凹腔火焰稳定器阻力特性的实验研究

 在超燃冲压发动机直连式实验中,模拟马赫数1.92、静温509K、静压86.6kPa来流,采用等截面燃烧室构型,利用推力测量系统对不同结构尺寸的开式凹腔火焰稳定器的冷流阻力和热试阻力进行了研究。通过对深度分别为10,15,20mm,长深比4~10,后壁倾斜角18°~60°的凹腔火焰稳定器的冷流阻力比较,实验表明凹腔火焰稳定器的冷流阻力与凹腔深度成正比;也与凹腔长深比成正比;并随后壁倾斜角的增大先减小后增大,在30°~60°范围内应存在一个角度使得冷流阻力最小。实验还以氢气为燃料,利用火花塞点火器进行点火,在燃烧模态下对不同喷注位置、不同当量比时的凹腔火焰稳定器阻力特性进行了对比,结果表明凹腔火焰稳定器的热试阻力比冷流阻力小,且受燃料喷注方式的影响较大;在实际超燃冲压发动机工况下,凹腔火焰稳定器的阻力随着当量比的增加而减小,并最终会表现为正推力。

Experimental Investigation on Drag of Cavity Flame Holder

Experimental investigation on the drag of cavity flame holder was conducted by force measurement system. Integrated fuel injector/flame holder cavity module was installed in a constant area ground direct-connect test combustor, which simulated the incoming flow conditions of Ma=1.92, T=509 K, P=86.6 kPa. Various cavities were studied with several depth (D=10, 15, 20 mm), length-to-depth ratios (L/D=4-10) and trailing wall angles θ=18°, 30°, 45°, 60°). Results of cold flow experiment indicate that cavity drag increases with increasing D and L/D, and decreases between θ=18°-45°, followed by increasing between θ=45°-60°, which suggests that there might be a critical θ (between 30°-60°) at which the drag of a cavity are minimal. The drags of cavities under combustion condition, with hydrogen fuel ignited by a spark igniter, were investigated with two groups of fuel injectors on different positions and several fuel equivalence ratios. It is found that the drag of cavity under combustion condition is less than the drag of cold flow, and affected greatly by the fuel injectors position. The drag of cavity decreases with increasing fuel equivalence ratio, and could be converted into the thrust, instead of drag, under combustion mode which is close to real statue of scramjet.