中心支板式RBCC发动机引射模态流动与燃烧研究

Flow and Combustion of Central-Strut Based RBCC Engine in Ejector Mode

关键词:  组合循环发动机  引射模态  燃烧  空气引射  掺混  预混燃烧

Key words:  Combined cycle engine  Ejector mode  Combustion  Air entrainment  Mixing  Premixed combustion

摘要:

为了深入认识引射模态工作机理，针对中心支板式RBCC发动机，在飞行马赫数2、不同内置火箭流量时的工作情况进行了全流道一体化的数值模拟，并对其内流场特征、火箭射流/引射空气掺混发展特征以及复合型释热规律和火焰结构等开展了详细分析。研究发现：RBCC发动机引射模态下的流动掺混燃烧过程是一个复杂且高度耦合的过程。在即时预混燃烧（SMC）模式下，燃烧过程主要在内置火箭射流与来流空气之间形成的剪切层内进行；流道上游剪切层厚度较薄，温度和组分浓度梯度较大，掺混速率快；高释热区集中分布在流道上游，可分为超声速释热区和亚声速释热区；流道内的燃烧反应以扩散燃烧为主，随着掺混过程的进行逐渐向预混燃烧过渡。提高火箭流量，流道内温度升高，反应持续距离增加，但掺混效率降低。

Abstract:

In order to realize a deeper understanding of the operational mechanism in the ejector mode， fully channel integrated numerical simulations were carried out on a central-strut based RBCC engine within different built-in rocket operational conditions at a typical flight Mach number of 2. In detail， the internal flow characteristics， the mixing and development characteristics of rocket jet and entrained air， as well as the heat release and flame structure were analyzed. It has been found that the mixing and combustion process in the RBCC engine adopting the Simultaneous Mixing and Combustion（SMC） cycle in the ejector mode was a complex and highly coupled process. In SMC combustion mode， the combustion was mainly carried out in the shear layer formed between the built-in rocket jet and the incoming air. The thickness of the shear layer at the upstream of the flow channel was thinner， the gradients of temperature and component concentration were larger， and the mixing rate was higher. The high heat release zone was mainly distributed in the upstream of the channel， which could be divided into supersonic and subsonic heat release zones. The reaction in the channel was mainly diffusion combustion， and gradually transited to premixed combustion along with the mixing process. With the increase of the rocket mass flow rate， the temperature and the reaction distance increases， however， the mixing efficiency decreases.