Ethylene-fueled scramjet combustor is numerically explored. Three-dimensional Favre Averaged Navier Stokes equations and the Reynolds stress transport equation model are solved. A single-step global reaction with infinitely fast chemistry is considered to model turbulence–chemistry interaction. Experimental condition of a backward-facing step-based combustor where gaseous ethylene is injected from the floor of the combustor into Mach 2.5 vitiated air is taken as the test case for validation. Both non-reacting and reacting flows are simulated. Insight into the combustion process inside the combustor is obtained by analyzing various flow parameters. For a higher equivalence ratio, there is significant upstream interaction. Computed wall pressure matches very well with the experimental results for non-reacting and reacting flows.