Radiation-turbulence interactions in pulverized-coal flames. Technical report for quarter VI, December 15, 1994--March 30, 1995

The purpose of this paper is to discuss the nature of the unsteady interactions between buoyant turbulence and radiation feedback to the center of flames. An unfiltered additive turbulent decomposition (ATD) is carried out in a manner similar to that originally developed by McDonough and co-workers for studying Burgers` equation. The new approach is philosophically similar to LES; namely, treat the large and small scales separately. However, the technique requires no formal filtering or averaging for the large-scale equations. and the corresponding subgrid-scale models are obtained as local spectral approximations of the original governing equations. In the present work, only the small-scale part of the governing equations has been solved, and the large-scale parameters are to be obtained directly from either a global computer program or from corresponding experimental results. Preliminarily calculated results show that the radiation in the flame markedly influences the flow in the center of flame, and even periodic radiation fluctuations can lead to chaotic behavior of the flow. The extent to which the flow fluctuates not only depends on fluctuation of radiative properties, but also on the profile of the mean absorption coefficient