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Technical Paper
Chris Manzie, Harry C Watson
The variability of in-cylinder combustion of gasoline at idle has been investigated previously, culminating in the development of a model relating the past and future indicated torque deviations from the mean at given engine operating conditions of intake manifold pressure, engine speed and spark advance. The developed model has the potential to be used in an idle speed control algorithm to improve vehicle noise vibration and harshness (NVH) at low engine speeds and loads. While environmental considerations have spawned the development of liquefied petroleum gas (LPG) as a viable alternative fuel, adaptation of the variability model to multipoint LPG injected automotive engines is complicated by the fact that the fuel mixture concentrations of propane and butane are subject to wide variations depending on a variety of factors including geographic location and local market pricing.
Technical Paper
Chris Manzie, Harry C Watson, Paul Baker
Combustion in the cylinder of a spark ignition engine, particularly under low load conditions, is subject to cycle-by-cycle variations due to factors such as mixture quality and quantity and internal exhaust gas recirculation. The major result of this phenomenon is an increase in the variability of indicated engine torque at a given engine operating point. Automotive control problems dealing with torque production at low engine loads, particularly the control of idle speed, rely on accurate information about the transfer functions of different engine subsystems, however combustion variability and the effect it has on torque production is often overlooked. In this paper we illustrate the effects that combustion variability at idle has on different transfer functions related to indicated torque, and propose new models for torque production at constant operating points.
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