PRV Induction 1

8/14/2019 PRV Induction 1

1/11

PRV Induction 1

PRV Induction Technical Overview

James Meyer

Aspen Engineering Services (dba PRV Performance)

18990 W 54th Place, Golden, CO 80403

303-887-2032, [email protected]

July 23, 2009


2/11

PRV Induction 2

Table of Contents

Abstract.......................................................................................................................................... 3

1.0 Identification and Significance of the Innovation ................................................................ 4

2.0 Background ............................................................................................................................. 5

2.1 The Conventional Intake Manifold ................................................................................... 5

2.2 The Pintle-Regulated Venturi (PRV) Concept............................................................. 5

2.21 Fuel Economy Improvement from Reduced Pumping Loss ..................................... 7

2.22 Improved Engine Torque ............................................................................................. 8

2.23 Fuel Economy Derived from Pre-Vaporized Fuel ..................................................... 9

2.24 Reduced Greenhouse Gas Emissions .......................................................................... 9

2.25 Ethanol-Fueled Engine Performance Expectation .................................................... 9

2.26 Initial Prototype Results............................................................................................. 10

References .................................................................................................................................... 11


3/11

PRV Induction 3

Abstract

PRV PERFORMANCE has developed and patented an improved automotive fuel

induction system to improve engine torque and reduce throttling losses for improved vehicle

efficiency. Improved pre-mixing of fuel and air lowers tailpipe emissions.Pintle-regulated Venturi (PRV) induction, with fuel injection directly at the Venturi

throat, effectively mixes fuel and air due to the high velocity and reduced pressure at the vapor-

liquid contact region, while pressure is recovered in the expansion section. Fuel vaporization in

the confined Venturi volume facilitates air flow into the PRV entrance.

PRV improves fuel economy and increases engine torque by

1. reducing piston pumping loss;2. pre-vaporizing fuel upstream of the engine, thereby cooling the fuel/air mixture

and lowering the mixture density; and

3. eliminating fuel stratification on cylinder wall.


4/11

PRV Induction 4

PRV Induction Technical Overview

Aspen Engineering Services (dba PRV Performance)

18990 W 54th

Place, Golden, CO 80403James Meyer, 303-887-2032, [email protected]

1.0 Identification and Significance of the InnovationPintle-regulated Venturi (PRV) induction is a cost effective, patented fuel/air induction

system for improving the performance of spark-ignited automotive engines system (U.S. patent

6,868,830). The proposed induction system uses a (PRV) to create a convergent-divergent nozzlethat can significantly recover the pressure drop across the pintle body and maintain a higher engine

intake manifold pressure to boost engine torque. With a higher engine torque using the same

amount of fuel, the fuel economy will be increased significantly. On the contrary, a conventional

throttle plate causes unrecoverable pressure loss, reducing engine torque and efficiency.Specifically, engine torque is increased and fuel economy is improved while exhaust pollutants and

greenhouse gases are significantly reduced by exchanging a conventional intake manifold with a

pintle-regulated Venturi (PRV) induction system on a conventional spark-ignited engine. A

schematic comparison of the two induction systems is shown in Figures 1 and 2.

PRV Performance has been developing the proposed system for five years, and a recent on-road testindicated that the gasoline engine vehicle could achieve 58 mpg for a 204-mile round trip with an

average speed of 65 mph. Recently, the Obama Administration declared that vehicles must reach an

average of 35.5 mpg before 2016. PRV technology will enable troubled US automakers to producecars and trucks to meet the new fuel/emission standards with little or no expense to retool their

factories, making it imperative to bring this proposed technology to market. The engine

performance improvement using the proposed system is derived from four attributes of a PRV

Figure 1: Conventional manifold at

partially open throttle that creates

unrecoverable pressure loss such that the

piston must pull against a vacuum,

resulting in high pumping loss.

Figure 2: PRV manifold that is designed to

recover pressure drop across the pintle in order to

maintain a high intake pressure, boosting engine

torque and fuel economy. A PRV is implemented

for each cylinder.


5/11

PRV Induction 5

induction system:

PRV induction improves fuel economy. First, PRV fuel induction substantially reduces pistonpumping losses. With a conventional manifold, pumping losses account for 16 to 40% of an

engines efficiency loss under normal cruising conditions because the air intake is at vacuum

pressure (Heywood, 1988; Ferguson and Kirkpatrick, 2001). The air intake plenum of a PRV isnever under vacuum and consequently, the piston pulls initially against full ambient (or turbo)

pressure. Fuel efficiency is substantially improved because the wasted work of pulling against a

vacuum is eliminated. Second, PRV induction vaporizes the fuel before the engine whereas aconventional manifold does not fully vaporized fuel until the compression stroke. The compression

work used to vaporize fuel is eliminated with PRV induction. Third, the cooler, denser charge

reduces the friction loss across the intake valves thereby further reducing pumping loss.

