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Hydrogen electronic injection system for a dieselpower generator

Alex de Oliveira 1, Eduardo Chaves Moreira dos Santos 2,Gerson Castanheira Botelho 3, Osmano Souza Valente 4, Jose Ricardo Sodre*

Pontifical Catholic University of Minas Gerais, Department of Mechanical Engineering, Av. Dom Jose Gaspar, 500,

30535-610, Belo Horizonte, MG, Brazil

a r t i c l e i n f o

Article history:

Received 7 February 2013

Received in revised form

19 April 2013

Accepted 21 April 2013

Available online 18 May 2013

Keywords:

Hydrogen

Injection system

Electronic control

Diesel engine

Power generation

* Corresponding author. Tel.: þ55 31 3319 49E-mail addresses: alexoem@gmail.com (A

hotmail.com (G.C. Botelho), osmano.valente1 Tel.: þ55 31 9793 5407; fax: þ55 31 3319 42 Tel.: þ55 31 8429 3482; fax: þ55 31 3319 43 Tel.: þ55 31 8897 6721; fax: þ55 31 3319 44 Tel.: þ55 31 9951 5567; fax: þ55 31 3319 4

0360-3199/$ e see front matter Copyright ªhttp://dx.doi.org/10.1016/j.ijhydene.2013.04.1

a b s t r a c t

This work presents an electronic control system developed for hydrogen injection in a

diesel power generator. The full system is basically constituted by a gas fuel injection rail

with injection valves, a speed sensor and an electronic control unit. The electronic injec-

tion system was installed and tested in a diesel power generator of 44 kW rated power. The

tests were carried out with hydrogen injected in the intake manifold and diesel oil directly

injected in the combustion chamber. The results show the injection valve opening periods

necessary to obtain hydrogen mass flow rates equivalent to 5%, 10%, 15% and 20% of the

diesel oil mass replaced. The measured hydrogen mass flow rate injected is presented as a

function of load power demand and hydrogen concentration in the fuel.

Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights

reserved.

1. Introduction pollutant emissions than diesel oil or gasoline fueled engines,

Studies about engines fueled by hydrogen date from more

than 200 years ago [1]. In 1807 Francois Isaac de Rivaz invented

an internal combustion engine fueled by hydrogen and oxy-

gen with electric ignition and, one year later, this engine was

adapted to a vehicle, being the first automobile moved by an

internal combustion engine. In 1863, Etienne Lenoir invented

a single cylinder engine fueled by hydrogen that proved

instant success. The use of hydrogen as an engine fuel has

a main advantage the production of lower amounts of

11; fax: þ55 31 3319 4910.. de Oliveira), eduardocm@gmail.com (O.S. Valente910.910.910.910.2013, Hydrogen Energy P18

the exception being oxides of nitrogen (NOX) [1e4]. Particu-

larly, compression ignition engines can be adjusted to dual

fuel operation, having diesel oil as the pilot fuel and hydrogen

as the complementary fuel [5]. Thus, the possibility to use

hydrogen as fuel for diesel engines represents an alternative

to partially solve major problems associated to the use of

conventional fuels: limited availability of fossil fuels and the

need to reduce pollutant emissions.

Hydrogen can be used in diesel engines with few modifi-

cations [6]. The gas fuel can be introduced in the engine via

oreira@hotmail.com (E.C. Moreira dos Santos), gerson_botelho@), ricardo@pucminas.br (J.R. Sodre).

ublications, LLC. Published by Elsevier Ltd. All rights reserved.

Fig. 1 e Hydrogen injection valves installed in the intake

manifold.

i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n en e r g y 3 8 ( 2 0 1 3 ) 7 9 8 6e7 9 9 3 7987

indirect injection in the intake manifold or direct injection in

the combustion chamber. If hydrogen is stored at a pressure

around 200 bar there is no need to use a fuel pump to conduct

the fuel through the injector and inside the combustion

chamber [4]. The installation of a pressure reduction valve in

the fuel line is recommended for better control of hydrogen

injection. The indirect injection method requires lower mod-

ifications in the engine, although it is less efficient than the

direct injection method. In any case ignition must be initiated

by diesel oil or another fuel. Hydrogen injection may have a

mechanical or electronic control system. The electronic sys-

tem gives faster response, allowing for better control of in-

jection timing and injection valve opening [7].

