Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
EVALUATION OF THE WSGG MODEL FOR COUPLED CALCULATIONS OF LAMINAR FLAMES
Submission Author:
Pedro Wink Guaragna , RS
Co-Authors:
Pedro Wink Guaragna, Guilherme Crivelli Fraga, Fernando Pereira, Francis França
Presenter: Pedro Wink Guaragna
doi://10.26678/ABCM.COBEM2021.COB2021-1138
Abstract
Radiation in participating media is an important subject in thermal engineering due both to its great complexity and importance in a variety of phenomena, including furnaces, fires, and flames. The rate at which typical combustion gases emit and absorb radiation is heavily dependent on the wavenumber spectrum, and this dependence is very irregular and characterized by hundreds of thousands of absorption lines. Among the models that represent this dependence that are available in the literature, the weighted-sum-of-gray-gas (WSGG) stands out for its compromise in reliability and computational cost. The WSGG model represents the spectrum with a few gray gases that occupy certain portions of the spectrum plus a transparent window, and various recent studies have shown that the model is capable of fully accurate predictions of the radiative heat flux and heat source. However, the majority of studies have assessed the WSGG model for decoupled radiative transfer calculations, i.e., where the radiation field is computed from predetermined fields of pressure, temperature and species concentration. In practical applications, though, radiation is coupled to all other physical processes, and it is known that inaccuracies in the prediction of the radiation field can lead to errors in other scalars, such as the temperature and the rate of species formation. In the framework of combustion processes, this can be particularly important, since it is critical to accurately capture formation of some species (e.g., NOx). Therefore, this study carries out an evaluation of different formulations of the WSGG model for coupled radiation-combustion calculations of a set of one-dimensional, laminar flames. The calculations are performed in the CHEM1D code, on which the WSGG model (and the line-by-line integration method, which serves as the benchmark for the comparisons) has been implemented. Results for the fields of temperature and species concentrations, as well as the radiation field, will be analyzed. Comparisons with calculations that neglect radiation or use the optically thin approximation to account for the radiative transfer will also be performed.
Keywords
Radiation heat transfer, Combustion, laminar flames, emission
