Numerical Investigation of Hypersonic and Scramjet Combustor Phenomenology

Abstract

Numerical calculations were completed to simulate the physical processes occurring within scramjet combustor flow fields and to determine the effects of different fuel injection schemes on the overall scramjet combustion efficiency. T he numerical approach solves the full 3 -D Navier -Stokes equations supplemented with a finite rate chemical kinetic model for the combustion of ethylene fuel and air. The kinetic model is comprised of 20 chemical reactions and 13 chemical species, specific ally, C2H4 (ethylene), C2H2, O2, CO2, H2O, CO, H2, OH, H,NO,N,N2 and O. The location of the fuel injectors and the angle of the injector orifices are varied to determine the optimum injection scheme. The fuel injector locations include the combustor inle t region upstream of the cavity, the cavity floor, and locations on the cavity upstream step and the downstream ramp. The angle s of the fuel port injection slots include combinations of parallel, 27 deg , and 90 deg to the airflow inside the cavity. All combustor configurations include a common single -cavity combustor system to provide flameholding and stabilization in a supersonic combustor environment. The mixing efficiencies predicted for 10 different injection configurations are compared. The compara tive results indicate that the fuel injection configuration with opposing injector pairs located within the cavity on the step and the ramp are the most efficient, resulting in 73 -percent combustion efficiency.