矩形中庭顶部开口比例对火灾烟气扩散的影响研究

Study on the influence of the ratio of the top opening of the rectangular atrium on the fire smoke diffusion

为探究带回廊的矩形中庭内顶部开口比例对火灾烟气扩散规律的影响,改善建筑防排烟条件,以某矩形中庭商场为例,运用火灾动力学模拟(Fire Dynamics Simulator,FDS)软件设置了温度测点,模拟了不同顶部开口比例下的矩形中庭底层起火时的烟气流场,基于线性回归模型拟合了烟气温度随顶部开口比例变化的关系,并以缩尺模型试验进行了验证。结果表明:矩形中庭内烟气在有顶部开口的情况下能在短时间内向上扩散至顶部,同时在各层回廊顶部水平扩散,在400 s内填充整个空间;烟气温度与顶部开口比例的关系总体为线性负相关,在开口比例从1下降到1/2时能见度下降最快;试验中的烟气温度变化规律与模拟结果相吻合,验证了FDS用于火灾烟气研究的可行性。

This study aims to explore the smoke movement model of a rectangular atrium in case of fire,and provide a scientific basis for the smoke control system.Based on the large eddy simulation method and smoke control theory,the fire dynamics software Fire Dynamics Simulator(FDS)is used for numerical simulation.With the flue gas temperature as the main parameter,different top opening ratios are set to study the influence of the fire on the smoke diffusion law in the bottom of the rectangular atrium.In addition,the reliability of the simulation method is verified by similar model tests.The numerical simulation results show that the smoke diffuses upward rapidly due to the suction effect when there is an opening at the top and can reach the ceiling in about 60 s.At the same time,due to the existence of the corridor,the smoke will diffuse horizontally in each layer after the flue gas forms a ceiling jet.It diffuses at the top layer,and then gradually cools down and settles to the lower floor.The ratio of the top opening has an obvious influence on the diffusion of fire smoke.The relationship between the flue gas temperature and the ratio of the top opening is generally linear and negative,and it will be different in the part near the fire source.The smoke diffusion dynamic charts reflect that the visibility in the building rapidly decreases when the opening ratio changes from 1 to 0.5.In atrium buildings,the ratio of the top opening should be enlarged to improve the smoke effect.When it cannot be fully opened,the effect is better when the opening ratio reaches more than 0.5.Besides,attention should be paid to the control of fire hazards.