Relationship between wall surface roughness and fuel film evaporation for spray impingement

抄録

In this study, formation and evaporation of fuel films on various surface roughness walls were investigated. Iso-octane was injected from multi-hole DISI injector. Injected spray was impinged on an aluminum wall having low or high roughness (R_a = 0.63 μm to 8.30 μm) and fuel film was formed on the wall. Wall surface temperature before fuel spray impingement was controlled by an electric heater (25°C to 130°C). Fuel film behavior with elapsed time under various wall conditions was captured by a high-speed camera. Fuel film spreading area change and evaporation lifetime of the fuel film were obtained from the captured top view image. As a result, it was found that the fuel film spreading area became narrower with an increase of the surface roughness. The evaporation lifetime of fuel film became shorter with an increase of the surface roughness. Therefore, it was considered that heat transfer from the wall to the fuel film increased owing to an increase of a substantial contact area between the wall surface and the fuel film.