way to seal the fuel system without having to make modifications.

The fuel rail came equipped with a fuel feed line, a fuel recirculation line, a threaded fuel

pressure relief fitting and a pressure regulator. As shown in figure 5.1, the fuel feed line

was lengthened and connected to the pump and the recirculation line was connected to 2-

way solenoid valve #2. Since the fuel rail pressure could be released by disconnecting the

fuel rail feed line, the fuel rai1 pressure relief fitting was used to acquire a fuel rail

pressure and temperature reading. A 3.2 mm Swagelok T fitting was adapted to the

pressure relief fitting. On either side of the T fitting an analogue pressure gauge and a K-

type ungrounded thermocouple were mounted using Swaplok. AS shown i n the figure,

the pressure regulator rnaintained a fuel rail pressure relative to atmospheric. One side of

the repulaior, usually connected to the intake manifold which is at a vacuum under

normal engine operating conditions, was left open to atmospheric pressure and the other

side monitored fuel rail pressure. When the pressure in the rail exceeded 39 psig the

pressure regulator opened a fuel recirculation valve and allowed fuel to flow back

towards Zway solenoid valve #2. In this way, the fuel rail pressure was maintained at 39

psig.

high flow rate pressure reguIator

plate

hot water feed

water r e m

'/ I upper manifold , lower manifold

cylinder 4 1 1 fi~el feed

condenser J7

injected fuel collection

Figure 5.2 Ford fuel injector setup.

5.6. Stanadyne Injector Fuel Supply System

The Stanadyne injector was chosen because it is a mechanically actuated injector

and was deemed suitable for modifications and for high temperature fuel flow. The fuel

supply system for the Stanadyne injector is shown in figure 5.3 in schematic form. This

injector required the use of a single cylinder Bosch rotary pump (senal #

PFRIKSOA427/1 l) , often referred to as a jerk pump, in order to develop the necessary

injector opening pressures. The maximum pressure the pump was capable of developing

was approximately 5000 psia, well within experimental requirements. The purnp has a

barre1 diarneter of 7.50 mm with a range of delivenng quantities from O to 120

mm3/stroke. Under normal operation, a mechanical injection pump would be coupled to

an engine camshaft, which turns at half the crankshaft rpm. In this modified, research

application, the pump speed was set and maintained with the aid of a 1 hp Woods SCR

motor and controller (serial # 1382). The motor used 208 VAC, 3 phase supply voltage

and provided a maximum speed rating of 1750 rpm but was only used up to 600 rpm.

Initially, the pump and rnotor were rigidly mounted and the shafts were directly linked

through a steel coupling. A number of configurations were tested before it was

determined that a gearing system was necessary. A 2.9 to 1.0 gear ratio was chosen to

allow the rnotor to rotate closer to its normal operating speed limit. This lowers the

torque requirernents and provides as constant a rotational speed as possible. This specific

ratio was chosen due to limitations in space around the pump and motor. Toothed gears

and a toothed belt were chosen to avoid slippage. The motor controller allows

independent rnotor torque and speed settings, however, maximum torque was the only

setting used during expenmentation because the torque requirement for the pump varied.

In an attempt to rnaintain a constant pump rotational speed it was detemined that the

maximum torque setting would minirnize speed variations particularly at low rpm. The

electric fuel purnp, that was part of the main fuel delivery and measuring system, was

used to supply the inlet to the mechanical fuel pump with fuel at 40 psig. This pressure

was set with a Swagelok, variable opening pressure, relief valve (mode1 #B-KA-50).

The supply pressure to the pump was relatively low so 7.9 mm diameter rubber fuel line

was used to allow for simple system rearrangements. The fuel line from the pump to the

Stanadyne injector was a 3.0 m length of stainless steel chromatographie tubing with an

44

intemal diameter of 1 mm. This small diameter tubing was chosen to minimize the

internai volume from the pump to the injector in order to minimize fuel compressibility.

The fuel line pressure rating was well above experimental levels whiie the tubing wall

thickness was thin enough to allow for small radius bends. A Iength of 3.0 m allowed

enough fuel line to tightly wrap around the heater bar and maximize the heat transfer to

the fuel.

fuel reservoirs - - - -?, pressure relief

valve

electric fiel pump

l torque 0 l

Stanadyne

isolated rneasurement

Figure 5.3 Stanadyne Injector fuel suppl y system.

5.7. Fuel Heating System

Two heaters were used to achieve the desired liquid fuel temperatures just

upstream of the injector. The complexity of the heat transfer problem made it difficult to

calculate the system requirements necessary to heat the liquid fuel to the desired

temperatures. Some of the issues involved included heat transfer to the liquid fuel

through a complex geomtry, intermittent liquid flow and liquid compressibility. It was

not realistic to attempt an accurate calculation including al1 of the variables involved. A

high wattag heater was chosen to ensure that the desired temperatures were attainable

and a secondary heater system was included as a factor of safety. The primary heater was

a Caloritech 3500 W. stainless steel cartridge heater (CIR 4360). The heater was 15.9

mm in diameter and 9 14.4 mm in length. It was capable of temperatures up to 650°C but

the unit was chosen for its high heat flux capability. A number of accessories were

needed in order to accurately set and control the heater temperature and a wiring diagram

is shown in figure 5.4. An Omega CN77332-A2 digital feedback control unit was used in

conjunction with an Omega solid state relay (Omega SSR, 220 VAC, 25 A, 3-32 VDC

control) for this purpose. The digital control was equipped with a PID option with

temperature feedback. This option was chosen in order to maintain the heater

temperature as close as possible to the desired set point temperature. The PID settings

used were proportional band of 300°C, reset of 300°C and rate of 0.0 s (i.e. not in use).

As figure 5.4 shows, it was necessary to use three different power supplies for the heater

control system. 120 VAC to power the digital controller, 12 VDC to actuate the SSR and

a single phase of a 208 VAC line to supply current to the heater through the high voltage

side of the SSR. An ungrounded thermocouple (GKQSS-18U-12) was used as the

feedback source to the controller.

t feedback thermocouple

-

t emperature controller

i i

I I l

i l

Figure 5.4 Heater control system.

The secondary heater was an Omega 120 VAC, 720 W heater and controller

(HTWC 10 1-010). The heater strap was 25.4 mm in width and 254.0 mm in length. This

heater was wrapped around one of the fuel supply reservoirs in order to give the bulk fuel

mass any desired amount of preheat up to approximately 50°C. The heated fuel supply

reservoir was Iocated before the electric fuel pump so to avoid fuel pump damage it was

decided not to exceed approximately 50°C. The heater was tightly wrapped around the

metallic reservoir and three layers of fiberglass insulation with a maximum temperature

rating of 550°C (Intertex Textiles) were wrapped around the heater. A simple analogue

control unit was used to set the heater temperature. No attempt was made to implement a

feedback control system for this heater because accurate temperature was not crucial this

far upstrearn of the injector. The heater

checked during each expenment and was

ternperature was set to the desired value and

found to maintain the reservoir at a constant

value. The important temperature value was the fuel temperature at the entrance to the

injector and the primary heater was used to obtain an accurate temperature at this point.

With both heaters working it was found that after a sufficient soak time of approximately

10 or 15 minutes, the primary heater temperature would not vary from the set point

ternperature by more than 0S0C. It was found that the fuel preheating system was

capable of supplying fuel up to a temperature of 220°C with a 95.0% confidence interval

of less than 0.7"C on the mean fuel temperature in an experirnental set.

5.8. Exhaust Management

A custom designed system was assembled to collect fuel in liquid and vapour

form. Any fuel injected onto the valve of the experirnental apparatus would flow down

the cylinder head wall surfaces and into the cylinder. A valve was placed at the bottom of

the simulated cylinder for liquid fuel collection. Any entrained or vaporized fuel that

found its way beyond this point was condensed in a cold trap. The trap was made

primarily of ABS plastic and a schematic is shown in figure 5.5. When the heated fuel

injection experiments were carried out, ice water and liquid nitrogen were used to cool

the condenser walls. The fuel vapour and nitrogen mixture would flow through the

condenser core with ice water in the outside 50.8 mm enclosure and liquid nitrogen in the

inner 6.4 mm enclosure. The fuel vapour would condense on the outer surface of the 6.4

mm Swagelok tubing and on the inner surface of the 50.8 mm A13S enclosure.

Figure 5.5 Condenser system.

5.9. Data Acquisition Hardware

In order to cany out the fuel injector calibrations and to acquire data at moderate

acquisition rates for al1 the experiments a relatively versatile data acquisition (DAQ)

board was needed. For that reason, a National Instruments ATMIO16E-IO board was

purchased dong with a SC-2070 termination board.

The National Instruments ATMIOl6E-IO board is a 100000 Hz board, equipped

with 16 single ended or 8 differential analogue inputs, digital input and outputs. The

board was configured in the differential mode of operation for the purpose of data

acquisition. Seven of the eight analogue inputs were used to acquire differential voltage

signals. Five digital lines were also used as counters, triggers and timing signais

acquisition, event coordination and injector pulse control. The following is a s

table of the channel configurations and channel types used.

Table 5.2 Data acquisition channel information.

for data

~umrnary

- I - -

Channel Label Channel Function

/ differential analogue O** 1 cold junction

differential analogue

L

differentia1 analogue

thermocouple

1,9 thermocouple


1 differential analogue

' differential analogue

MAP pressure sensor

1


3,11

4,12

hotwire fiow meter

thermocouple

thermocouple

counter


injector puIse

counter gate

7,15 Schaevitz pressure transducer

Ctrgate

I trigger 1 PFIO

putse gate

external trigger

camera trigger and injector lift counter I

counter

digital output

Ctr 1

counter

relay control

A shielded cable (National Instruments SH6850) connected the data acquisition board to

the SC-2070 termination board. The SC-2070 board was used for signal termination,

signal filtering and thermocouple cold junction compensation. The SC-2070 board was

PFI2 extemai timing

incorporated into a surge protection box in order to protect the data acquisition board

from signai line spikes.

5.10. Sensors

A range of sensors were impiernented to fully characterize the fuel injection event.

In fact, a number of sensors were caiibrated and later determined to be unsuitable for use

before a functional data acquisition system was in place. A surnmary of both sensor

location and sensor noise level are listed in table 5.3. The calibration equations that were

developed for each sensor are listed in the sections to follow. The developed equations

were incorporated into the LabView data acquisition software. The calibration

procedures are listed in Appendix E.

Table 5.3 Sensor locations and noise levels.

Sensor

chip

themocouple

t hermocouple

therrnocouple

thermocouple

MAP

hotwire

Schaevi tz

Sensor Location

on board cold junction compensation

upper intake manifold temperature

injected fuel temperature

injector body ternperature

local cylinder head temperature

intake manifold

upstream of throttle

high pressure feed line

Signal Noise LeveIs [mV]

Al1 the thermocouples were K-type, low noise and ungrounded sensors with

ground straps (GKQSS- 18U- 12). LabView prograrns were developed to carry out cold

junction compensation and voltage-to-temperature conversion. The thermocouples were

304.8 mm in length with a diameter of 3.2 mm to allow for mounting with 3.2 mm

Swagelok fittings.

The manifold absolute pressure ( M M ) sensor was used to measure upper

manifold pressures in order to characterîze the downstream injection environment. The

device was a 0.0 to 2.0 bar General Motors MAP sensor. A pressure tap was made in the

manifold and connected to the sensor input via 6.4 mm diameter tubing. The linear

relation developed for this sensor, relating absolute pressure to voltage, is listed in

Appendix E.

To measure nitrogen flows through the experimental apparatus a Nissan hotwire

anernometer was used (Nissan, Hitachi, 22680 53J00, AFH50-06, 0x23). The meter was

used to measure flowrates up to approximately 1000 slpm, which was well within the 0.0

to 2000.0 slpm range. The flow meter was positioned just upstream of the engine throttle

body. The calibration curve for the sensor and the charactenstic equation are listed in

Appendix E.

After testing was carried out, the best available method of acquiring a fuel line

pressure was a strain gauge pressure transducer. The sensor calibrations and the steps

taken in developing a pressure measurement system are discussed in Appendix E. A 0.0

to 1000.0 psig Durham Instruments Schaevitz transducer (P 102 1-0005, senal # 1006 15)

and a bridge amplifier were used to acquire the fuel line pressure. The transducer had a

frequency response of 3 kHz. This sensor was located just upstream of the Stanadyne

injector mounted on the end of 3.2 mm diameter, 254.0 mm length of Swagelok tubing.

A Swagelok, 0.0 to 1000.0 psig pressure relief valve (SS-R3A-KI-C) was placed in the

fuel supply line near the pressure sensor to protect it from over-pressure. The calibration

and the equation converting voltage to pressure are listed in Appendix E.

To calibrate the modified Stanadyne injector a method was needed to coont the

number of injection events during a given time period. For this purpose a lift sensor

system was developed. A Wolf Controls Corporation Hail effect micosensor was used in

conjunction with two custom designed circuits to count injector pulses. When a current is

passed through a thin metal foi1 in the presence of a magnet a current a voltage is

produced. The Hall effect is utilized in the lift sensor to produce an analogue voltage

signal that is proportional to the injector needle movement. The injector was fitted with a

custom made magnet and a sensor holder assembly. The primary circuitry used linear

differential amplifiers, a differential emitter follower output and a voltage regulator.

Since an actual lift quantity or distance could not be detemined from the analogue output

signal it was converted to a TTL pulse with the aid of secondary thresholding circuitry.

The TTL pulses were read into the National Instruments board and were counted using

the LabView software. The method for counting injections was later modified due to

poor operation of the lift sensor at elevated temperatures. The fuel line pressure sensor

signal was used as a threshold signal input to the thresholding circuitry instead of the lift

sensor signal. In that way TTL pulses were produced when the pressure signal rose above

3 set value.

