Effects of wind flow and sidewall restriction on the geometric characteristics of propane diffusion flames in tunnels

Diffusion flame characteristics are important for predicting and controlling the energy transfer to fuel surface and surrounding targets during an undesirable energy source releasing in a tunnel. To explore the effects of wind flow and sidewall restriction on the geometric characteristics of turbulent diffusion flames in tunnels, experiments of propane burner fires were performed in a bench-scale wind tunnel. Two different fire source positions, i.e., centerline fire and sidewall fire, were considered. The energy (heat) release rate of the fire source and the ventilation velocity were varied in the range of 15-105 kW and 0-3 m/s, respectively. The flame shape, flame tilt angle and flame drag length were investigated. The results suggest that the flame tilt angles of two fire source positions both increase faster first and then increase slowly with increasing ventilation velocity, and the flame tilt angle of the sidewall fire is smaller than that of the centerline fire due to the inhibition of the frictional drag force. With the increase in ventilation velocity, the flame drag length of the centerline fire is first smaller than, and then approaches, and eventually exceeds that of the sidewall fire owing to the varying force mechanism. Finally, correlations of flame drag length were proposed and compared with previous experimental results. (C) 2020 Elsevier Ltd. All rights reserved.