Penetration and Spreading of Liquid Jets in an External-Internal Compression Inlet

Abstract

Injection of liquid fuel in the inlet of a vehicle e ying at hypersonic speed is related to the development of liquid fuel-based supersonic-combustion ramjets as a means to increasetheresidence timeand achieve partial fuel premixing priorto arrivalat thecombustion chamber. The strong liquid interactionwith theinlethigh-momentum aire owand shock wavesystem offersa mechanism forrapid jetand droplet breakup and, hence, improved mixing. The penetration and spreading of liquid jets in a two-dimensional external ‐internal compression inlet at Mach 3.5 using a noncombustible mixture that simulated the viscosity and surface tension of JP-10 was evaluated. Schlieren imaging has been used as the visualization technique for penetration studies, as well as light scattering for jet spreading. By using thin pylons to create a low-pressure region at the liquid injection station, the penetration increased compared with a nonpylon cone guration while reducing the pressure losses associated with transverse jet injection. The pylons contributed to lift the liquid from the injection surface with less lateral spreading than the nonpylon-injection case, thus avoiding the presence of a low-speed combustible mixture in the inlet/isolator boundary layers and providing a mechanism to eliminate potential e ashback.