不同壁温及差分格式下超燃冲压发动机的仿真

Simulation of scramjet with different wall temperatures and difference schemes

针对圆截面超燃冲压发动机相关实验进行数值仿真,采用了不同的壁面温度条件和差分格式,并探究其对仿真结果的影响规律。结果表明采用常用的绝热壁面边界条件会导致激波边界层交互位置处的回流区变大,进而导致流道收缩,壁面压力升高。采用高精度格式不仅不能更为精确地计算回流区的大小,反而会使回流区面积变得更大。通过改变壁面边界条件,采用300 K的等温壁面,可以使激波边界层交互位置处的回流区变得极小,使仿真结果与实验结果十分吻合。计算结果表明,针对当前构型与实验条件,盲目提高数值格式的精度并不一定会得到更好的结果,相反可能会使仿真与实验更加偏离,而适当修改壁面温度条件,即使数值格式精度较低,仍然可以得到很好的仿真结果。最后,针对与实验结果吻合的仿真结果,分析了圆截面超燃冲压发动机的流场特性,重点研究了凹腔剪切层及其质量交换特性。

In this paper,numerical simulation is carried out for circular scramjet with different wall temperature conditions and difference schemes,and their influence on the numerical results is investigated.The results show that the widely used adiabatic wall boundary condition will lead to the overestimation of the recirculation zone at the interaction position of shock and boundary layer;the flow path contracts and the wall pressure increases.Using high-precision difference scheme cannot calculate the size of recirculation area more accurately,would instead,aggravate the boundary layer separation.The recirculation zone at the interaction position of shock and boundary layer can be minimized when adopting the isothermal wall of 300 K.The simulation results are in good agreement with the experimental results.The numerical results show that for the current configuration,blindly improving the accuracy of the numerical scheme does not get better results.On the contrary,it could make the simulation deviate from the experiment.If the wall temperature conditions are properly modified,perfect simulation results can be obtained even if the accuracy of the numerical scheme is low.Finally,according to the simulation result which is consistent with the experiment,the flow field characteristics of circular scramjet are analyzed,with emphasis on the cavity shear layer and the mass exchange characteristics.