Effect of oxygen concentration on the velocity in buoyant turbulent diffusion flames

Abstract

To better understand fire dynamics of buoyant turbulent diffusion flames under different oxygen concentrations (OCs, volumetric basis), we have recently conducted measurements on the flame temperature, radiation, and soot temperature and volume fraction under normal and reduced OCs. In the present study, particle image velocimetry (PIV) technique was employed to investigate the effect of OC (20.9%, 16.8%, and 15.2%) on the velocity field of the same flames with a theoretical heat release rate (HRR) of 15 kW. The statistics of the velocity field, such as mean and standard deviation of velocity, turbulent kinetic energy, Reynolds stress, and turbulent viscosity, were investigated and compared among different OCs. Results show that OC has minimal effect on the velocity distribution at heights close to the flame length. However, at lower heights above burner (HABs), turbulent mixing is reduced under reduced OCs, and the velocity shows an increased value at the flame centerline but with a narrower profile along the radial direction. Finally, a comparison with previous data was conducted and analyzed to further explore the fire dynamics. This study improves the physical understanding of related fire dynamics under reduced OCs and provides a comprehensive dataset for turbulent fire modeling validation.