LASER-INDUCED FLUORESCENCE MEASUREMENTS OF VELOCITY IN SUPERSONIC REACTING FLOWFIELDS (PC-159)

THIS PHASE I PROPOSAL DESCRIBES AN INNOVATIVE APPROACH TO NON-INTRUSIVE VELOCITY MEASUREMENTS IN REACTING FLOWFIELDS BASED ON THE DOPPLER-SHIFTED FLUORESCENCE OF THE OH RADICAL. IT ADDRESSES A CRITICAL NEED IN THE AREA OF NON-INTRUSIVE COMBUSTION DIAGNOSTICS AND FINDS PARTICULAR APPLICATION IN THE DESIGN OF SUPERSONIC RAMJET PROPULSION SYSTEMS. THE INNOVATION IS BASED ON THE DOPPLER-SHIFT OF A MOVING ENSEMBLE OF MOLECULES RELATIVE TO A STATIONARY ENSEMBLE. BY RECORDING THE RELATIVE FLUORESCENCE PROFILES OF A STATIONARY AND MOVING GROUP OF MOLECULES, THE MEAN VELOCITY COMPONENT ALIGNED WITH THE LASER BEAM MAY BE DETERMINED. IN REACTING FLOWS, THE RADICAL OH WILL BE DISTRIBUTED OVER A LARGE PORTION OF THE FLOWFIELD AND IS PROPOSED AS THE FLUORESCENCE TRACER SPECIES. IN FLOWS WITHOUT CHEMISTRY, POSSIBLE TRACERS INCLUDE NO, SEEDED INTO THE FLOW, OR O2. THIS APPROACH CIRCUMVENTS INHERENT LIMITATIONS IN LASER DOPPLER ANEMOMETRY AND HOT-WIRE TECHNIQUES. PRELIMINARY SIGNAL ESTIMATES WITH OH SHOW GOOD SENSITIVITY FOR VELOCITIES AS LOW AS 3 X 10(4) CM/S.