Effects of charge temperature and fuel injection pressure on HCCI engine

This work investigates the effect of both inlet air temperature and fuel injection pressure on performance and emission behaviour of homogeneous charge compression ignition engine (HCCI) fuelled with diesel fuel. In this investigation, HCCI engine operates with different inlet air temperature and fuel injection pressure, and analysis the effect of these variables on HCCI engine performance and emissions. The inlet air temperatures are varied between 40 °C and 70 °C and the injection pressure in the port fuel injector is varied from 3 bar to 5 bar respectively. From the results, the optimum inlet air temperature and fuel injection pressure for efficient HCCI engine operation are identified. The result shows that, brake thermal efficiency of HCCI is nearer to the value of conventional diesel engine, and can be obtained if HCCI engine operates with 5 bar injection pressure and 60 °C air temperature and a simultaneous reduction in oxides of nitrogen (NOx) and smoke emissions compared to conventional diesel engine. However, when inlet air is heated for improvement of vaporisation of diesel fuel, the higher inlet air temperature limits the operation range of HCCI engine, due to high knocking intensity, high NOx emissions and misfire of charge. The fuel injection pressure is also limited due to high level of HC and NOx emissions.