Parametric study on mixing augmentation mechanism induced by air injection in a shock-induced combustion ramjet engine

The fuel-air mixing process plays an important role in the shock-induced combustion ramjet (shcramjet) engine. In the current study, the investigation of front fuel jet and rear air jet is provided in order to study the mixing effect induced by the air jet and reveal the mixing augmentation mechanism and formation of several recirculation zones. Some parameters are also provided to evaluate the flow field properties quantitatively, namely the mixing efficiency, the total pressure recovery coefficient, the fuel penetration depth and the mixing length. The obtained results predicted by the three-dimensional Reynolds-average Navier-Stokes (RANS) equations coupled with the two equation shear stress transport (SST) k-omega turbulence model show that the additional air jet is really beneficial for accelerating the mixing process and improving the mixing efficiency. The shear vortex and air injected are the key sources for the mixing enhancement mechanism of the dual injection strategy. The formations of recirculation zones midstream and downstream are provided as well. The midstream recirculation zone "R-2" is related to both front fuel jet and rear air jet, and "R-3" is related to the air jet only. The downstream recirculation zone1 is composed by flows from the fuel jet and the air jet, and the downstream recirculation zone2 is formed by hydrogen flows. (C) 2019 Elsevier Ltd. All rights reserved.