SMC模式下RBCC发动机4 Ma工况性能仿真

为研究SMC模式下火箭混合比对RBCC发动机性能的影响规律,完成了氢/氧火箭推力室中心布局、二元定几何结构模型发动机飞行马赫数Ma₀=4、高度H=17 km弹道点流场仿真,获得了不同火箭混合比(MR=2、3、4、5、6、8)及燃烧室长度的推力、比冲性能。研究表明:在火箭燃气富燃条件下(MR<8),产生了正的火箭推力增益,且随着混合比的减小,火箭推力增益增加;二次燃烧过程受火箭射流与冲压主流剪切层掺混主导,在给定的基准燃烧室长度下,燃烧效率随着混合比的提高而增加,且火箭射流与冲压主流的超/超射流剪切层燃烧过程一直持续到喷管出口;通过增加燃烧室长度,火箭富燃燃气获得更为充分的燃烧,发动机性能显著提升,但在具体发动机设计中,燃烧室长度的选取需在燃烧效率与结构惩罚之间进行权衡。

Performance simulation of 4 Ma operating condition under SMC mode for RBCC engine

In order to obtain the influence of rocket mixing ratio on RBCC engine performance under SMC mode,the flow field simulation of Ma₀=4、H=17 km was conducted for the engine with the center layout of H₂/O₂rocket trust chamber and two-dimension fixed structure.The engine thrust and specific impulse of different rocket mixing ratio(MR=2,3,4,5,6,8)and combustor lengths were analyzed also.The studies indicates that:1)Positive rocket thrust augmentation is obtained when the rocket operating under rich-fuel state(MR<8),and rocket thrust augmentation reduces with the rocket mixing ratio increasing;2)The secondary combustion process is dominated by the shear layer mixing effect between the supersonic rocket gas jet and the supersonic air flow captured by ramjet combustor.Under the given reference combustor length in this paper,the combustion efficiency increases with the improvement of mixing ratio,and the supersonic/supersonic jet shear layer combustion process lasts until the nozzle outlet;3)Engine thrust and specific impulse can be significantly enhanced by increasing the combustor length so that the rocket fuel-rich gas can be fully burned.However,in the specific engine design,the selection of the combustor length should be balanced between the combustion efficiency and the engine structure penalty.