Two methods were used to monitor Bosch fuel pump rotational speed. Initially a

hand held digital tachometer (Veeder Root Mode1 #66 I 1) was used to obtain a rotational

speed. After preliminary tests with the DC motor drive and fuel purnp it was determined

that a more accurate method of monitoring pump speed was necessary. A sixty tooth gear

was adapted to the coupling shaft between the DC motor and the fuel pump. A magnetic

pickup (Airpax 1-0002) was then mounted perpendicular io the sixty toothed gear at a

distance of approximately 2 mm. The magnetic pickup signal was amplified and

displayed on a Daytronic frequency indicator/controller (mode1 #3 MO). During testing

the pump speed was monitored for each set of experiments.

To trigger the camera for the Stanadyne fuel injector experiments an optical

switch was used. Since the fuel injector opened once every fuel pump revolution, a signal

produced each revolution was chosen as an external timing event. The sensor was a

reflective type optical switch (senal # OPB 701), with a custom made circuit to convert

the output to a TTL signal. The circuit was developed to convert the sensor signal to a

TTL signai only when a threshold level was exceeded. In order to minimize room

lighting effects a relatively high threshold value was chosen. In addition, the sensor was

shielded from external light. A reflective surface, approximately 30 mm in diameter, was

mounted to the gear on the Bosch fuel supply pump. The sensor was rigidly mounted to a

stand to allow positioning perpendicular to the reflective surface. In summary, figure 5.6

iIlustrates the signal connections for al1 calibrations and experiments.

Generator [ ~ ~ ~ h i l s e ; - ~ . 7 r ~ i i m a 7

From MAP sensor

From Nissan Flowmeter

From Schaevib Tranducer Bridge Amplifier

From Lift Sensor Circuit

Data Acquisition and Termination Boards (ATM10 16E-10 and SC2070)

Tirnebase Signai (PFI.2)

CJC Temperature (ACHO)

Plenum Temperature (ACH 1)

Injector Fuel Temperature (ACH 2)

hjector Body Temperatlue (ACH 3)

Local Cylinder Head Temperature (ACH 4)

Plenum Pressure (ACH 5) Solenoid Actuation @IO O)

htake Manifold (ACH 6) ihjector Pulse (Ctr O) N2 Flowrate

Fuel Line Pressure (ACH 7) Camera (Ctr 1)

Injection Count (CTRl)

- (~uel System ~elaysl

4 Injector circuit 1

4 Camera Circuit]

Figure 5.6 Data acquisition signal connections.

5.11. Data Acquisition Software

The software used to coordinate events and acquire data was National Instruments

(NI) LabView Software version 4.1. LabView is a visual programming Ianguage, which

was used to calibrate the injectors and acquire data during injection events. Using the

software terminology, the programs are referred to as virtual instruments (VI) and sub-

VIs. Each program consists of a front panel and a back panel. The front panel displays

control switches, filename inputs and numerical outputs and the back panel displays the

program structure. A brief description of the LabView programs developed for this

project are listed in Appendix B.

5.12. Data Acquisition Triggers

In order to capture an image of the fuel spray it was necessary to develop a

repeatable method of camera control for both experimental setups. Camera triggering

was accomplished with a unique method for each injector. The camera, motor driver and

flash unit were tested in order to quantify the time delay between the carnera receiving a

trigger and the flash finng. This value was found to be 92.0 ms +/- 0.3 ms rneasured with

an oscilloscope and a photoresistor circuit. For the Ford injector, correcting for this delay

was accomplished by incorporating a variable time delay into the software. For the

Stanadyne injector, the flash timing was coordinated with a software delay and proper

trigger sensor positioning. The sensor used for triggering the expenment was discussed

in section 5.10. The reflective surface was mounted such that the trigger signal would be

sent approximately 210 degrees before the cam in the pump started to lift the pump

pIunger. The start of the plunger lift is approximately the start of injection. With the

reflective surface appropriately located, the flash timing could be accurately controlled

using LabView.

5.13. Optical Access

Optical access was obtained through two view ports, one through the cylinder

head and upper manifold and the second through the lower intake manifold. The top

view-port was design to observe the fuel spray developrnent downstream frorn the

injector whiIe the bottom view-port was designed to make observations at the injector

exit. The view ports were designed to accept an 8 mm diameter Olympus Industrial fiber

optic borescope. The view port locations were shown in figure 5.2. Both ports were

designed to align the fiber optic borescope axis with the center axis of the hiel spray in

the intake port. The upper view port required significant modification of the plenum and

the cylinder head in order to position the borescope at the desired viewing angle. A

channel was machined through the plenum to accept a sleeve, which was slightly larger

than the borescope diameter. The sleeve would act to support the borescope and to seal

the plenum against nitrogen leaks. A hole was bored and an 8 mm diameter Swagelok

adapter was mounted into the cylinder head to accept the borescope. When the borescope

was inserted, it would first be push completely through the plenum and out the other side.

It would then be inserted into the cylinder head section of the view-port and Iocked down.

The second view port was located perpendicular to the tip of the injecter. A block of

aIuminum was welded to the Iower manifold and again a hole was bored and an 8mm

Swagelok adapter was mounted. Teflon ferniles were used to lightly clamp the borescope

into place in each of the view port locations.

5.14. Photographic Equipment

Obtaining photographic images of the injection event at different fuel preheat

temperatures was the primary objective of this research. Much like the sensor

instrumentation, the photographic system involved a trial and error process to acquire

quality images.

As discussed in the previous section, optical access was developrd to

accommodate an Olympus series 5 Industrial fiber optic borescope (R080-024-000-

50ILG) and OIympus light source (KLS-13 1). The borescope wcrs used for a11

expetirnentai image acquisition and provided a direct view dong the axis of the scope

body with a focusing range of 5 mm to infinity. Adapters were purchased in order to

adapt the borescope to a 35 mm camera (Nikon T-Mount and T-2 Mount adapter) and a

high speed ICCD camera (Nikon T-Mount and T-MD Mount adapter). The borescope

was equipped with an integrated light p i d e to supply illumination to the tip. Numerous

atternpts were made to increase the light intensity produced by the light source by adding

higher wattage bulbs and a custom made cooIing system but it was later determined that

only flash photogaphy could produce the necessary light intensity.

A 35 mm camera with flash photography was determined to be the best method of

acquiring images. The unit included a Nikon FM2 camera, MD12 rnotor driver and a

Vivitar 185HV flash unit. Fuji 1600 speed black and white film was used to acquire al1

fuel spray images. After a great deai of trial and error testing, the camera was set to 1/250

s exposure time (the maximum sink rate for use with a flash) and a film speed of 1600.

The flash unit was capable of producing a fiash duration between 111000 and 1130000 s

when set in automatic light detection mode. For this experimental setup, the flash

duration was effectively the exposure time. The flash unit was set to maximum intensity

and the automatic light detection mode was chosen to minirnize exposure times. To

further minimize exposure times, different light intensities, targeted at the flash unit light

sensor, were tested until. A signal from LabView was used to tngger the camera through

custom made control circuitry. A l'TL pulse entered the camera control circuit, resulting

in a shorted output terminal to the motor driver. The motor driver then actuated the

camera shutter and the camera actuated the flash unit.

6. Experimental Procedures

6.1. Calibration Procedures

The calibration procedure for each of the tv JO fuel injectors utilized the m a s

measunng and fuel supply apparatus described in sections 5.4,5.5 and 5.6 of the previous

chapter. Iso-octane was used for al1 experiments and a detailed list of the fuel properties

has been included in Appendix A. A standard calibration procedure was used to calibrate

the Ford fuel injector and is described in Appendix D. The raw data and a summary plot

characterizing the Ford injector are also included in Appendix D. A custom procedure

was utilized when calibrating the Stanadyne injector. An explanation for al1 calibration

and experimental conditions chosen has been covered in the next chapter.

6.1.1. Stanadyne Fuel Injector Calibration

A unique method was developed to calibrate the Stanadyne injector. The purpose

of the calibration procedure was to quantify the mass of fuel delivered per injection at

different Fuel temperatures. The fuel temperature was measured just upstream of the

injector. In order to reduce the experimental test rnatrix to a manageable size, the injector

pulse width, opening pressure and fuel supply purnp rotationaI speed were set to constant

values. The pulse width was set with the Bosch fuel pump rack setting. The calibration

procedure was as follows:

1. Fuel was added to each of the IO L fuel reservoirs. They were not fiIled to capacity.

2. R e f e ~ n g to figure 5.3, mechanical valves #1,2 ,3 and 4 were opened.

Using toggle switch controlled solenoid valve #3, the small fuel reservoir was filled

(gravity fed), whiie carefully observing the fuel level through the fbel level window.

Mechanical valve #3 was then closed.

The digital scale was leveled to horizontal in order to ensure consistent readings. The

scale was leveted using a leveling bubble.

The pressure sensor bridge amplifier and the injector needle lift circuitry were tumed

on and allowed 20 minutes to warrn up.

The pump was then actuated with a toggle switch mounted on the front panel of the

fuel system. As shown schematically in figure 5.3, the eiectric pump drew the fuel

from reservoir # 1 , through the fuel filters and delivered fuel to the Bosch fuel pump

inlet. The 40 psig pressure relief valve allowed the fuel to divert to solenoid valve #2

and back to reservoir #1.

The Bosch fuel pump speed was set to 400 rpm.

The LabView calibration proprams were loaded. Explanations of the programs are

covered in Appendix B.

10. The desired calibration temperature was set on the temperature control unit. The fuel

injector continued to deliver fuel, while the heater was allowed I O minutes to bring

the fuel to a steady state set point temperature. The injection fuel temperature was

monitored with a separate LabView propram.

11. When the fuel temperature reached a constant value the pressure data acquisition

program was used to acquire one fuel line pressure trace at the start of each

calibration. The pressure was monitored for repeatability over the entire calibration

procedure but on1 y one trace was acquired for each temperature.

12. The initial mass reading on the digital scale was recorded.

13. The fuel temperature Nas recorded.

14. The lift sensor program was run with the number of injections set to 500. Relay

controlled solenoid valves # 1 and #2, actuated by the software, diverting fuel flow to

the mass measuring side of the fuel system. SoIenoid valve switching was

coordinated with the start of injection counts through the software. When the number

of injections reached 500 the software switched the valves back.

15. The final mass reading on the digital scale was recorded.

16. After approximately two or three sets of injections, the fuel collection flask

downstream of the injector was emptied.

Steps 12 to 16 were repeated 10 times at each temperature in order to ensure statistical

significance. At each temperature the fuel supply system was flushed and filled with

fresh fuel. The resultant data from these calibrations are listed in appendix 1. A figure

showin; the quantity of fuel delivered per injection as a function of temperature is listed

in the followinp chapter.

6.2. Experimental Procedure

Separate procedures and experimental setups were used to acquire photographs

and data during experimentation with the two fuel injectors. Similar data acquisition

schemes were used with the most significant difference being the triggering and timing

procedures discussed in the previous chapter.

6.2.1. Ford Fuel Injector Experimentation

The following procedure was carried out to acquire an image of an injection event

and to acquire data during that event.

1. The MAP sensor and the Nissan flowmeter power supplies were tumed on and given

tirne to warm up.

2. Power was supplied to the fuel injector control circuitry and the nitrogen flow control

relays.

3. The fuel level was checked in the fuel supply reservoir.

4. The fiber optic borescope was mounted in either the top or bottom view port.

5. The camera was loaded with film and mounted on to the motor driver.

6. The motor driver base was then mounted to the tripod.

7. The camera was connected to the borescope with the alignment adapter. Careful

alignment was necessary to ensure that stress was no? applied to the borescope body.

8. The flash un i t was connected to the carnera body.

9. The electric fuel pump was turned on and using the Ford injector calibration program.

the injector was pulsed 500 times to prime the system. While the injector pulsed, the

borescope was focused on the fuel spray. A small, high wattage light source was used

to illuminate the spray through the borescope light guide.

10. After the borescope was focused the light guide tip was repositioned directly in front

of the flash unit.

1 1. Motor driver power and the flash power were tumed on.

12. The Ford injector data acquisition program was loaded.

13. The start of injection was set to delay 83.0 ms from the camera irigger signal.

14. The injector pulse width was set to 18.0 ms.

15. A data filename was entered for data collection.

16. The nitrogen control switch was turned to the on position, setting up the desired

nitrogen flow through the experimental apparatus. A shon period of time was

a1Iowed for the flow to reach a steady velocity.

17. The electric fuel pump was tumed on to supply the injector with fuel.

18. The high wattage Iipht source was placed in front of the Rash unit Light detector and

the lights in the test ce11 were tumed off. The lipht source forced the flash unit to

produce the shortest flash duration possible.

19. The data acquisition program was run, capturing an image and acquinng data for a

single injection even t.

Step 19 was repeated 36 times utilizing an entire role of film for a given test condition.

6.2.2. Stanadyne Fuel Injector Experimentation

Steps 1 through 8 used to acquire data for the Ford injector experiment were the same

for the S tanadyne inj ector experiment.

The Schaevitz pressure transducer bridge amplifier was tumed on twenty minutes in

advance of use.

The electric fuel pump and the Bosch fuel pump were turned on to inject fuel and

prime the system.

The desired calibration temperature was set on the temperature control unit. The fuel

injector continued to deliver fuel, while the heater was allowed 10 minutes to bring

63

the fuel to a steady state set point temperature. The injection fuel temperature was

monitored wi th a separate LabView prograrn.

While the injector pulsed, the borescope was focused on the fuel spray. A small, high

wattage light source was used to illuminate the spray through the borescope light

guide.

After the borescope was focused the iight guide tip was repositioned directly in front

of the flash unit.

Motor driver power and the flash power were turned on.

The Stanadyne injector data acquisition prograrn was loaded.

A data filename was entered for data collection.

10. The nitropen control switch was turned to the on position, setting up the desired

nitrogen flow through the experimental apparatus. A short period of time was

allowed for the flow to reach a steady velocity.

