1988-02-01

Evaluation of Four Mixing Correlations for Performance and Soot-Emission Characteristics for a Small Open-Chamber Diesel Engine 880599

A quasi-steady gas-jet model was applied to examine the spray penetration and deflection in swirling flow during the ignition-delay period in an open-chamber diesel engine timed to start combustion at top dead center. The input to the gas-jet model included measured values of ignition delay and mean fuel-injection velocity. Attempts were made to correlate measured fuel-consumption and soot-emissions data with mixing parameters based on calculated spray penetration and deflection. The engine parameters examined were piston-bowl geometry, compression ratio, speed, and overall air-fuel ratio.Four empirical correlations proposed in the literature were examined. The correlations, which were based on spray penetration and deflection in the swirl direction, represented overall degrees of fuel distribution in the combustion chamber and of utilization of the cylinder air. Two correlations, namely relative spray-penetration and air-to-fuel momentum ratio, showed potential for explaining the observed trends in specific fuel consumption and soot emission. However, a broader database obtained from specifically designed tests is needed in order to verify the conclusions.

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