An axisymmetric model scramjet assisted with cavity flameholder is numerically investigated. Three-dimensional Reynolds-averaged Navier-Stokes simulation is carried out to reveal the fuel mixing and combustion characteristics. The simulation results show reasonable agreements with experimental data. The analysis indicates that the axisymmetric and rectangular scramjet has some similarities to the cavity shear layer in the nonreacting flow field. The configuration of the cavity shear layer changes hugely due to the significant chemical reaction and heat release in the reacting flow field. Typically, two more configurations with different cavity aft wall angles are compared with the experimental configuration to optimize the configuration of the cavity. When the cavity aft wall angle is small, the cavity shear layer bends to the cavity floor and more fuel enters into and stays in the cavity, which results in poor fuel mixing performance. With the increase of the aft wall angle, the fuel distributes more uniformly and the fuel mixing efficiency improves. In the reacting flow field, the volume of the cavity full of hot products and free radicals increases while the interaction between the cavity and main flow decreases with the increase of the aft wall angle. The improved combustion efficiency shows that larger cavity volume weighs more than reduced interaction between the cavity and main flow. The combustion is more violent in the case with a larger aft wall angle. Therefore, a proper increase of the aft wall angle is beneficial to the performance of cavity-assisted axisymmetric scramjet when designing the cavity flameholder.

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不同后壁角空腔辅助轴对称模型超燃冲压发动机数值研究

对空腔火焰稳定器辅助的轴对称模型超燃冲压发动机进行了数值研究。进行三维雷诺平均 Navier-Stokes 模拟以揭示燃料混合和燃烧特性。仿真结果与实验数据显示出合理的一致性。分析表明，轴对称矩形超燃冲压发动机与非反应流场中的空腔剪切层有一些相似之处。由于反应流场中显着的化学反应和放热，腔体剪切层的配置发生了巨大变化。通常，将具有不同腔后壁角度的另外两种配置与实验配置进行比较，以优化腔的配置。当腔体后壁角较小时，腔体剪切层向腔体底部弯曲，更多的燃料进入和停留在腔体中，导致燃料混合性能差。随着后壁角的增大，燃油分布更加均匀，燃油混合效率提高。在反应流场中，随着后壁角的增加，充满热产物和自由基的空腔体积增加，而空腔与主流之间的相互作用减小。改进的燃烧效率表明，较大的腔体体积比减少腔体和主流之间的相互作用更重要。后壁角越大燃烧越剧烈。因此，在设计空腔火焰稳定器时，适当增大后壁角有利于空腔辅助轴对称超燃冲压发动机的性能。