Engine power output is increased. Engine power is directly proportional to air flow capacity.PRV induction vaporizes fuel upstream of the engine by injecting fuel directly into the high-

velocity air stream at the low-pressure throat of the Venturi. By conservation of energy, the latent

heat of the fuel is transferred into a cooled fuel/air mixture. Since a higher mixture flow rate isenabled with a cooled charge, the specific power output of the engine is increased. The cooler

(higher density) charge allows the engine to produce more torque and horsepower.

PRV induction reduces exhaust emission of CO2, CO and unburned hydrocarbons. A

conventional fuel injection system sprays droplets into the cylinder. Some of the droplets impingeon the cylinder walls. Those impinged droplets become entrained into crevices in the cylinder wall,

resulting in incomplete combustion of the fuel and the generation of CO and unburned

hydrocarbons. CO2 reduction is accomplished by improving fuel economy.

PRV induction will deliver an even greater benefit for ethanol-fueled engines than gasoline-

fueled engines. The power increase has been demonstrated on a dynamometer with a gasoline-

fueled engine. PRV will use the higher latent heat of ethanol to provide additional charge cooling

and in turn, a greater percentage increase in power relative to a conventional manifold.

2.0 Background

2.1 The Conventional Intake Manifold

The power of a spark ignited engine is directly related to the mass of air in the cylinder

when the intake valve closes. The mass of air in the cylinder is directly proportional to the pressureinside the cylinder. The cylinder pressure, with the air fed from by throttle plate, is controlled by the

pressure of a common manifold feeding all engine cylinders. While cruising, the throttle plate is

rotated open only a few degrees, imparting a large frictional loss causing a vacuum in the intake

manifold (Figure 1).

2.2 The Pintle-Regulated Venturi (PRV) Concept

Figure 3 is a three-dimensional drawing of a PRV induction manifold for a four-cylinderengine. Cylinder one is cut away to show the detail of the Venturi and the pintle. A PRV induction

system does not have a throttle plate. All pintles are withdrawn in parallel as the gas pedal is

pressed. The pintle movement along the axis of the Venturi (Figure 4) changes the flow area toprovide throttle control of the engine.


6/11

PRV Induction 6

The pressure profile of a PRV induction system is entirely different for two reasons. First,

the PRV intake pressure is always ambient (or turbocharger discharge) pressure. Second, when thecylinder valve closes, air from the plenum can flow around the pintle, equalizing the Venturi

discharge pressure with the plenum. There is plenty of time for this to happen because inlet valvesspend at least twice as long closed as open. Third, in comparison with a butterfly throttle which is asobstructive as one could imagine, the PRV is as streamlined as possible.

The throttle control fluid mechanics of a conventional throttle plate and PRV induction

system are entirely different, contributing to the improved fuel economy performance derived fromPRV. Throttle control with PRV is accomplished by the limitation of sonic velocity at the throat.

The velocity at the throat of the Venturi is determined by the speed of the piston and the annular or

area between the pintle and Venturi. Initially, the piston moves slowly and air easily flows throughthe streamlined Venturi. However, as the piston accelerates away, at some point the air flow

through the Venturi will approach sonic velocity. At sonic velocity, the pressure in the intake duct

can no longer influence the flow through the Venturi. The Venturi is said to be choked -- and in this

way, the streamlined PRV controls the power of the engine.The throttle control of the conventional throttle plate is accomplished by non-recoverable

frictional loss of the butterfly valve. Consequently, the piston is pulling against full vacuum for the

entire down stroke, resulting in substantially higher pumping losses than PRV induction.The intake pressure from PRV induction pulsates to reduce pumping losses whereas a

conventional manifold operates at a steady, but low, pressure (Figures 5 and 6). The streamlined

convergent-divergent Venturi nozzle accelerates airflow as the throat is approached and deceleratesairflow in the divergent section. Concurrently, as the air slows down, the pressure increases. The

pressure recovery process is governed by the conservation of energy as described by Bernoullis

principal (Perry & Chilton, 1973, pp. 5-18). The pressure recovery attribute of PRV improves the

piston-pressure history and, consequently, reduces pumping loss.

Figure 3: PRV Induction Manifold, Venturi 1 Cut-away Figure 4: PRV Cut-away View


7/11

PRV Induction 7

The fuel injector is aligned with the throat of the Venturi where the air velocity is at themaximum and the air pressure is at the minimum, thereby thoroughly vaporizing and mixing fuel

into the air stream. The fact that the Venturi throat is the low pressure point is counter-intuitive, but

consistent with the conservation of energy. The expansion of the vaporized fuel in the Venturipushes the fuel/air mixture into the engine, thereby improving torque and fuel economy.

