变结构RBCC发动机亚燃模态全流道数值模拟研究

Ramjet Mode of Variable Geometry RBCC via Full Flow Path Numerical Simulations

变结构燃烧室是提高宽范围工作火箭基组合循环(Rocket-based combined-cycle,RBCC)发动机性能的有效途径之一。通过全流道三维数值模拟的方法,研究变结构RBCC发动机在低来流马赫数条件下燃烧室与进排气匹配状况,以及采用变结构燃烧室进行亚燃模态可靠燃烧组织的可行性。针对Ma=3来流,研究了火箭冲压和纯冲压燃烧模式下的发动机性能,并实现了燃烧室工作模式的转变。通过研究得到以下结论:(1)在火箭冲压工作模式下,一次火箭小流量工作能够提高二次燃料的燃烧效率,冲压燃烧室比冲性能较优,燃烧室与进排气能够匹配工作。(2)燃烧室工作在火箭冲压模式时,采用燃料支板集中喷注燃料的性能优于隔离段和燃料支板分散喷注时性能;发动机工作在纯冲压模式时,燃烧效率将会下降,并且发动机冲压比冲比火箭冲压工作模式下降10.2%,全流道比冲则上升14.5%。

The use of a structurally variable combustor is one of the most effective methods to improve the performance of a rocket-based combined-cycle(RBCC)engine over a wide operating range.Aims to study the matching between the combustor and the inlet/exhaust of a variable geometry RBCC engine at low inflow Mach numbers via full flow path of three-dimensional numerical simulations.Furthermore,focus on the feasibility of using a variable geometry combustor to carry out a steady secondary fuel combustion organization in ramjet mode.Under the inflow condition of Ma=3,the engine performances were studied based on the rocket-ramjet and pure ramjet combustion mode,and the transition of the engine from the rocket-ramjet mode to the pure ramjet mode was obtained in the variable geometry ram combustor.Concluding remarks are summarized as:(1)In the rocket ramjet mode,the primary rocket has obvious positive effects on improving the secondary fuel combustion efficiency and results in a higher ramjet specific impulse.Matching of the combustor and inlet/exhaust has been realized under the rocket-ramjet mode.(2)In the rocket ramjet mode,improvement of the engine performances prefers a concentrated fuel injection rather than a dispersed injection through isolator section and pylons.In the pure ramjet mode,the specific impulse of the full flow path increases by 14.5%,compared with in the rocket-ramjet mode,despite the decrease of ram specific impulse by 10.2% due to a worsen combustion efficiency.