细水雾控制湿-热-风狭长空间火灾的机制研究

High humid environment enhances soot production of smoke in fire and inhibits water mist evaporation, hot temperature helps fuel ignition and water mist evaporation , ventilation aggravates water mist offset and mist momentum attenuation. On account of the aforesaid parameters, water mist fire control mechanisms in humid-hot-ventilated narrow and long spaces illustrate complexity and uncertainty. Firstly, scaled laboratory tests are conducted. In the 28~40℃ and RH 50%~90% surroundings, ventilation and water mist operation modes are adjusted, measurements include fuel mass loss rate, flame temperature and radiant heat flux, smoke composition and concentration, smoke layer temperature, height and spread velocity, fuel surface temperature and radiant heat flux, etc. Based on the analysis of the measured fire field parameters, fire radiation model and smoke spread dynamic equation in humid-hot-ventilated narrow and long spaces are established, heat transfer mechanisms and oxygen dilution effects are analyzed. Furthermore, water mist velocity field, particle size and distribution, and mist spray angle are measured by PIV technology to analyze atomization mechanisms and evaporation rate of water mist, energy conservation and momentum conservation equations for fire control by water mist in the humid-hot-ventilated narrow and long spaces are established, the dynamic mechanisms for water mist fire control and critical water mist driving force on fire plume are analyzed. On the combination of theoretical analysis, full scale tests and numerical simulation, similarity criteria of water mist fire suppression in humid-hot-ventilated narrow and long spaces and the prediction model of critical mist flux rate are analyzed and established, the optimum operation mode of water mist fire suppression in humid-hot-ventilated narrow and long spaces are analyzed and established. The study will provide theoretical and technical support for the promotion and application of water mist fire suppression technology.

高湿环境加剧火灾烟气炭黑生成、抑制细水雾气化；炎热环境促进燃料引燃和细水雾气化；通风会造成雾形偏移及雾动量下降；细水雾控制湿-热-风狭长空间火灾的机制呈现复杂性和不确定性。项目首先进行缩尺模型实验，在28~40℃、相对湿度50~90%条件下，调整通风和细水雾运行模式，测试燃料质量损失速率，火焰温度和热辐射，烟气浓度、温度、高度和蔓延速度，燃料表面温度和热辐射等，建立湿-热-风狭长空间火灾热辐射模型及烟气输运动力学模型，分析细水雾灭火热传递机制及稀释隔氧作用；测试细水雾雾滴速度、粒径分布和雾化角等，分析细水雾雾化机制和气化率，建立细水雾控制湿-热-风狭长空间火灾的能量守恒及动量守恒方程，分析细水雾灭火的动力学机制；结合理论分析、全尺寸试验和数值模拟，建立细水雾控制湿-热-风狭长空间火灾的相似准则和临界雾通量预测模型，分析系统最优化运行模式，为细水雾灭火推广应用提供理论和技术支持。

在矿井巷道、湿热地区公路隧道等高湿、炎热和通风的狭长空间环境中，一旦发生火灾，火场温度、火焰形态、火焰热辐射及烟气蔓延规律呈现特殊的规律, 亦增加了细水雾控制火灾机制的不确定性。本项目通过缩尺寸模型实验、全尺寸数值模拟和理论分析相结合的研究方法，建立了湿-热-风狭长空间火灾火焰热辐射模型，阐明了湿-热-风环境对狭长空间火灾发展和烟气蔓延规律的影响，建立了不同坡度倾斜巷道湿-热-风环境中巷道顶棚最高烟气温升预测模型；进行了细水雾场特性的全场诊断，揭示了细水雾控制湿-热-风狭长空间火灾的主导机理，分析了湿-热-风狭长受限空间细水雾灭火的机理、有效性和影响因素，得到了细水雾系统最优化的运行模式。主要结论如下：.（1）高温高湿的耦合作用，对柴油池火初起阶段的抑制作用更显著；并造成造成旺盛阶段酒精池火的严重程度显著降低，但对柴油池火的影响不显著。高湿和通风环境对火势的抑制作用，比环境温度升高的促进作用显著。.（2）随着巷道坡度和纵向通风风速的增大，顶棚最高烟气温度呈减小趋势，当坡度增加到20°以上时，烟气温度的衰减趋缓，大坡度倾斜隧道顶棚烟气温度纵向衰减趋势服从2个指数函数之和的分布特征。.（3）喷雾压力的增加可以显著提高雾滴速度，增大雾滴向下的推动力，对细水雾雾化具有促进作用，且高于温度增高和湿度降低的效果。.（4）在湿-热-风环境中，细水雾对烟气层的冷却作用和窒息作用优于常温常湿环境，其对热辐射的衰减和对火焰的冷却作用比常温常湿下弱，但均随着压力的增大而增大。 .（5）在湿-热-风狭长受限空间中，在优先保证细水雾初速度和雾动量的原则下，同时增加细水雾压力和流量，可以显著提高细水雾灭火有效性。.本项目的研究对湿-热-风狭长空间火灾危险性评价及火灾探测报警技术提供了理论和技术支持，为细水雾灭火系统工程设计和性能化分析提供动力学模型和实验数据支撑，为细水雾灭火技术的推广应用打下了坚实的理论基础。