1 1. The high wattage light source was placed in front of the flash unit light detector and

the lights in the test ce11 were turned off. The light source forced the flash unit to

produce the shortest flash duration possible.

12. The data acquisition program was mn, capturing an image and acquiring data for a

single injection event.

Step 12 was repeated a maximum of 36 times utilizing an entire role of film for a given

set of test conditions.

7. Results and Discussion

7.1, Overview

Expetiments have been conducted with fuel upstrearn of the injector nozzles

between roorn temperature and 220°C. Iso-octane was the fuel used for al1 experiments

in this study. A successful experiment resulted in: a photograph of the fuel spray as well

as rneasurernents of the fuel injection temperature, fuel injection pressure, fuel injector

body temperature, local cylinder head temperature, nitrogen flowrate and manifold

pressure.

Baseline testing was accomplished using a Ford production injector with fuel

upstream of the injector at room temperature. The fuel supply pressure for the Ford

injector was maintained at a constant 3.7 bar (39 psig). Testing with superheated fuel

was camed out using a modified Stanadyne diesel injector. Fuel injection temperatures

in a range from room temperature to 220°C were achieved with the Stanadyne injector

setup. Fuel supply pressure to the Stanadyne injector was acquired during

experimentation because it varied continuously throughout a given injection event.

The data acquisition process was triggered using different methods for each

injector but the data acquisition timing, number of data points acquired and the data

processing remained essentialiy the same. For each experirnental test point (fuel

injection photograph), 720 data points were acquired and processed for each signal. The

significance of acquiring 720 data points was that the DAQ program was deveioped to

function with an engine in the future and 720 data points would represent one data point

per CAD (crank angle degree) for one complete cycle. With a sampling rate of 1000

samples per second the entire acquisition would occur over 0.72 S. The Ford injector was

software controlled and only one injection occurred during each experimental cycle. The

S tanady ne injections were camshaft actuated and four injections would occur during the

0.72 s with image acquisition taking place during the first injection. The multiple

injections did not pose a problem because a11 acquired values were found to be constant

at each test condition (i.e. injection temperature) and did not Vary if acquired over a

separate set of injections. AH acquired values were averaged except for the Stanadyne

injector upstream pressure because this was the only value that was found to Vary with

tirne. Raw data for both sets of experiments can be found in appendix J. The average

data are organized in columns composed of thirty-six rows, one for each photograph.

Mean, standard deviation and 95.0% confidence intervals on these acquired averages

have been determined and are included at the end of each data set. The raw pressure data

for the Stanadyne injector have also been included in appendix J.

A total of approximately 360 experiments were camed out with the Ford injector

using both the bottom and the top view ports, where an experiment is considered to be the

acquisition of a single image and the corresponding data. Approximately 360

experiments were carried out with the Stanadyne injector over a temperature range from

room temperature to 230°C. Eight temperatures were chosen within this range and a

minimum of ten images and the correspondinp data were acquired at each temperature.

Images of the baseline Ford injector tests are presented in section 7.5. A sequence

of fuel spray photographs, produced with the Stanadyne injector at increasing

temperature, are also presented in section 7.5. A large number of fueI spray pictures were

acquired and from these the clearest typical images are presented. It should be noted that

the fuel sprays appeared to be very consistent at a given test condition and only the

quality of the photographs varied.

7.2. Ford Injector Experimental Data

Raw data for the baseline experiments are listed in Appendix J, tables J. I for the

data corresponding to the top view port image and J.2 for the data corresponding to the

bottom view port image. Plenum, upstream fuel, injector body and cylinder head

temperatures were found to remain constant at approximately 22, 22, 22 and 2I0C

respectively for the top view pon set of experiments. The manifold pressure remained at

a consistent 1 1 I kPa and the nitrogen flowrate was 9 13 sIpm. The temperatures acquired

durhg the bottom view port set of experirnents Iisted in the same order as above were 22,

22, 22 and 21°C respectively. The manifoId pressure was 11 1 kPa and the nitrogen

flowrüte was 966 slpm. An inconsistency in flowrate developed between the two sets of

experiments but was not considered to be a problem because different nitrogen flowrates

did not appear to strongly affect the injection process. The mass flowrate of fuel through

the Ford injector was deterrnined as described in Appendix D. The fuel injector delivered

0.038 g of fuel over an IS ms injection period.

7.3. Stanadyne Injector Experimental Data

Data for the high temperature fuel injection experiments has been listed in

Appendix J, tables 5.3 to J. 1 1 . The data has been orpanized in the same way as the low

temperature data acquired during the Ford injector experiments with measured spray cone

angles included in one additional column. The fuel spray cone angles were measured

from photographic prints. Fuel pressure upstream of the injector was also acquired

during each experiment and the data is included in table 1.12 of Appendix J. In some

cases a different number of experiments were carried out at each of the chosen upstream

fuel temperatures. A range from 7 to 38 experiments were run but this variation was not

considered to pose a problem because of the repeatability witnessed with the fuel spray at

a given temperature. In fact, repeatability testing was carried out when the system was

being debugpd and both photographic and visuai inspection showed consistency at each

temperature.

Figure 7.1 shows a typical injector pressure trace over the course of a single

injection event. The large peak indicates the lift pressure necessary to lift the pintle from

its seat. For the Stanadyne injections, image acquisition occurred at approximately 0.135

S. At 0.135 s the injection event was approximately 75 5% complete. The oscillations that

follow the large peak are thought to be reflected pressure waves rebounding between the

fuel pump plunger and the injector pintle. The peak pressure remained at a constant

value of 38 bar (540 psi@ for al1 experiments. The minimum fuel Iine pressure seerned

to be a function of temperature and varied from 12 bar (160 psig) to 14 bar (1 90 psig)

over the temperature range investigated.

- r

! - ! r

? t

- r - I

l , , , , , , , , , ! , , , , , , , I

, . I , . . , J . , . , .

O. 10 0.12 0.14 0.76 0.18 0.20 0.22 0.24

Time [s]

Figure 7.1 Fuel line pressure as a function of time.

7.4. Examining Experimental Test Conditions

The test conditions used dunng experimentation were chosen in an attempt to

reproduce a pon fuel injection event. The experirnents were designed to simplify the

environment into which the fuel is sprayed to a steady state system. A large number of

test variables were available and i t was necessary to fix as many of these as possible in

order to reduce the complexity of the experiment. Preheated fuel temperature just

upstream of the fuel injector nozzle was the test variable. In an attempt to achieve a

repeatable and meaningful experiment, al1 other test conditions that couid be controlled

were set to an appropriate value and held constant. Justification for the chosen test

conditions wilI become clear in the following sections.

7.4.1. Fuei-to-Air Equivalence Ratios

When the goals for the research were laid out, it was decided that cold engine start

conditions wouId be the focus. In order to start an engine under cold conditions the

combustion mixture m u t be enriched to compensate for fuel condensation losses and less

than optimum mixture preparation. This is accomplished by either extending the

injection times 1281 or under extreme conditions by double pulsing the injector 1291. For

this investigation, the Ford injector experiments were conducted at stoichiometric

equivalence ratios ($=1.0) and simulated wide-open throttle conditions where

equivalence ratio is calculated by dividing the measured fuel-to-air ratio by the

stoichiometric fuel-to-air ratio. This would be representative of a fuel delivery quantity

during cold starting if the injector was double pulsed. The Stanadyne injector system was

set up to deliver twice as much fuel as the Ford injector would for a single pulse since

double pulsing was nor possible. For both injectors, these fuel delivery strategies

represent an extreme condition that has been shown to exist in engines dunng cold start

W O I -

The amount of fuel delivered was of course controlled with a different method for

each of the two injectors. The fuel quantity deIivered for the Ford fuel injection

experiments was calculated based on a stoichiometric fuel-to-air ratio. The calculation to

determine fuel delivery quantity per injection for the Ford injector is included in section

G.2. of Appendix G. For the arnount of air delivered, an ideal gas assumption was used

to convert the volume per induction to a m a s of air per cycle. The stoichiometric ratio

was then used to determine the quantity of fuel required per cycle. With a required fuel

quantity of 0.037 ghjection, the injector cali bration equation developed earlier was used

to calculate an injector open duration or puise width of 18.0 ms. Typical pulse width

values Vary from approximately 2 to 20 ms over the engine load and speed range [3 11.

The 18.0 ms pulse width is representative of a wide-open throttle pulse width because

atmospheric pressure was chosen to calculate the inducted air volume. The injection

environment would be near atmospheric pressure only if the throttle was set to a wide-

open position. This was, in fact, the case during experimentation. The calculated pulse

width was implemented through software for the Ford injector.

The Stanadyne injector fuel deIivery quantity was controlled with the fuel pump

control rod setting. At room temperature the Stanadyne injector was found to deiiver

0.082 grarns of fuel per injection. Using 0.082 ginjection in conjunction with the fuel

density, the volume of fuel delivered per fuel pump stroke was approximately 120

cm3/stroke. Characteristic pump curves given in reference [32] provide a means of

detennining injection duration. With a volumetric delivery of 120 cm3/stroke and a fuel

pump speed of 400 rpm the injection duration was approxirnately 4.6 ms. This value was

also verified with the aid of the lift sensor and an oscilloscope. Therefore, the Stanadyne

injector was delivering twice as much fuel per injection in Iess than 113 of the time. In

fact 0.08 ghnjection corresponds to a fuel-to-air ratio of 0.14 gF/gA or an equivalence

ratio of 2.0 which is well above stoichiometric proportions but representative of a cold

start condition.

The important quantity for comparison is the fuel quantity delivered by the

injectors. It has already been shown that the Ford injector expenments were run with

approximately stoichiometric equivalence ratios. Higher equivalence ratios, achieved

with longer injection pulse widths, were tested and did not appear to change the nature of

the fuel spray. The high temperature expenments were run at an equivaience ratio of

approximately 2.0 because this value represents a bound on the equivalence ratio used for

enrichment purposes during engine cold starting conditions.

7.4.2. Nitrogen Volumetric Flowrate

Since the experimental apparatus was a steady flow system, calculations were

made to approximate the voiumetric flow past the injector at a simulated engine speed of

1000 rpm. The calculation for voiumetric flowrate is provided in section G.I. of

Appendix G. A volurnetric efficiency value of 0.85 was chosen based on typical values

listed in reference [3 I l . The single cylinder volume for the test engine was 0.475 L and

is inducted once every 2 crankshaft revolutions for a time duration equal to the intake

valve open duration. This calculation results in an average voiumetric flowrate during

the intake valve actuation period (opening and closing) in an actual engine.

Instantaneous values would be Iarper corresponding to the maximum piston velocity in a

fully functional engine [3 11. The actual value achieved with the nitrogen supply system

during experirnentation was approximately 940 slpm, which corresponds to an engine

speed of 970 rpm. The flowrate values measured during each set of experirnents (i.e. at a

given fuel preheat condition) appeared to be quite steady. The average flowrate values

were found to be within +/- 4 slpm of the mean flowrate value (with 95.0% confidence)

for al1 but two sets of experiments. The confidence intervals were larger for the

experiments carried out at fuel injection temperatures of 80°C and 125°C because there

was one high flowrate measured dunng each of these experimental sets. These variations

can be attributed to the finite time taken by the nitrogen fiow system to achieve a steady

flow condition. When the nitrogen system was turned on, initial flowrate values were

high and then the system would drop down to a steady value. The large fiowrate readings

probably occurred when the system was still corning to a steady state condition. Care

was taken to choose a picture where the flowrate did not Vary substantially from the mean

value.

Once a flowrate was established the values were quite constant, however, some

fluctuations in flowrate were observed to occur between sets of experirnents. The

measured flowrates were observed to be between 893 sIpm and 967 slpm for al1 the

experimental data sets however these values represent two extremes with most of the

measured values between 940 slpm and 960 slpm. The one extremely low value may be

due to a low supply Iine pressure. At the desired flowrates the nitrogen cylinders were

emptied quickly and this may explain the one relatively low value. This is not interpreted

to present a problem because the nitrogen flow did seem to strongly affect any of the fuel

sprays captured in the photographs.

7.4.3. Examining Fuel Injection Pressures

Fuel supply pressure just upstream of the injector is an important quantity to

charactenze the injection process. As discussed in chapter 5, the Ford injection pressure

was maintained using a stock Ford fuel rail arrangement. The pressure regulator

maintained the supply of fuel to the injector at 3.7 bar absolute pressure (39 psig)

resulting in a pressure differential across the injector nozzle of 2.6 bar just pior to

injection.

As discussed in chapter 5, a Bosch fuel pump was used to provide fuel to the

Stanadyne injector at a pressure high enough to invoke the needle lift. The fuel pressure

developed upstream of the Stanadyne nozzle is depicted in figure 7.1. The pressure

required to lift the injector needle from its seat wzs 38 bar (540 psig). This pressure

remained constant within +/- 5 psig for each set of experiments. Taking the measured

manifold pressure into account, the pressure differential across the nozzIe just prior to the

injection was 37 bar. The change in fuel pressure upstream of the nozzle during a single

injection event was measured to be a maximum of approximately 26 bar. This value was

lower at higher temperatures due to increasing fuel line minimum pressures with

temperature. The minimum line pressure was thought to increase because of the imposed

increase in fuel temperature. Increasing the fuel temperature descreases the fuel density

leading to an increase in line pressure. The fuel temperature increase was, of course,

primarily due to the imposed heat from the heater systern but secondary heating was aIso

witnessed to occur when the heater was tumed off. This secondary heating (24°C) was

most likely due to frictional heat dissipation in the fuel supply pump and was not found to

change the fuel line pressure characteristics. The maximum fuel line pressure (the

injector lift pressure) remained the sarne with increasing fuel temperature because this

value is not a function of themodynamic properties but is simply based on the chosen

fuel injector mechanical settings.

Having discussed the pressures measured upstream of the nozzle for each injector,

it is clear that the injectors operate under different pressure conditions. The Ford injector

was the baseline experiment to illustrate the inadequacies of the injector spray. The

Stanadyne injector experiments were then carried out from room temperature up to 220°C

to illustrate fuel spray improvements beyond the Ford injector spray.

