关键词: 缸内直喷, 光学发动机, 平面激光诱导荧光, 冷启动, 燃烧, 排放

Abstract:

Optical single cylinder engine and planar laser induced fluorescence technology were used to visualize in-cylinder air fuel mixing and combustion process of cold idle situation for gasoline direct injection engine. Transparent liner with pent-roof shape at the upper side and double sides split laser were used. Using statistical image evaluation method, images of the in-cylinder fuel concentration and combustion flame were obtained. Combustion stability was evaluated by cylinder pressure sensor and combustion analyzer. Exhaust gas analyzer and optical sensor were used to analyze hydrocarbon and soot emission separately. The results show that, HC emission is caused mainly by fuel impingement on cylinder liner at stable combustion situation, while soot is formed mainly by combustion of fuel film at the top side of piston. Suitable retarded injection time for the second injection is helpful to form stable rich fuel-air mixture near sparkplug, and then improve combustion stability and HC emission; too late fuel injection will increase soot emission dramatically, and too early injection will cause misfire, and increase HC emission.

Key words: gasoline direct injection, optical engine, planar laser induced fluorescence, cold start, combustion, emission