狭长空间内220 kV大截面电缆火灾燃烧特点及烟气控制实验研究

Experimental study on combustion characteristics and smoke control of 220 kV cable with large cross-section in long and narrow space

为避免或减小狭长空间内高压电缆发生火灾的可能性,建立实验模型,研究狭长空间内220 kV大截面电缆燃烧行为及火蔓延规律,分析电缆火灾下狭长空间顶棚温度分布特征,结合电缆燃烧过程,设置5种不同排烟风速,探究排烟风速对其排烟效率的影响。研究结果表明:大截面电缆阻燃外护套受火后会形成高温熔融物,滴落在底板上的高温熔融物燃烧形成的火焰不断撞击电缆底部,在电缆底部形成的拓展火焰持续加热,引燃电缆外护套的未燃段,进而导致电缆外护套底部火焰在热对流和辐射的作用下稳定蔓延;狭长空间顶棚温度峰值及熔滴火焰前锋位置随着电缆阻燃外护套的持续燃烧不断推移;大截面电缆火焰蔓延速度呈现先增大、后稳定、再减小趋势;电缆燃烧过程中会产生大量有毒烟气,采用侧向排烟模式能够有效降低狭长空间内烟气浓度。研究结果可为狭长空间内敷设电缆的消防排烟设计提供参考。

To avoid or reduce the possibility of fire on high-voltage cables in long and narrow spaces,an experimental model was built to study the combustion behavior and fire spread law of 220 kV cables with large cross-section in long and narrow space,and the temperature distribution characteristics beneath the ceiling of long and narrow space were analyzed.Combining the cable combustion process,five smoke exhaust velocities were set to study the influence of smoke exhaust velocity on the smoke exhaust efficiency.The results showed that the flame retardant outer sheath of cable with large cross-section will form high temperature melt after fire and drop on the bottom floor.The flame of high temperature melt will continuously hit the cable bottom,which will form flame expansion at the cable bottom,continue to heat and ignite the unburned section of the cable outer sheath,thus causing the lower half of the cable outer sheath to spread stably under the heat convection and radiation.After the flame retardant outer sheath of the cable burns,the peak temperature beneath the ceiling of long and narrow space and the front position of the droplet flame move with the continuous burning of the cable outer sheath.The flame spread velocity of cable with large cross-section increases first,then stabilizes,and next decreases.A large amount of toxic smoke will be produced during the cable combustion,and the lateral smoke exhaust mode can effectively reduce the smoke concentration in the narrow and long space.The results can provide reference for the fire and smoke exhaust design of cables laying in narrow and long spaces.