A spark ignition engine was modified by Ref. [2] to operate

with hydrogen. The hydrogen injection system consisted of

four fast-response electromagnetic injection valves and a

microcontroller. The valve actuation circuit included a sup-

pression diode to protect the system. Themicrocontroller was

used to control injection timing and injection valve open

period. The main input data to the controller was ignition

timing, crankshaft speed, load demand and intake air flow

rate. A satisfactory operation of the injection system was ob-

tained. For a power generator using a spark ignition engine

operating in dual fuel mode gasolineehydrogen, the gas fuel

injection was controlled using only the input signal from a

magnetic speed sensor mounted opposite to a phonic wheel

installed in the engine crankshaft [8].

A single cylinder diesel engine was adapted by Ref. [9] to

operate in dual fuel mode using diesel oil and natural gas. The

gas fuel volume injected and the injection timing were

controlled by a microcontroller commanded by an electro-

magnetic actuator. Themain input signal to the controllerwas

the engine crankshaft speed and piston position, given by a

magnetic speed sensor and a phonic wheel. The interface

between the controller and the computer was done through a

serial communication using an integrated circuit model

MAX232. The injection control software was developed in

Assembly software. The Assembly software is indicated to

obtain better results from low-cost microprocessors, as the

software allows for fast and precise estimation of data pro-

cessing and memory required [10,11].

A hydrogen injection electronic control unit (ECU) was

developed to operate a diesel engine operating in dual fuel

mode using diesel oil and hydrogen [3,12]. The ECU allowed for

tests varying the injection timing and the hydrogen mass

injected. A disc with a pointer installed in the engine crank-

shaft and an infrared sensor produced a voltage signal to the

ECU to indicate piston position. After processing the signal the

ECU could decide about the injection timing and duration. The

hydrogen flow rate was controlled by the injector open period

and by a pressure regulator.

This work presents a hydrogen injection system for appli-

cation to a diesel power generator. The injection system is

mainly constituted by four gas injectors installed in the intake

manifold and an electronic control unit (ECU). The ECU was

developed using three microcontrollers, differently from Refs.

[2,9], who used just one microcontroller. The main input

signal to the ECU was produced by a magnetic speed sensor

mounted opposite to a phonic wheel installed in the engine

crankshaft, as it has been employed by Ref. [8] for a stationary

spark ignition engine. The ECU software was developed in

Assembly platform, as its fast processing and other charac-

teristics make it suitable to low-cost microprocessors [10,11].

The hydrogen injection system was tested through exper-

iments carried out in a 44 kW diesel power generator with

varying load and hydrogen concentration in the fuel.

Hydrogen was indirectly injected in the intake manifold and

diesel oil (with 5% of biodiesel e B5) was directly injected in

the combustion chamber. Ignition was started by diesel oil,

which injection was controlled by the original engine me-

chanical injection system. The hydrogen injection control

system was set to inject the required amounts to replace 5%,

10%, 15% and 20% wt./wt. of diesel oil for load demands from

0 kW to 40 kW.

2. Hydrogen injection electronic control unit

A commercial multipoint gas fuel system was employed for

uniform hydrogen injection in four engine cylinders (Fig. 1).

The injection system adapted to the engine intake manifold

contains a fuel distribution rail (a) and four gas injection

valves (b). Fig. 2 shows the injection system installed in the

engine intake manifold. Installation of the hydrogen injection

systemwas done in a way that it did not cause any significant

interference when the engine was operated with diesel oil

only.

A programmable, multivariable transducer model UPD-200

was used to determine the load demanded from the power

generator. The transducer is controlled by a microprocessor,

and it performs measurements, calculations and allows for

visualization of the main parameters of three-phase electric

power distribution grids through a liquid crystal display. It has

a communication interface RS-485 with MODBUS RTU proto-

col that allows for communication with a computer or with

programmable controllers.

