古商业街木结构建筑防火间距的数值模拟研究

Numerical simulation of the fire separation distance between wooden structure buildings in ancient commercial street

古商业街木结构建筑较多,防火间距先天不足,发生火灾后蔓延迅速,有必要开展木结构建筑引燃特性研究以获得合理的防火间距设置参数。以古商业街为研究对象,以临界温度和热辐射强度作为着火建筑对面木结构建筑被引燃的判定指标,综合考虑环境风速、建筑间距、火源功率、喷淋系统等因素,运用火灾动力学模拟软件FDS分析系列火灾场景下的温度和热辐射强度特性,建立防火间距与火源功率、环境风速的关系式,获得适用于古商业街的防火间距控制参数及其相应的消防强化措施。结果表明:当建筑间距在3 m以下时高温引燃和热辐射引燃共同作用引燃正对面建筑,当建筑间距在3 m以上时以热辐射引燃为主;正对面建筑表面的热辐射强度先随环境风速增大而增大,达到最大值后随环境风速增大而减小;古街木结构建筑之间存在最小防火间距,该数值不受环境风速影响,仅与火源功率有关,在火源功率为3 MW~20 MW条件下,最小防火间距与火源功率满足线性关系。

Wooden structure buildings exist in ancient commercial streets,and the fire separation distance is usually inadequate due to the historic layout,which will result in rapid fire spread.It is necessary to study the ignition characteristics of such wooden structure buildings and obtain reasonable control parameters of the fire separation distance.The critical temperature and thermal radiation intensity were taken as the ignition criteria for the opposite wooden structure building across the ancient commercial street.The environmental wind velocity,building distance,fire source power,and sprinkler system were considered.The fire dynamics simulation software FDS was used to analyze the characteristics of temperature and thermal radiation intensity in various fire scenarios,and the relationship among fire separation distance,fire source power and environmental wind velocity was obtained.The reasonable control parameters of the fire separation distance and relevant fire service requirement are proposed in this paper.While the building distance is less than 3 m,the combination of high-temperature ignition and thermal radiation ignition causes the fire spread.While the building distance is more than 3 m,thermal radiation ignition mainly causes the fire spread.The intensity of thermal radiation near the objective building increases with the environmental wind velocity,and then decreases after reaching the maximum value.The minimum fire separation distance in not affected by the environmental wind velocity and is only related to the fire source power.While the fire source power is 3 MW~20 MW,the relationship is linear.