Numerical study on a novel device for hydrogen mixing enhancement in a scramjet engine: Coaxial injector

The mixing process between the fuel and air is very important for the efficient operation of the scramjet engine, and it has attracted an increasing attention all over the world. In this work, the coaxial injector was developed and investigated by means of the three-dimensional Reynolds-averaged Navier-Stokes equations coupled with the SST k-ω turbulence model, and the numerical approaches were validated against the non-dimensional experimental streamwise velocities in four different streamwise positions on the symmetry plane. Further, the influence of the jet-to-crossflow pressure ratio for the hydrogen and air is evaluated numerically as well. The obtained results show that the mixing process induced by the coaxial injector is conducted more quickly, and it is a promising mixing enhancement device for the scramjet engine. The smallest value of the mixing length for the cases studied in the current study is 1.69. It brings nearly no additional total pressure loss when compared with the single injector, and the jet-to-crossflow pressure ratio has only a small impact on the total pressure recovery coefficient.