SHOCK WAVES FOR ENHANCED MIXING IN SCRAMJET COMBUSTORS

AN EXPERIMENTAL INVESTIGATION OF SHOCK WAVE/SHEAR LAYER INTERACTIONS TO ENHANCE MIXING IN A SUPERSONIC COMBUSTION RAMJET (SCRAMJET) ENGINE IS PROPOSED. IN A SCRAMJET ENGINE OPERATING AT HYPERSONIC FLIGHT SPEEDS, THE SHORTER RESIDENCETIME AND DECREASED MIXING RATE CAUSE DETERIORATION IN THE COMBUSTION EFFICIENCY AS COMPARED WITH LOWER SPEEDS. A CONFIGURATION RECENTLY DEVELOPED TO PROMOTE RAPID MIXING IN A SUPERSONIC FLOW WILL BE EXPERIMENTALLY COMPARED WITH A BASELINE CONVENTIONAL CONFIGURATION. THE CONFIGURATION IS ASINGLE-STEP FLAMEHOLDER WITH A WEDGE ON THE OPPOSITE SUPERSONIC PASSAGE WALL TO INDUCE A WEAK SHOCK. THE OBJECTIVE OF THIS STUDY IS TO EVALUATE THE CONFIGURATION AS A MEANS FOR RAPID AND THOROUGH MIXING OF THE FUEL WITH THE SUPERSONIC AIR STREAM. DURING PHASE I, THE FEASIBILITY OF THE SCRAMJET MIXING CONCEPT WILL BE DETERMINED. PHASE I WILL INVOLVE AN EXPERIMENTAL STUDY OF THE CONFIGURATION USING A FACILITY SIMILAR TO A BLOWDOWN WIND TUNNEL. WE PLANTO MIX HELIUM WITH NITROGEN AND MEASURE THE CONCENTRATION PROFILE AT SUITABLE DISTANCES DOWNSTREAM OF THE STEP. IT ISEXPECTED THAT THE SHOCK WAVE/SHEAR LAYER INTERACTION WILL ALLOW THE HELIUM TO DIFFUSE MORE RAPIDLY ACROSS THE SUPERSONIC NITROGEN FLOW. WITH FAVORABLE RESULTS IN PHASE I, A PHASE II RESEARCH AND DEVELOPMENT PROGRAM WILL BE PURSUED TO PROVIDE PARAMETRIC INFORMATION FOR DESIGN OPTIMIZATION.