Flow field and fire characteristics inside a tunnel under the influence of canyon cross wind

摘要

A series of scale model tests were conducted to investigate the influence of canyon cross wind on burning and flame characteristics of ethanol pool fires inside a tunnel, considering pool size and fire location. At the same time, the characteristics of the flow field inside the tunnel were investigated by Fire Dynamics Simulator (FDS). Results show that an uneven three-dimensional flow field structure will be formed inside the tunnel with the effect of canyon cross wind, which can be divided into three zones, including the negative pressure zone, the transition zone and the unidirectional flow zone. Furtherly, the burning rates and flame shapes of pool fires with different fire locations will be varied. When pool fires are located in the negative pressure zone and the transition zone, the burning rates enhance linearly with the increase of canyon cross wind speed, and the flames appear with a fluctuation phenomenon. When pool fires are located in the unidirectional flow zone, the pool fires show a highly stable burning phenomenon and both the burning rates of the two pool sizes experience three stages with the increase of canyon cross wind speed. A new dimensionless flame length prediction model of pool fire is established based on the previous model proposed by Thomas, considering the effect of cross air flow on the burning rate. Findings of current study are helpful to enrich the tunnel fire research with external air flow.