Numerical Simulation For The Vertical Multi-Windows Plume Flame Merging In The High-rise Buildings

As one of the most common and threatening disaster of high-rise buildings,conflagration causes great loss of personal property in China every year.The conflagrations of high-rise buildings in recent years are almost all the three-dimensional fire which caused by external fire spread.For this purpose,it is necessary to analyze the effect of external fire spread in high-rise buildings.The external fire spread is mainly caused by the plume flame of vertical multi-windows which generated by indoor fire.In fact,the plume flame of vertical multi-windows can merge with each other.The temperature and height of plume flame of vertical multi-windows are higher than that of the single window.In this paper,the numerical simulation is used to study the plume fame merging of vertical multi-windows in high-rise buildings.The models are simulated that the plume fame merging of vertical multi-windows in non-side wall building and side wall building.By using the fire dynamic simulation software PyroSim,the fire models of eight storey residential building are established.And the longitudinal temperature distribution is analyzed from the data which sorted by software.The relationship is studied between the plume flame and vertical window number,window size,fire load density and so on.In order to compensate for the analysis shortage of the plume flame height in external fire spread which determined by 540? isotherm,it is defined T=540?,T1?350? T2=250?as the dangerous 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.According to analyze the numerical simulation of one window,vertical two windows and vertical three windows,the following conclusions can be obtained.For non-side wall building,the plume flame of vertical multi-windows can merge with each other,whereas the vertical two windows may have to face a similar dangerous temperature height in T1 and T2 with its vertical three windows.For 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.And the chimney effect is proportional to the length of side wall.Based on the temperature curves of window,the isotherms of temperature distribution and the previous research results the practical formulas for the height of dangerous temperatures T1 and T2 are inferred.The safety factors are also introduced to compensate for error.