초록
This study was performed to investigate the behavior and spatial distribution of fuel mixtures with different wall angle and diameter of piston cavity in a DI gasoline engine. The spatial distribution of fuel mixtures after impingement of the spray against a piston cavity is one of the most important. factors for the stratification of fuel mixture. Thus, it is informative to understand in detail the behavior and spatial distribution of fuel mixtures after impingement in the cavity. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze the behavior and distribution of fuel mixtures inside cylinder by exciplex fluorescence method. The exciplex system of fluorobenzene/DEMA in non-fluorescing base fuel of hexane was employed. Cavity wall angle was defined as an exterior angle of piston cavity. Wall angles of the piston cavity were set to 30, 60 and 90 degrees, respectively. The spray impinges on the cavity and diffuses along the cavity wall by its momentum. In the case of 30 degrees, the rolling-up moved from the impinging location to the round and fuel-rich mixture distributed at periphery of cylinder. In the case of 60 and 90 degrees, the rolling-up recircurated in the cavity and fuel mixtures concentrated at center region. High concentrated fuel vapor phase was observed in the cavity with 90 degrees. From. present study, it was found that the desirable cavity wall angle with cavity diameter for stratification in a Dl gasoline engine was demonstrated.
