TDLAS-based measurements of parameters for incoming flow hot-firing test of air-breathing rocket engine

Tunable diode laser absorption spectroscopy (TDLAS)-based sensor is applied to measurement of path-integrated static temperature, H₂O concentration and local velocity for incoming flow hot-firing test of air-breathing rocket engine. The measurements are achieved using time division multiplexing (TDM) system with scanned-wavelength method, which contains 1392 nm and 1395 nm distribute feedback (DFB) diode lasers. The absorption spectra of gases near 7185.597 cm^-1 and 7168.437 cm^-1 are obtained by modulating the two lasers alternately. The value of temperature is deduced from the ratio of two-line measured absorbances, and the water vapor concentration is deduced from the measured absorbance of one transition and the measured temperature, moreover, gas velocity is deduced from the measured Doppler-shift absorption of the two beams, which make an angle of 70°. Therefore, the in-situ and non-intrusive measurements of parameters are applied for gas in rocket engine.