The hydrogen injection electronic control unit utilizes

threemicrocontrollers model Freescale MC908HC08QY. These

Fig. 2 e Hydrogen injection system installed in the engine.

Fig. 3 e Schematics of circuit 1.

Fig. 4 e Voltage regulator circuit diagram.

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microcontrollers have thirteen programmable input and

output pins and a 16-bits internal clock. Two channels allows

for signal capture and generation of pulse-width modulation

(PWM). The microcontrollers are equipped with an analog-

digital signal converter and are easily programmable in As-

sembly software. The microcontrollers have high noise im-

munity, being the main characteristic why they have been

chosen for this application.

The hydrogen injection electronic control unit is

comprised of three electric circuits. The first circuit (1) is

constituted by a filter and a voltage regulator (Fig. 3). Together

with the engine alternator and the battery, this circuit is the

energy source to the ECU. Circuit 1 reduces the battery nom-

inal voltage from 12 V to 5 V, as required by the integrated

circuits to operate. The nominal voltage to operate the fuel

injectors is 12 V.

An integrated circuit model LM7805 was used to regulate

the voltage at 5 V. This circuit is a linear regulator recom-

mended to electric currents below 1 A. This element has a

protection against overheating and short circuit, and it is

mounted over an adequate heat sink. Decoupling electric ca-

pacitors are required between the system input, output and

the ground (GND). The diagram of the voltage regulator circuit

is shown by Fig. 4.

When varying the load applied to the power generator

electric voltage fluctuations are produced. Those fluctuations

can compromise operation of the microcontrollers or even

cause malfunction. The magnitude and duration of those

fluctuations are affected by load characteristics. Fig. 5 shows

the voltage fluctuations produced by the power generator

when disconnected from a load of 2.5 kW. A passive filter was

used to reduce those fluctuations.

The second circuit (2) contains the second and the third

microcontrollers and establishes communication with the

multivariable transducer UPD-200, commands the 7-segment

display and processes data to calculate injection timing

(Fig. 6). Circuit 2 is constituted by an electronic oscillator

(Fig. 7) able to produce periodic, quadratic waveform with

frequency 20 MHz. The circuit is stable and precise enough to

establish communication between the secondmicrocontroller

and the UPD-200 transducer at the set rate. The input signal is

obtained through the oscillator, which is controlled by a

quartz crystal. The signal generated by the crystal has an

alternate form and it is turned to quadratic wave through a

Schmitt-trigger circuit, for which an integrated circuit model

74LS04 was utilized. The Schmitt-trigger circuit receives the

sinusoidal signal from the crystal and produces a quadratic

wave of 20 MHz and peak voltage of 5 V.

Circuit 2 contains two light emission diodes, the control

buttons for the fuel amount injected, the controller that cal-

culates the injection timing, the 7-segment displays and mi-

crocontroller 3, which commands the displays. Circuit 2 is

connected to the third circuit (3) by a flat cable that commu-

nicates with multivariable transducer UPD-200, transfers

Fig. 5 e Transient voltage in the battery.

Fig. 7 e 20 MHz oscillator diagram.

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injection timing data to the first microcontroller and conducts

electric power to circuit 3.

Circuit 3 (Fig. 8) contains the first microcontroller and re-

ceives information from circuit 2, aids communication with

UPD-200 transducer, commands the hydrogen injector open-

ing period and receives the signal from the engine crankshaft

speed sensor. On circuit 3 is mounted the communication

interface between the ECU and the UPD-200 transducer, built

on an integrated circuit MAX232 like that employed by Ref. [9]

Fig. 6 e Circuit

(Fig. 9). This circuit converts the communication signals from

the serial port to 5 V, which is the adequate voltage level to the

circuit. The receptor converts EIA-232 inputs to 5 V TTL/CMOS

levels, while the transmitter does the opposite.

