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首页> 外文期刊>Journal of Thermophysics and Heat Transfer >Matching Flight Conditions on Sharp Leading Edges in Plasma Wind Tunnels
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Matching Flight Conditions on Sharp Leading Edges in Plasma Wind Tunnels

机译：等离子风洞中尖锐前沿的匹配飞行条件

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In free-flight blunt bodies exhibit a heat flux that, in the most severe reentry conditions, may amount to 50% higher for a fully catalytic wall than for a noncatalytic wall. Conversely, sharp bodies behave differently from blunt bodies when catalytic effects are taken into account: typically in free flight stagnation point heat flux for a sharp body is not greatly different (say about 10%) between a fully catalytic and a noncatalytic wall.rnWhen simulating the aerothermochemistry in a plasma wind tunnel of arc-jet type the catalytic characteristics of the wall are much more important than for free-flight conditions for both sharp and blunt bodies because of the large dissociation degree of both O_2 and N_2 in the test chamber airflow (which results from freezing of the composition in the nozzle). PWT testing at the same values of H_∞ and p_(02) may yield values of stagnation point heat transfer for a fully catalytic wall that may be 3 times larger than values for a noncatalytic wall. Thus, catalytic behavior is a relevant issue in PWT tests, as shown by CFD cases.rnThe third conclusion refers to the duplication of free-flight conditions in PWT with the same materials of free flight, (i.e., the same surface catalytic properties) at the same scale. It is simpler to simulate blunt bodies than sharp bodies. In the first case conditions in the shock layer are not expected to be dramatically different between free flight and PWT at the same H_∞ and p_(02). For fully catalytic sharp bodies duplication of the above parameters corresponds to the same heat fluxes. A dramatic difference does exist, however, when simulating a sharp noncatalytic body reentry because of the difficulty of reaching high values of (V_∞)_t in the tunnel: when trying to increase the energy content of the air stream above a certain value (say H_∞ ≈ 20 MJ/kg) by inputting more energy per unit mass, the surplus goes into dissociation energy that does not participate in the heat transfer to noncatalytic walls. The only choice is to have higher pressures rather than a larger H_0.
机译：在自由飞行中，钝态物体的热通量在最严酷的折返条件下，对于完全催化的壁，其热通量可能比非催化壁的热通量高50％。相反，当考虑到催化作用时，尖锐物体的行为与钝体不同：通常在自由飞行停滞点，完全催化和非催化壁之间的锋利物体的热通量相​​差不大（例如约10％）。电弧喷射型等离子风洞中的空气热化学，对于尖锐和钝体，壁的催化特性比自由飞行条件重要得多，因为测试室气流中O_2和N_2的解离度都很大（这是由于喷嘴中的成分冻结所致）。在相同的H_∞和p_（02）值下进行PWT测试可能会产生完全催化壁的停滞点传热值，该值可能是非催化壁的3倍。因此，正如CFD案例所示，催化行为是PWT测试中的一个相关问题。rn第三结论是在相同的自由飞行材料（即相同的表面催化特性）下，PWT中自由飞行条件的重复。一样的规模。模拟钝体比锐化体更简单。在第一种情况下，在相同的H_∞和p_（02）下，自由飞行和PWT之间的冲击层条件预计不会有显着差异。对于完全催化的尖锐物体，上述参数的重复对应于相同的热通量。但是，由于难以在隧道中达到（V_∞）_t的高值，因此在模拟急剧的非催化物体折返时确实存在巨大的差异：当试图将气流的能量含量增加到某个值以上时（例如H_∞≈20 MJ / kg），通过在单位质量中输入更多的能量，多余的能量就会分解为不参与热量传递至非催化壁的离解能。唯一的选择是具有更高的压力，而不是更大的H_0。

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