基于RANS/LES混合方法的双模态超燃冲压发动机燃烧室工作过程研究

双模态超燃冲压发动机模态转换过程中燃烧室内的流动燃烧现象高度复杂，给RANS/LES混合方法的应用带来了新困难。本项目拟基于RANS/LES混合方法开展双模态超燃冲压发动机燃烧室工作过程研究。首先，对DES类模型应用于超声速湍流燃烧流动数值模拟所呈现的性能开展评估工作，在此基础上建立考虑燃烧化学反应效应的可压缩DES改进模型，以提高其模拟超声速湍流燃烧流动的精度；其次，发展与可压缩DES类模型相匹配的“回收/调节”入口湍流脉动生成方法，缩减DES模拟复杂流动的庞大计算耗费，以期进一步将其推广至工程应用。最后，通过上述研究获得的适用于高速可压缩湍流燃烧流动RANS/LES技术，开展双模态超燃冲压发动机模态转换过程的高精度DES研究，掌握真实状态下飞行马赫数变化导致的模态转换过程中燃烧室内非定常流动燃烧特性，进而探索抑制火焰振荡造成的发动机推力不稳定等问题的途径。

The flow and combustion phenomenons in dual-mode combustors during mode transitions are highly complicated, which bring new problems for the application of RANS/LES hybrid methods. The present project plans to study the combustor operation process in dual-mode scramjets by RANS/LES hybrid methods. Firstly, DES models are widely employed in the numerical simulation of non-reacting turbulent flows and we will evaluate its performance in the numerical simulation of supersonic turbulent combustion flows. Then, the improved compressible DES models considering the combustion chemical reaction effects will be established. Secondly, we will extend the “Recycle/Rescaling” methods for the generation of inflow turbulent fluctuations under the framework of DES methods, in order to decrease the large computational cost of the DES studies of complicated turbulent flows and further popularize it to the engineering applications. Lastly, the high-accuracy DES studies for the mode transition process in dual-mode scramjets will be conducted with the above advanced RANS/LES techniques, which are designed for the numerical simulation of supersonic turbulent combustion flows. The aim of the DES studies is to obtain the characteristics of unsteady flow and combustion in dual-mode combustors during mode transition process driven by the change of the flight Mach number. Furthermore, we will explore the schemes to depress the unsteadiness of thrust caused by the flame oscillation in dual-mode combustors and the ways to prevent other relative problems during mode transition process.