The Influence of Temperature Ratio on the Dynamics of Bluff Body Stabilized Flames

The dynamics of bluff body stabilized flames are investigated using an unsteady, Lagrangian simulation technique . This paper presents an analysis of results from a parametric study of temperature ratio across a flame stabilized on a bluff body confined in a duct . The simulation presented in this study is a two -dimensional description of a premixed inflow of reactants with flame sheets attached to a triangular wedge. The analysis concentrates on flow field dynamics related to the transition from the asym metric Von Karman shedding found in non -reacting bluff body flows to independent shear layer vorticity commonly observed in many reacting flows. Details of this transition are described in terms of the instantaneous vorticity field, as well as mean and uns teady components of velocity and temperature. It is shown that for relatively small temperature differences across the flamesheets, the Von Karman shedding mode remains dominant, although the strength of the shed vortices decreases with increasing temperat ure ratio. As the temperature ratio increases, the Von Karman shedding mode is completely suppressed, and this suppression is clearly evident through RMS temperature profiles as well as turbulent stresses near the bluff body.