Performance Research On Ejectorjet Mode Of Rocket Based Combined Cycle (RBCC)

Rocket Based Combined Cycle (RBCC) will be one of the promising propulsion systems for single stage to orbit vehicle, and has extensively application foreground in both military and civil usage. Ejectorjet is the alternative power of RBCC during low-speed operation. The utilization of ejectorjet will be important for structural integration, and will decrease weight and complexity of the engine. Theoretical, numerical computation and experimental approaches are used in this paper to investigate the problem of structure integration and performance strengthen on ejectorjet.In the theoretical aspect, secondary combustion in ejectorjet and thermal throat was researched. Theory of duct flow was conducted, the difference and homology between heat added flow and entropy fixed flow was described. In divergent duct, adding heat can substitute the usage of geometry structure whatever mach number is. From force and thermodynamic cycle aspects, the effect of every components on engine performance was discussed. It indicates that thermal throat can substitute geometry throat, so structure integration can be achieved in ejectrojet mode. In addition, it showed that thermal throat will increase engine thrust and decrease specific impulse.In numerical computation aspect, by implying new computational geometric field, computation error caused by boundary condition was decreased. The effect of area ratio, Mach number, total pressure of primary rocket and geometry structure of primary rocket on ejectorjet performance was studied. The main results are: supersonic region and subsonic region can co-exist in flow path simultaneously, subsonic flow is insignificance for engine performance; total pressure of primary rocket should be decreased when Mach number is increased.In the experimental aspect, some components of ejectorjet experimental system were improved, ejectorjet experiments using alcohol as secondary fuel were conducted. The effect of secondary fuel nozzle location, the mass flow rate of secondary fuel and outlet area of ejectorjet were studied. The main results are: the geometry structure of ejectorjet can be compatible with other RBCC operation modes by secondary combustion organization; the distribution of secondary fuel on ejectorjet cross section is significant forsecondary combustion stability. SPI combustion organization method is promising.Thrust augmentation of ejectorjet can be obtained by adding heat in supersonic main flow. Structure design and operation parameter adjust should follow this rule. Secondary combustion should mainly heat the supersonic flow. SPI combustion organization has the latent to improve ejectorjet performance.