Abstract:

Reasonable water spray design parameters and smoke exhaust strategy can ensure the effective smoke exhaust and smoke layer stability of the tunnel, and provide a favorable environment for the safe evacuation of personnel. In order to study the optimal water spray flow rate and smoke vent design parameters when the smoke loses the stable critical state in the side smoke exhaust mode, FDS was used for a 15 MW fire scale with different water spray flow rate, smoke exhaust volume, distance or height of smoke exhaust vent. 19 groups of working conditions with different spray flow, smoke exhaust flow, distance or the height of the smoke exhaust port are simulated and calculated. The results show that: the greater the spray flow, the higher the height of the smoke layer, the lower the overall temperature of the tunnel, and the change of the spray flow has a little effect on the stability of the smoke layer, there is smoke retention in the tunnel space. The smoke exhaust port is 70 m3/s, the exhaust port spacing is 50 m, and the exhaust port height is 3.2 m or 4.0 m, which is the best parameter of the exhaust port when the smoke layer is in a critical state. At this time, the side suction force upward component and the thermal buoyancy is greater than the drag force of the water spray, the smoke layer is relatively stable, and there is no swirling and smoke retention in the tunnel space, which is beneficial for smoke exhaust and personnel evacuation. 

Key words: side point smoke extraction, water spray, smoke layer stability, numerical simulation