Supersonic combustion of liquid N-Decane in a dual-cavity based scramjet

Supersonic combustion of liquid n-decane in a dual-cavity based combustor was numerically investigated. Present work was motivated by the experimental investigations conducted in Beihang University’s Supersonic Combustion Facility. High enthalpy clean air was heated to a total temperature of 970K, entering the isolator entrance at a Mach number of 2.03. The fuel was injected through six transverse injectors upstream of the first cavity, and the flame was not able to self-sustain under this low inflow total temperature. Consequently, a transverse gas jet produced by a dependent gas generator was injected into the combustor from the bottom of the first cavity to aid the ignition and flame stabilization. Three-dimensional compressible, turbulent, non-reacting and reacting flow calculations with a single-step chemistry model were performed on the two arrangements with or without gas jet. The turbulence model adopted the shear stress transport (SST) k-ω turbulence model. The particles stochastic trajectory model was used to track the interactions between the liquid n-decane and main stream. The predicted static pressure profiles along the combustor upper and side walls were compared with the experimental data to validate the numerical model and provide insight into the experimental flowfield behavior. The axial variations of combustion efficiency and total pressure loss were obtained to assess the combustion performance of the model combustor. The non-reacting numerical results show that the transverse gas jet induced an intense bow shock wave which decelerated the inflow, resulting in an obvious recirculation region downstream of the first cavity. The reacting numerical results show that the stable combustion cannot be achieved without the ignition aid. The flame was limited in the vicinity of the upper wall and two cavities, and the combustion efficiency at combustor exit was 20%. With the aid of high temperature gas jet, the plume depth of flame was greatly enhanced, and the main stream was successfully ignited. Subsequently, with the gas jet turned off, the stable combustion remained, and the combustion efficiency at combustor exit was 88%.