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Deviations between transient and steady state operation of a modern light duty diesel engine were identified by comparing rapid load transitions to steady state tests at the same speeds and fueling rates. The validity of approximating transient performance by matching the transient charge air flow rate and intake manifold pressure at steady state was also assessed. Results indicate that for low load operation with low temperature combustion strategies, transient deviations of MAF and MAP from steady state values are small in magnitude or short in duration and have relatively little effect on transient engine performance. A new approximation accounting for variations in intake temperature and excess oxygen content of the EGR was more effective at capturing transient emissions trends, but significant differences in magnitudes remained in certain cases indicating that additional sources of variation between transient and steady state performance remain unaccounted for.

This computational study compares predictions and experimental results for the use of direct injected iso-octane fuel during the negative valve overlap (NVO) period to achieve HCCI combustion. The total fuel injection was altered in two ways. First the pre-DI percent, (the ratio of direct injected fuel during the NVO period “pre-DI” to the secondary fuel supplied at the intake manifold “PI”), was varied at a fixed pre-DI injection timing, Secondly the timing of the pre-DI injection was varied while all of the fuel was supplied during the NVO period. A multi-zone, two-dimensional CFD simulation with chemistry was performed using KIVA-3V release 2 implemented with the CHEMKIN solver. The simulations were performed during the NVO period only.

Ethanol has been injected through an atomizing nozzle into the intake manifold of a four cylinder turbocharged diesel engine. It was found that to avoid liquid droplet impingement on the compressor blades the injector needed to be located downstream of the compressor, in the high pressure section of the inlet manifold. 160 proof and 200 proof alcohols were investigated with a series of percentage substitutions at different speeds and loads. The fumigation of ethanol resulted in a slight improvement in thermal efficiency at high loads and a small reduction at light loads. The ignition delay and rate of pressure rise also increased significantly when ethanol was added to the engine. A change in the proof of ethanol from 160 to 200 did not produce any noticeable change in engine performance. Emission measurements were also made and are discussed. The problem of obtaining uniform cylinder to cylinder distribution of alcohol has been encountered.