Turbulent Temperature Fluctuations in Spark Ignition Engines and Their Effect on NOx Emissions 2004-01-0623
Temperature fluctuations in the turbulent flow-field inside an engine's cylinder are important because they enhance the rates of the NO forming reactions. This work presents a zero-dimensional model for the root mean square (r.m.s) temperature fluctuations in a spark ignition engine. A thermodynamic combustion model is used to compute the NO formation rates after accounting for the effect of temperature fluctuations on the reaction rates. The computed tailpipe Zeldovich NO emissions may be up to 25 % higher because of the inclusion of the effect of the temperature fluctuations. It may also be necessary to add the contribution of prompt NO and the turbulent N2O mechanism to the turbulent Zeldovich NO so as to match the experimentally observed values under lean conditions.