火箭垂直回收中发动机布局与喷流壁面效应影响研究

针对重复使用火箭垂直着陆过程的喷流流场问题开展研究，利用计算流体力学（Computational Fluid Dynamics， CFD)方法研究了壁面效应和发动机布局对超声速喷流的影响。研究表明，着陆距离（L）在2.24D~11.2D（D为喷管出口的直径）的范围内，地面效应对喷管出口中心处的温度分布影响较小；在当前计算条件下，当L<2.24D时，超声速喷流撞击地面会形成强烈的激波，随着离地高度的降低，该激波位置往喉部方向移动，由于壁面效应，喷管内部形成斜激波，导致中心喷管壁面处的温度升高；中心喷管相对外侧喷管往外突出增大了壁面流动速度，导致外侧喷管出口的温度降低；研究还表明子级火箭底部端面的喷管数量增加后，会导致喷管的温度升高。研究结果将为火箭发射及回收方案选取提供参考。

Investigations on the Influence of Engine Layout and Jet Wall Effect During Vertical Rocket Landing

In the present work, the jet flow structure of a rocket vertical landing is investigated. The impact of the wall effect and rocket engine distribution on the supersonic-impinging jets is studied by the CFD method. The results show that the wall effect hardly impacts the temperature distribution of the nozzle exit when the landing distance(L) varies from 2.24D to 11.2D. At the current calculation conditions, when L<2.24D, the supersonic jet forms a strong shock wave at the nozzle exit because of the wall effect. The shock wave location trends towards the throat as L decreases. Oblique shock waves are found at the exit edge of the center nozzle, resulting in a temperature increase at the inner wall. The near-wall air velocity would increase as the offset of the exit stretch, leading to a temperature decrease. The results also show that the nozzle exit temperature increases as the number of nozzles increases. The present findings would guide the selection of rocket landing and launch schemes in future studies.