Inlet Starting of High-Contraction Axisymmetric Scramjets

摘要

Reliable in-flight starting of the inlet is of critical importance for the successful operation of scramjet engines,nparticularly axisymmetric configurations with high-contraction inlets. The present research is undertaken tonexamine the capability of various inlet starting methods based on two principles: unsteady flow effects and variablengeometries. Time-accurate viscous computations have been performed to investigate the transitional flowfieldsnintroduced by a variety of methods that are applicable to axisymmetric geometries. Parametric studies have beennconducted for instantaneous rupture of conical diaphragms and addition of bleed slots, which induce highly unsteadynflow phenomena. Several methods employing variable inlet geometries have been tested for the latter principle,nincluding opening doors and sliding doors (or diaphragm erosion). Successful inlet starting has been achieved as anresult of unsteady transition induced by diaphragm rupture and quasi-steady transition, due to the sliding-doornopening process. In particular, a bleed addition to the diaphragm rupture method has been found to be highlyneffective and pronounced flow stability has been observed in the sliding-door process.