Operational sensitivities of an integrated aerodynamic-ramp-injector/gas- portfire flame holder in a supersonic combustor

Performance and operating limits of an ethylene-fueled injection and ignition/flame-holding system consisting of an aerodynamic-ramp injector and a gas-portfire were investigated both experimentally and numerically, using the scramjet direct connect facility at the Beihang University. The experimental operating conditions include (1) the fuel equivalence ratio, (2) the gas-portfire location, and (3) the gas-portfire gas-to-freestream momentum flux ratio (qg). The lean burn limit was at a fuel equivalence ratio of 0.05. The gas-portfire was placed downstream of the injector on the centerline at three different locations in order to find the best suitable gas-portfire/aero-ramp injector geometrical configurations. Results showed that the distance from the gas-portfire to the aero-ramp injector array was a critical parameter which influenced the combustion efficiency obviously. The ignition delay time was sensitive to the qg. When the qg was below 0.55, the ethylene cannot be ignited; when the qg was 0.64, the ignition delay time reached nearly 1s; the increase of the qg from 0.64 to 1.43 shortened the ignition delay time obviously, but had no influence on the combustion efficiency. The detailed combustion flowfields were investigated by the 3-D numerical study and the numerical results agreed well with the static pressure distributions obtained by experiments (average error<5%).