隧道纵向通风对火灾规模和火灾蔓延的影响

Influence of Longitudinal Ventilation on Fire Size and Propagation in Tunnels

隧道纵向通风一方面会给火源提供大量氧气,扩大火灾规模,增加火灾蔓延的可能性;另一方面又可以带走大量热量,减小火灾蔓延的可能性。目前,这两方面影响的相对重要性还没有被很好地研究。本文对纵向通风对隧道火灾蔓延的影响进行了研究,首先分析了纵向通风对隧道火灾规模的影响,然后利用火灾动力学模拟程序FDS,对不同通风速率及相应火灾规模条件下隧道内车辆间的火灾蔓延进行了数值模拟,得出了不同通风速率条件下火灾蔓延的规律,并提出了控制隧道火灾蔓延的措施。结果表明,增加通风速率能较大地增加货车火灾的热释放速率,当通风速率小于2 m/s时,火灾蔓延的距离随通风速率的增加而增大,当通风速率大于2 m/s时,火灾蔓延的距离受通风速率的影响很小;对于客车火灾,通风对火灾的热释放速率影响较小,并且火灾蔓延的距离随通风速率的增大而减小。

Longitudinal ventilation is widely used to control smoke movement in tunnels in the case of fire; however, the influence of longitudinal ventilation on fire propagation in tunnels has not been thoroughly investigated for the influence includes two contrary aspects. On the one hand longitudinal ventilation can supply abundant oxygen which can enlarge the fire size and increase the probability of fire propagation; on the other hand longitudinal ventilation can carry much of the heat away from tunnels and decrease the probability of fire propagation. This paper investigates the influence of longitudinal ventilation on fire propagation in tunnels. First, the influence on fire size is analyzed; then, the Fire Dynamics Simulator （FDS） is utilized to simulate the fire propagation between vehicles under different ventilation velocities and corresponding fire sizes. The laws of different longitudinal ventilation velocities on fire propagation are achieved and the measures to control fire propagation are proposed. The results show that, along with the increase of ventilation velocity, the heat release rate of fire is greatly increased; as for the influence on fire propagation, when the ventilation velocity is lower than 2 m/s, the distance of fire propagation increases with the velocity＇s increase, but when the ventilation velocity is larger than 2 m/s, it has little influence on fire propagation.