开放和封闭空间内不同间隙的竖向电缆燃烧试验研究

On the vertical cable tray combustion in regard to the different cable allocation in the open and wrapped-up space

为了研究封闭空间对竖向电缆燃烧过程的影响,在开放空间和封闭空间内分别进行了一系列不同间隙的竖向电缆燃烧试验。通过分析开放空间和封闭空间内不同电缆间隙的竖向电缆燃烧过程中质量损失速率,得到电缆之间的间隙对竖向电缆燃烧速率有着决定性的影响。通过对比开放空间和封闭空间内竖向电缆的燃烧过程发现,封闭空间对竖向电缆燃烧过程的影响作用存在一个临界区间,该区间的临界判据是由电缆燃烧火焰对电缆的热作用和封闭空间内烟气层对电缆的热反馈决定的。基于封闭空间内的竖向温度分布,通过分析其无量纲温度梯度,得到封闭空间内竖向电缆燃烧过程存在一个特征明显的温度过渡区域。

The given paper is to provide its investigation results of the impact of the enclosed space on the combustion tendency of the vertical cable tray（ VCT） due to the different placing ways between the cables. For the said purpose,we have done a series of fire-hazard catching experiments on VCT in the enclosed and open spaces,respectively,with the enclosed space in a 3 m × 3m × 3 m compartment with the door shut-up. While the temperature can be measured up via an armored K type thermocouple,the electronic scale（ Sartorius LA64001S） can be used for recording the mass changes. In so doing,comparing the mass loss rate（ MLR） of VCT with the different cable spacing manners in an enclosed and/or in an open space,we can first of all find that the spacing between the cables tend to significantly increase the MLR,for the MLR for VCT combustion with the finite spacing between the cables can likely reach approximately twice as much as for the zero spacing. On the other hand,for the VCT with finite spacing,the cable spacing size may only have little effect on the combustion behaviors. Secondly,for the VCT fire with zero spacing,the heat feedback from the hot gas layer can potentially impact VCT fire trends significantly and the combustion trend.For example,in regard to the MLR in the open space,the peak value of the MLR for the cable fire can be made so high as 1. 4times of that in a closed compartment. Or for more specific,for the cable spacing of 4 mm and 8 mm,respectively,little effect has been found on the cable spontaneous burning,for the heat feedback from the hot gas layer proves much less than that generated by the cable flame. What is more,we have also identified and determined that there may exist a critical point for the effects of the heat feedback from the hot gas layer on VCT fire behaviors. And,finally,our analysis of the vertical temperature profile and dimensionless temperature gradient during the VCT combustion shows that it would be possible for us to divide the fire environment of VCT combustion into the aforementioned three zones,i. e. the upper hot gas zone,the transition zone and the lower cool gas zone.