Abstract: In order to investigate the effects of active cavity injection on ignition at the inflow conditions of Ma=2.1 with stagnation state [T0=846K，p0=0.7MPa]，high speed photography was used to compare the parallel injection with the ramp injection in the ethylene ignition experiments. Based on the image processing statistical analysis of high-speed photographic，it is revealed that under the ignition working conditions，the ramp injection makes it easier to form a stable flame in the whole cavity at the active injection equivalent ratio of 0.03 when it is compared with the parallel injection. Under the condition of the ramp injection，the flame will penetrate the shear layer，ignite the transverse jet downstream of the cavity and form a stable combustion in the scramjet at the active injection equivalent ratio of 0.06 and the overall equivalent ratio of 0.17. Using the parallel injection and the ramp injection together in the cavity will further promote the formation and propagation of the initial flame kernel，and the flame will penetrate the shear layer，ignite the transverse jet downstream of the cavity and form a stable combustion in the scramjet at the active injection equivalent ratio of 0.05 and the overall equivalent ratio of 0.16.

Key words: Cavity；Ignition；Equivalent ratio；Active injection

摘要： 为了研究在总温846K，总压0.7MPa，入口来流马赫数2.1的超声速来流条件下凹腔主动喷注对点火过程的影响，利用高速摄影相机进行观测，对比了凹腔前壁喷注、后壁面喷注等组合喷注方式下开展的发动机乙烯点火试验。基于对高速摄影图像处理的统计分析，研究发现在点火工况条件下，凹腔后壁面喷注相比于前壁喷注更容易使整个凹腔内形成稳定的火焰，当凹腔主动喷注当量比达到0.03时就能使凹腔内形成稳定的火焰；在凹腔后壁面喷注的条件下，当凹腔主动喷注当量比达到0.06，全局当量比达到0.17时，火焰就会穿过剪切层引燃凹腔下游横向射流，在整个发动机中稳定燃烧；凹腔前壁喷注和后壁面喷注相结合的喷注方式能进一步促进初始火核的形成与传播，当凹腔主动喷注当量比达到0.05，全局当量比达到0.16时，火焰就能穿过剪切层引燃凹腔下游横向射流，在整个发动机中稳定燃烧。

关键词: 凹腔；点火；当量比；主动喷注