The Influence of Boost Pressure and Fuel Chemistry on Combustion and Performance of a HCCI Engine

The influence of boost pressure (Pin) and fuel chemistry on combustion characteristics and performance of homogeneous charge compression ignition (HCCI) engine was experimentally investigated. The tests were carried out in a modified four-cylinder direct injection diesel engine. Four fuels were used during the experiments: 90-octane, 93-octane and 97-octane primary reference fuel (PRF) blend and a commercial gasoline. The boost pressure conditions were set to give 0.1, 0.15 and 0.2MPa of absolute pressure. The results indicate that, with the increase of boost pressure, the start of combustion (SOC) advances, and the cylinder pressure increases. The effects of PRF octane number on SOC are weakened as the boost pressure increased. But the difference of SOC between gasoline and PRF is enlarged with the increase of boost pressure. The successful HCCI operating range is extended to the upper and lower load as the boost pressure increased. The maximum achievable load of gasoline is higher than that of PRF with the cases of supercharging. The PRF octane number has a little effect on HC, CO and NOX emissions when supercharging is employed. Nevertheless, the HC, CO and NOX emissions of gasoline are higher than those of PRF with the cases of supercharging.