Predictions of the Knock Onset and the Effects of Heat Release Pattern and Unburned Gas Temperature on Torque at Knock Limit in S.I. Engines

A reduced chemical kinetic model has been developed using temperature history measured by Coherent Anti-Stokes Raman Spectroscopy (CARS) and sensitivity analysis. Predictions of knock occurrence by this model show that the chemical role of residual gas and the intake flow have little effect on the knock occurrence crank angle. Furthermore, the effectiveness of the combustion period and the unburned gas temperature before spark ignition on the torque at trace knock limit (TTKL) has been clarified Under certain conditions, it is shown that the increase in torque, caused by the combustion duration shortened by ∼25%, is negated by the temperature rise of ∼15K before spark ignition.