Study Of Efficient And Accurate Non-gray Gas Radiation Models

The importance of thermal radiation heat transfer in combustion systems and flames has been paid unprecedented attention due to its often dominant role in heat transfer. Thermal radiation also offers various ways to reveal the state of combustion through inverse analysis from the detected radiation signals. Ultrafast pulse radiation is rapidly being deployed in many new applications. However, accurately modeling of thermal radiation is a formidable task due to the spatial and direction dependence of radiation intensity and extremely rapid variation of the absorption coefficient of gaseous species such as CO2 and H2O. Thermal radiation modeling has received attention in the 1950's. The last 20 years have witnessed rapid progress in the development of accurate and efficient modern non-grey gas radiation models. More research is required to improve the current modeling methods in terms of gas mixture treatment and non-grey particle scattering treatment. Therefore, this article will concentrate on further improve the current non-grey radiation models in terms of accuracy, or efficiency, or both. Specifically as follows:Firstly, the statistical narrow-band (SNB) model and SNB correlated-K method were employed to study the effect of soot volume fraction up to 1 ppm on the source term, the narrow-band radiation intensities along a line-of-sight, and the net wall heat fluxes were investigated for a wide range of temperature. In addition, the Planck-mean absorption coefficients were obtained using these models.Line-by-line calculations using the high-resolution spectral databases were conducted for six test cases of radiative heat transfer in one-dimensional enclosure between two parallel plates. This study demonstrates the importance of spectral database to the accuracy of line-by-line calculations through a systematic comparison of line-by-line results from different databases. The agreement between the LBL results using the HITEMP2010 database and the results of the SNB model was found to be very good for both the wall heat flux and the radiative source term.Radiation heat transfer in two-dimensional rectangular enclosures containing CO2/H2O/N2 mixtures was calculated using the line-by-line and the statistical narrow-band correlated-k models. The present line-by-line results can serve as benchmark results for the purpose of validating other approximate models. The SNBCK results were found in good agreement with those of the LBL model. Therefore, it can provide benchmark solution in the absence of LBL results in multi-dimensional gas radiation heat transfer problems.Databases of the absorption line blackbody distribution function (ALBDF) of CO2 and H2O were firstly generated over a wide range of gas and blackbody temperature and the full range of gas concentration from line-by-line (LBL) calculations using the latest version of HITEMP. Proper orthogonal decomposition (POD) and the new hyperbolic correlations (HC) were developed and used for rapid calculation the ALBDF value at an arbitrary combination of gas and blackbody temperatures and gas concentration. Then, the POD-SLW model was proposed.Narrow-band transmissivities in the spectral range were calculated using the statistical narrow-band model and the line-by-line method along with the HITEMP high-resolution spectral database. New Planck-mean absorption coefficients formats were developed based on these two methods. Planck-mean absorption coefficients obtained using LBL method were applied to the two-dimension diffustion flame.The effect of radiation at different gravity on flame structure and soot formation in coflow CH4/air diffusion flames were investigated.In summary, the LBL and SNB models are flexible and valid computation methods for high temperature gas radiative properties and radiative transfer simulation.