NONINTRUSIVE FAST RESPONSE OXYGEN MONITORING SYSTEM FOR HIGHTEMPERATURE FLOWS

A FAST-RESPONSE METHOD FOR MEASUREMENT OF MOLECULAR OXYGEN CONCENTRATIONS IN HIGH TEMPERATURE FLOWS IS NEEDED FOR WIND TUNNEL RESEARCH ON HYPERSONIC AIR-BREATHING ENGINES AS WELL AS OTHER APPLICATIONS IN COMBUSTION RESEARCH OR CONTROL. THE PROPOSED INNOVATION WILL UTILIZE INEXPENSIVE ROOM TEMPERATURE LASER DIODES TO MEASURE ABSORPTION BY OXYGEN AT NEAR-INFRARED WAVELENGTHS. THESE LASERS WILL BE USED IN COMBINATION WITH HIGH FREQUENCY FM DETECTION TECHNIQUES TO DEVELOP AN OXYGEN MONITORING METHOD WITH HIGH SENSITIVITY, WIDE DYNAMIC RANGE, AND THE CAPABILITY FOR EXTREMELY FAST TIME RESPONSE. AN IMPORTANT CHARACTERISTIC OF THIS INNOVATION IS THAT THE MEASUREMENTS ARE NONINTRUSIVE, AS CONTRASTED WITH ELECTROCHEMICAL METHODSWHERE GASES MUST BE TRANSPORTED INTO A SENSOR CHAMBER. IN COMPARISON WITH OTHER POTENTIAL OPTICALLY-BASED METHODS FOR MEASURING OXYGEN CONCENTRATIONS, THE PROPOSED APPROACH USES EXCEPTIONALLY RELIABLE AND INEXPENSIVE LASER SOURCES WHICH CAN READILY BE COMBINED WITH FIBER OPTICS FOR MULTI-POINT MONITORING. THE FEASIBILITY OF THE TECHNIQUE WILL BE DEMONSTRATED IN PHASE I BY MEASUREMENTS IN A ROOM TEMPERATURE ABSORPTION CELL AND IN THE POST-FLAME GASES OF A METHANE-OXYGEN FLAME.