钢箱梁内敷电缆火灾辐射影响范围研究

Study on the influence range of fire radiation of steel box girder inner cable

为揭示钢箱梁内敷电缆火灾的辐射分布特征,采用FDS数值模拟,研究了电缆尺寸和横隔板间距对辐射范围的影响,分析了钢箱梁起火腔室内的火焰辐射与烟气辐射特征,并构建辐射预测公式,进而得到临界安全距离。结果表明:随火源功率的增加以及横隔板间隔的减小,辐射影响范围明显增大,考虑钢箱梁多腔室与钢结构传热特性,修正后的McCaffrey烟气层温度误差可小于5%;综合考虑火焰辐射与烟气辐射的辐射分布预测模型可有效预测钢箱梁内距火源中心大于0.6 m区域的辐射分布。以10 kW/m^(2)作为临界引燃热通量界定箱梁电缆敷设的临界安全距离,则钢箱梁内电缆敷设的最小安全距离为0.8 m。

To reveal the radiation distribution characteristics of cable fires inside steel box girders,FDS was used to simulate and study the radiation influence range under different fire source pow⁃ers and diaphragm spacing.The flame radiation and smoke radia⁃tion characteristics received by targets in the fire chamber of steel box girders were analyzed,and the radiation prediction formula was constructed to obtain the critical safety distance.The results show that with the increase of the ignition source power and the decrease of the diaphragm spacing,the radiation influence range increases significantly,and the temperature error of the modified McCaffrey flue gas layer can be less than 5%considering the heat transfer characteristics of the multi-chamber steel box girder and the steel structure.The radiation distribution prediction model considering flame radiation and flue gas radiation can effectively predict the radiation distribution in the area of the steel box girder in the area greater than 0.6m from the center of the fire source.Using 10 kW/m^(2) as the critical ignition heat flux to define the criti⁃cal safety distance of box girder cable,the minimum safety dis⁃tance of cable laying in steel box girder is 0.8m.