A tunable diode laser-based H2O 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 μs facility test time. Key parameters provided by the diagnostic include the temperature, H2O 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 μm 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. Presented as Paper 2011-5600 at the 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, San Diego, CA, 31 July-3 August 2011
Quantification of Supersonic Impulse Flow Conditions via High-Bandwidth Wavelength Modulation Absorption Spectroscopy
AIAA journal ; 53 , 10
2015
Article (Journal)
English