Large Eddy Simulation of the fuel transport and mixing process in a scramjet combustor with rearwall-expansion cavity
Large Eddy Simulation of the fuel transport and mixing process in a scramjet combustor with rearwall-expansion cavity
复制标题
后壁膨胀腔超燃冲压发动机燃烧室燃料输送和混合过程的大涡模拟
DOI：
10.1016/j.actaastro.2016.05.010
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发表时间：
2016
影响因子：
3.5
通讯作者：
Xue-Song Bai
中科院分区：
文献类型：
--
作者：
Zun Cai;Xiao Liu;Cheng Gong;Mingbo Sun;Zhenguo Wang;Xue-Song Bai
采用大涡模拟（LES）方法研究了带有后壁膨胀凹腔的乙烯燃料超燃冲压发动机燃烧室中的燃料/氧化剂混合过程。数值求解器首先验证了一个实验流，DLR支杆为基础的超燃冲压发动机燃烧室的情况下。将数值模拟得到的激波结构和壁面压力分布与实验数据进行了比较，数值模拟结果与实验数据吻合较好。研究了喷射位置对流动和混合过程的影响。研究发现，随着空腔上游喷射距离的增加，燃料被输送到主流中的距离要远得多，并且在空腔内形成较小的亚音速区。反之，喷射距离越短，燃料越多地被夹带到凹腔中，凹腔内部形成较大的亚音速区，这有利于凹腔内的点火。对于后壁扩张型凹腔，上游喷射距离较长时，最佳点火位置应在凹腔中部底壁;上游喷射距离较短时，最佳点火位置应在凹腔前侧底壁。通过在后壁上采用空腔直接喷射，由于这种燃料供给，空腔内的燃料质量分数和局部湍流强度都将增加，并且它还将增强混合过程，这也将导致混合效率增加。对于后壁膨胀型腔，组合喷射方案有望成为一种优化的喷射方案。
Large Eddy Simulation (LES) was employed to investigate the fuel/oxidizer mixing process in an ethylene fueled scramjet combustor with a rearwall-expansion cavity. The numerical solver was first validated for an experimental flow, the DLR strut-based scramjet combustor case. Shock wave structures and wall-pressure distribution from the numerical simulations were compared with experimental data and the numerical results were shown in good agreement with the available experimental data. Effects of the injection location on the flow and mixing process were then studied. It was found that with a long injection distance upstream the cavity, the fuel is transported much further into the main flow and a smaller subsonic zone is formed inside the cavity. Conversely, with a short injection distance, the fuel is entrained more into the cavity and a larger subsonic zone is formed inside the cavity, which is favorable for ignition in the cavity. For the rearwall-expansion cavity, it is suggested that the optimized ignition location with a long upstream injection distance should be in the bottom wall in the middle part of the cavity, while the optimized ignition location with a short upstream injection distance should be in the bottom wall in the front side of the cavity. By employing a cavity direct injection on the rear wall, the fuel mass fraction inside the cavity and the local turbulent intensity will both be increased due to this fueling, and it will also enhance the mixing process which will also lead to increased mixing efficiency. For the rearwall-expansion cavity, the combined injection scheme is expected to be an optimized injection scheme.