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A new type of ignitor, the railplug, shows promise of extending the dilution limits for spark ignition engines. While much of the effort expended in our study of railplugs has focused upon demonstrating their effectiveness, it is recognized that railplug durability is presently not acceptable for production engine applications. The goal of the present study was to examine the factors that affect durability. The results of two types of investigations are reported. The effects of rail materials, pressure, delivered energy, and voltage at constant delivered energy on electrode erosion rates were studied for repeated firings in air at constant pressure. Railplug durability in a four-stroke SI engine was also evaluated, including examination of the effects of delivered energy, current pulse characteristics, and materials.

An investigation of cyclic variability in a spark ignition engine is reported. Specifically, the predictions of an engine code have been compared with experimental data obtained using a well-characterized SI engine. The engine used for the experimental work and modeled in the code is the single cylinder research engine developed at Sandia National Laboratories and now operating at Drexel University. The data used for comparison were cylinder pressure histories for 110 engine cycles gathered during operation at a single engine operating condition. The code allows the various factors that could influence cyclic variability to be examined independently. Specifically, a model has been used to independently examine the effects of variations in equivalence ratio and of the turbulence intensity on cycle-to-cycle variations in the peak cylinder pressure, the crankangle of occurrence of peak pressure, the flame development angle, and the rapid burning angle.