The effects of back pressure and cavity L/D ratio on the shock wave structure in the cold flow field of a typical cavity-based scramjet combustor with combined inlet and isolator is investigated numerically in the selected scramjet models. The scramjet with a throat ratio of TR 0.0 and cavity L/D 6.04 was analyzed. To perform such analysis, steady, 2-D RANS was used with SST k-ω. From the analysis, the value of static pressure along the cowl surface, contours of Mach number and pressure were obtained. The scramjet was modeled with different TR 0.1, 0.2, 0.25 and 0.3 with the same cavity L/D 6.04 and different cavity L/D 4.04, 9.04 and 12.04 with the same TR 0.25. All the models were analyzed with the same inlet conditions and the results were obtained. From the analysis, it was observed that the increase in back pressure moves the shock train towards the inlet of the isolator which leads to ‘engine unstart’ after the throat ratio of TR 0.1. Also, it is observed that there is an optimal L/D ratio of the cavity L/D 9.04 which restricts the propagation of high-pressure waves obtained in the combustor.

中文翻译：

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典型的带双入口的基于腔的超燃冲压燃烧器冷流场的数值研究

在选定的超燃冲压发动机模型中，以数值方式研究了背压和空燃比L / D比对典型的基于腔的超燃燃烧器的进气口和隔离器组合的冷流场中冲击波结构的影响。分析了喉比为TR 0.0和腔体L / D为6.04的超燃冲压发动机。为了进行这种分析，将稳定的2-D RANS与SSTk-ω一起使用。通过分析，获得了沿前围表面的静压值，马赫数轮廓和压力。用相同的腔L / D 6.04和不同的腔L / D 4.04、9.04和12.04用相同的TR 0.25对不同的TR 0.1、0.2、0.25和0.3建模超燃冲压发动机。在相同的入口条件下分析了所有模型，并获得了结果。根据分析，可以观察到，背压的增加将冲击波移向隔离器的入口，这导致在TR 0.1的咽喉比之后“发动机启动”。同样，观察到腔L / D 9.04具有最佳的L / D比，这限制了在燃烧器中获得的高压波的传播。