2.21 Fuel Economy Improvement from Reduced Pumping Loss

The pressure equalization before each intake stroke, combined with the streamlined flow

attribute of PRV induction, reduces pumping loss. How important is the pumping loss? John C.

Hilliard et al. (1984) explains,

Assuming that the exhaust manifold pressure is about 1 inch of mercury above atmospheric

pressure, an intake and exhaust pumping loss of approximately 7 hp can be calculated,

which equals 0.072 of the total fuel supply. While this number is not absolutely accurate itdoes illustrate the importance of the loss. At 50 mph road load the pumping losses almost

40% of the engine brake power. (Hilliard and Springer, 1984).

Blackmore and Thomas (1977) write, "... pumping loss varies from 3.5% at wide-open

throttle (WOT) to nearly 100% for a full throttled idling engine". Accordingly, the pumping loss for

a compact U.S. 10:1 compression-ratio car cruising at 40 mph is about 16% (Blackmore & Thomas,1977). Pumping loss is highly dependent on the throttle position in the specific engine design. In

any case, most of the pumping loss is recovered by PRV induction.

Figure 7 compares the in-cylinder pressure of a conventional manifold to a PRV induction

system. When the intake valve opens on a conventional manifold, the cylinder pulls air from aplenum under vacuum. In contrast, the PRV plenum is constantly at ambient pressure. The bottom-

dead-center cylinder pressures are identical for both intake systems because the engine torque is

dependent on the amount of mixture at the end of the intake cycle. Since the pressure trace is muchhigher for PRV induction, there is a cumulative saving of work by the piston. The work saving is

reflected in the fuel economy improvement demonstrated by early PRV prototypes.

The benefits of using PRV induction can be further expanded for a turbocharged engine.During cruise, the conventional manifold will exhibit the same pressure profile. The profile does not

change because the pressure at bottom dead center must be the same. Consequently, the plenum

pressure must also be the same. The pressure differential between the turbocharger and plenumpressure is regulated by the throttle. In contrast, the PRV plenum pressure is set directly by the

Figure 6: Cylinder pressure comparison of a PRV and a

conventional manifold while cruising; data from Honda

D15B engine at 2300 rpm at 5700 feet of elevation.

Figure 5: typical P-V diagram

for a four-stroke engine with a

conventional intake manifold.


8/11

PRV Induction 8

turbocharger (Figure 7). The PRV induction system combined with the turbocharger will requireeven less work to be done by the piston to draw the charge into the engine, implying an even greater

fuel efficiency gain.

Individual throttle plates are much less effective for reducing pumping loss for two reasons.

First, individual throttle plates preclude mixing and vaporizing fuel upstream of the engine and,consequently, the charge cooling effect is lost. Second, a throttle plate obstructs flow whereas the

Venturi enhances flow. Although the manifold pressure will be the same as a PRV inductionsystem, the in-cylinder pressure profile of PRV is much better than a throttle plate. Figure 7illustrates the difference in pressure profile of a conventional manifold, individual throttle plate and

PRV induction.

Figure 7: cylinder pressure of a conventional manifold versus individual throttle plates and PRV

induction; normally aspirated engine (conventional manifold data from Taylor, 1985, p. 345, PRV

data from prototype measurement).

2.22 Improved Engine Torque

A cooler charge mixture improves the torque of the engine because a cooler charge mixture

has a higher density. The higher density provides for more fuel/air mixture to be in the cylinder atthe time the intake valve closes. A computer simulation shows that a pintle-regulated Venturi

induction completely vaporizes the fuel before the mixture reaches the engine head (Meyer, 2009).

Taylor states that if fuel evaporation is complete before inlet valve closing, the charge temperaturedecreases by 44 F, based on octane thermal properties. The temperature decreases in good

agreement with the authors computer simulations. Results from the chassis dynamometer test on the

initial prototype are shown in Figure 11 (section 2.8).Since PRV induction increases torque, automakers can produce smaller and lighter vehicles

to comply with the 2009 fuel economy standards to be phased in by 2016.


9/11

PRV Induction 9

2.23 Fuel Economy Derived from Pre-Vaporized Fuel

Taylor elaborates on fuel evaporation in his highly acclaimed book, The Internal

Combustion Engine in Theory and Practice. Specifically, Taylor writes that although some of the

fuel is vaporized from heat transfer with the cylinder wall, evaporation is seldom complete beforethe intake valve closes (Taylor, 1985, p. 185). Consequently, the efficiency is lost because work is

required to evaporate fuel.

2.24 Reduced Greenhouse Gas Emissions

CO2 emission is directly related to fuel consumption. Consequently, any improvement in

fuel economy will decrease the CO2 emitted and the associated effect on global warming.Hydrocarbon and CO emissions are produced when the combustion process is not complete.