7.4.4. Stanadyne Injector Fuel Delivery at Elevated Temperatures

It was necessary to quantify the injector fuel delivery at elevated temperatures

because it could be expected to change relative to the low ternperamre calibration. A

method to characterize the Stanadyne injector m a s flowrate was developed and carrïed

out as described in the Experimental Procedure chapter. Fuel delivery measurements

were made at the corresponding test temperatures to determine if the quantity of fuel

delivered was dependent on temperature. Ten sets of 500 injections were canied out at

each test temperature to accurately quantify fuel delivery. Figure 7.2 shows a summary

of the results obtained from the injector calibration experiments with mass flow quantity

plottea versus reduced ternperature, where reduced ternperature is defined as the ratio of

the upstream injection temperature to the critical temperature of the fuet. Raw data from

the calibrations has been included in Appendix I with a calculation of 95.0% confidence

intervals on the mass of fuel delivered per injection. The quantity of fuel delivered per

injection for this set of experiments did not exhibit a strong dependency on temperature

as shown in the figure. The fuel quantity was approximately 0.083 ghjection, however,

a statistically significant but small increase in mass flow quantity was witnessed over the

experimental temperature range. Statistical significance was determined based on the

overall increase in mass delivered (0.002 ginjection) compared to the 95.0% confidence

intervals (+/- 0.0006 ghnjection on the mean).

It was anticipated that the mass of fuel delivered would remain approximately

constant with increasing fuel temperature because the pressure required to lift the injector

needle remained constant. A slight increase in delivered mass per injection was

measured for the temperature range investigated. With a temperature change from 0.55

Tc to 0.87 Tc an increase from 0.082 to 0.083 gram per injection was measured which

corresponds to an increase of approximately 1.0%. Statistically this quantity was

determined to be significant and there are a number of factors that could explain this

increase. The injection pressure traces were individually checked and although the peak

pressures remained constant the average pressure during the injection duration increased

slightly with temperature. The increase may be due to fuel property changes at elevated

temperature. As the fuel temperature was increased the minimum fuel supply pressure

increased therefore requirïng the pump to produce less of a pressure increase for an

injection to occur. One possible explanation can be drawn from the way in which Bosch

injection pump operates. If the required developing pressure decreases, more cam travel

is available to produce fuel flow and the flow will occur at a higher average delivery

pressure. A second factor that rnay be involved is fuel viscosity decreases with

temperature. As the viscosity decreases, the fuel flow rate through the nozzle will

increase although the injection duration may shorten and counter balance this flow

increase. More expenmentation specifically designed to investigate the fuel deiivery

system would be necessary to conclusively determine the fuel delivery dependence on

upstream temperature. The measured increase is quite small and is presurnably

insignificant with respect to the focus of this study.

Figure 7.2 Mass flowrate as a function of temperature.

7.4.5. Examining Manifold Pressure and Secondary Temperatures

Manifold absolute pressure (MAP) rneasurements were made for al1 of the

experimental tests. The manifold pressure values were found to remain quite constant

during each test and between each set of experiments. Over a11 the experiments the

minimum mean pressure measured was 110 kPa and the maximum was 1 1 1 kPa. The

maximum 95.0% confidence interval on a mean rneasurernent was found to be 0.2 kPa.

The measured pressures were found to be slightly higher than the atmospheric value used

to calculate injector pulse widths. This was probably due to minor flow restrictions

downstream from the pressure measuring point in the steady flow system. Modifying the

calculation for an average manifold pressure of 110 kE% increases the pulse width by less

than 1 ms and pulse width was already conchded to have very little effect on the

acquired images.

The remaining measured temperatures include plenum nitrogen temperature,

injector body temperature and local cylinder head temperature. Al1 measured

temperatures appeared to stay consistent throughout each set of experimen ts. Variation

in the measured nitrogen temperature that occurred between sets of experiments can be

attributed to changes in ambient conditions. The minimum mean measured nitrogen

temperature was 22°C and the maximum was 24°C for al1 sets expenments. The injector

body temperature appeared to increase with increasinp preheated injection temperatures.

The injector body was not insulated and a temperature differential between the fuel

temperature and injector body temperature developed during each experiment. With fuel

temperature of 80°C the injector body temperature was measured to be 49°C and at the

highest levels of preheat the injector body reached a temperature of 105°C. Local

cyIinder head temperatures also followed the injected fuel temperature increases as was

expected. The local cylinder head temperature measurement was made where the fuel

impinges on the port wall. The temperature reached a maximum of 36°C which

represents a temperature increase of approximately 1 6°C.

This acquired data was of secondary importance compared to the fuel injection

upstream temperature and pressure measurements. The secondary data, overall, appears

to be representative of steady state conditions which was the objective.

7.5. Examining the Fuel Spray Images

The test conditions summarized above were average values over the entire set of

experiments. The data corresponding to each photograph has been included in Appendix

J. Figure 7.3 shows the results of baseline testing with the Ford fuel injector. Figure

7.3(a) shows a fuel injection from the top view port. The highly reflective surface at the

edge of the photograph is the machined entry into the intake port. In the background of

the photograph the intake valve stem and the seat are visible. It should be noted that the

top of the valve stem is tilted slightly towards the view port. The fuel spray can be seen

in the center of the picture with liquid droplets moving from right to left across the

borescope field of view. Figure 7.4 is a schematic diagram of the image, which has been

included to further describe the fuel spray. In figure 7.3(a) the liquid droplets appear

mainly as streaks across the field of view because the exposure time (flash duration) was

not short enough to completely stop the liquid droplet motion. Large variations in droplet

size can be observed from the image with liquid fuel concentration near the center-line of

the spray. The spray appears to be a relatively thin stream compared to the size of the

intake port. To pive the fuel spray scale, the intake valve stem diameter is 8 mm and

looks to have a diameter similar to the fuel spray. The valve stem could not be used to

accurately measure the fuel spray geometry because it in not in the sarne pIane as the fuel

spray.

Figure 7.3(b) shows the fuel injection event from the bottom view-port. Figure

7.5 is a schematic diagram that has been included to aid in the explanation of figure

7.3(b). From the bottom view port, the fuel injector is perpendicular to the field of view

and fuel motion is from left to right as shown in figure 7.5. The liquid fuel stream

appears to be a thin jet with a very smdl cone angle. In fact, the Iiquid fuel Stream does

not appear to expand very much in diameter above the exit diameter of the nozzle.

Noticeable expansion of the spray can be seen to occur between the two view-ports. The

top view port was located approximately 50 mm downstream from the bottom view pon.

Figure 7.3 Ford injector fuel injections at rocjrn temperature shown from: a) the top view port and b) the bottom view port.

intake valve stem

approximate fuel spray b oundar y

valve seat

borescope field of view

Figure 7.4 Schematic diagram illustrating a fuel spray captured in the top view port.

machined surface

approximate / I fuel spray i

1 I

boundary

1 Ford injector exit flush with surface

borescope field of view

Figure 7.5 Schematic diagram illustrating a fuel spray captured in the bottom view port,

The transition from a cold liquid fuel spray to flashing flows is illustrated in

Figure 7.6(a) to (0 with sprays produced by the Stanadyne injector. Plenum temperature,

injected fuel temperature, injector body temperature, cylinder head temperature, manifold

pressure and nitrogen flowrate values have been averaged over the entire set of

experiments at each temperature and are summarized in table 7.1.

Table 7.1 Mean data corresponding to figure 7.6.

Figure Label

1 . , I I 1 - -

I

Note: AI1 temperatures are listed in Celsius.

7.6(a) 7.6(b) 7.6(c)

The precise values corresponding to the chosen photographs are included in Appendix J

Plenum Temp.

and are closely represented by the values listed above. Figure 7.7 is a schematic diagram

23 22 23

illustrating some of the major points that are visible in the photographs. In al1 the

Injected Fuel

photographs included in figure 7.6, the injector body sits in the center of the picture

Temp. 25 80 125

surrounded by the lower intake runner surface, which is slightly out of focus. The

Injector Body

surface appears dark with reflective spots, which is simply the roughness due to casting

Temp. 24 49 68

of the part. The target for focusing the images during experimentation was rnidway

Cylinder Head

between the base of the spray at the injector exit and the end of the visible spray. In

Temp. 19 23 28

general, this area looks clear in each of the photographs. The injector body appears to be

Manifold Pressure

reflecting some light back to the Dorescope tip in all of the photographs. The injector

Nitrogen FIowrate

[ k W 110 I l 0 110

body was a mildly polished surface and seerned to collect a liquid film near the tip,

b lpm] 92 1 950 893

producing a reflection. The fuel jet issuing from the injector tip appears as a dense white

spray with fluid movement from left to right in each of the pictures. Fuel droplets are not

distinguishable in any of the pictures due to the limitations of the photographie imaging

system, however, useful information about the jet shape and cone angIe can still be

determined. In al1 the acquired images the fuel spray appears to be centered slightly off

the axis of the injector due to a small machining flaw in the injector tip modification.

Figure 7.6 Fuel injection through the Sianadyne injector shown from the bottom view port location at increasing upstream temperature: a ) 35°C (0.55 Tc), b) 80°C (0.65 Tc) ..

Figure 7.6 continued. Fuel injection through the Stanadyne injector s h o w from the bottom view port location at increasing upstream temperature: c) 125°C (0.73 Tc), d) 142°C (0.76 Tc).

Figure 7.6 continued. Fuel injection through the Stanadyne injector shown frorn the bottom view port location at

increasing upstream temperature: e) 174OC (0.82 Tc), f) 207°C (0.88 Tc).

approximate fuel spray boundary

Stanadyne inj ector exit

Figure 7.7 Schematic diagram illustrating a fuel spray captured in the bottom view port.

Since this appears to be present in a11 of the photographs it is not deemed to introduce

significant problems to the resuIt however a small error may result in measurements

taken from the images. It should also be noted that the orientations of the pictures are not

precisely the same in each case due to the need for occasional borescope tip cleaning and

realignment.

The fïrst two photographs in the series (figure 7.6) show fuel being injected at

35°C and 80°C. Figures 7.6(a) can be used as the cornparison case for the rest of the

photographs in the series. There does not appear to be significant change in the spray

appearance between figures 7.6(a) to (c). When the temperature was increase beyond

1 Q°C the fuel spray cone angle appeared to increase with increasing temperature.

7.6. Liquid to Liquid Injections

Both the Ford fuel injector and the Stanadyne fuel injector were used to inject

1 iquid fuel at arnbient temperatures. Two injectors were required because heating the

Ford injector to the desired temperatures was not a feasible option as discussed earlier.

Stanadyne injector experiments were carried out at room temperature in order to illustrate

how closely the fuel spray it produces resembles the Ford injector spray. Experiments

using the stock Ford injector were camed out to show the inadequacy of the fuel spray

that it produces.

Figure 7.3 shows fuel injections through the Ford injector from the top and

bottom view ports. Figure 7.3(b) illustrates the nature of a fuel injection event in a

typical port injection application. The liquid fuel exits from the nozzle in a very thin

cylindrical stream with no measurable cone angle. Figure 7.3(a) shows the spray under

the same conditions. Although the fuel droplets are rnoving too quickly to be captured by

the photographie system, large droplet streaks can be seen in the picture. The injected

fueI travels 50 mm between the two view ports, but this distance does not appear to be

long enough for the fuel spray to develop. The increase in the fuel spray cone angle

between the two view ports can be attnbuted to mechanical break up of the liquid stream

due to injector geometry and to aerodynamic effects produced by the high speed nitrogen

flow in the port.

Figure 7.6(a) shows a fuel spray produced by the Stanadyne injector with a

measured fuel temperature upstream of the injector of 25°C. Comparing this fuel

injection image to the fuel spray produced by the Ford injector depicted in figure 7.3(a),

it is clear that the Stanadyne injector induces a slightly larger amount of liquid fuel

atomization than the Ford injector. Exactly reproducing the ambient temperature Ford

injector fuel spray with the Stanadyne injector was not realistic. However, the

photographs show that the baseline tests carried out with the Ford injector are quite

comparable to the baseline tests carried out with the Stanadyne injector.

The Ford injector does not appear to create a finely atornized spray but instead

produces a spray with large variations in droplet size. This type of spray is not ideal for

fuel preparation because it Ieads to significant and localized wall wetting.

7.7. Preheated Fuel Flow through the Stanadyne Injector

The series of injections in figure 7.6 shows the transition from hydrodynamic and

instability controlled flow to a regime where thermal effects dominate. The performance

of any given type of atomizer depends on its size and geometry and on the physical

properties of the liquid being atomized [33]. Secondary atomization that occurs after the

liquid exits the nozzle is a function of the gaseous medium into which the liquid is

discharged. The modified Stanadyne diesel injector is a pressure atomizing injector. The

fuel spray break up and development is due prirnarily to the geometry of the injector at

low temperatures. The liquid fuel is discharged through a srnaIl aperture under relatively

high pressure and the pressure energy is converted to kinetic energy.

The first two photographs in the series (figure 7.6) show fuel being injected at

25°C and 80°C. This is often referred to as a liquid-to-liquid injection because no

flashing can occur at these temperatures. Only mechanical fuel break up induced by the

injector geometry occurs at the nozzle exit. The normal boiling point for iso-octane is

9g°C so as the fuel undergoes a pressure drop from the fuel line pressure to the manifold

pressure, injections at temperatures of less than approximately 9g°C do not cross the

liquid saturation boundary. There doesn't appear to be significant change in the spray

appearance between figures 7.6(a) to (c) aithough the fuel temperature increases by

100°C. A further fuel temperature increase of 17OC appeared to change the physical

appearance of the fuel spray quite significantly. The spray seemed to spread out with a

greatly increased cone angle at 142°C compared to the first three experirnental

temperanires. Further increases in cone angle can be seen to occur as the temperature

was increased to a maximum of 207OC. In addition to cone angle increases, the outer

edges of the spray seem to be more strongly affected by the nitropen flow at higher

temperatures. The fuel spray nearer to the right side of the borescope field of view looks

to be approaching a more cylindrical arrangement rather than an expanding conical

arrangement as it does at lower temperatures.

