超高速流动气动热及壁面催化效应试验研究

Experimental study on aerodynamic heat and wall catalytic effects of hypervelocity flow

飞行器以近、超轨道速度进入或再入大气层时必须经受超高速流动环境的考验,强激波压缩产生的高焓气流会对飞行器造成剧烈的气动加热作用,此时气动热载荷的准确预测变得尤为困难.膨胀管/风洞是少数几种具备超高速流动模拟能力的地面设备之一,中国科学院力学研究所的JF-16膨胀风洞已成功获得了速度超过10 km/s的超高速试验气流,并在此基础上开展超高速流动气动热测量及壁面催化效应相关试验研究.在高温、强冲刷气流,微秒量级试验时间内,获得了近、超轨道速度气流条件下标准球模型的驻点热流结果,在试验气流总焓超过45 MJ/kg时,模型驻点热流试验测量结果超出了经验公式及CFD完全催化条件的预测值.同时,对表面镀有两种不同催化特性材料的标准球模型进行了对比试验,试验结果表明,催化壁面(Cu镀膜)比非催化壁面(Al2O3镀膜)的驻点热流率高出53.93%.数值分析表明,超高速流动模型驻点处在非催化条件下仍保留有22.5%的O原子和37.3%的N原子成分,而在完全催化条件下则全部复合成分子并引起热流显著增加,这一分析证实了试验结果与试验发现.

When aircraft enter/reenter the atmosphere at near and super-orbital speeds, such aircraft need to endure challenges posed by a hypervelocity flow environment. High enthalpy gas generated by strong shock wave compression causes violent aerodynamic heating to such aircraft. At this time, accurately predicting the aerodynamic thermal load becomes extremely difficult. Expansion tubes/tunnels are one of the few types of qualified ground facilities that can simulate hypervelocity flow. The JF-16 expansion tunnel at the Institute of Mechanics, Chinese Academy of Sciences, has successfully generated hypervelocity flows with speeds of more than 10 km/s. Accordingly, experiments have been conducted measuring the hypervelocity aerothermal and wall catalytic activity. The stagnation heat flux of a spherical model at high temperature and strong scour test flow with near and super-orbital velocities was successfully obtained at microsecond resolutions. It was found that the experimental stagnation heat flux is higher than the predicted levels according to the empirical formula and CFD simulations when the total enthalpy of the test gas is greater than 45 MJ/kg. In addition, the experimental stagnation heat flux based on a fully catalytic wall(with a Cu coating) is 53.93% higher than that based on a non-catalytic wall(with an Al2O3 coating). The numerical analysis indicated that 22.5% O and 37.3% N atoms remain at the stagnation point of the model under the non-catalytic condition. Meanwhile, under the fully catalytic condition, the atoms are all combined and cause a significant increase in the heat flux at the stagnation point. This analysis confirmed the experimental results.