公路隧道机械排烟和细水雾耦合灭火效果研究

发布时间：2019-03-16 20:29

【摘要】：作为在时间和空间上失去控制的主要危害之一,火灾带给人们巨大的经济损失和人员伤亡。而隧道火灾由于其独特的空间特性,一旦发生,隧道内浓烟密布和远离消防大队等原因对火灾扑灭造成很大程度的影响。细水雾作为近年来出现的替代性环保灭火剂,发展迅速,与其他系统的联动控制使得细水雾在能够在有效时间内抑制火灾、控制火情的进一步蔓延。FLUENT通过对火灾偏微分方程组进行数值求解来得到火灾过程中特性参数的空间及时间分布,可以模拟火灾发生时烟气的温度及浓度变化过程,为研究相应的消防设施对火灾的抑制提供理论帮助。应用FLUENT研究细水雾的优化参数设计及与机械排烟设备的联动控制显得尤为重要。本文选择戊烷和庚烷作为火源燃料,采用非预混燃烧模型,在单室和隧道情况下,研究不同工况下施加细水雾对整个空间内温度和烟气浓度的变化情况,分析不同细水雾流量、喷雾方式、雾滴粒径及排烟方式对火场内温度场和浓度场产生的影响。(1)借助细水雾灭单室非正下方火源时火源远端的温度随时间变化的数据,进行对比验证,证明FLUENT进行细水雾灭火降温的可靠性,分析误差原因。在对比验证模型的基础上,设置火源功率为60Kw,改变模拟工况,得出结论:采用下喷方式,当其粒径为100μm,保证细水雾流量或流速任一变量恒定,细水雾流量或流速的增加都会减少细水雾对火灾的抑制时间,同比例增加的流量或流速,流速产生的抑制效果要优于流量;当改变下喷细水雾粒径为300μm时,选择最优流量及流速,发现细水雾对火源的抑制效果总体上要低于100μm细水雾;侧喷方式下,粒径为100μm,最优流量及流速,火源根部受到细水雾的冷却效果并不强烈,很难对整个火场空间降温灭火。(2)稳态模拟的公路隧道模型下,分析不同细水雾雾化锥角对火场空间的温度场影响,得出90o时,细水雾对整个火场的控火效果最优;当细水雾与纵向排烟耦合使用时,排烟与细水雾的耦合使用可以有效降低火场温度和排除有毒烟气,效果要优于单独施加细水雾工况,但排烟风速会对流量较小的细水雾灭火产生负面影响。(3)模拟不同机械排烟工况与细水雾的耦合作用对隧道空间温度场及烟气浓度产生的影响,结果表明:顶部排烟耦合细水雾对隧道空间的温度场及烟气浓度的控制效果要优于单独施加细水雾,可以降低烟气层厚度,但可能会产生烟气的倒流及温度场漩涡。纵向通风的效果要优于顶部排烟,进口端通风的送入使得高温烟气在推力的情况下向出口端排出,防止烟气倒流,但会影响细水雾雾滴的运动轨迹及对火源的抑制效果。纵向通风+下游顶部排烟效果最优,结合前面两种排烟工况的优点,同时使得隧道空间内温度及烟气浓度达到有效控制。
[Abstract]:As one of the main hazards out of control in time and space, fire brings huge economic losses and casualties. Because of its unique spatial characteristics, the tunnel fire has a great influence on the fire extinguishment due to the dense smoke in the tunnel and the distance from the fire-fighting brigade, once the fire occurs, the smoke in the tunnel is dense and far away from the fire-fighting brigade. Water mist, as an alternative environmental extinguishing agent appeared in recent years, has developed rapidly. The linkage control with other systems makes it possible for water mist to suppress fire within an effective time. By numerically solving the partial differential equations of fire, the spatial and temporal distribution of characteristic parameters in the fire process can be obtained, which can simulate the temperature and concentration changes of flue gas during the fire. It provides theoretical help for the study of the fire suppression of the corresponding fire fighting facilities. It is very important to use FLUENT to study the optimization parameter design of water mist and the linkage control with mechanical smoke exhaust equipment. In this paper, pentane and heptane were selected as fire source fuels, and non-premixed combustion model was adopted. Under the condition of single chamber and tunnel, the variation of temperature and smoke concentration under different working conditions were studied, and the different water mist flow rates were analyzed. The effects of spray mode, droplet size and smoke exhaust mode on the temperature field and concentration field in the fire field. (1) the temperature at the far end of the fire source was compared and verified with the help of the data of the temperature at the far end of the fire source with the help of the data of the water mist extinguishing the non-positive lower fire source in one chamber. It is proved that FLUENT is reliable for water mist fire extinguishing and cooling, and the cause of error is analyzed. Based on the comparison and verification of the model, the power of the fire source is set to 60kw, and the simulated working condition is changed. The conclusion is drawn: when the particle size is 100 渭 m, the flow rate or velocity of water mist can be kept constant, and the flow rate of water mist can be kept constant. The increase of water mist flow rate or velocity can reduce the fire suppression time of water mist. The same proportion of the increase in flow rate or velocity, the velocity of flow control effect is better than the flow rate; When the particle size of spray water mist is 300 渭 m, the optimal flow rate and flow rate are selected, and it is found that the effect of water mist on fire suppression is lower than that of 100 渭 m water mist on the whole when the particle size of spray water mist is 300 渭 m. Under the side spraying mode, the particle size is 100 渭 m, the optimal flow rate and velocity, and the cooling effect of water mist on the root of the fire source is not strong, so it is difficult to cool and extinguish the fire space in the whole fire field. (2) under the steady-state simulation of highway tunnel model, the cooling effect is not strong. The influence of different water mist cone angle on the temperature field space is analyzed. The results show that the water mist has the best fire control effect on the whole fire field at 90 o. When the water mist is coupled with the longitudinal exhaust smoke, the coupling use of the water mist and the water mist can effectively reduce the temperature of the fire field and remove the toxic flue gas, and the effect is better than that of applying the water mist alone. But the wind speed of exhaust smoke will have a negative effect on the fire extinguishing of water mist with small flow. (3) simulate the coupling effect of different mechanical smoke exhaust conditions and water mist on the space temperature field and smoke concentration of tunnel. The results show that the control effect of the coupling water mist on the temperature field and smoke concentration of tunnel space is better than that of applying water mist alone, which can reduce the thickness of smoke layer, but it may result in the backward flow and temperature field vortex of flue gas. The effect of longitudinal ventilation is better than that of the top exhaust. The inlet ventilation makes the high temperature flue gas exit to the outlet end under the condition of thrust to prevent the smoke from flowing backwards, but it will affect the trajectory of water mist droplets and the suppression effect of fire source. Longitudinal ventilation has the best exhaust effect on the top of downstream, combining the advantages of the previous two exhaust conditions, and the temperature and smoke concentration in tunnel space can be effectively controlled.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U458

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