Certain Investigations of Numerical Simulation on Supersonic Combustor of Staged Transverse Injection behind a Backward Facing Step with Cavity

Abstract

Within the available space and residence time constrain, it is a herculean task to design scramjet combustor. Numerical simulation is carried out to investigate the cavity formation in the scramjet combustor model with staged transverse injection behind the backward facing step (BFS). This paper presents the result of a numerical study that investigates the effect of four different scramjet combustor models on fuel mixing characteristics with Free-stream air at Mach 2, and the fuel injection through both the injectors at Mach 1. In this study, the flow is treated as non-reacting (Cold flow) and the fuel is injected normal to the free-stream direction. Numerical simulation is accomplished by employing the finite volume based code Computational Fluid Dynamics (CFD) ANSYS/Fluent-14 with two equation turbulence models (Shear Stress Transport K-ω). The performance characteristics of the scramjet combustor is assessed by the following parameters such as maximum mole fraction of injectant (fmax), streamwise vorticity (ζ), average stagnation pressure (Poavg) and air fuel mixing efficiency (m). In order to study the performance of the scramjet combustor with cavity formation with staged transverse injection behind the BFS, four different scramjet combustor models are created by introducing a slab between the injectors. The slab shape for the first one is a rectangular, followed by triangular with right side ramp, then triangular with left side ramp and wedge (both side ramp). In all four models, the slab is placed at mid portion of total distance between the staged transverse injector. The study reveals that the air fuel mixing efficiency of the Triangular slab with left side ramp (TLR) placed at a mid portion of the total length between staged injectors comparatively better off than the other cases.