A diode laser absorption sensor for rapid measurements of temperature and water vapor in a shock tube
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 μ 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 H$_2$O-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 H2/O2/Ar and heptane/O2/Ar mixtures in the shock tube.
KeywordsShock Tube Homogenous Charge Compression Ignition Shock Test Wavelength Modulation Spectroscopy Sensor Validation
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