Circuit 3 contains the commander microcontroller and the

interface between the hydrogen injectors and the injection

system sensors. The hydrogen injectors cannot be directly

actuated by themicrocontroller, as they demand around 1.7 A

of peak current. The injectors were actuated by Darlington

transistors, which require much lower electric current levels.

The recommended transistor power is TIP 122, with heat sink

and/or forced convection. The resistors that connect the mi-

crocontroller to the transistor limit the transistor polarizing

current. In order to avoid reverse current in the transistors,

suppression diodes were installed parallel to the injector

2 diagram.

Fig. 8 e Circuit 3 diagram.

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terminals, as it has been applied by Ref. [2]. Fig. 10 shows a

diagram of injector actuation.

During the tests of the ECU it was noticed that the engine

crankshaft speed sensor was susceptible to external noise

when the engine was turned off. A pull-up resistor was

inserted between the sensor and themicrocontroller to reduce

Fig. 9 e Serial port comm

external noise level (Fig. 11). The resistor makes the signal in

the transmission line be in high logic level (þVcc) when the

sensor circuit is disconnected or fluctuating. The sensor and

the hydrogen injectors were connected to the ECU through

connectors model DB15. Table 1 shows the connector pin

distribution.

unication diagram.

Fig. 10 e Diagram of injector actuation.

Table 1 e DB15 connector pin distribution.

Pin number Function

1 Actuation of hydrogen injector 1

2 Actuation of hydrogen injector 2

3 Actuation of hydrogen injector 3

4 Actuation of hydrogen injector 4

5 Not in use

6 Connection to crankshaft speed

sensor (GND)

7 Vcc ¼ 14 V

8 Connection to crankshaft speed

sensor

9 Connection to optical sensor

(collector)

10 Connection to optical sensor

(emitter) (GND)

11 Connection to infrared light

emitter (Vcc ¼ 5 V)

12 Connection to infrared light

emitter (GND)

13 GND

14 GND

15 GND

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3. Results

The hydrogen injection ECU was installed in a diesel power

generator, which main characteristics are shown by Table 2.

The engine crankshaft speed was kept at 1800 rev/min during

operation. The load demand to the power generator is pro-

vided by bank of electric resistances with maximum power of

50 kW, at 220 V. The resistances were grouped in modules of

2.5 kW, 5 kW and 10 kW, so that theminimum load increment

was 2.5 kW. K-type thermocouples were installed for tem-

perature reading at the engine intake air measuring system

inlet, intake pipe, exhaust pipe and ambient air. Pt-100 ther-

moresistors were installed for temperature measurement at

the engine cooling system inlet and outlet, and in the diesel oil

tank. Ambient air relative humidity was measured by a ther-

mohygrometer. The intake air flow rate was determined

through an orifice plate, and the diesel oil consumption was

measured by an electronic balance positioned under the diesel

oil tank. Monitoring of the input and output signal from the

ECU was done through a digital oscilloscope of 100 MHz

bandwidth and real time sampling rate of 2 GS/s per channel.

Hydrogen consumption was measured by a diaphragm

type volumetric flow rate measuring device, with measuring

Fig. 11 e Pull-up resistor.

range from 0.060 m3/h to 10 m3/h and maximum operating

pressure of 100 kPa. A primary pressure regulator was

installed in the hydrogen storage cylinder to reduce the

pressure in the hydrogen line, as it was recommended by Ref.

[4]. A secondary pressure regulator was installed just before

the measuring device to control hydrogen injection pressure,

which reading was done through a digital manometer with

resolution of 0.001 bar. A plenum chamber was installed be-

tween the secondary pressure regulator and the hydrogen

injectors to attenuate pressure waves in the regulator gener-

ated by the injectors.

From an analysis of the hydrogen injection ECU it was

noticed that the main variable parameters to obtain a speci-

fied fuel mass amount injected were hydrogen injector

opening period and injection pressure. The injector opening

period was defined considering the hydrogen amount to be

injected at each operating condition and the injection pres-

sure. From a preliminary study equations for the injector

opening period were defined as a function of load demand,

Table 2 e Diesel engine and generator details.

