The influence of intake pressure and EGR in the combustion timing of a gasoline fuelled HCCI engine developed from single cylinder CI engine

The study is aimed to obtain suitable methods in controlling the combustion timing of Homogeneous Charge Compression Ignition (HCCI) engine. HCCI is a combustion technology alternative that has potentials to obtain higher efficiency with lower exhaust emissions. For that, a single cylinder CI engine was modified into a gasoline fuelled HCCI engine and coupled with an appropriate dynamometer. The accuracy of the timing was evaluated by measuring the engine torque generated. The experimental variables are the percentage of exhaust gas recirculation and inlet pressure variations as a replacement for compression ratio variation. Fuel-air mixture is maintained at stoichiometric. Results indicate that timing of HCCI combustion could be regulated by both methods. Intake pressure has a more dominant influence on the combustion timing. However, too low inlet pressure would make the engine stall due to very advance timing of combustion. Applying EGR on HCCI engine gives the effect of retarded combustion timing and reduced torque. Applying EGR was also a suitable method to control the HCCI engine load.