A tunable diode laser-based H 2 O absorption diagnostic has been developed to characterize transient phenomena within the Stanford Expansion Tube Flow Facility. A measurement rate of 25 kHz was achieved to identify and investigate transient flow structures within the 600 μ s facility test time. Key parameters provided by the diagnostic include the temperature, H 2 O mole fraction, and velocity time histories of the supersonic test gas, as well as the structure and timing of the test gas contact surfaces. The presence of water within the test gas affords well-established rovibrational transitions near 1.4 μ m that are probed using calibration-free, scanned wavelength-modulation absorption spectroscopy with second harmonic detection. This technique offers the sensitivity and noise resistance necessary for in situ temperature, velocity, and mole fraction measurements within the harsh conditions of the expansion tube. A rigorous scanned wavelength-modulation absorption spectroscopy with second harmonic detection theory has been employed to account for nonideal laser performance associated with high-bandwidth tunable diode laser absorption spectroscopy measurements. The measurements carried out with this sensor provide a quantitative characterization of the test gas conditions produced in the expansion tube and thus lay an essential foundation for supersonic combustion experimentation within the facility.


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    Title :

    Quantification of Supersonic Impulse Flow Conditions via High-Bandwidth Wavelength Modulation Absorption Spectroscopy


    Contributors:

    Published in:

    AIAA Journal ; 53 , 10 ; 2978-2987


    Publication date :

    2015-10-01




    Type of media :

    Conference paper , Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English