Effects of Fuel-Lean primary rocket on bypass ratio in RBCC ejector mode

As ejector modes of RBCC exist from takeoff to low supersonic flight speed and play an important role in the engine performance, a high bypass ratio is hence expected in order to improve the specific impulse. Basically, the bypass ratio varies with the primary rocket mixture ratio which results in a DAB or SMC mode in RBCC, hence CFD study was conducted in the paper to investigate the effects of fuel-lean primary rocket on the bypass ratio. The results showed that the bypass ratio increased when the primary rocket operated at fuel-lean conditions, on the contrary, a lower bypass ratio was resulted from a higher pressure in the combustion chamber. Studies were found also that second-fuel injection showed advantages by optimizing in positions and amounts on bypass ratio.