J.H. Sun

Experimental study on influence of stack effect on fire in the compartment adjacent to stairwell of high rise building

AbstractIn this paper, to study the influence of stack effect on fire in the compartment adjacent to a stairwell, a set of experiments were conducted by varying the pool size, top vent state and bottom vent size in a 1/3 scaled 12-layer-stairwell configuration. The phenomenon of methanol flame tilting in the fire room was observed and studied. Results showed that the flame tilt angle increases with an increase of Ri-1. The temperatures of hot gases in the fire room decrease due to the cooling effect of fresh air induced by stack effect. The mass loss rate of methanol fuel is influenced by fresh air flow sucked into fire room due to stack effect. On the basis of the experimental results, we conclude that the velocity of air flow into fire room is proportional to 1/3 power of the heat release rate in the stairwell.

Effects of vertical shaft geometry on natural ventilation in urban road tunnel fires

AbstractA set of burning experiments were conducted to investigate the effect of vertical shaft geometry on natural ventilation in urban road tunnel fires. Results show that using vertical shafts to discharge smoke leads to a boundary layer separation near the right-angle connection of the shaft and the tunnel ceiling. In a low shaft, the turbulent-boundary-layer separation phenomenon causes relatively large-scale vortexes and restricts smoke from being exhausted, resulting in a negative effect on natural ventilation. Replacing the right-angle connection with the bevel-angle connection was proposed to split one separation point into two separation points, to attenuate the negative effect. The detailed characteristics of the separation phenomenon were analysed and the proposition was verified by Large Eddy Simulation. Results show that there are no relatively large-scale vortexes in shafts with bevel-angle connections, resulting in improved natural ventilation effectiveness. For lower shafts, the advantage...

Numerical studies on smoke spread in the cavity of a double-skin façade

AbstractIn this paper, influence of two key factors, fire room height and outer pane tilt angle, on smoke spread in the cavity of a double-skin facade (DSF) was studied numerically. The fire room was located adjacent to the DSF on the 2nd, 4th and 6th floors, respectively. The outer pane tilt angle varied at 80°, 90° and 100°. All cases were under two fire heat release rates of 1 MW and 5 MW. Results suggested that fire room height and outer pane tilt angle had significant effects on smoke spread in the cavity. For different fire room heights, there were two markedly different scenarios of smoke spread in the cavity between two vertical panes in a high-rise building. For outer pane tilt angle, the DSF with an inward tilted or vertical outer pane was dangerous for the upper floors due to hot smoke adhering to the upper inner pane. However, the turbulent vortex in the DSF with an outward tilted outer pane prevented hot smoke flowing out from the fire room.