Hilliard and Springer (1984) writes, "The major source of hydrocarbons found in the exhaust results

from that portion of the fuel-air intake charge that is trapped during the compression stroke, and

subsequent pressure rise during combustion, inside of crevices in the cylinder into which the main

combustion flame cannot enter... In the exhaust port and exhaust manifold, a portion of the residualhydrocarbons are combusted to CO or CO2." (Hilliard and Springer, 1984, p. 61). PRV induction

pre-vaporizes the fuel and, consequently, less fuel is trapped in the cylinder wall crevices therebyreducing hydrocarbon and CO emissions.

2.25 Ethanol-Fueled Engine Performance ExpectationEthanol is more difficult to disperse from a fuel injector because of the higher viscosity.

Ethanol also has a lower vapor pressure and a higher heat of vaporization. Consequently, with a

conventional fuel injection system, more of the fuel evaporation (in comparison to gasoline) will

occur during the compression cycle. Conversely, the higher heat of vaporization of ethanol meansthat pre-mixing of ethanol by PRV lowers the charge mixture more than gasoline. The lower charge

temperature and improved dispersion upstream of the engine, provided by PRV, is exactly what anethanol-fueled engine needs for improved power. The physical properties of ethanol and gasolineare compared in Table 1.

Blackmore and Thomas (1977) reported

that vaporized fuel improves the fuel

economy of a spark ignition engine. The

percentage improvement is reflected inFigure 8.

Figure 8: Economy Improvement from Vaporized

Fuel, data from Blackmore & Thomas, 1977, p. 106


10/11

PRV Induction 10

Table 1: Physical Properties of Gasoline and Ethanol (US Department of Energy)

Heat of vaporization, Btu/lb @

60 F.

Viscosity,

mm2/s.

Reid vapor pressure (100 degrees

F.), psi

Gasoline 150 0.55 8-15

Ethanol 396 1.5 2.3

2.26 Initial Prototype Results

Figure 9: Torque and Horsepower of a Gasoline-

fueled Normally Aspirated Engine with

Conventional Manifold and PRV Manifold

Test results with the gasoline prototype have

demonstrated a 21% increase in highway fueleconomy with a stoichiometric air/fuel ratio and

35% increase in highway fuel economy within

air/fuel ratio of 16.8. Torque is increased 15-20%on a normally aspirated engine fueled by

gasoline (Figure 9). These results were obtained

after a series of 10 prototypes were developedand tested over 5 years. Test results have been

validated repeatedly over a 203 mile highwaycycle is 65 mph, delivering 53 mpg at a

stoichiometric tune to 58 mpg for a lean-burntune.


11/11

PRV Induction 11

References

Blackmore, D. R., & Thomas, A. (1977). Fuel economy of the gasoline engine. New York: JohnWiley &, Inc.

Energy efficiency and renewable energy news. (2008, March 12). US ethanol production totaled

6.48 billion gallons in 2007. Retrieved April 13, 2009, fromhttp://apps1.eere.energy.gov/news/news_detail.cfm/news_id=11633.

Energy Information Administration. (2009, February 1). 1 (Petroleum Basic Statistics). Retrieved

April 13, 2009, from http://www.eia.doe.gov/basics/quickoil.html.Environmental Protection Agency. Fuel economy of motor vehicles. 40 CFR 600.

Ferguson, C. R., & Kirkpatrick, A. T. (2001).Internal combustion engines applied

thermosciences. New York: Wiley.Gold, A. What it is, how it works. Retrieved from about.com:

http://cars.about.com/od/thingsyouneedtoknow/a/directinjection.htm.

Heywood, J. B. (1988).Internal combustion engine fundamentals. McGraw-Hill.

Hilliard, J. C., & Springer, G. S. (1984). Fuel economy and road vehicles powered by spark ignitionengines. New York, New York: Plenum publishing.

Kelly, K. M. (2009, April 1). Ricardo's ethanol boosted direct injection. Automotive Design &

Production, 121(4), 13.Meyer, J. M. E. A. (2005, March 22). US patent 6,868,830 (U. S. Patent & T. Office, Eds.).

6.868,830.

Perry & Chilton. (1973). Chemical engineer's handbook. New York: McGraw-Hill.Stress Engineering Services Inc. Venturi mixer. Retrieved April 28, 2009, from Process Technology

Group: http://www.processinnovation.com/venturi.html.

Taylor, C. F. (1985). The internal combustion engine in theory and practice. Cambridge MA: MIT

press.US Department of Energy.Alternative fuels and advanced vehicles data center. Retrieved April 26,

2009, from US Department of Energy: http://www.afdc.energy.gov/afdc/.

PRV Induction 1

Documents

Transcript of PRV Induction 1