Tae-Ho Song

Data Base of WSGGM-based Spectral Model for Radiation Properties of Combustion Products

Abstract This work completes the preceding low-resolution spectral modeling of the authors based on water vapor. It is extended to water vapor, carbon dioxide and their mixtures by applying the weighted-sum-of-gray-gases model (WSGGM) to each narrow band. Proper modeling scheme of gray-gas absorption coefficients vs. temperature relation is suggested. Comparison between the modeled emissivity calculated from this relation and the ‘true’ emissivity obtained from the high-temperature statistical narrow band parameters (Soufiani and Taine. Int J Heat Mass Transfer 1997;40:987–91) is made for a few typical narrow bands. Low-resolution spectral intensities from one-dimensional layers are also obtained and examined for uniform, parabolic and boundary layer-type temperature profiles using the obtained WSGGMs with several gray gases. The results are compared with the narrow band spectral intensities obtained by a narrow band model-based code with the Curtis–Godson approximation. Good agreement is found between them. Database including optimized modeling parameters and total and low-resolution spectral weighting factors are developed for water vapor, carbon dioxide and their mixtures. This model and obtained data bases, available from the authors’ internet site, can be appropriately applied to any radiative transfer equation solver.

Measurement of gas temperature distributions in a test furnace using spectral remote sensing

This work has been supported by the Brain Korea 21 project and the National Research Laboratory project of the Ministry of Science and Technology, Korea, and the Korea Science and Engineering Foundation (996-1000-001-2).

Conservative Interpretation of Nonconservative Discrete Ordinates Radiative Intensity Distribution

The discrete ordinates interpolation method (DOIM) and the finite element discrete ordinates method (FEDOM) show good accuracy and versatility for calculation of radiative intensity. However, these methods are nonconservative since the intensity is computed only at grid points without considering control volume. When these methods are to be used together with a finite volume-based code for fluid flow and transport analysis, intensity at the center of control volume or surface, whichever is missing, needs to be calculated, and the control volume photon balance should be evaluated. For this reason, the method of satisfying control volume photon balance, without sacrificing the accuracy, is critically discussed first. Based on this rationale, the supplementary DOIM (SDOIM) is proposed to calculate the missing intensity. In addition, the integration method of RTE (IMRTE), used in DOM or FVM to satisfy the control volume photon balance, and linear interpolation method (LIM) are also examined to compare with the SDOIM. The accuracy, physical reliability and smoothness of the intensity obtained by using the three methods are carefully analyzed. Application of the SDOIM shows reliable results which are accurate and free from physically unrealistic intensity distribution.Copyright

SRS Inversion of Flame Temperature/concentration Profile with Radiation/Turbulence Interaction

The SRS method is applied to a turbulent flame with radiation/turbulence interaction to invert the temperature and concentration profile. The flame is conditioned as optically thin per each fluctuation length and the flame spectral intensity is measured for inversion. From inversion result, we find that SRS can successfully invert the coupled temperature/concentration fluctuation amplitudes. For two cases of experiments, inverted values are within approximately 1% over the full range of fluctuation amplitude. However, SRS cannot find the detailed local fluctuation parameters such as pattern and phase, etc. as far as they do not affect the resulting radiation intensity. Important available parameters are the mean temperature and the temperature fluctuation amplitude. The radiation/turbulence interaction effect is verified to play an important role in the radiation.

Error analysis of spectral remote sensing by CO2 4.3 μm band in various temperature profiles

Abstract The inversion error of temperature profiles reconstructed by the spectral remote sensing (SRS) technique is analyzed by using CO 2 4.3 μ m band. Total of 14 narrow bands averaged over 25 cm −1 spectral width is selected as the low-resolution sensing spectra from 2050 to 2400 cm −1 . The HITRAN line-by-line database enhanced with hot line data is utilized as the tool to generate the reference spectral intensity. The medium is assumed to be filled with nonisothermal pure CO2 gas at 1 atm. Four temperature profiles are tested in this work: three boundary layer types, and one prabolic type. Continuous temperature distribution is assumed by specifying three pointwise temperatures. Through this work, it is investigated how much inversion error of temperature is induced per unit relative error in ‘true’ and ‘measured’ intensities when changing the number of sensing narrow bands, combination of narrow bands, path length, temperature profile shape, temperature level, and temperature gradient. The error analyses show that the SRS inversion with this band gives accurate inversion of temperature within 1% error when both of the measured and the reference intensities have 1% error for any temperature profile up to 2500 K and up to about 10 m path length. It is also found that a cold layer behind a hot layer is not accurately detected for higher path length, so the sensor is better to be located at the colder side.