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A Compact Sensor Based on Near Infrared Absorption Spectroscopy for Flow Diagnostics in a Low Density Hydrogen and Oxygen Combustion Driven Shock Tube
X.L. Yu, F. Li, L.H. Chen, and X.Y. Chang

A water vapour absorption-based fast-response tunable diode laser (TDL) sensor is developed for flow diagnostics in low density hydrogen and oxygen combustion driven shock tubes. The absorption system was operated in the rapid time-division-multiplexing (TDM) wavelength scanning mode to probe two water vapour absorption features at repetition rate up to 45.5 kHz. Temperature was determined from the ratio of the integrated absorbance of the two individual transitions near 7185.597 and 7168.437 cm-1, which have high sensitivity of temperature measurement in the range of 500-1300K. Experiments were performed in a 800 mm diameter hydrogen and oxygen combustion driven shock tube. Time resolved temperature and water vapour mole fraction of the driver gas at the fixed position of the test section are provided. Facility test time was also deduced from the non-absorption light intensity signal. The simple data processing and convenient operation made the sensor became a potential routine application for low density shock tube/tunnel.

Keywords: Tunable diode laser absorption spectroscopy (TDLAS), combustion, rapid time-division-multiplexing (TDM), temperature, water vapour concentration, low density shock tube

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