Modelagem da radiação térmica em chamas laminares da combustão de metano em ar

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

2011

RESUMO

This work analyses the effects of thermal radiation heat transfer on methane-air laminar diffusion flames. The analysis is based on the solution of the equations of continuity, fluid motion, species mass-fraction and enthalpy. The soot formation is accounted with a twoequation model while a chemistry mecanism with 112 reactions is used for the combustion of methane. To evaluate the effects of thermal radiation, the divergence of the radiative heat flux is calculated based on four different gas models: the gray gas, the weighted sum of gray gases, the SLW and the CW model. In the modeling, it is considered a participating media composed of carbon monoxide, carbon dioxide, water vapor and soot. Both in the gray gas model and in the weighted sum of gray gases model, the absorption coefficient of the mixture is obtained by correlations that depend on the local temperature and concentration of the medium. On the other hand, in the SLW and CW models, the absorption coefficient is calculated based on the HITEMP spectral database. Thus, the results of the divergence of the radiative heat flux are compared with the different gas models based on a temperature and concentration fields previously obtained, and then, the four gas models used are considered in the entire combustion process to verify the influence of the radiation heat transfer. The results obtained for the divergence of the radiative heat flux considering the four different radiation models used showed an avereged difference of 20%, with a maximum local difference of more than 50%, when the WSGG model was considered. On the other hand, in situations where the whole combustion process is considered, the major difference occurs when is compared the results obtained with a radiation model and the ones where it is neglected. The effects observed with the different radiation models in the temperature field and the gas concentrations were small. Thus is observed that, even in optically thin media, the thermal radiation gas modeling is necessary, and in this particular kind of media, the use of sofisticated gas models are not necessary, because the absorption effect fo the gases are small when compared with their emission.

ASSUNTO(S)

thermal radiation combustão participating media transferencia de calor combustion modelos matematicos radiação térmica soot

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