水颗粒作用下火灾烟气层沉降的数值模拟

Numerical Simulation of Downward Smoke Displacement in Fire Under the Effect of Water Droplets

基于火灾双层模型思想及基本物理定律,通过分析单个水颗粒与热气流的相互作用,研究水颗粒群对火灾烟气层的影响,建立了水颗粒作用下火灾烟气层沉降的数学模型,模型与实验值的对比误差为±0.3 m.利用该模型模拟研究发现:增大喷头流量速率、减小水颗粒喷射夹角、减小水颗粒粒径会加剧烟气层沉降;在同一喷水条件下,低温、薄烟气层更易于沉降,当烟气层厚度薄于某一临界值时,烟气沉降距离会大幅度增加;常用的12.7 mm喷淋喷头的工作压力不宜大于20 m.该模型可有效缓解喷水对实际火灾烟气层的沉降作用.

Based on the basic physic laws and the idea of two-zone model of fire,a mathematical model of the downward smoke displacement in fire under the effect of water droplets is constructed by analyzing the interaction between a single droplet and hot air flow and by investigating the impact of water droplets on the smoke layer of fire. Then,the constructed model is compared with the measured data,finding that the error of the constructed model is ± 0. 3 m. The modeling results show that( 1) increasing the flow rate of nozzles and decreasing the size and spray angle of water droplets can increase the downward smoke displacement;( 2) under the same spray condition,the downward smoke displacement is easy to occur in a thin and low-temperature fire smoke layer;( 3) when the thickness of the smoke layer is less than a critical value,the downward smoke displacement distance will greatly increase;and( 4) the operation pressure of the commonly-used sprinkler nozzle with a 12. 7 mm orifice should not be larger than 20 m,so that the impact of the water droplets on the downward smoke displacement can be effectively reduced.