Equipment Parameter Type or value

Cycle Four strokes

Diesel oil injection Direct

Bore � stroke 102 � 120 mm

Engine Number of cylinders 4, in line

Total displacement 3.922 L

Intake system Naturally aspirated

Rated power 44 kW

Number of poles 4

Voltage 220 V

Generator Number of phases 3

Rated power 55 kVA

Frequency 60 Hz

Table 3 e Hydrogen injector opening conditions.

Condition Concentration(%)

Power,W (kW)

Pressure(kPa)

1 5 <25 2

2 5 �25 25

3 10 <10 2

4 10 �10 25

5 15 <32.5 25

6 15 �32.5 70

7 20 <20 25

8 20 �20 70

Table 4 e Injector open period.

Condition Open period, t (ms)

1 t ¼ 0.013W2 þ 0.193W þ 0.725

2 t ¼ 0.0017W2 þ 0.0586W � 0.11429

3 t ¼ 0.98W þ 4.9

4 t ¼ 0.0048W2 þ 0.116W þ 0.5233

5 t ¼ 0.0052W2 þ 0.3233W þ 1.0434

6 t ¼ 0.012W2 þ 1.218W þ 19.765

7 t ¼ 0.01W2 þ 0.446W þ 2.48

8 t ¼ 0.0035W2 þ 0.2078W þ 0.6208

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injection pressure and hydrogen concentration (Tables 3 and

4). These equations were loaded in the ECUmemory. The ECU

was set to inject hydrogenmass amounts corresponding to 5%

(B5H5), 10% (B5H10), 15% (B5H15) and 20% (B5H20) of the en-

ergy amount contained in the total mass of injected fuel,

including diesel oil (B5). Hydrogen injection started at the

beginning of the intake process.

Before initiating the tests the diesel engine was operated

for, at least, 5 min before stabilization of the temperatures of

engine coolant and lubricating oil. The intake air temperature

was kept between 20 �C and 30 �C, and the exhaust pressure

was maintained at 1.08 � 0.03 bar. The tests were executed at

steady state condition, with the engine operating at 1800 rev/

min crankshaft speed, with a tolerance of �50 rev/min. The

0 5 10 15 20 25 30 35 40LOAD PO WER (kW)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

HY

DR

OG

EN

MA

SS

FLO

W R

ATE

(kg/

h) B5H5B5H10B5H15B5H20

Fig. 12 e Variation of hydrogen (H2) mass flow rate with

load power and hydrogen concentration in the fuel.

load was varied from 0 kW to 40 kW. The stabilization period

of the engine was from 2 min to 10 min, and the data

acquisition period was, at least, 30 s at each operating

condition.

The ECU tests allowed for the construction graph plots

with the experimental results for the different test conditions.

Fig. 12 shows the hydrogen mass flow rate obtained for the

hydrogen concentrations used at the different loading condi-

tions. The hydrogen flow rate to the engine is increased with

increasing hydrogen concentration in the fuel and with

increasing load demand. The trends observed are according to

what should be expected, indicating a satisfactory operation

of the hydrogen injection system. During the tests the system

produced a fast response to load demand and no anomalies

were noticed.

4. Conclusions

A hydrogen injection system constituted by an electronic

control unit (ECU) and gas fuel injectors installed in the engine

intake manifold has been presented. The electronic control

unit (ECU) developed for hydrogen injection using the signals

from an engine crankshaft speed sensor and a multivariable

transducer for engine load power reading as main input pa-

rameters demonstrated proper operation for a variety of loads

and hydrogen concentrations in the fuel. The ECU main

structure was comprised of three electric circuits and three

microcontrollers. Mathematical correlations between the

injector open period and load power using different injection

pressures were loaded in the ECU, allowing for diesel oil (B5)

substitution by hydrogen at the concentrations of 5%, 10%,

15% and 20% onmass basis. Hydrogenmass flow rate injected

was increased with increasing load power and hydrogen

concentration in the fuel.

Acknowledgments

The authors thank ANEEL/CEMIG GT-292 research project for

the financial support to this work.

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