水蒸汽凝结对超声速风洞蒸汽引射系统的影响

Effect of vapour condensation on hot steam ejector system of supersonic wind tunnel

蒸汽引射方案是引射式超声速风洞的可选方案,为考察该方案产生凝结激波的条件及其水蒸汽凝结对引射系统性能的影响,在F luent平台上采用自定义模块耦合希尔动量模型,编写了能模拟高速气流中水蒸汽凝结的计算程序。校验了数值模型和方法的可靠性。在此基础上,对蒸汽引射流场内的水蒸汽凝结问题进行了初步数值研究。得到喷管、引射流场参数以及液滴质量百分数、结核增长率的分布。结果表明:(1)水蒸汽凝结主要发生在引射喷管和喷管出口膨胀区中。其中,在引射喷管内的蒸汽凝结占大部分。凝结核增长为主要特征。(2)初始结核区位于超声速气流是凝结激波产生条件。采用饱和蒸汽引射可避免产生凝结激波。(3)尽管是否考虑凝结/无凝结效应会造成引射流场产生差异,但两者总体相似。(4)水蒸汽凝结会给引射系统带来较大的性能损失,但通过改进气动轮廓可减小其影响。

Hot steam ejector is a candidate for combustion-heated supersonic wind tunnel. The purpose aim of this study is to predict the vapour condensation and its effect on ejector performance. The Hill model of moment, which is used to describe natural condensation of steam in high-speed flow, was incorporated into commercial software Fluent by UDF. The method was validated by a question of a nozzle steam flow. Then, the subscale hot steam ejecting system was preliminarily designed and predicted numerically. The results show that （ 1 ） Vapour condensation occurs in ejector nozzles as well as at the regions just downstream the nozzle exit. The condensed nuclei grow up continuously in these regions. （2） If the condensing nucleation starts in the supersonic flow, this leads to the generation of the condensation shock. But this phenomenon can be avoided by using saturated vapour. （3） Although the flow fields are a little different from the conditions whether the condensation is considered in the model, they are generally similar except the distribution of Mach number and temperature. （4） Steam condensation results in a large performance loss of the hot steam ejector, but it can be reduced by the optimization of nozzle contours.