Research on mixing characteristics of scramjet combustor equipped with strut injector

•The mixing performance with single nozzle and multiple nozzles are analyzed.•The mechanism and influencing factors of separation zone and vortex are discussed.•The fuel diffusion characteristics with the action of vortex are investigated.•The vortex development and mixing performance with oxygen supplement is discussed. The combustor is the core component of the scramjet. The mixing of fuel and oxidizer is an important prerequisite for the efficient operation of the combustor. A thin strut configuration with supplemental oxygen at the trailing edge is proposed to enhance the mixing of fuel and oxidizer. In this paper, a series of large eddy simulations are carried out at the combustor inlet conditions of Ma = 2.8, Tt = 1680 K, and Pt = 1.87 MPa to optimize the fuel injection strategy and clarify how supplementation oxygen affects the mixing performance. The results show that injecting fuel from the upstream nozzle will form a more complex flow separation region and a stronger vortex, and increase the mixing efficiency from 0.18 to 0.26 compared with the downstream nozzle. The diffusion of fuel interacts strongly with vortexes. A unique separation zone was observed near the upstream nozzle for the first time. Compared with a single nozzle of fuel injection, the coordinated injection of two nozzles can increase the dimensionless fuel penetration depth by 30%. Supplementing oxygen at the trailing edge of the strut can significantly increase the turbulence to generate a variety of vortices and enhance the mixing of fuel and oxidizer, and the mixing efficiency can be increased by more than 20%.