巷道火灾火焰局部阻力模型构建及参数识别

Development of local resistance model of roadway fire flames and parameter identification

针对巷道火灾绕火源火焰的局部阻力计算及阻力系数的确定问题,建立按火焰断面积来计算的模型,其中的火焰局部阻力系数是火焰截断面积的函数,指出火焰面积是在特定巷道火灾条件下火源燃烧强度与风流速度相互作用的结果,确定阻力系数值必须考虑到巷道风流对火焰的压制作用。分析火焰局部阻力与风流速度、火源燃烧强度的关系,即随着火源燃烧强度的增大,火焰面积和局部阻力增大,风速降低,出现所谓的节流现象。当风速等于富氧燃烧临界风速时,火源燃烧充分,火焰面积和火焰局部阻力最大;当风速小于该临界风速时,火源燃烧减弱,火焰面积和局部阻力变小;当风速过大时,风流压缩火焰,火焰截断面积和火焰局部阻力减小,火焰局部阻力在风速中低时为最大。上述变化规律与点火源和线火源两组经典的实验结果相吻合;依据实验数据拟合确定出模型的参数,依火源强度不同,最大火焰面积系数取值一般在0.285~0.410。

In order to solve the problems associated with the local resistance calculation of roadway fire flames around fire source and resistance coefficient determination,a model based on flame cross-section area calculation was developed,where the flames local resistance coefficient is a function of flame truncated area. The study points out that the fire area is the result of roadway fire combustion intensity under certain conditions and merry speed interaction,and determines that the resistance coefficient values must take into account the deterrent effects of roadway romantic flame.The analysis on the relationship of local resistance with airflow velocity flame and fire burning intensity shows that with the increases of flame intensity,the flame area and local resistance increase,the wind velocity decreases and the phenomenon of so-called throttling occurs. When the wind speed is equal to the critical velocity of oxygen-enriched combustion,the fire source fully combusted,the flame area and flame local resistance reach maximum values. When the wind speed is less than the critical velocity,the source of fire burning is weakened,the flame area and local resistance become smaller. When the wind speed is too large,the wind flow velocity compresses flame,fire truncated area andflames local resistance decrease. The above variations are obtained with two classic experimental results of ignition sources and line sources match. The parameters of the model can be determined based on the experimental data. According to the different strength of the fire source,the coefficient values of the largest flame area are generally between0. 285 to 0. 410.