Mixing efficiency of hydrogen multijet through backward-facing steps at supersonic flow

Increasing the fuel mixing performance in the combustor of scramjet substantially improves the overall efficiency of the scramjet engine. In this article, computational fluid dynamic is used to study the impacts of hydrogen jets injection through the backward-facing multi-steps on the fuel distribution and mixing zone at the supersonic air stream of Mach = 4. This study also analyzes the jet flow feature and circulation of jets in different sections of the combustor at downstream of the multi-injectors. Reynolds average Navier-Stocks equations are solved with SST turbulence model for achieving a precise and acceptable solution. The effects of step height on the jet features are also examined. According to circulation evaluation, low jet total pressure (pressure ratio = 0.1) and high step depth (step depth = 1 mm) is the optimum condition for achieving high circulation value. Our investigations show that the mixing efficiency of the hydrogen multijets improves up to 15% when the step height increases from 0.5 mm to 1 mm.