Research Papers: Internal Combustion Engines

Study of Fuel Temperature Effects on Fuel Injection, Combustion, and Emissions of Direct-Injection Diesel Engines

[+] Author and Article Information
Gong Chen

Department of Mechanical Engineering, Gannon University. Erie, PA 16541

J. Eng. Gas Turbines Power 131(2), 022802 (Dec 18, 2008) (8 pages) doi:10.1115/1.3019006 History: Received October 24, 2007; Revised August 23, 2008; Published December 18, 2008

The influence of inlet liquid fuel temperature on direct-injection diesel engines can be noticeable and significant. The work in this paper investigates the effects of inlet fuel temperature on fuel-injection in-cylinder combustion, and output performance and emissions of medium-speed diesel engines. An enhanced understanding and simplified modeling of the variations in the main fuel-injection parameters affected by inlet fuel temperature are developed. The study indicates that the main injection parameters affected include the injection timing at the injector end relative to the injection-pump actuation timing, the fuel-injection rate, the fuel-injection duration, and the injection spray atomization. The primary fuel temperature effects on the injection parameters are from the fuel bulk modulus of elasticity and the density with the fuel viscosity less significant as the injector-nozzle flow is usually in a turbulent region. The developed models are able to predict the changes in the injection parameters versus the inlet fuel temperature. As the inlet fuel temperature increases, the nozzle fuel-injection-start timing is predicted to be relatively retarded, the injection rate is reduced, and the needle-lift duration is prolonged from the baseline. The variation trends of the engine outputs and emissions versus fuel temperature are analyzed by considering its consequent effect on in-cylinder combustion processes. It is predicted that raising fuel temperature would result in an increase in each of CO, HC, PM, and smoke emissions, and in a decrease in NOx, and may adversely affect the fuel efficiency for a general type of diesel engine at a full-load condition. The experimental results of the outputs and emissions from testing a medium-speed four-stroke diesel engine agreed with the trends analytically predicted. The understanding and models can be applied to compression-ignition direct-injection liquid fuel engines in general.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

Indication of engine inlet fuel temperature

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Figure 2

Temperature effects on modulus of elasticity, density, and viscosity of liquid fuel

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Figure 3

Fuel compressibility versus fuel temperature (pj0=100 MPa)

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Figure 4

Predicted fuel temperature effects on fuel acoustic velocity and SOI-timing lag (pj0=100 MPa)

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Figure 5

Predicted fuel temperature effect on start of injection timing (pj0=100 MPa, θi0/θs0=θj0/θs0=0.5)

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Figure 6

Predicted changes in line pressure, injection rate, and injector needle-lift duration versus inlet fuel temperature (pj0=100 MPa)

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Figure 7

Variation of engine outputs versus inlet fuel temperature (full load)

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Figure 8

Engine emissions versus inlet fuel temperature (full load)



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