Injections at preheat values of less than 0.73 Tc are though to be prima-ily

controlled by hydrodynamic forces and instabilities produced by the injector geometry.

Above this superheat level, the thermodynamic mechanisms begin to take over. The

transition is quite clearly indicated in figure 7.8 where a sharp transition in spray cone

angle occurs at 0.73 Tc for the iso-octane data acquired during experimentation with the

Stanadyne injector. Spray cone angle was referred to in a qualitative sense in the above

descriptions of figure 7.6. An atternpt was made to measure the spray cone angle at each

of the test temperatures to obtain a more meaningfül quantitative value. For each set of

experiments, two photographs were enlarged to make accurate cone angle measurements.

The best photographs, with respect to image quality, were chosen from the contact sheets

for each data set and cone angle measurernents were taken. Further, although less

accurate, measurernents were made from the negatives in order to increase the sample

size for each cone angle value. Cone angle data has been listed with the corresponding

data set in Appendix J with an asterisk beside the measurements taken from enIarged

photographs. AI1 other cone angle values are measurernents made from the negatives.

No detectable discrepancies were found between the cone angles rneasured from the

enlarged photographs and those measured from the negatives. It should be noted that

cone angle measurements required a subjective choice of the outer fuel spray boundary.

Figure 7.8 is a plot of cone angle in degrees versus reduced temperature. Additional data

has been included on in figure 7.8 to aid in the comparison of the results to the

preliminary experiments and to work by other authors. The maximum reduced

temperature shown on the plot is 0.9 1. The value 0.9 1 Tc represents a physical limitation

in the apparatus, above which, liquid fuel wiIl begin to boil in the line. The figure

indicates a slight increase in cone angle up to a reduced temperature of 0.73 for iso-

octane injections using the Stanadyne injecter. From 0.73 Tc to 0.76 Tc there appears to

be a rapid increase in cone angle from approximately 3 4 O to 8O0, although further testing

would be necessary to conclusively comment on this trend. From a reduced temperature

of 0.76 to 0.91 the cone angle increase appears to be approximately linear from 80° to

115". The fuel spray cone angles increase and from the photograph in figure 7.6 the

penetration distance seems to shorten as upstream temperature increases.

Figure 7.8 Cone angIe as a function of reduced temperature. + Iso-octane fuel injection data through the Stanadyne injecotor. o Iso-octane fuel injection data from the preliminary experiments. Sloss dodecane fuel injection data.

A similar transition location of approximately 0.75 Tc was observed in an

expenment with a converging nozzle by Sloss [23] and Athans [34] and was further

substantiated dunng the preliminary experirnental work carried out in this study. As

shown in figure 7.8, data corresponding to the injection of dodecane through a

converging nozzle carried out by SIoss has a similar upper cone angle limit of 120° and a

similar abrupt increase in cone angle at a comparable reduced temperature. In fact,

similar experiments carried out by Sloss using kerosene and diesel fuel exhibited a

similar cone angle transition point of 0.75 Tc. Although only two cone angle

rneasurements can be obtained from the preliminary iso-octane experiments carried out

during this study, they more closeIy represent the test conditions used by Sloss and

therefore have been included in figure 7.8 to aid in the cornparison of the data. It is

interesting that the cone angIe rneasuremen ts obtained from the S tanadyne injector

experiments exhibit similar trends as the dodecane experiments camed out by Sloss even

though there were so many differences in experimental conditions. The reduced pressure,

measured upstream of the nozzle, corresponding to the Stanadyne injector experiments

was 1.5, while Sloss used 0.5. The fuel type was different, the nozzle geometnes were

different and the Stanadyne injector experiments produced intermittent sprays while the

apparatus developed by S loss produced a continuous spray.

As discussed in the Theory chapter, Jakob number is a measure of superheat.

Instead of using reduced temperature, Figure 7.6 could also be descnbed in terms of

Jakob number. The corresponding Jakob numbers for figures 7.6(a) to (0 are 0.00, 0.00,

0.23, 0.40, 0.74 and 1.1 1. A table of Jakob numbers and the corresponding fuel

temperatures are listed in Appendix H. The Jakob numbers are calculated using upstream

temperature and a downstream pressure of I atm to characterize a given fuel spray. The

images indicate that a Jakob nurnber significantly greater than zero must be reached

before flashing occurs. To more accurately comment on the transition, finer increases in

experimental temperatures wouId be required.

Bubble nucleation and growth are responsible for the transition to a flashing type

jet. Heterogeneous nucleation requires less energy than homogeneous nucleation and is

most likely the mechanism responsible for bubble formation. Heterogeneous nucleation

sites usuaIly exist at the interface between the metastable phase and another phase, either

liquid or solid and it is unclear whether nucleation is beginning inside the injector or just

downstream from the nozzle. Further expansion of the jet with increasing temperature

was presumably due to the increased number of critical nuclei at increasing Ievels of

superheat.

Figures 4.2 and 4.3 show the progression of a liquid jet frorn a thin stream

breaking up due to aerodynamic forces to fuel jets that are breaking up more due to

thermodynamic mechanisms. This is an interesting observation because the Stanadyne

injector appears to impose substantially more rnechanical fuel break up than the nozzle

used in the preliminary experimentation. This implies that the critical superheat value

may be independent of the mechanical fuel break up imposed by the injector geometry.

Clearly, further research is necessary to substantiate this observation but the fact remains

that increased atomization was obtained with increasing levels of preheat.

Before implementing a fuel preheating system in a practical application such as a

port injected engine, an understanding of the energy requirements is a necessary first

step. The Jakob number is essentially the ratio of the superheat energy divided by the

heat of vaporization of the fuel. The highest level of superheat achieved in the present

study was a Jakob number of 1.1 1. Multiplying the Jakob number by the heat of

vaporization of the fuel ana dividing by the lower heating value of the fuel, a crude

estimate of the preheating system enegy requirements can be obtained. The heat of

vaporization for iso-octane at 1 bar is approximately 308 KT/kg. The lower heating value

for iso-octane, which is essentialiy the chemical input energy to an engine, is

approxirnately 44 MJ/kg. This implies that the preheating process requires less than 1 %

of the chemical energy that the fuel is capable of delivering. Thus, the proposed

preheating techniques may be feasible in a functional port injected engine.

8. Conciusions and Recommendations

In this research, the effects of preheating liquid fuel prior to injection has been

studied as a means of improving fuel spray charactenstics in a multi port fuel injected

engine configuration. Useful conclusions can be drawn from the results obtained during

experimentation and from the expenence gained during instrumentation. Single shot 35

mm photography in conjunction with a fiber optic borescope was used to capture the fuel

injection events at two different view port locations. Research grade iso-octane, a pure

hydrocarbon, was injected through a Ford fuel injector at ambient temperatures and

throuph a Stanadyne injector over a range of temperatures from arnbient to 220°C.

The Ford injector appeared to produce a spray that is considered inadequate for

cold engine stan conditions. Poor fuel atomization was observed from the injector, which

illustrates a need for improvement over the present port injection technology.

The possibility for irnprovement was shown to exist with the implementation of

preheating techniques and the modified injector. As the fuel was preheated above

approximately 0.73 Tc, there appeared to be a sharp increase in spray cone angle and

shortened penetration distance indicating increased fuel atomization. Fuel spray break up

at temperatures less than 0.73 Tc is due to a combination of injector geornetry effects and

aerodynamic effects produced by the high speed nitrogen flow. Further fuel spray break

up and development at temperatures above 0.73 Tc is due primanly to thermal effects

superimposed on the physical break up mechanisms. This improvement in fuel spray

characteristics during cold engine start up conditions could prove to be extrernely

beneficial in improving fuei-to-air ratio control and in reducing HC emissions.

To continue this project the next logical step would be to convert the steady flow

system to a fully functional single cylinder engine. A number of me necessary steps for

the conversion have been completed in the development of the present study. A similar

test matrix could be designed and both motored and eventuaily fired engine testing could

be camed out. Improvement of the image acquisition system would allow droplet size

measurements and therefore a more quantitative discussion of fuel atomization

improvements. Under fired engine conditions, engine power testing and HC emissions

testing in addition to fuel spray image acquisition would prove to be a valuable tool in

further verifying the hypotheses laid out in the present work.

References

1. Fox, J.W., Min, K.D., Cheng, W.K. and Heywood, J.B. "Mixture Preparation in a SI Engine with Port FueI Injection During Starting and Warm-Up." SAE Paper No. 922 170, 1992.

2. Carey, V.P. Liquid-Vapor Phase Change Phenomena. Hernisphere Publishing Corporation, U.S.A., 1992.

3. Oza, R.D. and Sinnamon, J.F. "An Experimental and AnaiyticaI Study of Flash Boiling Fuel Injection." SAE Paper No. 830590, 1983.

4. Brown, Ralph and York, Louis J. "Sprays Formed by Flashing Liquid Jets." A.1.Ch.E. Joumal, 1962, pg. 149- 153.

5. Oza, R.D. "On the Mechanism of Fiashing Injection of Initially Sub-cooled Fuels." Vol. 106/105, March 1984.

6. Plesset, M.S., and Zwick, S.A. "The Growth of Vapour BubbIes in Superheated Liquids." Joumal of Applied Physics, Vol. 25, No.4, 1954, pg.492-500.

7. Cheng, Chun-On, Cheng, Wai K. and Heywood, John B. "Intake Port Phenomena in a Spark-Ignition Enpine at Part Load." SAE Paper No. 9 1240 1, 199 1.

8. Shin, Younggy, Cheng, Wai K. and Heywood. John B. "Liquid Gasoline Behavior on the Engine Cylinder of a SI Engine." SAE Paper No. 941872, 1994.

9. Meyer, R. and Heywood, J.B. "Liquid Fuel Transport Mechanisms into the Cylinder of a Firing Port-Injected SI Engine During Start Up." SAE Paper No. 970865, 1997.

lO.Shin, Younggy, Min, Kyoungdoug and Cheng,Wai K. "Visualization of Mixture Preparation in a Port Fuel Injection Engine During Engine Wann-up." SAE Paper No. 95248 1, 1995.

1 l.Cheng, Wai K., Hamrin, Douglas, Heywood, John B., Hochgreb, Simone, Min, Kyoungdoug and Norris, Michael. "An Overview of Hydrocarbon Ernissions Mechanisms in Spark-Ignition Engines." SAE Paper No. 932708, 1993.

12.Glockler, Otto, Knapp, Heinrich and Manger, Hansjorg. "Present S tatus and Future Development of Gasoline Fuel Injection Systems for Passenger Cars." SAE No. 800467, 1980.

13.Galliot, F, Cheng, W.K., Cheng, C., Szetenderowicz, M. and Heywood, J.B. "In Cylinder Measurements of Residual Gas Concentration in a Spark Ignition Engine." SAE Paper No. 900485, 1990.

14.Aquin0, Charles and Plensdorf, William D. "An Evaluation of Local Heating as a Means of FueI Evaporation for Gasoline Engines." SAE Paper No. 860246, 1986.

lS.Boyle, R.J., Boam, D.J. and Finlay LC. "Cold Start Performance of an Automotive Engine Using Prevaponzed Gasoline." SAE Paper No. 9307 10, 1993.

16.Berg, Peter G. "Cold Weather Diesel Fuel Preparation with PTC Heaters." SAE Paper No. 840539, 1984.

17.Chen, f .L. and Chen, Grant "Slow Heating Process of a Heated Pintle-Type GasoIine FueI Injector." SAE Paper No. 950068, 1995.

18.Williams, Paul and Beckwith, Paul. ''The Effect of Fuel Composition and Manifold Conditions Upon Spray Formation from an SI Engine Pintle Injector." SAE Paper No. 94 f 865, 1994.

19.Sait0, Kirnitaka, Sekiguchi, Kiyonori, Imatake, Nobuo, Takeda, Keiso and Yaegashi, Takeda. "A New Method to Analyze Fuel Behavior in a Spark Ignition Engine." SAE Paper No. 950044, 1995.

20.Yang, Jilian, Kaiser Edward W., Siegel, Walter 0. and Anderson, Richard W. "Effects of Port-Injection Timing and Fuel Droplet Size on Total and Speciated Exhaust Hydrocarbon Emissions." SAE Paper No. 9307 1 1, 1993.

21.Shayler, P.J., Davies, M.T., Coiechin, M.J.F. and Scarisbrick, A. "Intake Port Fuel Transport and Emissions: The Influence of Injector Type and Fuel Consumption." SAE Paper No. 961996, 1996.

22.Che1-1, Gang, Vincent, Michael T. and Gutermuth, Terry R. "The Behaviour of MuItiphase Fuel-Fiow in the Intake Port." SAE Paper No. 940445, 1994.

23.Sloss7 Clayton. "Experimental Smdy of Preheated Fuel Injection through a Nozzle." Masters Thesis, University of Toronto, Toronto, Canada, 1996.

24.Vesik, W.H. "A Thermodynamic Analysis of Evaporation Waves in an Expanding Jet." Masters Thesis, University of Toronto, Toronto, Canada, 1997.

25.Kessler, C . Personal Communications, unpublished, 1998.

26.Beha.r, E., Simonet, R. and Rauzy, E. "A New Non-cubic Equation of State." Fluid Phase Equilibria, Vol. 2 1,237-255, 1985.

27.Julian, S., Barreau, A., Behar, E. and Vidal, J. "Application of the SBR Equation of State to High Molecular Weight Hydrocarbons." Chernical Engineering Science, Vol. 44, NO. 4, 1004-1006, 1989.

28.Lenz, P. Mixture Formation in Spark-Ignition Engines. SAE Inc., 1992.

