Experimental study of the effects of free stream turbulence on lean blowoff and near blowoff dynamics of a bluff-body stabilized conical premixed propane flame

摘要

This experimental investigation focuses on the blowoff dynamics of a bluff body stabilized flame subjected to different levels of turbulence intensities in the approach flow. Experiments were performed using propane-air mixture at atmospheric conditions. The mixture approach velocities were varied from 5 to 15 m/s. By using suitable arrangements, mean turbulence intensity levels between 4 and 30% were obtained. Simultaneous imaging of OH, CH_2O species by planar laser induced fluorescence (PLIF) and velocity field by particle image velocimetry (PIV) were performed to study the interaction of the heat release/flame zone with the flow field. The flame structure was observed to be strongly modified by the turbulent flow field which affects the lean extinction limits. The blowoff equivalence ratio increased with higher turbulence levels in the approach flow owing to strong interactions of the turbulent flow with the flame and the resulting modification of flame surfaces and local flame extinction.