COMBUSTION DIAGNOSTICS FOR MICROGRAVITY RESEARCH USING NEAR-IR DIODE LASERS

IMPROVED METHODS FOR MEASURING SPECIES CONCENTRATIONS AND TEMPERATURE ARE NEEDED FOR MICROGRAVITY COMBUSTION RESEARCH AS WELL AS OTHER APPLICATIONS IN COMBUSTION RESEARCH OR CONTROL. THE PROPOSED INNOVATION WILL UTILIZE INEXPENSIVE ROOM TEMPERATURE LASER DIODES TO MEASURE ABSORPTION BY IMPORTANT COMBUSTION FUEL, OXIDIZER, AND PRODUCT SPECIES AT NEAR-INFRARED WAVELENGTHS. THESE LASERS WILL BE USED IN COMBINATION WITH HIGH FREQUENCY DETECTION TECHNIQUES TO DEVELOP A DIAGNOSTIC WITH HIGH SENSITIVITY, WIDE DYNAMIC RANGE, AND THE CAPABILITY FOR EXTREMELY FAST TIME RESPONSE. THE DIAGNOSTIC COULD ALSO BE USED FOR MEASUREMENTOF GAS TEMPERATURE IN COMBUSTION FLOWS. AN IMPORTANT CHARACTERISTIC OF THIS INNOVATION IS THAT THE MEASUREMENTS ARE NONINTRUSIVE. IN COMPARISON WITH OTHER POTENTIAL OPTICALLY-BASED METHODS FOR MEASURING COMBUSTION SPECIES 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-AIR FLAME.