29.Probst, C.O. How to Understand, Service and Modifv Ford Fuel Iniection and EIectronic Engine Control. Robert Bentley hc., 1993.

30.Quader, A.A. "Single-Cylinder Engine FaciIity to Study Cold Starting-Results with Propane and Gasoline." SAE Paper No. 92000 1, 1992.

3 1 .Heywood, I.B. Intemal Combustion Engine Fundamentals, McGraw-Hill, 1 988.

32.Robert Bosch. PF Fuel Injection Purnps. GMBH Sttuttgart.

33.LefebvreT A.H. Atomization and Sprays. Hemisphere Pub

34.Athans, R.E. "The Rapid Expansion of a Near-Critica Thesis, Rensselaer Polytechnic Institute, Troy, NY, 1992.

lishing Corporation, 1989.

.1 Retrograde FIuid." PhD

35.Reid, R.C., Prausnitz, J.M. and Poling, B.E. The Properties of Gases and Liquids. 4'h ed. McGraw-Hill Book Company, Toronto, 1987.

36.1995 SAE Handbook. Gasoline Fuel Injector SAE J 1832 Nov89, vol.2, pg.26.265.

A. Fuel Data

Table A. 1 Listing of fuel properties [35].

Fuel Parameter iso-Octane (CsH 18)

(2,2,4 Trimethylpentane, (CH3)3CCHgH(CH3)~)

Omega

p [gml @ 25"C]

0.303

0.668

B. LabView Virtual Instruments

B.1. Ford Fuel Injector Calibration Program

The program used to calibrate the Ford injector controlled pulses to the injector

and the fuel measurement system. The front panel for this program is shown in figure

B.1 and the back panel is shown in figure B.2. The number of pulses, pulse frequency,

duty cycle and fuel system relay control (off/on switch) were used as inputs to the

Relay Actuation OFF - - ON 1

. . . . . .................

< F I > to stop -2 1

'OFFI S T O P 1

d ~ t y cycle (0.5) i fjo.so!

- - - - - - -

numb;r-of pulses (cont:O)

:I5 O---

lnjector Operation Time ( s ) ]

2 .50 -1

lnjector Open Time (s) .-

1.25 l

pulse polarity (high:O)

$ high pulse I[c gate mode ( u r q a t e d : ~ ) - _"_1_1___ --- --P.".".- - , $ ungatedlsoftware start ][O

. - -- - - -

(tasklD of counter] 1 &-000001

1 l

ac tua l ara met ers

1

pulse widthl

10.00003 . - - A - - . - - - -- 1 12.50

Figure B. 1 Ford fuel injector calibration program front panel.

. . - .

1- [ninjeîtor o p e n Tirne ( r ) ]

l n h c t o r Operalion Time (s)/ :=

Figure B.2 Ford fuel injector calibration program back panel.

B.2. Stanadyne Fuel Injector Calibration Programs

Three different VIS were devetoped to calibrate the Stanadyne injector. The main

VI was used to count injections frorn a signal produced by the lift sensor and control the

fuel measurement system. Figure B.3 shows the front panel and figure B.4 shows the

back panel of the VI. To acquire fuel line supply pressure data just upstream of the

injector, a separate VI was developed. The pressure acquisition VI saved data to a file

and allowed sample rate and sarnple number inputs. The pressure trace was also

displayed on a plot on the front panel. Figures B.5 and B.6 show the front and back

panel respectively. The third program was used to rnonitor injection temperature just

upstream of the injector.

- - - . .. - Relay Actuation off on I over f low?

Figure B.3 Stanadyne fuel injector calibration program front panel.

, .. .

Figure B.4 Stanadyne fuel injector caiibration program back panel.

- - - number of s a m ~ l e s l

Wrile t o - ~ G e file path (dialog i f empty)]

3 / c : \~ i ke \Da ta \~a i i b ra t i on \~ ressu re \ 5 9 8 ~ 8 ~ 1 apressure -- ---

-- -- - -- -. - -- -- -.-

new file path (Not A Path i f cancelled)

! c : \ ~ i k e \ ~ a t a \ ~ a l i b r a t i o n \ ~ r e s s u r e \ E980727dpressure - I

. . . . . . . . . . . . . . - .. . . . . . . . . . . - sample rate (1000 1 Pressure (psig)]

II

1 ' 400.0 - I i

high limit (0.0) low limit (0.0)/

r$z-r :lo.oo- waveform

sample # J-1 - -. . O 10000 20000

-- .-

Pressure actual sample period (sec) 1 -

0.00

Figure B.5 Fuel line pressure front panel.

$ample rate (1000 sampleslsec) ]

Figure B.6 Fuel line pressure back panel.

B.3. Experimental Data Acquisition Prograrns

Figure B.7 shows the front panel of the experimental DAQ program developed for

the Ford injector. This VI used numerous sub-VIS to accomplish the desired set of tasks.

The program was designed to activate the fuel injector and the camera and to acquire data

durinp the injection event. A scan rate of 1000 Hz was used to acquire data from

differential analogue channels as discussed in chapter 5. The data was processes by the

software after the acquisition was complete. The temperature, pressure and flowrate

signals were converted from voltages (using the calibration equations), averaged over the

acquisition penod and stored to a data file. A 1000 Hz function generator signal was

used as an input to the DAQ board to control the injector pulse characteristics. Since the

injector was computer controtled, an extemal trigger was not necessary for this VI.

Starting the VI was al1 that was necessary for DAQ. The camera was also controlled by

software. The camera had a slow response, which made it necessary to incorporate a

variable time delay for the start of injection. In this was, the VI coordinated image

acquisition with fuel injection and DAQ.

The program used to acquire data for the high ternperature Stanadyne injection

experiments was based on the Ford DAQ program. Two changes were incorporated into

the Stanadyne injector DAQ program. A fuel pressure sensor was used in the DAQ setup

and was therefore added to the software. The injection pressure trace was recorded to a

sepante data file and was unprocessed by the program. The second change made to the

VI was do to the change in injector control strategy. The S tanadyne injector could not be

controlled through software so an extemal trigger was incorporated into the VI in order to

initiate DAQ.

- - - -- - -- - - 7 1

Pulse lnjector !Actual lnjection ICDM p u l s e s per CADI Off On :parameters Used E / i I r

10 F F] ~ S O S O ( C A D iftu non- f i r ing

j 10.50 -pi TDC o r s tartscan) A-

Sta tus I /Y +Il O 0

Number of cycles1 to acquire

I

I A- .VI 1

- - - - Number o f c y c l e s /

i lnaci ive 1 / S T O P 1 - - - - - - - - - . - .

In ject ion Durat ion (CAD) Wr i te Data to Spreadshee t F i l e

1.û F F] - - S imu la ted Engine R P M

Ave. Data F i le Narne & 9 3 0 00A

[ c : \ M i k e \ ~ a t a \ ~ x ~ e r i m e n t \ ] vL

- acqui red 1 [i--

: Fordlnjector\Avgdata\ 1980808 - Pulse Wid lh [1ns]1

Wr i te Pressure Data to 17 .92 A

Spreadshee t F i le

O F F )

~ c h a e v i t z Volt. Data F i l e Name -

1 Addit ional Tr igger

b S tanadynelnjector\ window s i z e coupling

i mode (O: no change) ;no -

d e l a l skip count ]

t r igger type

1 Plenum Temperature ( K ) 1 ,-- - 127.49

ln jector Fuel Ternpirature 1

ln jector Body Temperature

F3r-T Local Cy l inder Head Temperature

Hotwi re Flowrate (slpm) T Schaevitz Pressure (psig) 1 115.18

Figure B.7 Experimental data acquisition front panel.

C. Stanadyne Injector Modifications

The injector initially had four injection holes located radially around the injector

nozzle that injected fuel perpendicular to the injector body. Ln order to use the injector

under port injection conditions it had to be rnodified to deIiver fuel through a singte hole

dong the axis of the injector. To maintain injector fuel delivery characteristics the

surface area of the original four holes were equated to a single hole surface area.

Measurements were made using srnall dimeter wires with accurately known diameters.

The original holes were 0.23 mm in diameter and the final hole diameter was calculated

to be 0.46 mm. The tip of the injector was composed of hardened steel and it was

necessary to machine the hole using a irecision EDM (electrode discharge machining)

process to a through depth of 0.5 1 mm. The EDM process was chosen to avoid material

burring and to allow for an accurate hole size. The second step taken to convert the

injector to a single orifice design was to plug the original holes. A number of methods

were attempted before a final working injector was developed. The injector was

completely disassernbled to allow optical access to the tip from the large end with a light

source and a magnifying glass. Epoxy was used to hold 0.23 mm diameter stainless steel

plugs in place and the depth of insertion of these plugs was monitored so that the plugs

would not interfere with the needle and seat surfaces. It was found that under heated

injection conditions the epoxy would fail and the holes would open. Another method

used to plug the original holes was to use oversized plugs and shrink fit thern into place

with liquid nitrogen. This method also failed because it was difficult to get the plugs to

contract the necessary amount to produce a tight interference fit. The final method

attempted was to silver solder the plugs in place. A custom designed plug was made for

insertion into the large end of the injector body. The tip of the injector was then packed

with graphite powder through the existing large diameter orifice in order to prevent the

flow of solder into the injector and ont0 the needle seat surface. The plugs were low

temperature silver solder into place and the injector was flushed free of any graphite

powder. This modification method proved to be successful after testing and this injector

was used for al1 high temperature experimentation.

The injector had a high-pressure fuel fitting for fuel delivery and a modification

was made to the injector for fuel overflow. The manufacturer claimed that fuel overflow

could leak past the spring housing in the injector so a 50.00 mm length of 6.35 mm

diameter tubing was adapted to the injector body above the fuel input connection in order

to collect the overflow. In actual fact, fuel did not ovefflow under any of the

experimental conditions used.

The Stanadyne injector was a rnechanically actuated device and it was necessary

to monitor the injector pulse frequency with a lift sensor. The details of the sensor itself

are discussed in the Experimental Apparatus chapter of the document. A modification

was made to the injector lift pressure control end in order to accommodate the lift sensor.

The sensor diameter was slightly smaller than the control spring inner diameter, which

allowed a secondary threaded adapter of smaller diameter than the lift pressure set screw

to be rised. The adapter was cylindtical in shape with the end exposed to fuel closed and

was designed to thread into the lift pressure set screw used for cornpressing the control

spring. It was threaded such that the depth into the housing could be adjusted and a lock

not was used to maintain the desire depth.

injector adjustment

fbeI feed

Figure C. 1 S tanadyne injector modification.

D. Ford Fuel Injector Calibration

D.1. Ford Injector Calibration Procedure

SAE 11832 standard calibration procedure for gasoline fuel injectors [36] was

followed when calibrating the injector. The purpose of calibrating the injector was to

quantify the mass of fuel delivered per injection at a range of injector pulse widths. This

calibration was performed with room temperature fuel. Al1 equiprnent mentioned in the

procedure refers to figure 5.1. The procedure carried out was as follows:

1. Fuel was added to each of the 10 L fuel reservoirs. They were not filled to capacity.

2. Mechanical valves #1,2, 3 and 4 were opened.

3. Using toggle switch controlled solenoid valve #3, the small fuel reservoir was fiiled

(gravity fed), while carefully observing the fuel level through the fuel level window.

4. MechanicaI valve #3 was then closed.

5. The digital scale was leveled to horizontal in order to ensure consistent readings. The

scale was leveled using a leveiing bubble.

6. The pump was actuated with a toggle switch mounted on the front panel of the fuel

system. As shown schematically in figure 5.1, the fuel was drawn from reservoir #1,

through the fuel filters and the pump to the fuel rail. The pressure regulator allowed

the fuel pressure in the fuel rail to build to 39 psig. The fuel was then diverted to

solenoid valve #2 and back to reservoir #1.

7. The LabView calibration program was loaded. An explanation of the LabView

cal i bration program was covered in section 5.1 1.

8. The injector pulse frequency had a software setting of 20 Hz for al1 the calibration

experiments.

9. With the pump running as described in step 5, the relay actuation switch on the front

panel of the LabView calibration VI was set to off.

10. The injector was pulsed 10000 times as laid out in the SAE standard. This primed the

system and 'broke-in' the injector to ensure consistent operation.

1 1. The total number of injection was then set to 1000.

12. The relay actuation switch on the front panel of the LabView VI was set to on.

13. The desired injector pulse width was set.

14. The initial mass reading on the digital scale was recorded.

15. With the fuel pump still running the LabView program was activated. With the reIay

actuation switch set to on, the computer actuated relay controlled solenoid valves # 1

and #2 and simultaneously began pulsing the injector. In this configuration, the fuel

was drawn from the small reservoir to the fuel rail, through mechanical valve #4,

solenoid vaIve #1, the filters and the pump. From the fuel rail, the fuel would flow

back to the srnall reservoir through solenoid valve #2. When the 1000 injections were

completed the computer program stopped the pulses to the injector and

sirnultaneously de-energized the relay retuming solenoid valves #I and #2 to their

default positions.

16. The final mass reading on the digital scale was recorded.

17. After approximately two or three sets of injections, the fuel collection flask

downstream of the injector was emptied. The frequency with which this flask was

emptied depended on the duty cycle. At higher duty cycles, the injector delivered a

larger arnount of fuel.

Duty cycle (D) is defined as,

Phase1 is the 0.0 VDC portion of the TTL pulse to the injector control box and phase2 is

the 5.0 VDC portion. Changing the duty cycle effectively changes the injector open time.

Duty cycles from 0.2 to 0.8 (20 to 80 9%) in increments of O. 1 were mn through in random

order for statistical purposes. With a pulse frequency of 20.00 Hz, a duty cycle range of

0.20 to 0.80 was equivalent to a pulse width range of 10.00 to 40.00 ms. At each duty

cycle, thirty mass measurements were taken to improve the overall calibration. The

calibration curve that was developed to characterize the injector mass flowrate is shown

in figure D. 1. On the vertical axis of the graph is a dynamic flowrate in units of mg/pulse

and on the horizontal axis is pulse widrh in units of ms. The data fiom the calibration

experiments are listed in table D. 1 with a data summary listed in table D.2.

