American Institute of Aeronautics and Astronautics 1 OH PLIF Visualization of the UVa Supersonic Combustion Experiment: Configuration A C.T. Johansen * , C.D. McRae † University of Calgary, Calgary, AB, T2N 1N4 P.M. Danehy ‡ NASA Langley Research Center, Hampton, VA, 23681-2199 E. Gallo § , L. Cantu ** , G. Magnotti †† , A. Cutler ‡‡ The George Washington University, Newport News, VA, 23602 R.D. Rockwell §§ , C.P. Goyne *** , J.C. McDaniel ††† University of Virginia, Charlottesville, VA, 22904 Hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) measurements were performed in the University of Virginia’s dual-mode scramjet experiment. The test section was set up in configuration A, which includes a Mach 2 nozzle, combustor, and extender section. Hydrogen fuel was injected through an unswept compression ramp at two different equivalence ratios. Through the translation of the optical system and the use of two separate camera views, the entire optical range of the combustor was accessed. Single-shot, average, and standard deviation images of the OH PLIF signal are presented at several streamwise locations. The results show the development of a highly turbulent flame structure and provide an experimental database to be used for numerical model assessment. I. Introduction HE main motivators for developing scramjet engines are to realize high speed, long distance transport, improve missile efficiency, and to reduce the cost of placing payloads into orbit. The inherent advantage of scramjets over conventional rocket engines is the ability to use atmospheric oxygen instead of carrying an onboard oxidizer. This results in an increase in the engine’s specific impulse over a wide range of Mach (Ma) numbers. 1 A recent analytical study by Tetlow and Doolan shows that, for a given payload mass, a hydrogen- or hydrocarbon-fueled scramjet stage uses significantly less fuel than a fully rocket-powered stage for orbital insertion. 2 They also show, however, that to be economically viable, the scramjet stage must be reusable since it has more structural mass than an equivalent fully rocket-powered system. This requires a robust design, a long operating life, and an easily recoverable system. A logical solution is to integrate the engine with a lifting vehicle airframe. Although recent flight experiments 3,4 and demonstration projects 5,6 have shown that scramjets are feasible in principle, many technical hurdles still remain. One significant hurdle is that the engine is unable to operate over the complete range of flight conditions (0 < Ma < 25) needed to achieve orbital insertion. 7 Scramjets rely on aerodynamic compression through a series of oblique shock waves and can only operate over a limited Mach number range (5 < Ma < 15). 8,9 Through normal-shock compression and combustion at subsonic speeds, ramjets * Assistant Professor, Department of Mechanical and Manufacturing Engineering, Member AIAA. † Graduate Student, Department of Mechanical and Manufacturing Engineering, Member AIAA. ‡ Research Scientist, Advanced Sensing and Optical Measurement Branch, MS 493, Associate Fellow AIAA. § Doctoral Student, Department of Mechanical and Aerospace Engineering, Member AIAA. ** Doctoral Student, Department of Mechanical and Aerospace Engineering, Member AIAA. †† Doctoral Student, Department of Mechanical and Aerospace Engineering, Member AIAA. ‡‡ Professor, Department of Mechanical and Aerospace Engineering, Associate Fellow AIAA. §§ Senior Scientist, Department of Mechanical and Aerospace Engineering, Member AIAA. *** Research Associate Professor, Department of Mechanical and Aerospace Engineering, Associate Fellow AIAA. ††† Professor, Department of Mechanical and Aerospace Engineering, Associate Fellow AIAA. T