Velocity Fields of Nonpremixed Bluff-Body Stabilized Flames

Abstract

The velocity fields of nonpremixed circular-disk stabilized flames are measured by a two-component laser Doppler velocimeter. The results are presented in different flow regimes: prepenetration, penetration, and large shear flow. The velocity-vector fields, streamline patterns, corresponding flame appearances, and axial length of recirculation bubble in different flow regimes are illustrated and compared. Mean velocity and turbulent stresses along the central axis are presented and discussed. The combustion characteristics in different characteristic flow regimes are presented through the discussion of entrainment, diffusion, mixing capabilities, flow patterns, and turbulence properties. The detached flames, particularly operating in the transition flow regime, offer a relatively efficient combustion situation. Operating the concentric-jets burner in the regime of high shear flow do not benefit mixing and flame stability through the bluff-body effect. [S0195-0738(00)00102-3]