0.00 10.00 20.00 30.00 40.00 50.00 Pulse Width [ms]

Figure D. 1 Characteristic ifijector flow curve.

D.2, Ford Injector Calibration Data

Table D. 1 Calibration data.

Exp. Rep. #

Mean Std. Dev.

95.0% Con.

Note: A11 measurements are listed in units of grams.

Table D.2 Calibration summary data.

8 9 10 I 1 12 13 14 15 I6 17 18 19 20

Mean S td. Dev.

95 .O% Con.

-28.83 -93.23 38.63 -28.20 33.84 -32. I6 -96.69 43.79 -23.47 34.69 -31.08 -95.78 -92.40

64.48 65.96 66.93 65.67 66.12 64.45 65. I7 67.13 63.99 65.89 64.70

-93.3 1 - 159.19 -28.30 -93.87 -32.28 -96.6 1 - 16 1.86 -23.34 -87.46 -3 1.20 -95.78

-161.35 - 158.48

-65.84 16.49

-62.39 23.10

18.3 1 -59.08 19.58

-59.07 27.82

~ u t y cycle

0.2

- 143.35 -62.38 -139.58 -55.80

-55.75-131.7475.99 -59.1 1 - 136.37 -59.1 1

-135.64 -49.99

-49.97-127.52 -5 1.68 -46.26

Period [s/pulse]

0.05

Pulse Width

0.0 1

77.5 1 78-57 77.29 78.90

77.42 77.29 78.69 76.57 77.8 1

77.55 78.56 77.86 77.7 1 0.97

0.42 1

65.57 66.08 65.47 1.16

0.5 1

42-10 -48.7 1 29.60 -59.52 37.87 -50.20 42.70 -46.08 42.48 -47.32 74.40 -14.73 -54.56

' 26.88 3 1-60

-48.73 - 137.62 -59.70 - 147.48 -50.25 - 138.00 -46.19 - 134.14 -47.33 - 136.18 -14.75 -102.20 - 144.20

Qd [mg/pulse]

19.09

Pulse Width [msl 10

90.83 88.9 1 89.30 87.96 88.12 87.80 88.89 88-06 89.8 1 88.86 89.15 87.47 89.64 89.15 1.08

0.47

FIowrate [g,/ 1 OOOpulses]

19.09

86.42 8 1.76 -29.56 83.79 83.00 -30.29 28.60 87.86 -25.95 57.22 101.95 - 12.49 0.95

-27.2 1 -29.42

-143. I8 -30.7 1 -30.17 -140.79 -86.14 -25.94

-134.09 -6 1 .O3 -12.49 - 125.46 -1 14.20

1 13-63 1 1 1.18 1 13.62 I 14.50 113.17 1 10.50 1 14-74 1 13-80 108.14 1 18-25 114.44 1 12.97 1 15-15 1 13.00 3.3 I

1 -45

E. Transducer Caiibration Procedures and Curves

The manifold absolute pressure (MAP) sensor was used to measure upper

rnanifoId pressures in order to characterize the downstream injection environment. The

device was a 0.00 to 2.00 bar General Motors MAP sensor with a custom made 5.0 VDC

power supply. The linear relation used for this device relating absolute pressure to

voltage was:

P = 39.625 *V + 10.649 E. 1

In equation 5.1, P is absolute pressure in kPa and V is voltage measured in volts.

To measure nitrogen flows through the experimental apparatus a Nissan hotwire

anemometer was used (Nissan, Hitachi, 22680 53J00, AFH50-06, 0x23). A custom 12

VDC power supply was made to provide power the sensor. The sensor was cylindrical in

shape with a diameter of 88.9 mm. This diameter matched the throttle body diameter,

allowing the sensor to be positioned just upstream of the throttle plate. Since this

instrument was calibrated to rneasure air flowrates, a srnaIl correction factor was

necessary to measure nitrogen flowrates. The original regression equation for the air

mass flowrate was multiplied by the ratio of specific heats of air to nitrogen at 298K to

yieid the equation

Q = 128.46v3 - 3 17.42~' + 5 14.70~ - 283.75 E.2

In equation 5.2, Q is volumetric flowrate in slpm and v is voltage in volts. The correction

amounted to a change of 3.27% from the original regression equation produced with the

air calibration. The calibration curve for the sensor is shown in figure E. 1.

O .O 0.5 1 .O 1.5 2 .O 2.5 3 .O 3 -5 4.0 Voltage [VI

Figure E. 1 Nitrogen flowrate vs. voltage.

After testing was camed out, the best available method of acquiring a fuel line

pressure was a strain gauge pressure transducer. A 0.0 to 1000.0 psig Durham

Instruments Schaevitz transducer (P 102 1-0005, serial # 1 O06 15) and a bridge amplifier

were used to acquire the fuel line pressure. The transducer had a frequency response of 3

kHz at 4 dB cutoff. The sensor was not mounted closer to the injector because the fuel

supply line was heated. The sensor had a maximum operating temperature of 80°C so

minimizing heat transfer to the sensor was a priority. The tubing the sensor was mounted

to was essentially a stagnation tube so this aiso limited the transfer of heat to the sensor.

The linear relation produced from the calibration was found to be

P = 29 1 . 6 2 ~ + 14.62

In equation 5.3, P is pressure in psig and v is voltage in volts.

To calibrate the modified Stanadyne injector a method was needed to count the

number of injection events during a given time period. For this purpose a lift sensor

system was developed. A Wolf Controls Corporation Hall effect micosensor was used in

conjunction with two custom designed circuits to count injector pulses. When a current

is passed through a thin metal foi1 in the presence of a magnet a current a voltage is

produced. The Hall effect is utilized in the tift sensor to produce an analogue voltage

signal that is proportional to the injector needle movement. The injector was fitted with a

custom made magnet and a sensor holder assembly. The primary circuitry used linear

differential amplifiers, a differential emitter follower output and a voltage reguiator.

Since an actual lift quantity or distance could not be determined from the analogue output

signal it was converted to a TTL pulse with the aid of secondary thresholding circuitry.

The TTL pulses were read into the National Instruments board and were counted using

the LabView software. The method for counting injections was later modified due to

poor operation of the lift sensor at elevated temperatures. The fuel line pressure sensor

signa1 was used as a threshold signal input to the thresholding circuitry instead of the lift

sensor signal. In that way TTL pulses were produced when the pressure signal rose

above a set value.

Two methods were used to rnonitor Bosch fuel pump rotational speed. Initially a

hand held digital tachometer (Veeder Root Mode1 #661 1) was used to obtain a rotational

speed. An extemal shaft rotational speed rneasurement was made and then converted to

the actual pump speed. After preliminary tests with the DC motor drive and fuel pump it

was determined that a more accurate method of monitoring pump speed was necessary.

A sixty toothed gear was adapted to the coupling shaft between the DC motor and the

fuel pump. A magnetic pickup (Airpax 1-0002) was then mounted perpendicular to the

sixty toothed gear at a distance of approximately 2mm. The magnetic pickup signal was

amplified and displayed on a Daytronic frequency indicator/controller (mode1 #3340).

During testing the pump speed was monitored for each set of experiments.

Fuel pressure upstream of the Stanadyne injector was a crucial experimental

quantity and proved to be the most difficult quantity to obtain. The factors considered

when sizing a pressure sensor were frequency response, maximum working temperature

and maximum working pressure. Initial pressure testing was attempted with high-speed

piezoelectric pressure transducers, which are normal1 y used for in c y1 inder pressure

measurements. A 0.0 to 150.0 bar AVL transducer (1 2QP505C 1) and a 0.0 to 150.0 bar

Kistler transducer were calibrated and tested. A Kistler 5004 charge amplifier was used

for both of the piezoelectric transducers. Both had an adequate frequency response but

measure the rate of change in pressure rather than an actual pressure value. In order to

use the rate of change of pressure, an actual pressure value at some point during the

injection process would have to be known and al1 other values could then be referenced

to this known quantity. There were no accurately known pressure Ievels in the Stanadyne

injector fuel supply line so the piezoelectric transducers were ruled out. After further

testing it was determined that a strain gauge pressure transducer would be suitable for

pressure acquisition. The Schaevitz transducer calibration curve is shown in figure E.2

and was incorporated into the LabView software.

0.4 O .6 0.8 Voltage fV]

Figure E.2 Schaevitz tranducer pressure vs. voltage.

F. Data Sheets

F.1. Ford Injector Calibration Sheet

Date:

Mass Measurement FiIe Name:

I I . 12.

Repetition Nurnber 1.

Start M a s [grams] End Mass

F.2. Stanadyne Injector Calibration Sheet

Date:

Mass Measurement File Name:

Fuel Line Pressure Measurement File Name:

Repetition Number

1. 2.

Start Mass [grams]

End Mass

Fuel Temperature ["cl

Pump Speed frpml

Notes

F.3. Experimental Data Sheet

Date:

G. Calculations

G.I. Volumetric Flowrate

rev linduction Q z 0.85(970-)( ) G 9401pm

min 2rev

G.Z. Ford Injector Pulse Width Calculation [31]

For iso-octane

- PV m~ - = cycle R T

From equation G.3

\ cycle J

in F = (0.066 1 F)(0.562g,) g = 0.037 1 cycle !?A cycle

g, cycle

The characteristic fuel injector equation developed during calibration was

y = 2 . 3 3 ~ - 4.23 G.7

In equation G.7, y represents the dynamic flowrate calculated in equation G.6 and x

represents the pulse width.

mg F 37.1 - = 2 . 3 3 ~ - 4.23 pulse

From G.8, the pulse width used for experimentation was calculated to be 18.0 ms.

H. Jakob Number Data

Table H. 1 Temperatures and corresponding Jakob numbers for iso-octane.

1 Ternperature[K] 1 Jakob Number 1

1. Stanadyne Injector Calibration Data

Table 1.1 Stanadyne injector calibration data.

Injection Temperature

[Celsius] 23.62

24.64


Std. Dev. 95.0% Con.

1 Injection 1 Pump 1 Injection 1 Start 1 End 1 Delta 1 FueUInj. 1

Pump Speed [rpm]

400.00 400.00 400.00 400.00 400.00 400.00

0.00067 0.00042

Injection Count

500 500 500 500 500 500

Temperature [Celsius] 121.53

Con. 95-0% l Mean

Std. Dev.

S tart Mass

90.20 49.17 8.27

-32.60 -72.91 -114.37

Speed [rpm]

400.00

120.62 120.27 119.27 117.51 1 17.30 1 17.24

1 18.13 1

End M a s

49.76 8.34

-32.60 -72.90 -114.37 -155.48

Count

500

400.00 400.00

Delta Mass

40.44 40.83 40.87 40.30 41.46 41.11

Mass

55.26

1

Fuelnnj. Wi nj . 1

0.0809 0.08 17 0.08 17 0.0806 0.0829 0.0822

500 500

0.00068

Mass

13.71

155.56 114.26

400.00 400.00 400.00 400.00

Mass

4 1.55

0.082

73.02 32.04 -9.24

500 500 500 500

[ d i nj -1

0.083 1

1 14.26 73.03 32.05 -9.23

-50.15

4 1.30 4 1.23

0.0826 0.0825

40.97

-50. T 5

0.08 19

4 1 .90 -92.05 0.0838

4 1.27 40.9 1

0.0825 0.08 18


Injection Pump Injection S tart End Delta FueIAnj. Temperature Speed Count Mass Mass Mass Winj -1

[Celsius] [rpm] 146.15 400.00 500 153.91 112.59 41 -32 0.0826

1

141.12 400.00 500 7 2.25 30.14 41.1 1 0.0822 138.38 400.00 500 30.14 -11.36 4 1.50 0.0830 137.13 400.00 500 - 1 1.37 -52.55 41-18 0.0824 137.42 400.00 500 -52.55 -94.27 4 1.72 0.0834 144.3 1 400.00 500 155.50 1 13.76 41 -74 0.0835 143.57 400.00 500 113.75 71.79 4 1.96 0.0839 142.19 400.00 500 7 1.78 30.2 1 4 1.57 0.083 1

140.56 400.00 500 30.21 -1 1.48 41.69 0.0834

Mean 14 1 -508 0.083 Std. Dev. 0.00055

TabIe 1.4 Stanadyne injector calibration data.


[Celsius] 179.90

Mean Std. Dev.

95.0%

Pump Speed [rpm]

400.00

Con. 1 I

175.58 173.05 176.737

I

Injection Count

500

400.00 400.00

Start Mass

155.46

500 500

End Mass

1 13.6 1

74.56 32.84

Delta Mass

4 1-85

Fuelhj . W ~ J - 1

0.0837

32.87 -7.87

41 -69 40.7 1

0.0834 0.08 14 0.083

0.00080 0.00049



[Celsius] 206.30 204.79

1 con. 1 I I

S td. Dev. 95.0%

Note: Al1 mass measurements are Iisted in units of grams.

Pump Speed [rpm]

400.00 400.00

0.00 1 04 0.00065

Injection Count

500 500

Start Mass

156.10 113.88

End Mass

113.90 71.67

Delta Mass

42.20 43.2 1

Fuelhj. [ gh j .]

0.0844 0.0844

J. Experimental Data

J.1. Ford Injector Experimental Data

Table J. 1

Photograph Number

1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17

18 19 20 2 1 22 23 24 25 26 27 28 29

Ford injector

Plenum Temp.

21.520 2 1.476 21.502 2 1.385 2 I .400 21.415 2 1.376 21.420 2 1.38 1 2 1.28 t 2 1-35 1 21.339 2 1.707 2 1.685 2 1.675 2 1.704 2 1 -688 2 1.660 2 1.689 2 1 -704 2 1.708 2 1.648 2 1.636 2 1.677 2 1.674 2 1 -682 2 1.687 21.681 21 -664

bottom

Knjected Fuel

Temp.

