The Simulation of Autoignition and Knock in a Spark Ignition Engine with Disk Geometry

The Computational Fluid Dynamics (CFD) code KIVA has been modified to include a combustion model and the Shell autoignition mechanism, and has been applied to a disk-chambered homogeneous charge spark ignition engine. The effects of ignition timing, turbulent kinetic energy and EGR were investigated for offset ignition. The effects of swirl and central ignition were separately investigated. For the central ignition case the influence of asymmetry of piston and cylinder head surface temperatures was also considered.

The results of the computational study are in general agreement with experimentally observed trends regarding heat release rate and phasing and their influence on cylinder pressure development, autoignition and knock. With the CFD code it was possible to observe, following autoignition, large amplitude pressure waves and acoustic resonant modes in the combustion chamber, which are generally in agreement with the published literature. This aspect of the present study merits further attention in relation to combustion noise and engine roughness.