The question of solving the inverse problem of gas medium optics to determine the partial pressure and gas temperature using artificial neural networks is considered. The analysis of the errors of the obtained models was carried out depending on the number of used spectral centers and the size of the training sample, which showed a tendency to decrease the magnitude of errors with the growth of these parameters. The models were obtained that provides a solution to the inverse optical problem of determining the partial pressure and temperature of carbon monoxide and water vapor with a relative error of less than 3 % and 3.5 % respectively.
The method of simultaneous determination of the temperature and partial pressures of gaseous mixture components on the basis of measured spectral characteristics is considered. The transmittances of a gaseous mixture consisting of H2O, CO2, CO and NO gases, which were simulated by the line-by-line method using the HITEMP2010 database, are considered. It is shown that the potential accuracy of the method depends only on the agreement between the theoretical and experimental spectra of gases. The influence of the error in the transmittance on the errors in finding the temperature and partial pressures of gases is discussed.
The criteria for choosing optimal wavelengths for remote sensing of gaseous media are considered on an example of CO2 laser. The influence of various factors on the experimental and theoretical values of the spectral characteristics of the medium is estimated.
In this work the contributions from the hot bands in the total absorption of H2S, SO2, and NO2 were calculated at temperatures of 300 – 1000 K. The high-temperature spectroscopic databases of the authors were applied for calculating the sum absorptions. The reasons of the different contributions from the cold and hot bands in the absorption spectra of the considered gases are discussed.
A numerical model of a multicomponent gas-aerosol medium designed for studying the transmission function in the visual and IR ranges has been proposed. Taking into account the molecular absorption by the gas component and also the light scattering and absorption by the aerosol, the radiation extinction is determined. To calculate the optical characteristics of a dispersed component, the Mie theory is applied. Methane is selected as the main gas component of the medium. The separate and combined contributions of molecular absorption and aerosol extinction to the transmission of optical radiation by a gas-aerosol medium are analyzed.
In this work the temperature dependences of the integrated intensities of the absorption bands of the asymmetric top molecules – H2O, H2S, SO2, and NO2 were analyzed. A different view of the temperature dependences was shown for cold bands including fundamental ones. For calculating the integrated intensities, the spectral line intensities were used from the known and author’s spectroscopic databases. The reasons are discussed which lead to increasing and decreasing the integrated intensities at high temperatures (T>300 K).
The method of approximation polynomials for simultaneous determination of the temperature and concentration of a heated gas from its spectral characteristics is considered. The accuracy of finding the experimental values of the thermodynamic parameters was increased by using an arbitrary number (≥ 2) of spectral centers and taking into account the measurement error of the transmission function. Approbation of the improved technique was carried out using the most accurate measurements of the transmission function of carbon dioxide in the temperature range 500-1770 K and the partial pressure ρCO2 = 0.17-1 atm.
The analysis of the calculation results of extinction coefficient, scattering coefficient, and absorption coefficient of aerosol, as well as transmission function under the joint and separate impact of components of mixture containing trioxide dialuminum was carried out. The spectral features of the optical characteristics of the medium at various parameters of particle size distribution function were illustrated.
A complete set of dipole moment function parameters of sulfur dioxide (32S16O2) were determined up to the second order inclusively. For determining the parameters, the experimental vibrational transition moments of the ν1, ν3, ν1+ν3, and 2ν3 bands were used from literature. The vibrational transition moments of the ν2, 2ν2, ν1+ν2, ν2+ν3, and 2ν1 bands with uninvestigated experimentally line intensities were obtained in this work on the basis of the ab initio line intensities of 32S16O2. The results of this work were validated by a comparison of the simulated absorption coefficients with the measured data taken from the Pacific Northwest National Laboratory.
The CO2 transmission function was calculated and compared with the experimental data in the spectral range of 450- 7600 cm-1. The spectral ranges suitable for a determination of temperature and concentration of CO2 were determined. The influence of polynomial degrees on errors of approximating the transmission function and the influence of a number of spectral regions on errors of determining the temperature and partial pressure were analyzed.
A validation of spectral line parameters of hydrogen sulfide (H232S) from the spectroscopic databases HITRAN2012 and GEISA2009 was carried out. For this aim, the absorption coefficient of H232S calculated by a line-by-line method is compared to experimental data from the Pacific Northwest National Laboratory. A list of the spectral line parameters of H232S of the authors is also used for the comparison. The line positions and intensities from the author’s line list were calculated by the effective operator method. The parameters of the effective dipole moment of the ν2 band of H232S were determined. Finally, the HITRAN2012 and GEISA2009 data differ from the experimental ones in the ν2 band and there are errors in line positions of the first and second triad bands from HITRAN2012.
A description of an Internet accessible software «Optics and spectroscopy of gas-aerosol media» is represented. The new software is focused on research in the field of direct and inverse problems of optics and spectroscopy of gas-aerosol media.
In this work, a numerical study of the transmission function, extinction coefficient, scattering coefficient, and absorption coefficient of the aerosol generated by the jet engine emissions was performed. Analyzing the calculation results of the IR optical characteristics of anthropogenic emissions containing the dialuminum trioxide was carried out. The spectral features of the optical characteristics of the medium caused by the average size, concentration and complex refractive index of the particles were illustrated.
Calculated absorption spectra of the mixture of gases (H2O, CO, CO2, NO, NO2, and SO2) and aerosol (soot and Al2O3), contained in the exhausts of aircraft and rocket engines are demonstrated. Based on the model of gas-aerosol medium, a numerical study of the spectral dependence of the absorptance for different ratios of gas and aerosol components was carried out. The influence of microphysical and optical properties of the components of the mixture on the spectral features of absorption of gas-aerosol medium was established.
The modelled absorption coefficients of 14N16O2 are performed in the range of pure rotational and vibrational-rotational transitions at T = 300 K and T = 1000 K temperatures. The calculations were carried out on the basis of the developed by authors high-temperature database of NO2 spectral line parameters and database HITRAN2012. The dipole moment function parameters of NO2 up to the second order inclusive were also determined.
The intensities of water vapor in the range of pure rotational transitions were calculated up to high quantum numbers (Jmax ~ 30 and Ka max ~ 25). The diagonalization of the effective rotational Hamiltonian, approximated by Pade-Borel method, is applied to obtain the eigenvectors. The centrifugal distortion perturbations in line intensities were taken into account by the traditional equations for matrix elements of the transformed dipole moment, including eight parameters, and previously developed by authors Pade approximant. Moreover, to conduct the calculations, the rotational wavefunctions of the symmetric rotor molecule were applied. The results were compared with the known theoretical data.
Review of the authors' works devoted to research of properties of high-temperature gas mixtures and advancement of methods of a remote diagnosis of their optical and physical characteristics is presented. Results of the formation of the informational resource on mathematical, spectroscopic, software and hardware support of passive and active remote sensing techniques of gas-aerosol media are discussed.
A numerical study of the gas-aerosol transmission function in IR range for various optical and microphysical parameters has been performed. Limit values of the aerosol particle concentration and effective radius that allow us to estimate a contribution of the gas and aerosol components to the radiation extinction have been determined.
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