Experimental study on the characteristics of fire smoke longitudinal crossflow in adjacent tunnels

Abstract

Tunnel fire smoke is an important fatal factor. For the adjacent tunnels, fire accidents in the upstream tunnels often produce a large amount of toxic smoke, which may have a certain impact on the downstream tunnels under the external wind. Based on the influence of external wind on fire smoke crossflow in adjacent tunnels, a series of experimental studies are carried out in this paper. Through experiments, it is found that the factors affecting the critical crossflow velocity between adjacent tunnels mainly includes the tunnel section itself, the separation distance between adjacent tunnels, and fire heat release rates. By changing different influencing variables, the critical crossflow velocity value under different test conditions is experimentally obtained. Combining experimental phenomena and theoretical analysis, it is also found that the Froude number (Fr), which represents the competition between external wind flow and thermal buoyancy, maintains a small range fluctuation of about 0.75 under the conditions of critical crossflow velocities. Under certain conditions, the critical crossflow velocity is proportional to the third power of fire heat release rate. Finally, a prediction correlation of the critical crossflow velocity of fire smoke in adjacent tunnels under the action of external wind was proposed.