燃烧室工作过程对冲压发动机性能潜力的影响研究

Study on the relation between performance and process in combustor for dual-mode and ram jet engine

用准一维分析方法,在相同的入流条件下,假设将当量比为1的燃料热量全部添加到气流中,研究了燃烧室工作过程与性能之间的关系。结果表明,随着特征马赫数的增加,在相同飞行马赫数下,亚声速燃烧室所需扩张比逐渐减小,而双模态燃烧室所需扩张比逐渐增大;亚声速燃烧室出现所需最小扩张比和最大比冲的特征马赫数分别是1和0,双模态燃烧室在最小特征马赫数时所需扩张比最小,获得的比冲最大,且与亚声速燃烧室能获得的最大比冲相差不大,在飞行马赫数4、5、6时,差值分别为5%、4%、3%;特征马赫数在亚声速范围内变化时发动机比冲的曲线比较平缓;壁面摩擦系数的变化对燃烧室所需扩张比的影响大于对比冲的影响。直连式实验获得的等截面燃烧室极限加热量数据证明了本方法的合理性。

In this paper the relation between the process and performance in a dual-mode and a ram （subsonic） combustor is studied with a quasi one dimensional method. It is proposed that the two kinds of combustors have the same incoming flow conditions when the flight Mach numbers are the same, and the fuel energy is fully added into the flow with the equilibrium ratio of 1. A term of combustor characteristic Mach number is defined in this paper. In a subsonic combustor, it is the Mach number at the section just upstream the nozzle; In a dual mode combustor, it is that in a divergent part where the flow Mach number will keep constant. The results indicate that, with the same incoming condition, the needed divergent ratio of the subsonic combustor de- creased and that of the dual-mode combustor increased as the combustor characteristic Mach num her increased. For the subsonic combustor, the minimal divergent ratio and maximal performance correspond to the characteristic Mach number of 1 and 0 respectively. For the dual-mode combus- tor with the minimal divergent ratio, the maximal performance is achieved when the characteristic Mach number tends to be minimal. The minimal divergent ratio for the two kinds of combustors is about the same. The maximal performance for the dual-mode combustor is a little lower than that for the subsonic one. At flight Mach number of 4, 5 and 6, the difference is about 5~, 4~//00 and 3 ~ respectively. The comhustor divergent ratio is affected by the wall friction seriously, but the performance slightly. A few experiment results obtained in a direct-connected combustion test with a dual-mode combustor and transformed into the heat-limit for the correspond section, have validated this method.