Numerical Investigation Of Thermal Radiation Effects Of Non-premixed Flames

Probability density function (PDF) method is used to investigate turbulence-radiation interactions (TRI) and thermal radiation effects of non-premixed flames in this work.In order to predict thermal radiation effects accurately in high-temperature turbulent processes, it is necessary to consider the effects of TRI. Unfortunately, traditional moment methods fail to obtain closure of the turbulent-radiation interaction terms because too many additional partial differential equations need to be generated, modeled and solved. By now, it is believed that PDF methods, which have already been widely used in the study of turbulent chemical reactions, is the only practical method that can provide an elegant solution of TRI. Part of this thesis is devoted to studying TRI by PDF method. Through numerical cases, reasons that may cause TRI are discussed and factors that may influence the "size" of TRI are discussed.The second half of this thesis aims at studying the thermal radiation effects in turbulent non-premixed flames and two flames, namely Sandia flame L and Sandia flame D are chosen as simulation cases. As preparation, solution algorithms of Finite Volume Method (FVM), which is chosen as the solver of Radiative Transfer Equation (RTE), in structure/unstructured grids are presented and models for absorption coefficient, especially, Plank mean absorption and correlated- k distribution (CK) model, are introduced.In the simulation of Sandia Flame L, unstructured grids based consistent hybrid algorithm FVMC2D is implemented for the simulation of turbulence and combustion, and finite volume /Plank absorption is implemented to solve the radiative heat transfer equation with the effects of TRI are taken into account. The combustion and radiative heat transfer are coupled for the first time in the algorithm FVMC2D. The influence of thermal radiation, mainly, on temperature field is thoroughly discussed. In FVMC2D, particle tracing scheme is used to solve joint fluctuating velocity-frequen--cy-composition PDF composition equation, while Reynolds averaged mass, momentum and energy equations are solved by finite volume method.In the simulation of Sandia flame D, multiple-time scale (MTS) k - ε turbulence...