Supersonic combustion using a stinger-shaped fuel injector

The authors developed a stinger-shaped injector (stinger injector) for supersonic combustors in cold-flow experiments. The stinger injector has a port geometry with a sharp leading edge in front of a streamwise slit. This injector produced higher jet penetration at a lower jet-to-crossflowmomentumflux ratio J than a conventional circular injector.We applied the injector in a Mach 2.44 combustion test at a stagnation temperature of 2060 K. At a low fuelequivalence ratio φ regime (i.e., low J regime), the injector produced 10% higher pressure thrust than the circular injector because of high jet penetration as expected from the cold-flow experiments. Even at a moderate φ regime, the stinger injector produced higher pressure thrust than the circular injector. At moderate φ, the stinger injector held the flame around the injector and generated a precombustion shock wave in front of the injector. The presence of the precombustion shock wave decreased the momentum flux of the crossflow air and diminished the advantage of the injector for jet penetration. The injector, however, produced higher pressure thrust because better flame-holding produced higher pressure aroundthe injector.At a higher φ regime, the precombustion shock wave went upstream with both injectors. The far-upstream presence of a precombustion shockwave increased the turbulence in the crossflow and spread the fuel from both injectors. Thus, the difference in injector shape was insignificant for thrust performance.