侧墙结构纵向多窗口羽流火焰融合的数值模拟

为了给高层建筑外部火蔓延防控提供参考,利用火灾动态仿真模拟软件PyroSim对无侧墙建筑的纵向多窗口羽流火焰与侧墙建筑的纵向多窗口羽流火焰进行了数值模拟,并改变侧墙长度,引入危险温度T=540℃、T1=350℃及T2=250℃,综合分析窗口温度曲线及等温线数据。结果表明:纵向多窗口羽流火焰产生相互融合现象,无侧墙建筑纵向相邻两窗口与三窗口的危险温度高度相似,比单窗口的危险温度高度提升了2.5~3.0 m;侧墙结构引起烟囱效应的作用效果与侧墙的长度呈正比,侧墙长度为3.6 m时,纵向多窗口的危险温度高度与无侧墙建筑相比,对T1和T2,高度提升了2.0~2.5 m,而对T,高度的影响较弱,羽流火焰的形状在纵向被拉长。

Numerical simulation for the vertical multi-windows plume flame merging in the side-wall structure

The paper is aimed to present a simulated investigation and analysis of the effect of the side wall structure through the vertical windows plume flame that may occur in the buildings with and without such side walls. For this purpose,it is necessary to analyze the effect of the side wall on the vertical windows plume flame and disclose the variation between the plume flame and the side wall length in preventing from and controlling the external fire in the high-rises and draw the temperature curve and the isotherm to be recorded by the thermo-couples and slice via the software for the Fire Dynamic Simulation. In proceeding with the research, the paper has established two side wall 1. 6 m long and 3. 6 m long. As a result of our experiment,we have identified and determined the highest point of the plume flame temperature at 540 ℃ isotherm,with the neutral surface of the fire source window being the lowest. Furthermore,T = 540 ℃,T1 = 350 ℃, T2 = 250 ℃ have been defined as the dangerous risk temperatures, which can be taken as the determined plume flame temperature heights,with the burning point of the polyethylene foam and the window-breaking temperature,respectively. Thus,the numerical simulation of the vertical windows plume flame indicates that it would be possible for the vertical windows plume flame to merge with each other,whereas the two vertical windows may have to face a similar dangerous temperature height with its three vertical windows in the building with no side walls,though the height can be improved by 2. 5-3. 0 m as compared with the single window one. For the side wall building,it is possible for the side wall to block the plume flame from entering through the both sides of the window,in addition to the likeliness of the air entering from the window above,which may result in the chimney effect and elongate the plume flame in the vertical direction. For in such a situation,the heights of T1 and T2 can be increased by 2. 0-2. 5 m while the height of T may not be obviously affected by the side wall of 3. 6 m long as compared with the building with no side walls. Thus,it can be concluded that the simulation results help to disclose the proportional effect of the chimney to the length of the side wall.