21.296 2 1 -244 21.262 2 1.280 2 1 -26 1 21.259 2 1.292 21.315 2 1.35 1 2 1.277 2 1.3 13 21.373 2 1 .548 2 1 .572 2 1 .590 2 1.582 2 1.540 2 1.606 2 1.542 2 1.565 2 1.539 2 1.555 2 1 .574

view-port

Injector Body

Temp.

21.195 2 1.1 13 21.178 2 1 .O90 2 1 .O7 1 21.142 2 1.154 21.168 2 1 .O85 2 1.070 2 1.204 21.162 22.742 22.628 22.563 22.432 22.483 22.24 1 22.2 1 1 22.150 22.28 1 22.253

experimental

Cylinder Head

Temp.

20.913 20.9 1 1 20.917 20.909 20.869 20.972 20.879 20.852 20.967 20.897 20.934 20.897 20.974 20.948 2 1 .O64 2 1 .O 13 20.896 20.855 20.965 20.936 20.89 1 20.8 18

data.

2 1.622 2 1.632 2 1.568 2 1.620 21.512 2 1.652

22.2 16

Manifold Pressure

[kPa]

110.818 1 10.807 110.822 1 10.835 1 10.839

22.179 22.124 22.088 22.109 21.965 21 -999

Nitrogen Flowrate

[slpm]

965.845 965.072 964.425 975.794 964.594

966.638 957.658 964.434 962.843 964.482 972.002

20.872 20.924 20.890 20.899 20.792 20.885

1 1 1.559 1 1 1 .552 1 1 1.546 1 1 1.540 111.528 1 1 1 SOI

968.000

110.844 1 10.852 120.844 1 10.854 1 10.554 1 10.860 110.856 1 12.146 1 1 1.837 1 1 1.65 1 1 1 1.573 1 1 1.568 1 1 1 -565 1 1 1.575 1 1 1 .566 1 1 1.569 1 1 1.563

20.8 t 9

963.005 972283 965.684 964.685 965.086 978.229 971.942 998.386 979.3 80 966.708 956.250 954.009 97 1.304 965.538 977.097 957.962 960.442

1 1 1 .560

30 3 1 32 33

Average Std-Dev.

95 .O% Con.

Table 5.2

Photograph Number

1 2 3 4 5 6 7 8 9

1 I o 11 12 13 14 15 16 17 18 19 20 2 1

22 23 24 25 26

2 1 .705 2 1 -663 2 1 -59 1

2 1.664 2 1 -577 0.141 0.048

Ford injector

Plenum Temp.

22.058 22.034 22.038 22.02 1 22.025 22.000 22.0 13 2 1 -988 22.0 17 21.875 21.912 21.811 21.845 2 1.909 22.018 2 1.976 21.894 21.902 22.153 22.073 22.073 22.092 22.009 21.992 2 1.988 2 1.958

2 1 .592 2 1 .596 2 1.603 2 1.6 17 2 1.477 0.146 0.050

top view-port

Injected Fuel

Temp.

2 1.795 2 1.828 21.803 2 1.8 1 1 2 1.845 2 1.790 21.794 2 1.76 1

2 1.842 21.513 21.521 21.521 21.520 2 1.672 21.587 2 1.737 21.605 21.665 2 1 .767 2 1.643 2 1.680 2 1.735 2 1.790 21.800 2 1.795 2 1.829

22.002 2 1.956 2 1.939 2 1.86 1 2 1.820 0.559 0.191

Injector Body Temp.

22.304 22.449 22.34 1 22.337 22.2 13 22.246 22.229 22.205 22.16 1 22.186 22.051 32.106 22.034 22.206 22.105 22.055 21.904 22.110 22.880 22.82 1 22.795 22.687 22.598 22.442 22.320 22.274

20.947 20.943 20.942 20.9 14 20.9 12 0.055 0.019

experimental data.

1 1 1 -490 1 1 1 -494 1 1 1.474 1 1 1.462 1 1 1.3 15 0.383 0.131

952.684 957.9 19 962.525 958.205 966.397

8.815 3 .O07

Cylinder Head

Temp.

2 1.466 2 1.38 1 21.425 2 1.390 2 1.449 2 1.49 1

2 1.525 2 1.464 2 1.398 21.083 21.074 21.091 21.019 2 1.242 21.179 2 1.255 21.141 21.247 2 1.226

Manifold Pressure

[kPa]

1 10.570 1 10.373 1 10.404 1 10.420 1 10.424 1 10.450 1 10.458 1 10.476 1 10.495 110.522 110.536 110.540 110.560 1 10.570 110.586 1 10.607 110.613

2 1 .O95

Nitrogen Fïowrate [slpm]

90 1.470 900.069 909.965 898.344 90 1 .O44 902.323 903.822 90 1.722 906.085 898.320 895.710 910.518 916.758 906.08 1 914.762 9 10.2 18 915.144

' 920.329 9 10.343 9 12.445 919.891 9 12.163 922.8 1 1

2 1 .O40 2 1.2 13 2 1.22 1 21 -209 2 1.22 1 2 1.238

110.617 1 1 1.43 1 1 10.841 1 10.626 1 10.649 1 10.667 1 10.690 1 10.739 1 10.768

919.924 952.254 924.940

Average 1 2 1.979 1 2 1.744 1 22.298 1 2 1.262 ( 1 10.645 1 9 12.674

Std. Dev. 1 0.071 1 0.1 10 1 0.225 1 0.138 1 0.188 1 10.934 1 95.0% 1 0.023 1 0.036 1 0.074 1 0.045 1 0.061 1 3.5721 Con.

5.2. Stanadyne Injector Experimental Data

Table 5.3 Stanadyne injector experimental data.

: Photograph Plenum

Number Temp. Tnjected Injector Cylinder Manifold

Fuel Body Head Pressure Temp. Temp. Temp. [kPa]

Ni trogen Spray Flowrate 1

c;; 1 [slpm] Angle

934.522

TabIe 5.4 Stanadyne injector experimental data.

19 20 21 22 23 24 25 26 27 28 29 30 3 1 32 33 34 35 36 37 38

Average Std.Dev.

95.0%

23 .582 23.578 23.591 23.490 23.561 23.446 23.271 23.305 23.27 1 23.196 23.275 23.200 23.149 23.263 23.162 23.166 23.162 23.166 23.1 16 23.086 23.549 0.299 0.095

Photograph Number

24.82 1 24.809 24.805 24.805 24.822 24.835 24.839 24.885 24.889 24.893 24.872 24.898 24.830 24.93 1 24.906 24.885 24.940 24.9 19 24.977 24.935 24.782 0.130 0.041

Plenum Temp.

23.692 23.767 23.675 23.801 23.784 23.793 23.797 23.755 23.822 23.839 23.767 23.839 23.877 23.826 23.839 23.885 23.864 23.793 23.978

Injected Fuel

Temp.

Injector Body Temp.

1 8.903 18.898 18.805 18.869 18.861 18.835 18.717 18.653 18.7 17 18.591 18.541

Local Cylinder

Head

1 10.076 1 10.093 110.089 1 10.104 1 10.103 1 1 O. 1 09 110.126 110.120 1 10.124 110.131 110.138

Manifold Pressure

[kPa]

Nitrogen Flowrate

[slpm]

922.769 92 1.333 6.236 1.983

1 10.158 1 10-070 0.091 0.029

23.864 23.6 13 0.252 0.080

Spray Cone Angle

30

922.32 1 928.444 930.414 92 1.275 927.126 927.062 926.912 923.028 922.785 929.568 921.756

18.602 18.435 18.437 18.442 18.455 18.39 1 18.298 18.37 1 18.323 18.930 0.443 O. 141

30 30 30 30 30 30 30 30* 30 30 30-

926.865 924.317 924.7 19 9 16.9 1 1 926.555 926.930 924.9 12 925.907

1 10.149 1 10.134 1 10.156 1 1 O. 154 1 10- 155 1 IO. 154 1 IO. 145 1 10- 153

30 30 30 30 30 30 30 30

Table 5.5 Stanadyne injector experirnental data.

10 1 1 12

Average Std.Dev. 95.0% Con.

22.499 22.312 22.514 22.4 13 0.102 0.057

Photograph Number

1 2 3 4 5 6 7 8 9 10 1 1

Average Std. Dev.

-

Table 5.6 Stanadyne injector experimental data.

78.798 78.981 78.61 1 79.878 0.893

95.0% Con.

Photograph Number

Plenum Temp.

23.191 23.229 23.073 23.069 23.015 22.989 22.851 22.804 22.632 22.598 22.93 1 22.944 0.207

48.706 48.636 48.439 49.054 0.729

Locai Cylinder

Head Temp. 28.867 28.704 28.498 28.352 28.176 28.051 27.925 27.900

O. 122

Lnjector Body Temp.

Injected Fuel

Temp.

125.468 125.614 125.60 1 125.485 125.572 125.572 125.531 125.472 125.2 15 125.227 125.0 1 1 125.433 0.196

Plenum Temp.

22.246 22.181 22.034 22.56 1 0.684

0 . 5 0 ~ ~ 0 . 3 8 7 ~ 1 6 8 ~

Injector Body Temp.

70.883 70.072 69.583 69.323 68.793 68. 104 66.910 66.620

Manifold Pressure

[kPa]

109.165 109.199 109.2 24 109.228 109.250 109.275 109.300 109.3 15

O. 1 16

Injected Fuel

Ternp.

66.1 14 65.792 69.57 1 68.342 1.738

Local Cylinder

Head

1 10.261 110.244 110.250 1 10.394 0.298

Nitrogen Flowrate

[slpm]

867.477 872.649 865.17 1 881.637 876.569 880.736 884.575 878.885

1 .O27

Manifold Pressure

[kPa]

Nitrogen FIowrate

[slpm]

Spray Cone Angle

34 34* 34 34 34 34 34 34-

27.339 27.188 28.227 28.1 12 0.518

Tern~.

Spray Cone Angle

944.250 952.904 947.1 18 949.552 17.217

30 30 30*

109.422 109.420 1 12.7 1 1 lO9.Sg 1 1.038

32.247 I

0.306

879.3 19 879.578 1056.555 893.0 14 54.569

0.614

34 34 34

P

06 06

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Table 5.8 Stanadyne injector expenmental data.

Photograph Number

1 2 3

7 Average

Table J.9 Stanadyne injector experirnental data.

Plenum Temp.

22.812 22.766 22.708

Std.Dev. 95.0% Con.

22.649 22.74 1

Injected Fuel

Temp.

173.880 174.0 1 1 173.803

0.070 0.05 1

173.964 173.875

Photograph Number

1 2

1 1 Average Std. Dev.

95.0% Con.

Injector Body

Temp.

89.575 88.595 87.546

0.128 0.095

Manifold Pressure

[kPa]

1 10.705 1 10.574

85.980 87.450

Plenum Ternp.

23.364 23.259

22.74 1 23.060 0.197 0.1 16

Locai Cylinder

Head Ternp. 31.120 3 1.1 1 1 3 1 .O57

1.247 0.924

Nitrogen Flowrate [slpm]

952.485 939.954

30.848 30.997

Spray Cone Angle

102 102'

192.382 192.704 0.306 0.181

Manifold Pressure

[kPa]

110.447 1 10.420 t 10.4 16

0.106 0.079

Local Cylinder

Head Ternp. 36.691 36.41 7

Injected Fuel

Temp.

193.052 192.848

1 10.43 1 1 10.428

Injector Body Temp.

99.043 98.26 1

9 1.776 95.102 2.370 1.401

Nitrogen Flowrate

[slpm]

931.917 94 1.426 938.521

0.011 0.008

Spray Cone Angle

90 90 90.

945.235 940.43 1

8.493 6.292

34.084 35-25 1

0.938 0.554

90

1 10.72 1 1 10.604 0.073 0.043

948.929 940.6 14 7.073 4.180

102

Table J. 10 Stanadyne injector experimental data.

Photograph Plenum Injected Injector Locai Number Temp. FueI Body Cylinder

Temp. Temp. Head Temp.

1 23.339 208.170 105.70 1 36.899 2 23.036 208.297 104.148 36.7 12

Manifold Nitrogen Spray Pressure Flowrate Cone

[kPa] [slpm] Angle

1 Average 1 22.909 1 206.865 1 100.273 1 35.553 S td. Dev. 0.153 1.235 2.622 0.816 --

95.0% 0.083 0.672 1.425 0.444 Con.

- - -- -. . --

Table J. I 1 Stanadyne injector experirnental data.

Photograph Plenum Injected Injector Local Number Temp. Fuel Body CyIinder

Ternp. Temp. Head Temp.

1 23.175 2 18.549 107.659 36.687

Manifold Pressure

W a I

Nitrogen Spray Flowrate Cone

[slpm] Angle

Table 5.12 S tanadyne injector experimental pressure data. Matching pressure data for the data listed in tables 5.3 to J. 1 1.

12 13 14

Average Std. Dev.

95.0% Con.

Time 1 Table 1 Table 1 Table 1 Table 1 Table 1 Table 1 Table 1 Table 1 Table

22.800 22.809 22.807 22.907 0.122 0.064

217.414 2 16.945 217.026 2 17.739 0.593 0.31 1

102.965 102.936 102.846 104.465 1.348 0.706

34.762 34.72 1 34.737 35.5 1 1 0.641 0.336

110.722 1 10.734 110.741 1 10.722 0.037 0.019

953.226 949.069

961,594 952.7 1 1 4.260 2.232

115 '

1 15 1 15

Note: Al1 temperature measurements are listed in units of Celsius. Al1 cone angle measurements are listed in units of degrees. Al1 pressures listed in table J. 12 are in units OS psig.

INFORMATION TO USERS - University of Toronto T-Space...Table 1.3 Stanadyne injector calibration data...

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