电缆火灾烟雾生成特性及声波团聚消烟的实验研究

由于城市建设的需要,越来越多的城市采用地下电缆隧道输送电力,隧道火灾事故严重威胁城市安全与电力输送。电缆火灾生成的烟雾是妨碍消防人员施救过程的重要因素,现有的烟雾控制方法主要从隧道的通风角度出发,考虑如何快速将烟雾排出隧道,主要包括自然排烟与机械排烟2大类,均存在一定的局限性。声波团聚技术是一种利用高强声场快速消除气溶胶的处理技术,已有文献表明该技术可有效消除聚苯乙烯燃烧烟雾。本文进行了声波团聚技术消除电力隧道火灾烟雾的实验研究。采用TSI 3330光学粒度仪测量火灾烟雾颗粒粒径,结果表明,VV电缆烟雾的粒径主要分布在1μm附近,而YJV电缆烟雾除了1μm左右的细颗粒外,还包含了较多0.3μm的亚微米颗粒。测试水平敷设、垂直敷设条件下电缆火灾烟雾的产烟特性,电缆外护套层、填充层及绝缘层的产烟特性,电缆持续受热、受热20 s和受热50 s情况下的产烟特性,并通过测量透射光强度计算其烟雾透光率、能见度、产烟速率等参数。结果表明,电缆材料对其燃烧产烟影响较大,VV电缆产烟量较大,燃烧约60 s后其透光率便降至0.2附近,而YJV电缆的产烟量少于VV电缆;水平燃烧时,其整体烟雾透光率低于垂直燃烧;电缆外护套层材料燃烧后产烟量最多,约60 s时透光率降至0附近,团聚室内充满了大量白色烟雾。设计并搭建了声波团聚消除电力隧道烟雾的实验平台,由信号发生器产生正弦信号,经功率放大器放大后,通过驱动压缩式驱动器发出高强声波,分析有、无声波作用下电缆火灾烟雾的透光率变化。实验表明,声波团聚能够迅速提升电缆火灾烟雾的能见度,当声功率为12 W、频率为1.5 kHz时,仅需0.2 min便可使团聚室的透光率提升至0.6,达到人员逃生阈值。声波消烟过程中,声频率是关键参数。电缆火灾烟雾的团聚效果对声波频率十分敏感,最佳频率为1.5 kHz,偏离最佳频率越多,声波团聚的效果越差;声功率对消烟效果影响较大,声功率越大,消烟效果越佳,当声功率达到一定程度时,团聚效率提升速率减缓。

Test of cable fire smoke characteristics and experimental study of acoustic agglomeration to eliminate smoke

Due to the needs of urban construction, more and more cities adopt underground cable tunnels to transmit electricity. The tunnel fire accidents threaten city safety and power transmission seriously. The smoke generated by the cable fire is an important factor hindering the rescue process of firemen. The current existing smoke control methods mainly consider how to discharge the smoke from the tunnel quickly from the perspective of tunnel ventilation, mainly including natural smoke exhaust and mechanical smoke exhaust, which has certain limitations. Acoustic agglomeration is the process in which an intense sound field is applied to promote relative motion and rapid agglomeration among aerosol particles. The existing literature show that the use of acoustic agglomeration technology can effectively eliminate polystyrene fire smoke, and the characteristics of power tunnel fire smoke are similar to polystyrene.So we attempt to use acoustic agglomeration technology to eliminate power tunnel fire smoke.The TSI 3330 optical particle size analyzer was used to measure the particle size of fire smoke particles, the results show that the particle size of VV cable smoke is mainly distributed around 1 μm, while YJV cable smoke contains more 0.3 μm particles in addition to fine particles of about 1 μm submicron particles. By measuring the transmitted light intensity, the smoke transmittance, visibility, smoke rate and other parameters can be calculated. The smoke generation characteristics of cable fire smoke under the conditions of horizontal and vertical laying was tested. Smoke generation characteristics of cable outer sheath, filling layer and insulating layer, the smoke generation characteristics of the cable under continuous heating, heating for 20 s and heating for 50 s, were tested too. The results show that the cable material has a greater impact on its combustion and smoke production. The VV cable produces a large amount of smoke. After burning for about 60 s, its light transmittance drops to around 0.2, while the YJV cable produces less smoke than the VV cable; When burning horizontally, the overall light transmittance of smoke is lower than that of vertical burning; the smoke produced by the outer sheath material of the cable is the most after burning, and the light transmittance drops to around 0 at about 60 s, and the agglomeration chamber is filled with a lot of white smoke.Lastly, the acoustic agglomeration platform was built to eliminate smoke in power tunnels. The sound wave is generated by a signal generator, amplified by a power amplifier, and then driven by a compression driver to sound, to analyze the change of light transmittance of cable fire smoke with and without sound wave. The result shows that acoustic agglomeration can quickly increase the visibility of cable fire smoke. When the sound power is 12 W and the frequency is 1.5 kHz, it only takes 0.2 min to increase the light transmittance of the reunion room to 0.6, reaching the threshold of safe escape. Frequency is the key parameter when sonic smoke is eliminated. The agglomeration effect of cable fire smoke is very sensitive to the frequency of sound waves. The best frequency of cable fire smoke is 1.5 kHz. The smoke effect has a greater impact. The greater the sound power, the better the smoke suppression effect. When the sound power reaches a certain level, the rate of increase in the reunion efficiency slows down.