S形进气道锤激波的动态特性

Dynamic characteristics of hammershock in S-shaped inlet

进气道的锤激波载荷是由发动机喘振引起的,是进气道结构设计的最大载荷。为了解进气道锤激波动态载荷特性,对M2129型S形进气道模型进行了三维非定常数值模拟。采用了直接在进气道出口给定压力变化波形的方法模拟喘振压升现象,分析了来流马赫数为0.65,初始进气道换算流量为60kg/s(即出口马赫数为0.44)时锤激波传播过程中进气道壁面压力和进气道内部流动的动态演化过程。发现上下壁面的动态峰值压力可以达到来流静压的2.3倍以上。在锤激波下游,可观察到回流产生,并出现复杂的三维流动结构。锤激波发生0.185s后进气道流动逐渐恢复正常。进一步的研究对比了不同换算流量、锤激波超压比和进气道中心线几何形状对应的锤激波压力变化。发现在较低流量和较大超压比时进气道所受峰值压力更大,锤激波沿进气道传播速度更快。进气道中心线形状的改变会影响锤激波压力的大小和分布,曲率大的地方易产生较大的锤激波峰值压力。

Hammershock loading is caused by engine surge,and is the maximum loading in the inlet structure design.To understand the dynamic characteristics of the hammershock,unsteady numerical investigations on the flow inside the M2129 S-shaped inlet are conducted.An unsteady back pressure boundary condition at the exit of the inlet is used to simulate the overpressure during engine surge.The detailed time history of the pressure and flow field inside the duct during the hammershcok are presented at the condition that the free-stream Mach number is 0.65 and the initial corrected mass flow is 60 kg/s（the Mach number at the exit of inlet is 0.44）.It is found that the peak pressure inside the inlet duct can be at least 2.3 times of the free-stream static pressure.The backwards flow and the three-dimensional flow structure can be found at the downstream of the hammershock.After the engine surge occurred,it takes about 0.185 sfor the flow inside the inlet to return to the steady state.This work also discusses the effects of the corrected mass flow,hammershock over pressure ratio and the S-ducts centerline.It is found that the peak pressure on the duct is higher and the hammershock spreads faster at a lower corrected mass flow condition or a higher over pressure ratio.The centerline curvature distributions can affect peak pressure distribution.A higher peak pressure appears at the sections of larger curvature.