Performance comparison of aero-ramp and transverse injector based on gas-pilot flame

A direct performance comparison between the four-hole aero-ramp injector and single transverse injector in a dual-mode scramjet combustor was conducted.The mixing characteristics of two injectors were calculated by solving the three-dimensional(3-D)compressible Reynolds-averaged Navier-Stokes equations(RANS),with the help of the shear-stress-transport(SST)k-ωturbulence model.The numerical results show that the far field mixing efficiency of the aero-ramp injector is higher than that of the single transverse injector.High enthalpy vitiated air was heated to a total temperature of 1 200Kby hydrogen-oxygen combustion, entering the isolator entrance at a Mach number of 2.0.Non-reacting experimental conditions involved sonic injection of nitrogen to safely simulate ethylene injected into the combustor at a jet-to-free stream momentum flux ratio of 2.6.Schlieren photographs were obtained to analyze the shock structure around the injectors.Reacting test conditions involved sonic injection of ethylene at the jet-to-free stream momentum flux ratios ranging from 0.5to 2.7.High speed camera was used to capture the flame structures in the near-field combustion. The experimental results show that the aero-ramp injector produce sustained combustion over a wider range of fuel-air ratios than the single transverse injector.At the identical jet-to-free stream momentum flux ratio,the aero-ramp has a larger isolator margin than the single transverse injector,demonstrating a better ability for avoiding overflows.However,the air specific impulse and total temperature recovery of two injectors,which are calculated by the one-dimensional(1-D)performance analysis code,are almost identical.

A direct performance comparison between the four hole aero-ramp injector and single transverse injector in a dual-mode scramjet combustor was conducted. The mixing characteristics of two injectors were calculated by solving the three-dimensional （3-D） compressible Reynolds-averaged Navier-Stokes equations （RANS）, with the help of the shear-stress-transport （SST） k 02 turbulence model. The numerical results show that the far field mixing efficiency of the aero ramp injector is higher than that of the single transverse in- jector. High enthalpy vitiated air was heated to a total temperature of 1 200 K by hydrogen oxygen combustion, entering the isolator entrance at a Mach number of 2.0. Non-reacting experimental conditions involved sonic injection of nitrogen to safely simulate ethylene injected into the combustor at a jet-to-free stream momentum flux ratio of 2.6. Schlieren photographs were obtained to analyze the shock structure around the injectors. Re- acting test conditions involved sonic injection of ethylene at the jet-to-free stream momentum flux ratios ranging from 0.5 to 2.7. High speed camera was used to capture the flame structures in the near-field combustion. The experimental results show that the aero-ramp injector produce sustained combustion over a wider range of fuel-air ratios than the single transverse injector. At the identical jet to free stream momentum flux ratio, the aero-ramp has a larger isolator margin than the single transverse injector, demonstrating a better ability for a- voiding overflows. However, the air specific impulse and total temperature recovery of two injectors, which are calculated by the one dimensional （l-D） performance analysis code, are ahnost identical.