纵向通风在超长隧道中排烟效果的研究

Study on the Smoke Exhaust Effect of Longitudinal Ventilation in Ultra-long Tunnels

采用FDS耦合Fluent进行数值模拟的方法,研究了过江电缆隧道火灾过程,以及火灾结束后的全隧道排烟过程,分析了以设计断面风速为2.2m/s时进行全隧道排烟期间的烟气流动规律。结果表明,在纵向通风气流作用下,防火墙仅在通风5min前对烟气阻挡;在全隧道排烟中,通风气流不断推动烟气前进,同时烟气浓度被稀释。对于不同长度的隧道排烟时,存在临界隧道长度,若隧道长度小于临界长度,实现烟气安全浓度依赖于通风气流把烟团推出隧道;若隧道长度大于临界长度,烟气在被推动到临界长度时已降低到安全浓度以下,无需再继续排烟到排风口处。据此得出了不同隧道长度下所需排烟时间。

Using FDS coupled Fluent numerical simulation method to study the fire process and the smoke exhaust process of the entire tunnel in the ultra-long river crossing cable tunnel.The smoke flow law during the smoke exhaust process of the entire tunnel was analyzed at a design cross-sectional wind speed of 2.2m/s.The results show that under the action of longitudinal ventilation airflow,the firewall only blocks the smoke 5 minutes before ventilation;In the entire tunnel smoke exhaust,the ventilation airflow continuously drives the smoke forward,while the smoke concentration is diluted.When exhausting smoke from tunnels of different lengths,there is a critical tunnel length.If the tunnel length is less than the critical length,achieving the safe concentration of smoke depends on pushing the smoke out of the tunnel;If the tunnel length is greater than the critical length,the smoke has already decreased to a safe concentration below the critical length,and there is no need to continue to exhaust smoke to the exhaust outlet.Based on this,the required smoke exhaust time for different tunnel lengths was obtained.