A three-dimensional computational study of the effect of the inlet conditions on supersonic mixing and combustion

In recent years, a significant amount of high-speed combustion research has been directed toward optimization of scramjet combustors, and in particular on the efficiency of fuel–air mixing and reaction taking place in the engine. This article numerically investigates the flow characteristics of a dual-mode scramjet–combustor configuration. Results are presented for a three-dimensional combustor model with a single wall-mounted raised (compression) ramp as a fuel injector. Hydrogen is used as the fuel and is injected through the raised ramp (which has an aspect ratio of 0.5) parallel to the air stream. Vitiated air with different concentrations of H2O and CO2 are used at the inlet boundary. Three equivalence ratios were simulated, 0.25, 0.31, and 0.41. Numerical results are obtained using a finite volume computational fluid dynamics code. Initially, three forms of the two-equation k–ε turbulent model were tested: the standard, the RNG, and the realizable with unstructured grids. Final results were obtained with the RNG form of the k–ε turbulent model. Results show that the combustion efficiency decreases with the increase of the equivalence ratio. Also, the cases with CO2 show slightly higher combustion efficiencies.