Hydrocarbon-fueled ramjet/scramjet technology program, phase 2 extension

摘要

The United Technologies Research Center conducted an experimental program to develop technology for a hydrocarbon-fueled ramjet/scramjet engine for operation at flight Mach numbers up to 7. As part of this program, connected-pipe combustion tests of key pilot and fuel injector components were performed in a variable-geometry two-dimensional test section over a range of combustor entrance conditions simulating the intended flight regime. A supersonic-inlet, air-breathing pilot was developed under the program that also incorporates an external mainstream fuel injector which serves as a primary fuel injection stage for the supersonic combustor. In previous tests at simulated Mach 5.6 flight conditions (comprising a combustor entrance Mach number of 3.0), it was demonstrated that the pilot promoted efficient combustion of gaseous ethylene that was injected into the supersonic mainstream flow as a primary fuel. The idea of using the air-breathing pilot and distributed secondary fuel injection to achieve efficient supersonic combustion of ethylene over a wide range of equivalence ratios was also experimentally demonstrated; during tests with staged fuel injection, high secondary fuel combustion efficiencies were achieved and smooth transitions from fully supersonic to mixed mode (supersonic/subsonic) operation were demonstrated at high overall equivalence ratios. The air-breathing pilot was also shown to effectively isolate the inlet from the combustion process even at the high combustor pressures experienced during mixed mode operation. Most of the testing was done with gaseous ethylene fuel which was chosen to simulate both prevaporized liquid fuels and the gaseous products of the endothermic reaction of liquid hydrocarbon fuels. Limited combustor testing was done with liquid hydrocarbon fuels. Work was done to expand the related data base with liquid hydrocarbon fuels and to investigate the effects of a wider variety of combustor configurations and entrance conditions on component and combustor performance.