Abstract
Time-resolved measurements of gas temperature and water vapor concentration are made in a shock tube using a novel diode laser absorption sensor (100 kHz bandwidth). Gas temperature is determined from the ratio of fixed-wavelength laser absorption of two water vapor rovibrational transitions near 1.4 mu m, and H2O concentration is determined from the inferred temperature and the absorption for one of the transitions. Wavelength modulation spectroscopy is employed with second-harmonic detection to improve the sensor sensitivity. The sensor is validated in a static cell and shock tests with H2O-Ar mixtures, yielding an overall accuracy of better than 1.9% for temperature and 1.4% for H2O concentration measurements over the range of 500-1700 K. The sensor is then demonstrated in a preliminary study of combustion in H-2/O-2/Ar and heptane/O-2/Ar mixtures in the shock tube.