Validation of the Remote Method of Determining the Temperature and Concentration of High-temperature Water Vapor from the Reference Transmission Spectra

Abstract

The remote method of simultaneous determination of the temperature and concentration of hot gases from experimental spectral characteristics is validated on the example of the transmission spectra of water vapor measured with an average error of 5% at temperatures in the range 500–1770 K and concentrations 0.17–1 atm with resolution of 1 cm^–1. When solving the direct optical problem, the parameters of water vapor spectral lines comprised in the HITEMP2010 database are analyzed with allowance for the last measurements of the absorption spectra with high resolution at Т ≈ 1300 K. It is demonstrated that overestimated values of the intensities of some hot water vapor spectral lines can be a reason for the deviation of the theoretical absorption predicted on the basis of the HITEMP2010 database from the experimental one. To increase the accuracy of solving the inverse optical problem, the data from several (up to eight) fragments of the spectral ranges 1000–2500 and 2600–4400 cm^–1 are used. As a result, it is demonstrated that this allows the average error of determining reference values of the water vapor temperature and concentration to be decreased approximately to 0.3%, which corresponds to the average approximation error of theoretical values of its transmission function.