1998-05-04

Crossed Study of Residual Gas Rate - Firing Device for a Better Understanding of SI Engines Cycle-to-Cycle Variations 981434

This SI engine research investigation extends a previous study [14] concerning one kind of non-conventional firing device: the Pulsed Jet Combustion (PJC) igniter.
The PJC device was compared to a conventional spark plug during operation in a 4-valve single cylinder engine at 2000 rpm and a variety of air/fuel ratios and loads. Additionally, skip-firing was used to vary the residual gas rate. The mass fraction burned intervals were calculated from the pressure trace for each cycle via a heat release analysis that accounted for cycle-to-cycle variations in the trapped mass of fuel. Statistical analyses were performed for 100 cycles of operation for each test condition.
Similar results were found for the PJC device as for the spark plug with zero residual (five skipped cycles). For both igniters, the cycle-to-cycle variability increased with increasing residual, but the variability was less pronounced for the PJC device. It is concluded that the residual within the vicinity of the spark plug has a strong influence on cyclic variability. Therefore, it appears that the major advantage of the PJC device is that it enflames several flame kernels.
However, the exhaust HC emissions are much higher for the PJC device than for the spark plug. This factor remains a critical issue in development of the PJC device for use in conventional engines.

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