纵向排烟与集中排烟下烟气控制效果的对比研究

以某特长公路隧道为研究背景,采用缩尺寸试验测试、数值模拟的方法分别对纵向排烟和集中排烟模式下隧道内火灾烟气的蔓延特性进行了研究,并对比分析了两种排烟系统在火灾工况下对烟气的控制效果。结果表明,纵向排烟模式将火灾烟气控制在火源下游并从隧道出口排出,高温烟气蔓延范围较长;集中排烟模式通过排烟阀将烟气抽离行车道,有效地控制了烟气蔓延和沉降,高温烟气维持在行车道的上部空间,主要通过竖井排出隧道。采用纵向排烟模式的坡度隧道烟气控制受烟囱效应影响较大,而在设置排烟道的坡度隧道中,将排烟阀开启进行自然排烟就能有效地减弱烟囱效应。因此,采用集中排烟模式的防灾安全性能要优于采用纵向排烟模式。

Comparative study between the longitudinal ventilation smoke control mode and the central smoke exhaust mode

In the present study,we would like to introduce the findings of our comparative study between the longitudinal ventilation smoke control mode and the central smoke exhaust mode.Based on the practice of an extra-long road tunnel,we have chosen our topic of comparative study on the fire-induced smoke development in tunnel under longitudinal ventilation mode and the central exhaust mode through similarity model tests and numerical simulation.Since the experimental data of similarity model can be transformed to full-scale data based on Froude theory,it is believed that numerical simulation can provide significant information so as to carry out our comparative study effectively.In our research,we have compared the smoke control effects in tunnel fires under two smoke exhaust modes from such aspects,as the smoke spreading range,the smoke temperature distribution,smoke exhaust efficiency,visibility distribution,the smoke development in sloping tunnel as well as the chimney effect.The results of our tests show that when smoke is blown downstream of the fire source,traveling further from the fire source,it can be removed from the tunnel portal under longitudinal ventilation mode.If the smoke is extracted from the roadway through smoke dampers,it can keep on staying on the roof of the tunnel.In such a situation,it can be controlled effectively in the small area near the fire source,and make it exhausted out of tunnel through shaft.However,when the smoke temperature at the upstream position from the fire source is low under longitudinal ventilation,the temperature at the downstream position would be higher than that under the central smoke exhaust mode.Besides,since the influence of chimney on the smoke control in sloping tunnel is significant under longitudinal ventilation mode,it can be reduced effectively with the smoke exhaust duct with the smoke dampers being open.Thus,it can be concluded that the longitudinal ventilation mode can only be used in one-way traffic tunnel,the central smoke exhaust system is supposed to be superior in guaranteeing the fire safety in case of longitudinal ventilation.