开放与受限条件下电缆燃烧特性模拟对比研究

为对比研究开放与受限条件下的电缆火灾燃烧行为，采用CFD数值模拟软件建立了全尺寸电缆燃烧模型，同时考虑了不同间距对电缆燃烧特性的影响，并将开放与受限条件下的计算结果进行对比，分析了两种条件下电缆火灾中各工况的温度、O₂浓度。结果表明：开放条件下的电缆燃烧主要属于燃料控制型，而受限条件下的电缆燃烧主要属于先燃料控制型，后通风控制型。在开放条件下，氧气充足，燃烧更为充分，形成的火焰高度及温度更高，更容易引燃上方可燃物体；而在受限条件下，电缆火焰受到顶板限制形成的顶棚射流，会加强火焰对电缆的热辐射作用，有助于电缆燃烧。但由于侧壁的存在，电缆燃烧过程中的空气卷吸受到了一定的限制，由于通风不足，受限空间内的O₂浓度逐渐下降，电缆燃烧受到抑制，甚至熄灭，而随着空气的补充，电缆将可能出现复燃现象。此外，两种条件下电缆间距对燃烧的影响均较为明显，当间距较小时，燃烧电缆之间的影响显著，燃烧更为剧烈，而随着电缆间距增大，燃烧电缆间的相互热辐射减弱，更接近于单根电缆的独立燃烧，其中开放条件下相对更为明显。

A comparative study on the combustion characteristics simulation of cables under open and confined conditions

A full-scale cable combustion model was established using CFD numerical software to compare the combustion behaviours of cable fire under open and restricted conditions. The influence of different distances on the combustion characteristics of the cable was considered, and the calculation results under open and restricted conditions were compared. The differences in the top maximum temperature and O2 concentration of each working condition in the cable fire under the two conditions were compared and analyzed. The results show that cable combustion under open conditions is mainly fuel controlled, while cable combustion under restricted conditions is mainly fuel controlled, followed by ventilation controlled. Under the open condition, the oxygen is sufficient, the combustion is more sufficient, the flame height and temperature are higher, and it is easier to ignite the combustible objects above. Under restricted conditions, the ceiling jet formed after the roof restricts the cable flame will promote the thermal radiation effect of the flame on the cable and help the cable combustion. However, due to the existence of the side wall, the air entrainment in the cable combustion process is limited to a certain extent. At the same time, due to insufficient ventilation, the O2 concentration in the confined space gradually decreases, and the cable combustion is restrained or even extinguished. With the supplement of air, the cable may re-ignite. In addition, the influence of cable spacing on combustion is significant under both conditions. When the spacing is small, the influence between combustion cables is significant, with more intense burning. With the increase of cable spacing, the mutual thermal radiation between combustion cables is weakened.