Application of the weighted-sum-of-gray-gases model in a simulation of a open flame with ANSYS/FLUENT
Luís Gustavo Pires Rodrigues1; Fernando Marcelo Pereira1; Paulo R. Pagot2; Francis Henrique Ramos França1
1 Federal University of Rio Grande do Sul; 2 CENPES/ PDEP/ TPP - PETROBRAS
doi:10.20906/CPS/COB-2015-0768
Resumo
In this study the weighted-sum-of-gray-gases model is applied to an ANSYS/Fluent simulation of an open flame. The flame is diffuse and turbulent, and composed of methane and air. The problem is first solved only for the combustion process, and after convergence the radiation model is included in the analysis. For the flame both transient (until stabilize) and steady (until convergence) states were considered. To solve the radiative transfer problem in the non-homogeneous, non-isothermal medium the discrete ordinates combined with the weighted-sum-of-gray-gases model is adopted. The participating medium is divided into four gray gases. The absorption coefficient of each gray gas was computed by taking account the local concentration of each of the participating species (in this study carbon dioxide and water vapor in a ratio of partial pressures or molar concentrations of 2/1) making use of a user-defined function (UDF) written on a C programming language. The emissivity weighting factor of the participating medium, for each gray gas, is computed as a function of local temperature making use of the UDF as well. A few cases that vary the inlet rates of air and fuel are tested and compared with solutions available in the literature. The obtained results show that the weighted-sum-of-gray-gases model is viable and accurate alternative to solve problems of thermal radiation in participating media even with its simplicity.
Palavras-chave: Radiative transfer; WSGG model; combustion; CFD