Experiments on hydrocarbon fuel ignition for scramjet at Mach 4

Hydrocarbon fuel ignition experiments were performed on directly connected pulse combustion facility.The test inflow parameters included stagnation temperature of 935K and the Mach number of 4 at the entrance of isolator. Gaseous ethylene was ignited successfully and combustion was maintained stable by employing three combination assistant ignition methods: torch igniter combined with pilot hydrogen, self-combustion of pilot hydrogen and air throttle combined with pilot hydrogen. The experimental results indicate that when employing self-combustion of pilot hydrogen, the mass flow rate of hydrogen should be ranged from 0.43~12.61g/s, and higher mass flow rate of hydrogen isn't helpful to ignition; for air throttle combined with pilot hydrogen ignition method, the injection pressure of hydrogen should be set at 5MPa, and the throttle mass flow rate should be 10%~30% of inflow mass flow rate. At last the lean blow-out limit and rich operation limit of scramjet were researched with ethylene injected from upstream of cavity or cavity floor.The results show that two injection schemes have similar lean blow-out limits at equivalence ratio of 0.077, and the rich operation limits varies a lot at equivalence ratios of 0.327 and 0.471 respectively.