An Experiment Study of Homogeneous Charge Compression Ignition Combustion and Emission in a Gasoline Engine

Homogeneous charge compression ignition technology has exhibited high potential to reduce fuel consumption and NOx emissions over normal spark-ignition engines significantly. Optimized kinetic process technology is implemented to realize homogeneous charge compression ignition combustion in a port fuel injection gasoline engine. The combustion and emission characteristics are investigated with variation of intake air temperature, exhaust gas recirculation rate and intake air pressure. The results show that intake air temperature has great influence on homogeneous charge compression ignition combustion characteristic. Increased intake air temperature results in advance combustion phase, shorten combustion duration, and lower indicated mean effective pressure. Increased exhaust gas re-circulation rate retards combustion start phase and prolongs combustion duration, while maximum pressure rising rate and NOx emission are reduced with increase of exhaust gas re-circulation rate. In the condition with constant fuel flow quantity, increased air pressure leads to retarded combustion phase and lower pressure rising rate, which will reduce the engine knocking tendency. In the condition with constant air fuel ratio condition, fuel injection quantity increases as intake air pressure increases, which lead to high heat release rate and high emission level. The optimal intake air temperature varies in different operating area, which can be tuned from ambient temperature to 220° by heat management system. The combination of exhaust gas recirculation and air boost technology could expand operating area of homogenous charge compression ignition engine, which improve indicated mean effective pressure from maximum 510 kPa to 720 kPa.