Effects of intake flow and coolant temperature on the spatial fuel distribution in a direct-injection gasoline engine by PLIF technique

► Characterisation of homogenous and stratified fuel mixtures using PLIF technique. ► Effects of coolant temperatures and intake flows on fuel mixtures were examined. ► Similar homogeneous fuel mixtures were found close to the ignition time for both charged motions. ► With late injection, the fuel mixture was stratified at the centre of the cylinder. ► The level of fuel concentration was reduced with the temperature at 120bar injection pressure. The spatial fuel distributions of the homogeneous and stratified charge of a high pressure 6-hole injector were examined in a single cylinder optical direct injection spark ignition (DISI) engine. The effects of in-cylinder charge motion, fuel injection pressure and coolant temperature were investigated using a planar laser induced fluorescence (PLIF) technique. It was found that in the case of homogeneous charge mode, early injection in the intake stroke generated similar fuel distributions at the crank angle of 12° BTDC regardless of the in-cylinder air motion at the coolant temperature of 90°C. In the case of stratified charge mode, the in-cylinder tumble flow played more effective role in mixture preparation than the swirl flow during the compression stroke; and the increase of the coolant temperature improved fuel evaporation; but the increase of the fuel supplying pressure could not change the pattern of the fuel vapour distribution against the expectation.