Visualization on combustion characteristic of gasoline/diesel fuel blends at different injection timings

In an optical engine, the combustion characteristics of pure diesel and the fuel blend (G 60) which consists of 60% volume ratio of gasoline and 40% volume ratio of diesel, was studied at different injection timings using a high-speed photography technology. Result show that the heat release rates of the two fuels present an unimodal patterns. Compared with pure diesel, p_max of G 60 fuel blend is more sensitive to the change of injection timing. With advancing the injection timing, the ignition delays of pure diesel and G 60 fuel increase linearly, and the ignition timings advance gradually. Ignition points are distributed in window edge, and the area of the luminance of flame decreases gradually, corresponding to the decrease of the diffusive combustion. The duration from CA 5 (50% cumulative heat release) to CA 50 (50% cumulative heat release) is decreased. Compared to diesel, G 60 has an extended ignition delay. Under lean combustion, the combustion duration from CA 5 to CA 50 is extended.