Gasoline spray characterization and droplets-wall interaction at different piston temepratures

Spray/wall interaction has a significantly influence on the mixture formation process in gasoline direct injection (GDI) engines. Moreover, the fuel wall film and the resulting delayed evaporation of the liquid fuel are the main sources of soot formation in the internal combustion engines. In this paper, the spray evolution from a multi-hole GDI injector was investigated into an optical accessible vessel and environmental controlled through optical diagnostic developed under different injection strategies varying the duration and pressure of injection. In particular, a set of measurements were performed to characterize the spray evolution and the spray impact at different wall temperature. 2D high temporal and spatial resolution images of fuel spray were collected to obtain information about the penetration length, and wall impact hence about mixture formation process. Firstly, the spray evolution was analysed through the measurement of penetration length by visible high speed camera; secondly, the impact on the wall piston was analysed by means infrared thermography. The results obtained highlight the influence of injection pressures on the penetration length and the importance of piston temperature during the spray/wall impact.