Experimental and analytical study on inclined turbulent fire in still air. Part 1. Line fire

Abstract

In this paper, an experimental and theoretical analysis is conducted on the behavior of the inclined turbulent line fires under different initial Froude numbers (Fr0) and initial flame angles (θ0). The flame temperature and flow fields are measured, and the flame geometry is extracted from video images. Experimental results show that the curvature of flame trajectory increases with the increase of Fr0 or the decrease of θ0. The axial temperature and flame length decrease as θ0 decreases under the same Fr0, indicating the enhancement of flame entrainment due to the cross stream-buoyancy. A prediction model to describe the flame motion is established by analyzing the mass and momentum equations. The model combined with the kinetic energy equation incorporates the effects of buoyancy and streamline curvature on the flame entrainment. The model predicts the flame trajectory and correlates the flame entrainment coefficient of turbulent line fires under different Fr0 and θ0. Model calculations show that the comprehensive effect of buoyancy and streamline curvature on the flame entrainment increases as Fr0 increases within a certain range or as θ0 decreases, in agreement with the experimental indications. The results of this paper are expected to help understand the flame motion and develop radiative heat transfer models of turbulent line fires.