ANALYSIS OF HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE WITH EMPHASIS ON COMBUSTION TIMING AND REACTION RATE

HCCI engines are a class of engines which use high compression ratio to ignite a charge of air-fuel mixture. This contrasts with diesel engines where the fuel is injected near the top dead centre of the compression stroke regime. Petrol HCCI engines are of significance because, it attempts to improve the characteristics of the engine for example the thermal efficiency. High compression ratio comes with higher thermal efficiency, yet the peak temperature remains low enough to have low production rates of harmful oxides of nitrogen and soot formation. However, there are certain challenges associated with such type of engine, one of which and perhaps the most important of all is how to control the combustion rate. Flow dynamics and chemical-kinetics analysis is essential to optimize combustion timing, duration and rate. The objective of this study is to analyse a HCCI engine using a zero-order model employing a one-step chemical kinetics and a CFD simulation incorporating complex chemistry for improved combustion prediction. Simulation is carried for a generic cylinder geometry. Sensitivity analysis of number of variables such as the compression ratio and rpm on the combustion time, burn duration, heat release is carried out.