Experimental and numerical study on smoke bifurcation in L-shaped passage fire under stack effect

Abstract

The L-shaped passage, widely used in subway entrances, mine laneways, and stairwells of high-rise buildings, is a confined corridor consisting of an inclined section and a horizontal section. Fires in L-shaped passages generate significant stack effect, leading to bifurcation phenomena in smoke flow within the passage. This study employs FDS software to numerically simulate smoke flow during fire incidents in L-shaped passages, investigating the effects of heat release rate (HRR), passage cross-sectional area, length of inclined segments, inclination angle, and ratio of horizontal to inclined segment lengths on stack effect and smoke bifurcation. The results indicate that passage height minimally affects smoke bifurcation, while HRR, passage width, length of inclined segments, and inclination angle significantly influence both the stack effect and the location of smoke bifurcation. Additionally, predictive expressions for the Froude number under different structural characteristics of L-shaped passages are proposed, along with criteria for evaluating smoke bifurcation phenomena under stack effect, as well as determining the location of maximum smoke temperature rise and smoke bifurcation. The findings provide valuable references for ventilation and smoke extraction design in buildings with similar structures.