Three Dimensional Flow Analysis of a Cavity-Based Scramjet Combustor

Abstract

This paper describes an effort to develop an efficient CFD tool to analyze the flow through the Scramjet with cavity recessed combustion chamber. Cavities has become one of the main interest area of the hypersonic propulsion community due to its effect on flame-holding and mixing efficiency. Cavities stabilize the flow and so enhance the supersonic combustion. Coupled Euler and finite rate chemical reaction equations are employed. Hydrocarbons are one of the most efficient fuels to be used in Scramjets. Reduced chemical reactions of Ethylene-Air is used in this study. Two different fuel injection configurations are compared; fuel injection only upstream of the cavity and fuel injection both from the upstream and downstream of the cavity. Fuel injection from only upstream of the cavity showed a better combustion performance since the amount of unburned fuel is less at the combustor exit. Nomenclature ̂ = conservative vector ̂,̂,̂ = flux vectors , , = curvilinear coordinates ̂ = chemical reaction source vector ρ = density u, v, w = velocity vector components p = pressure et = total energy per unit volume U, V, W = contravariant velocity components J = transformation matrix , , = transformation metrics K = total number of species ̇ = source term M = Mach number c = speed of sound = specific heat ratio Cp = specific heat Ru = universal gas constant W = molecular weight , ′ , , ′′ = stoichiometric coefficients = chemical symbol I = total number of reactions X = molecular concentration