Prediction of Autoignition Site in Spark Ignition Engines

Abstract

A three-dimensional knock model is developed to predict the knock occurrence and autoignition site in spark ignition engines. Weller's 1-equation combustion model and a flame wall quenching model a re applied to simulate flame propagation. A Reduced kinetic model developed by Keck and Hu is used to simulate autoignition in the unburned gas region. Engine experiments are performed to calibrate the reduced kinetic model and to verify the knock model. A spark plug integrated pressure transducer and 11 ion probes are installed in the cylinder head to detect knock occurrences, flame arrival angles, and autoignition sites. Autoignition site can be determined from the knock onset angle determined by cylinder pressure and flame arrival time determined by ion probes. Before the reduced kinetic model is combined with the combustion model, it was calibrated with measured cylinder pressure in a spark ignition engine. The cylinder pressure and flame arrival angles of numerical results are compared with the experiments. The numerical results are in good agreement with the experiments. The knock model developed in this study can predict knock occurrence and autoignition sites with reasonable accuracy.