Improvement of a model for calculation of oxides of nitrogen emissions from spark ignition engines

This work presents an optimized model that calculates the rate of formation of oxides of nitrogen in spark-ignited internal combustion engines. Model optimization was done by establishment of a correlation between the fuel-air mixture equivalence ratio and the first rate reaction constant of the Zeldovich's mechanism, which describes the kinetics of formation of nitric oxide. The calculated values by the model were compared to experimental data available from a single-cylinder engine, featuring a disc type combustion chamber, for variations of fuel-air mixture equivalence ratio. When the mixture equivalence ratio was varied, the optimized model produced calculated values much closer to the experimental results than the previous model, especially in the lean mixture region and in the peak region near to stoichiometry.