基于单缸二冲程光学发动机，开展了相同热力学条件下正十二烷在不同喷射策略下的油气混合及燃烧过程的可视化研究。采用高速纹影成像观测喷雾几何形状的瞬态变化并测量火焰浮起长度，通过气缸压力曲线来计算放热率以研究整个燃烧过程。燃油两段喷射策略的不同点主要在于不同的喷油间隔及初次喷油量。试验结果表明，喷油间隔和初次喷油量对第二次着火延迟期和火焰浮起长度没有明显影响，但火焰浮起长度对喷油间隔相较着火延迟期更敏感；整个喷射过程的总燃烧效率不会随喷油间隔或初次喷油持续期的变化而变化，但第二次喷射的燃烧效率总是高于初次燃油喷射的燃烧效率。

Based on a single-cylinder two-stroke optical engine, the visualization study of fuel-air mixing and combustion process of n-dodecane was carried out according to different injection strategies under the same thermodynamic conditions. High-speed schlieren imaging was used to observe the transient changes of spray geometry and measure the flame lift length. The heat release rate was obtained through the cylinder pressure curve to study the combustion process. The difference between the two-stage fuel injection strategies lied in the different fuel injection intervals and initial fuel injection volumes. The results show that the fuel injection interval and the initial fuel injection volume have no significant effect on the second ignition delay period and flame lift length, but the flame lift length is more sensitive to the fuel injection interval than the ignition delay period. The combustion efficiency of the entire injection process will not change with the change of fuel injection interval or the duration of first fuel injection, but the combustion efficiency of the second injection is always higher than that of the first fuel injection.