RBCC直扩燃烧室煤油喷雾燃烧火焰稳定与放热规律的数值模拟

Numerical Investigation of Flame Stability and Heat Release Laws of Kerosene Spray Combustion in RBCC Engine

扩张构型燃烧室的燃烧流动细节与放热规律是RBCC发动机设计中的核心技术。采用湍流流动的分离涡(DES)计算方法,数值计算了RBCC燃烧室以凹腔作为火焰稳定器的液态煤油喷雾燃烧三维两相流动。针对逐级扩张的RBCC燃烧室构型,详细研究了不同来流状态下的喷雾燃烧流动特征以及液态煤油分级喷注的放热规律。研究表明,高来流总温条件下,凹腔火焰稳定器可起到驻留火焰的作用,在相对较低来流总温条件下,凹腔并非是实现火焰稳定的充分条件,必须采用其他方式补偿液态燃料蒸发吸热所损失的热量。考虑到扩张构型的几何通道承受的压力提升范围有限,燃料喷注位置不宜安置在燃烧室上游流场;为了实现最大的燃烧效率以及发动机推力,采用前后级辅助喷注的方式是目前可行的解决措施。

The flame stability and heat release laws of kerosene spray combustion are the core technologies in RBCC engine. The Detached Eddy Simulation numerical method is used to investigate the performance of RBCC engine under different incoming flow conditions. The analytical results show that under the condition of high incoming total temperature, the cavity can play the role of flame stabilization, but under the relatively low incoming flow total temperature condition, cavity could not achieve a sufficient promise for stability of the flame. It must use other method to compensate the loss of heat caused by liquid kerosene evaporation. Considering the pressure in combustion chamber will affect the inlet working condition directly, the position of fuel injection should not be in front of the chamber, further, in order to achieve the maximum combustion efficiency and engine thrust, multi- stage fuel injection approach that combined the upstream and downstream fuel injection is the feasible solution.