AN INFRARED DIODE LASER SPECTROMETER WITH ENHANCED SENSITIVITY FOR COMBUSTION RESEARCH

THE DEVELOPMENT OF NONINTRUSIVE SENSORS TO MEASURE COMBUSTION SPECIES CONCENTRATIONS IN HIGH TEMPERATURE, PARTICLE-LADEN ENVIRONMENTS IS IMPORTANT IN KINETIC RATE STUDIES, IN FOLLOWING THE EVOLUTION OF REACTANT SPECIES IN LABORATORY-SCALE COMBUSTORS, IN STUDYING CORROSION PROCESSES, AND IN MONITORING CRITICAL SPECIES IN FULL SCALE SYSTEMS FOR CONTROLLING EMISSIONS OR FOR OPTIMIZING COMBUSTION EFFICIENCY. INSTRUMENTATION BASED ON TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY HAS WIDE GENERALITY FOR DETECTING MANY COMBUSTION SPECIES. TO DATE, HOWEVER, SUCH SYSTEMS HAVE USUALLY BEEN BULKY AND AWKWARD TO OPERATE AND DO NOT HAVE ADEQUATE SENSITIVITY FOR THE MEASUREMENT OF A NUMBER OF IMPORTANT SPECIES THAT EXIST IN COMBUSTION ENVIRONMENTS AT LOW CONCENTRATIONS. THE DEVELOPMENT OF A RAPID RESPONSE (FASTER THAN 0.1 SECOND), HIGH SENSITIVITY SENSOR USING SINGLE-MODE, LIQUID NITROGEN-COOLED, LEAD-SALT DIODE LASERS IS PLANNED. THE MAJOR OBJECTIVE OF THE PHASE I EFFORT IS TO USE SUCH INSTRUMENTS TO EXTEND THE SENSITIVITY OF DIODE LASER ABSORPTION MEASUREMENTS BEYOND PRESENTLY ATTAINED LEVELS. IN PARTICULAR, HIGH FREQUENCY OPTICAL HETERODYNE TECHNIQUES WILL BE STUDIED THAT SHOULD PERMIT DETERMINATION OF NOISE-LIMITED PERFORMANCE DURING THE LASER BURST. RESULTS OF THE PHASE I STUDY WILL PROVIDE THE REQUIRED DESIGN INFORMATION FOR THE PHASE II DEVELOPMENT AND TESTING OF A HIGH SENSITIVITY, COMPACT INSTRUMENT WITH WIDE APPLICATION FOR MEASUREMENT OF TRACE COMBUSTION SPECIES.