A Preliminary Study of Chemically Enhanced Autoignition in an Internal Combustion Engine

Chemically enhanced autoignition in a spark-ignited engine with a special design of piston geometry has been observed experimentally, in which the engine would operate stably without a spark, once it is started by spark ignition. Under this operation mode, the engine provides lower pollutant emissions including NO_x. In this process, the intermediate species left from the previous cycle play a key role in the low temperature autoignition. The objective of this study is to determine the effect of some important radical and intermediate species, such as HO₂, OH, and H₂O₂, on autoignition by a numerical modeling approach using a detailed chemical kinetic mechanism. The fuel studied is hydrogen. The effect of added HO₂, OH and H₂O₂ on the characteristics of the autoignition of H₂-air mixture is investigated.

Chemically enhanced autoignition of H₂-air in an internal combustion engine is also simulated. It is shown that the addition of intermediate species dramatically changes the pace of autoignition.