Liquid Fuel Impingement on the Piston Bowl of a Direct-Injection, Spark-Ignited (DISI) Engine under Stratified Operation

The behavior of the liquid fuel impinging on the piston top of a direct-injected, spark-ignited (DISI) engine operating under stratified conditions is investigated using floodlight laser-induced fluorescence (LIF). The combustion chamber geometry offers wall-guided stratification using a high-pressure injector impinging on an inclined piston bowl. The LIF signal is collected through the bottom of the quartz piston, allowing observation of the footprint of the spray during and after spray development. Nitrogen gas is used to replace air in order to minimize oxygen quenching and increase the signal. The results show that at typical piston top temperatures expected in warmed-up operation (150-180 °C), a liquid film and ring around the area where the fuel jet impinges is present through the time of spark (20° before top center). The presence of the fuel film is not very sensitive to the surface temperature.