Mixing augmentation mechanism induced by the dual injection concept in shcramjet engines

As one of the key techniques, achieving adequate fuel/air mixing before combustion is a task that must be addressed seriously for shock-induced combustion ramjet (shcramjet) engines. In this paper, dual injectors which have been combined by a front hydrogen jet and a rear air jet with different aspect ratios are placed on the second ramp of a shcramjet inlet to promote mixing process between fuel and hypersonic crossflow. At the same time, dual injectors with pure hydrogen injection and the single hydrogen injection with the same injection area are studied as well for comparison. Flow field properties are investigated numerically based on grid independency analysis and code validation. Obtained results predicted by the three-dimensional Reynolds-average Navier-Stokes (RANS) equations coupled with the two equation SST ( )kappa - omega turbulence model show that the grid scale makes only a slight difference to wall pressure profiles for all cases studied in this article. The dual transverse injection system with a front hydrogen jet and a rear air jet is beneficial for improvement of the mixing efficiency between hydrogen and air. Mixing efficiency in the near field increases with increase of aspect ratio of the air porthole. The air porthole in dual transverse injections would accelerate mixing process when compared with the single injection strategy irrespective of aspect ratio of the air porthole.