Experimental investigation of the effect of the intake air temperature and mixture quality on the combustion of a methanol- and gasoline-fuelled homogeneous charge compression ignition engine

Environmental concerns have increased significantly all over the world in the past decade. To fulfil the simultaneous emission requirements for near-zero pollutant and low carbon dioxide (CO2) levels, which are the challenges for the future powertrains, many studies are currently being carried out on new engine combustion processes, such as controlled autoignition for gasoline engines and homogeneous charge compression ignition (HCCI) for diesel engines. These combustion processes have the potential for ultra-low nitrogen oxide (NO2) and particulate matter emissions in comparison with conventional gasoline or diesel engines. In this paper, the combustion characteristics of a HCCI engine fuelled with methanol and gasoline were investigated on a modified two-cylinder four-stroke engine. The port fuel injection technique is used to prepare a homogeneous charge of fuel and air. The experiment is conducted with various intake air temperatures ranging from 120 degrees C to 160 degrees C at different air-to-fuel ratios, for which stable HCCI combustion is achieved. The experimental results indicate that the inlet air temperature and air-to-fuel ratio have a significant effect on the maximum in-cylinder pressure and its position relative to top dead centre, the shape of the pressure rise curve, and the heat release rates. The results confirm that the inlet air temperature is a very sensitive parameter in controlling combustion timing and thus the effectiveness of the HCCI combustion process.