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

Results are presented of experiments conducted in a supersonic wind tunnel on an integrated fuel injection/ignition system, consisting of an aeroramp injector and a gas-portfire igniter. The main goals of the work were to determine how the lifting effect of the gas-portfire affected the fuel from aeroramp jet, to ascertain how the injection of gas through the gas-portfire influenced the combustion in the combustor model, and to investigate any synergistic effects from the combination. The gas-portfire igniter/flame holder was placed downstream of the injector on the centerline at three different locations in order to find the best suitable gas-portfire injector geometrical configuration. The aeroramp was observed to generate a pair of streamwise vortex and gas-portfire had a strong lifting effect on this vortex. Experiments achieved a stable combustion when ethylene equivalence ratio was above 0.05. As the gas-portfire momentum flux ratios were increased from 0.64 to 1.43, the ignition delay time was shortened obviously while the combustion efficiency was not influenced. A 3-D numerical study was conducted to investigate the details of combustion flow structure. The pressure distribution obtained by experiment and simulation agreed well (average error<5%). The numerical and experimental results show that the distance between gas-portfire and aeroramp injector is a critical parameter which influences the combustion efficiency. The results demonstrate that the gas-portfire plays an important role in combustion enhancement. The ignition delay time is sensitive to momentum flux ratios of gas-portfire. When the momentum flux ratio is 0.64, the delay time reaches nearly 1s. One should note that ethylene fuel cannot be ignited when equivalence ratio was below 0.55.