Numerical simulation of the chimney effect on smoke spread behavior in subway station fires

Abstract

To reveal the chimney effect on smoke spread behavior, three-dimensional numerical simulations of subway station fires in a 1/8 scale model were presented by using large eddy simulation. The impacts of the cross-sectional area of the shaft, fire location and shaft height on the smoke spread behavior were analyzed. The results show that the chimney effect significantly influences smoke movement. For the cases with heights of 1 m for the left and right shafts and the fire location at the hall center, when the ratio of small cross-sectional area to large area equals 0.4 or more, the smoke exhausts from the shaft with a small area; otherwise, the smoke exhausts from the shaft with a large area. With equal cross-sectional areas and heights of 1 m or more for the two shafts, the smoke exhausts from the shaft closer to the fire location. The left and right shafts are both passages for flowing upward smoke and flowing downward air when the heights of the two shafts are less than 1 m. In the stable flow stage, the chimney effect increases with decreasing cross-sectional area and increasing shaft height and is not affected by the change in fire location.