Combustor Structural Changes On The Rockets Lead The Performance Impact Of The Shooting Modes

Rocket Based Combined Cycle (RBCC) is getting much more attention than ever before for its excellent performance, which should be the most potential propulsion system for the next generation launch vehicle. Considering the same flow-path for various operating modes, variable geometry is considered to be the most efficient approach for achieving the best performance during the entire trajectory. Effect of variable geometry for combustor on the engine performance during rocket ejector mode is investigated.After investigating the research status abroad of wide range air-breathing engine, two major variable geometry concepts, fully variable geometry and partially variable geometry, were proposed. It's concluded that, for the large scale engine, the engine performance could be improved efficiently, getting much benefit with the fully variable geometry designed for both inlet and combustor. For small scale engine, partially variable geometry should be the efficient way to compensate the inert mass penalty.Theoretical analysis and computation study were taken out to investigate the best thrust performance under rocket ejector mode. Under the circumstance of reaching thermal chock, analytical solution of the combustor exit plane area for the maximum thrust was developed. Quasi-ID flow equations published previously were adopted for studying the effect of variable geometry on thrust under different flight Mach number. It's concluded that, there is a proper combustor exit plane area helpful for reaching maximum thrust; the combustor exit plane area should be increased with the flight Mach number increasing, insuring the exhaust expanding properly.Based on the commercial CFD code, Fluent(?), three-dimension numericalsimulation model for RBCC engine internal flow was established, considering the two-phase flow and chemical reaction. Validated by the experimental results of direct-connected test for RBCC, a bias less than 10% is acquired, proving the feasibility on the following numerical study.Utilizing the numerical model established, RBCC engine internal flow field were studied with both fixed geometry and variable geometry. It shows that, the engine performance is suffering from severely under-expansion on the exit plane, while variable geometry for combustor can relax the problem with a better performance. A flap with adjustable convergent or divergent angle for combustor, can improve the...