18 March 1994 Water vapor measurements for combustion diagnostics using a 1350-nm tunable diode laser
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Abstract
The amount of water vapor formed in scramjet engines in high-enthalpy environments is a key parameter used to infer combustion efficiency. A H2O(V) concentration measurement system for combustion diagnostics in these high-temperature, high-velocity conditions has been developed at the NASA Langley Research Center and tested at General Applied Science Laboratories (GASL) in Ronkonkoma, NY. The system was first tested in an instrumentation shock tunnel using a H2/O2/N2 combustible mixture in the driven section for calibration and development purposes. The system uses a distributed feedback InGaAsP diode laser operating near 1350 nm. A wavelength modulation spectroscopy technique is used to achieve high detection sensitivity. The diode laser is modulated at radio frequency (rf), while the wavelength is scanned over two water vapor absorption lines by injection current tuning at a 5 kHz repetition rate. The detected rf signal is then demodulated at the modulation frequency (one f demodulation). Preliminary experimental results and data analysis are presented.
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Liang-Guo Wang, Liang-Guo Wang, Richard E. Trucco, Richard E. Trucco, Glen William Sachse, Glen William Sachse, Richard E. Campbell, Richard E. Campbell, Richard E. Davis, Richard E. Davis, } "Water vapor measurements for combustion diagnostics using a 1350-nm tunable diode laser", Proc. SPIE 2122, Laser Applications in Combustion and Combustion Diagnostics II, (18 March 1994); doi: 10.1117/12.171289; https://doi.org/10.1117/12.171289
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