Parametric experimental and numerical study on mixing characteristics in a supersonic combustor with gaseous fuel injection upstream of cavity flameholders

Abstract

Non-reacting experiments and numerical simulations were performed to investigate the mixing characteristics of gaseous fuel injection upstream of a flameholding cavity in supersonic vitiated air flow. The investigation considered the effects of various flow or geometry parameters, including injection stagnation pressure, cavity length to depth ratio, and distance between the injection orifice and the cavity front wall. The nanoparticle-based laser scattering technique was used. Mix the injection nitrogen gas with nanoparticles; the fuel distribution and instantaneous displacement demonstrated by the nanoparticles were imaged with laser sheet scattering measurement. The flowfields with various mixing schemes were calculated by large eddy simulation. Experimental and numerical results showed that most of the fuel flows away upon the open cavity and only a small portion of the fuel is convected into the cavity shear layer. Fuel distribution and convection around cavity flameholders are determined by the interaction of the lifting counter-rotating vortex structures induced by the jet with the cavity shear layer. With the reduction of cavity length to depth ratio, the increase in distance between the cavity front wall and the injection exit or the increase in injection pressure, the coupling interaction between the injection, and the cavity shear layer would be changed, and the intensity of fuel mass transport from the jet to cavity would decrease.