模型固体火箭发动机内涡脱落过程的大涡模拟

Large eddy simulation of vortex shedding for model SRM

关键词:  固体推进剂火箭发动机  非定常流  大涡模拟+  涡脱落+

Key words:  Solid propellant rocket engine  Unsteady flow  Large-eddy simulation~+  Vortex shedding~+

摘要:

为研究后向台阶结构引起的涡脱落对固体火箭发动机内流动稳定性的影响,采用大涡模拟技术,对模型发动机内的流动进行了数值模拟,获取了发动机燃烧室内压强随时间的变化曲线及其振荡频率,并和已有的计算结果及实验结果进行了对比分析。结果表明采用LES方法的计算结果明显优于采用k-ε湍流模型的计算结果;不考虑燃烧时模型发动机内由涡脱落引起的压强振荡的振幅较小,但频率较高,且随来流速度的增加而增大;在后向台阶这种结构中,涡一般会在台阶的边沿形成,并在其下游周期性地脱落;在保证y+较小的情况下,网格大小对计算结果的影响不明显。

Abstract:

In order to investigate the influence of vortex shedding initiated by backward stepping on the flow stability in the rocket motor, large-eddy simulation of the flow in a scale model solid rocket motor was carried out.Pressure evolution and its FFT results were gained.Also comparison was made between the numerical results and the experimental results as well as an existing numerical results.It is shown that the results calculated by LES model are more accurate than those computed by(k-ε) turbulence mode;the magnitude of the pressure oscillation in the scale rocket motor is small,but its frequency is high and also increases along with increasing incoming flow velocities;in backward stepping,vortex usually generates at the edge of the step and sheds periodically downstream;the size of the computational mesh has little influence on the computed oscillation frequency if y~+ is small enough.