An inverse radiation model for optical determination of temperature and species concentration: Development and validation

Abstract

a b s t r a c tIn this study, we present an inverse calculation model based on the Levenberg-Marquardt optimization method to reconstruct temperature and species concentration from measured line-of-sight spectral transmissivity data for homogeneous gaseous media. The high temperature gas property database HITEMP 2010 (Rothman et al. (2010) [1]), which contains line-by-line (LBL) information for several combustion gas species, such as CO 2 and H 2 O, was used to predict gas spectral transmissivities. The model was validated by retrieving temperatures and species concentrations from experimental CO 2 and H 2 O transmissivity measurements. Optimal wavenumber ranges for CO 2 and H 2 O transmissivity measured across a wide range of temperatures and concentrations were determined according to the performance of inverse calculations. Results indicate that the inverse radiation model shows good feasibility for measurements of temperature and gas concentration.

Open-Path FTIR Spectral Radiation Intensity Of Hot Combustion Gases – Measurement And Interpretation

“…The midinfrared region is dominated by the carbon dioxide band, which contains information about the observed path. A general feature of the 4.3 µm CO2 spectrum is higher temperature than concentration sensitivity, and therefore much better temperature determination [21]. The methods of utilizing the spectra can be divided according to the type of temperature heterogeneity of the studied environment and the specifics of the inversion algorithm.…”

Optical Determination of Temperature and Species Concentration for Homogeneous Turbulent Gas Medium

“…(12) and (13), the mean and variance for the turbulence optical thickness χ η need to be evaluated first. The mean is…”

“…The goal of inverse calculations is to minimize these two functions by properly guessing the parameter vectors until the best matches between the measured spectra and predicted spectra data are achieved. In our previous study [11,12], the LevenbergMarquardt optimization method was applied to retrieve temperatures and species concentrations for laminar gaseous media. We found the Levenberg-Marquardt optimization method to be relatively reliable, more accurate and requiring less computational effort than several other methods tested.…”

“…The Levenberg-Marquardt method increases the value of each diagonal term of the ill-conditioned Hessian matrix H (regularization), to mitigate the ill-posedness of the problem. Details for the computational algorithm using the LevenbergMarquardt method can be found in [11,12,50]. the procedure for retrieving all the parameters is summarized as follows 1.…”

“…Griffith et al [1,2] were the first to recognize that measurements of the transmissivity or emissivity of rotational spectral lines of a gas can reveal its temperature. Work has been done to extract temperature and species concentration for laminar combustion system [3][4][5][6][7][8][9][10][11][12] based on optical measurements of transmission or emission. For a turbulent system, it has long been recognized that the nonlinear interaction between turbulence and radiation (TRI) has profound effects on the heat transfer of turbulent combustion systems [13][14][15][16][17], leading to sharply increased radiative heat loads to the adjacent walls and surroundings.…”