Measurement of non-stationary gas flow parameters using diode laser absorption spectroscopy at high temperatures and pressures

The layout of an absorption spectrometer with diode lasers for contactless measurement of the temperature and water-vapor concentration in gas flows with mixture pressures of up to $3$ atm and temperatures of $300$–$2000$ K has been designed. The technique is based on the rapid tuning of the radiation wavelength of two lasers, the registration of the absorption lines of water molecules that are located in the tuning range, and the fitting of the experimental absorption spectra by theoretical ones that have been simulated using spectroscopic databases. The original components of the spectrometer and different algorithms of the processing of experimental spectra are described. The performance of the spectrometer and processing methods were tested in the laboratory with a cuvette at a pressure of $1$ atm and temperatures of $300$–$1500$ K. The different processing algorithms give a reasonable coincidence of data on hot zone parameters that were obtained by the method of diode laser absorption spectrometry, and the temperature that was measured using standard sensors. The designed layout of the spectrometer passed the first tests on the T-131 experimental stand at the TsAGI (Central Aerohydrodynamics Institute).