An Analytical Evaluation of the Effect of Leakage on NO Emissions from a Rotary Engine

A mathematical model describing the Wankel engine combustion process is developed to evaluate the effects of apexseal leakage on NO emissions. It is assumed that leakage occurs only during combustion and expansion and that only unburned gas leaks out during combustion and that only unburned gas leaks out during combustion and that during expansion, only burned gas leaks out.

A parametric study is performed to show the effects of such variables as equivalence ratio, compression ratio and engine speed. An experimentally obtained pressure time trace is used to show the accuracy of the model predictions.

It was found that under normal operating conditions (near F = 1), reductions in apex-seal leakage area will not cause an increase in NO emissions and that below 2500 rpm, mass leakage drastically increases with further reductions in speed.