纵向风与水雾耦合作用下城市隧道车辆火灾发展动力学特性研究

The vehicle types in urban tunnel are various, including heavy good vehicles and oversize vehicle. The clear height of urban tunnel is low. So in case of a vehicle fire, it is easy to form a ceiling jet flame in urban tunnel. To control fire in tunnel, more and more urban tunnel install automatic water spray system; to control fire smoke, the longitudinal ventilation is a main tunnel ventilation method. Previous research studied the efficiency of water mist in fire control and the influence of water spray on the stability of the smoke layer; but little research have focused on the characteristics of flame ceiling jet under the coupling effect of longitudinal ventilation and water spray. Ceiling jet flame not only can destroy the tunnel structure, would also cause the fire spread, and even a jump spread. In addition, the coupling application of longitudinal ventilation and water spray in tunnel will make ceiling jet flame become more complex. Through theoretical analysis, numerical simulation and experimental research of the project, the proposal will analyze the four kinds of effect of forced mixing, evaporation, flammable vapor dilution and blocking radiant heat feedback of water spray on the ceiling jet flame , analyze the three kinds of effect of air supply, heat convection and the water droplets’ drag force of longitudinal ventilation on the ceiling jet flame, reveal dynamics characteristics of vehicle ceiling jet flame in urban tunnel with the coupling effect longitudinal wind and water spray; study mass burning rate of vehicle fire, and fire control effect of water mist, reveal the relation of critical velocity that lead to the failure of water mist system with fire power and spray characteristics, and establish the critical velocity prediction model; study the smoke flow characteristics in downstream region outside water spray flooding area, and reveal the related characteristics of CO concentration stratification and wet smoke particle stratification outside water spray flooding areas. The results can be used for the design of water spray system and smoke control system, and structure protection of tunnel.

城市隧道车型多样且净高低，一旦发生车辆火灾，易形成顶棚射流火焰。为控制火灾，越来越多的城市隧道安装了自动水雾系统。前人对水雾的控火效果及对烟气层稳定性的影响开展了研究；但是对纵向风和水雾耦合作用下的顶棚射流火焰特性的研究却很少。顶棚射流火焰更危险，不仅会破坏隧道结构，还会引起火蔓延；而纵向风和水雾耦合作用下顶棚射流火焰的发展将更加复杂。本项目拟通过理论分析、数值模拟和实验研究，研究水雾作用下顶棚射流火焰发展特性，建立火焰长度等关键参数的随雾特性变化模型；研究纵向风和水雾耦合作用下车辆火灾质量燃烧速率和水雾控火效果，揭示导致水雾系统控火失败的临界纵向风速与火源功率、雾特性等关键参数的内在联系，建立导致水雾控火失败的临界风速预测模型；研究纵向风作用下水雾淹没区下游火灾烟气分层流动特性，揭示水雾淹没区下游烟气分层特性及纵向分布特征；结果可用于指导城市隧道水雾系统及纵向排烟系统设计和结构保护。

城市隧道车型多样且净高低，一旦发生车辆火灾，易形成顶棚射流火焰。为控制火灾，越来越多的城市隧道安装了自动水雾系统。前人对水雾的控火效果及对烟气层稳定性的影响开展了研究；但是对纵向风和水雾耦合作用下的顶棚射流火焰特性的研究却很少。顶棚射流火焰更危险，不仅会破坏隧道结构，还会引起火蔓延；而纵向风和水雾耦合作用下顶棚射流火焰的发展将更加复杂。本项目通过理论分析、数值模拟和实验研究，研究了顶棚射流火焰发展特性，建立火焰长度、火焰脉动等关键参数变化模型；为抑制顶棚射流火焰和火灾烟气，研究了纵向风作用下火灾烟气分层流动特性；通过水雾与射流的相互作用的流场结构分析，改进了细水雾喷头，并研究了改进前后水雾淹没区下游烟气分层特性及纵向分布特征；还研究了改进前后细水雾抑制顶棚射流有效性，分析了温度场、浓度场和火焰结构；结果可用于指导城市隧道水雾系统及纵向排烟系统设计和结构保护。