超声速来流稳焰凹腔上游气体燃料横向喷注的流动混合特征

Mixing characteristics of gaseous fuel injection upstream of a flameholding cavity in supersonic flow

关键词:  超音速冲压喷气发动机  火焰稳定器  剪切层  大涡模拟+

Key words:  Supersonic combustion ramjet engine  Flame holder  Shear layer  Large eddy simulation

摘要:

对Ma=1.7的空气超声速来流稳焰凹腔上游气体燃料横向喷注的流动混合特征进行了实验和数值模拟研究。在喷注的模拟燃料氦气中添加丙酮,采用平面激光诱导荧光技术(PLIF)观测了设置开式凹腔时燃料在展向和流向的空间分布。针对下游布置不同凹腔时燃料分布相似的实验结果,选取L/D=7的凹腔对其燃料混合流场进行了大涡模拟。实验和仿真结果表明:实验来流条件下喷注燃料大部分直接由喷流引起的上升反转旋涡对带走,只有小部分燃料经由喷流与凹腔流动涡结构的相互作用进入凹腔剪切层,并随剪切层运动对流进入凹腔内部。

Abstract:

Non-reacting experiments and numerical simulations were performed to investigate the mixing characteristics of gaseous fuel injection located upstream of a flameholding cavity in supersonic vitiated air flow with stream Mach number 1.7.Using helium as simulated fuel,the acetone vapor is adulterated into the fuel jet.The fuel distribution in spanwise and streamwise direction is imaged by the planar laser-induced fluorescence(PLIF) measurement.According to the similarity of experimental observations with different cavities,a typical L/D=7 cavity with aft wall angle 45° is chosen and the flowfield with the injection is calculated by Large Eddy Simulation.Experimental and numerical results have shown that most of the fuel flows away upon the open cavity with the lifting counter-rotating vortex structures induced by the transverse jet.Only a small portion of the fuel is convected into the cavity shear layer by the vortex interaction of the jet with cavity shear layer,and then transported into the cavity interior due to the cavity shear layer motion.