Numerical simulation of staged transverse injection of H₂ fuel in a ducted supersonic air stream with SST k-ω turbulence model

This work involves an application of computational fluid dynamics to a problem associated with the flow in the combustor region of a supersonic combustion ramjet engine (Scramjet). Numerical results are obtained with the FLUENT code solving SST-Kω turbulence model. Prior to the application of code to investigate the problem of interest, validation of the code was conducted with different test cases. The problem chosen is the staged normal injection of two jets of H2 fuel into a Mach 2 freestream of air behind a rearward facing step and the results obtained are compared with the available experimental results. To delineate the purely fluid dynamic effects, the flow is treated as nonreacting. The effect of grid resolution was investigated by obtaining solutions on grids of 99450 points, 276000 points and 589680 points. Since the differences in the solutions on the two finer grids of 276000 points and 589680 points were small, grid structure of 276000 points was used for detailed study. The profiles of static pressure, static temperature, two components of velocity and mole fraction of H2 at various locations of the flow field are presented. In order to assess the agreement between numerical and experimental values mean difference values are calculated. Computed values using SST-Kω turbulence model are found to have good overall agreement with experimental measurements and some discrepancies were observed for static pressure and static temperature in the vicinity of the jets due to unsteadiness in the shock system. Further, the variation of important parameters such as Peclet number, decay of maximum mass fraction, penetration distance of mass centre of fuel and average stagnation pressure loss are investigated for the nominal operating conditions and also for a range of injection Mach numbers from 1.0 to 2.0.