CO2中速度5~7 km/s自由飞圆球流场参数的实验测量和数值模拟

Measurement and numerical simulation of flow field parameters of free flight spheres with flight velocity from 5 to 7 km/s in CO2

为研究火星进入条件下的非平衡流动特性,在中国空气动力研究与发展中心超高速空气动力研究所弹道靶上测量了CO 2中针对火星探测器进入速度范围5~7 km/s条件下的自由飞圆球的激波脱体距离。实验数据基于阴影法测量,并将其与数值计算结果进行对比,进一步计算了实验流场温度和组分分布等流场参数。一般认为激波脱体距离随来流速度升高而呈单调减小趋势,但研究结果表明:实验状态下,圆球飞行速度约5.5~7.0 km/s的范围内,圆球激波脱体距离随飞行速度升高而增大;采用Park的双温度非平衡模型和5组分6反应的CO 2化学反应动力模型可基本再现本文自由飞圆球激波脱体距离的实验测量数据;根据计算结果推测,本实验状态下自由飞圆球波后靠近激波一侧区域的流场主要处于热化学非平衡状态;当来流速度在约5.5~7.0 km/s的范围内时,流场组分CO开始发生显著离解,是引起圆球激波脱体距离在该速度范围内随速度升高反而增大的可能原因。

To investigate the nonequilibrium flow characteristics under Mars entry condition,shock standoff distances over free flight spheres with flight velocities from 5 to 7 km/s in CO 2 are measured in the ballistic range at Hypervelocity Aerodynamics Institute of China Aerodynamics Research and Development Center(HAI,CARDC).Test data are measured by the shadowgraph and compared with calculated results,based on which the temperature and species profiles of the test flow field are further calculated.Shock standoff distance is generally supposed to decrease monotonously as the free steam velocity increases.However,it is found through the present test results that,the shock standoff distances over spheres actually increase with the increase of the flight velocity from 5.5 to 7.0 km/s.Using Park’s two-temperature model and a 5-species 6-reactions chemical reaction model can basically reproduce the measured shock standoff distances of the present test.It is shown from the test results that the flow field shortly after the shock over the spheres is mainly in theromchemical nonequilibrium.The specie CO starts to dissociate at the free stream velocity from 5.5 to 7.0 km/s,which is the possible cause of the increase of the shock standoff distances over spheres within this range of velocity.