Characteristics of Condensation Shock Waves

对超音速喷管内湿空气膨胀引发凝结激波的凝结流动进行了数值模拟和实验研究，并在超音速凝结流动中插入楔形激波发生器，对凝结激波与斜激波的相互作用进行了实验研究。结果表明，凝结激波的特性得到了明确的体现。结果表明：(1)当喷嘴内发生冷凝时，空气的熵增大，水蒸气的熵减小。冷凝产生的液滴的表面熵略有增加。因此，由于这些效应，混合物的熵增加。总压损失的计算值略小于实验值，约为2%~5%。初始过饱和度越大，湿空气初始温度越大，喷嘴膨胀率越大，总压力损失越大。(3)明确了斜激波相对于冷凝区的位置和凝结时斜激波的形状变化。工作在喷管壁面上的载荷随着初始过饱和度和初始温度的增大而增大。(4)定性地解释了凝结激波与斜激波的相互作用规律。当正凝聚激波与斜激波相互作用时，斜激波在一定条件下消失。当凝结作用大于此状态时，正常凝结激波位于上游位置，斜激波从楔形前缘再次出现。

Condensing flow with a condensation shock wave initiated by an expansion of moist air in a supersonic nozzle was investigated numerically and experimentally, and then by inserting a wedge-type shock generator in the supersonic condensing flow, the interaction of the condensation shock wave with an oblique shock wave was investigated experimentally. As the results, the characteristics of condensation shock wave are clarified. The results obtaind are summarized as follows.(1) When condensation takes place in a nozzle, the entropy of the air increases and that of the vapor decreases. The surface entropy of a droplet generated by condensation increases a little. Therefore, the entropy of the mixture increases due to these effects. As the results, the total pressure of the flow decreases.(2) The calculated value of the total pressure loss are a little smaller than those of the experimental results and they are about 2 to 5 percent. The larger the initial degree of supersaturation, the initial temperature of moist air and the higher the expansion rate of nozzle are, the larger the total pressure loss becomes.(3) The position of the oblique shock wave relative to the condensation zone and the change of shape of the obligue shock wave due to condensation are clarified. The load working on the nozzle wall increases with an increasing in the initial degree of supersaturation and the initial temperature.(4) The interaction patterns of the condensation shock wave with the oblique shock wave are explained qualitatively. When a normal condensation shock wave interacts with an oblique shock wave, the oblique shock wave disappears under a certain condition. When the effect of condensation becomes stronger than this state, the normal condensation shock wave stands more upstream position and then the oblique shock wave appears again from the leading of wedge.