Abstract: To investigate the supersonic combustion characteristics of parallel cavity flameholders，a series of direct-connected combustion tests under a wide range of equivalence ratios φ=0.43～1.07 were conducted in a single-side expansion combustor with ethylene injected upstream of cavities. The inflow conditions are Ma=3.46 and stagnation temperature Tt=1430K. Based on the static pressure distribution along the combustor wall，thrust increments，fuel specific impulses，high-speed flame luminosity and schlieren images，the flame structure，flowfield characteristics and combustor performance under different equivalence ratio were analyzed. The results show that the flow conditions near the cavity mounted in the upper and bottom wall are extremely different，and the strongly coupled interaction between the combustion process and local flow conditions results in a remarkably asymmetric flame distribution in the combustor. The combustor performance shows strong sensitivity to equivalence ratio. With the increase of equivalence ratio，the static pressure level and thrust increment continuously increase，but the growth rate under φ=0.43～0.62 is much larger than that of φ=0.76～1.07. The fuel specific impulse and combustion efficiency increase with equivalence ratio in the range of φ=0.43～0.62. However，with further increase of equivalence ratio in φ=0.76～1.07，both the fuel specific impulse and combustion efficiency decrease.

Key words: Scramjet engine；Parallel cavity flameholders；Asymmetric flame；Combustion characteristic；Ethylene

摘要： 为研究并联凹腔火焰稳定器的超声速燃烧特性，通过在凹腔上游喷注乙烯，采用单边扩张型燃烧室在当量比φ=0.43～1.07内进行了一系列直连式燃烧试验。模型燃烧室入口参数为Ma=3.46，总温Tt=1430K。基于燃烧室壁面静压分布、推力增益、燃料比冲和燃烧流场的可见光与纹影图像分析了并联凹腔在不同当量比下的火焰结构、流场特征和燃烧性能。结果表明，上、下壁面凹腔附近的流动条件差异显著，燃烧过程与当地流动条件之间的强烈耦合作用使得燃烧室内火焰分布显著不对称。发动机燃烧性能对当量比十分敏感，壁面静压水平和推力增益随当量比增加持续升高，但φ=0.43～0.62时的增加速率远大于φ=0.76～1.07时的。φ=0.43～0.62时，燃料比冲和燃烧效率随当量比增加而升高；而φ=0.76～1.07时，燃料比冲和燃烧效率随当量比增加而降低。

关键词: 超燃冲压发动机；并联凹腔火焰稳定器；非对称火焰；燃烧特性；乙烯