﻿ 不同顶棚高度下船舶狭长通道细水雾灭火研究
 舰船科学技术  2020, Vol. 42 Issue (11): 66-71    DOI: 10.3404/j.issn.1672-7649.2020.11.014 PDF

Water mist extinguishing fire in ship narrow passages with different ceiling heights
SU Shi-chuan, CHEN Lu, WANG Liang, MU Xin, GENG Shan-shan, CAO Jia-bin
School of energy and power engineering, Jiangsu university of science and technology, Zhenjiang 212003, China
Abstract: The narrow and long passages and different ceiling heights in ships can cause the rapid spread of pollutants and the occurrence of ceiling jet phenomenon in fire process, which have an important impact on the development of ship fires and personnel escape. In this paper, based on the large eddy simulation technology, the fire evolution characteristics of "T-shaped" narrow passages with ceiling heights of 1.8 m, 2.6 m, 3.4 m and 4.3 m were numerically simulated. By analyzing heat release rate, O2 concentration, smoke stratification and temperature distribution, it is concluded that water mist can effectively suppress the spread of fire in the T-passage. After releasing water mist, the heat release rate of 1.8 m and 2.6 m narrow passages decays faster, O2 concentration drops rapidly to 14%. The heat release rate of 3.4 m and 4.3 m narrow passages decays relatively slow, O2 concentration is higher. The smoke layer height increases with the passage ceiling height. And water mist can reduce effectively the fire temperature.
Key words: ship fire     narrow and long passage     ceiling height     water mist
0 引　言

1 模型建立 1.1 数学模型

 $\frac{{\partial \rho }}{{\partial t}} + \nabla \cdot \rho \vec u = 0,$ (1)

 $\frac{{\partial \left( {\rho {Y_i}} \right)}}{{\partial t}} + \nabla \cdot \left( {\rho {Y_i}\vec u} \right) = \nabla \cdot {\left( {\rho D} \right)_i}\nabla {Y_i} + {W_i}^{\prime \prime \prime },$ (2)

 $\rho \left( {\frac{{\partial \vec u}}{{\partial t}} + \left( {\vec u \cdot \nabla } \right)\vec u} \right) + \nabla p = \rho g + \vec f + \nabla \cdot \tau ,$ (3)

 $\begin{split}&\frac{{\partial \left( {\rho h} \right)}}{{\partial t}} + \nabla \cdot \left( {\rho h\vec u} \right) = \frac{{\partial p}}{{\partial t}} + \vec u \cdot \nabla p - \nabla \cdot q +\\& \nabla \cdot \left( {k\nabla T} \right) + \mathop \sum \limits_i \nabla \cdot \left( {{h_i}\rho {D_i}\nabla {Y_i}} \right),\end{split}$ (4)

 $pM = \rho RT\text{。}$ (5)

1.2 物理模型建立

 图 1 某船舶典型T型狭长通道结构图 Fig. 1 Typical T-shaped narrow passage structure diagram of a ship

 图 2 计算模型结构图 Fig. 2 Calculation model structure diagram

1.3 网格划分

 ${D^*} = {\left( {\frac{Q}{{{\rho _{\rm{\infty }}}{c_{\rm{p}}}{T_{\rm{\infty }}}\sqrt g}}} \right)^{2/5}}\text{。}$ (6)

2 结果与分析 2.1 火焰热释放率及热辐射强度变化

 图 3 不同顶棚高度下细水雾对热释率及热辐射强度的影响 Fig. 3 Effect of water mist on heat release rate and heat radiation intensity under different ceiling heights
2.2 烟气浓度及其分层变化

1）烟气浓度变

 图 4 横向通道内烟气浓度随时间变化关系 Fig. 4 The relationship between smoke concentration and time in the transverse passage

2）烟气层分区

 图 5 烟气层分区高度随时间的变化关系 Fig. 5 The relationship between the height of the smoke layer and the time
2.3 温度场分析

1）通道内温度变化

 图 6 T型通道内温度随时间变化关系 Fig. 6 The relationship between temperature and the time in T-passage

2）温度云图

 图 7 不同顶棚高度横向通道内温度分布云图 Fig. 7 The temperature distribution in the transverse passage with different ceiling heights
3 结　语

1）细水雾能够有效抑制T型通道内火灾的蔓延。释放细水雾后火焰热释放速率迅速下降。低顶棚（1.8 m和2.6 m）狭长通道内热释放率衰减速度较快，而高顶棚（3.4 m和4.3 m）狭长通道，由于细水雾雾动量不足，热释放率衰减速度较慢。

2）释放细水雾之后，1.8 m和2.6 m顶棚狭长通道内O2浓度可快速降到14%，火焰基本熄灭。而3.4 m和4.3 m顶棚狭长通道内O2浓度较高，但燃料燃烧速率可被得到有效抑制。

3）1.8 m高通道的烟气层较低，随着顶棚高度增加烟气层升高。通道顶棚高度在2.6 m以上能够减少高温烟气对火场人员疏散的影响。

4）细水雾能够有效降低通道内的火场温度，尤其对低顶棚（1.8 m和2.6 m）通道的降温效果较好；高顶棚（3.4 m和4.3 m）通道内由于火焰仍以较低燃烧速率燃烧，油池上方区域温度仍然较高，但其周围空间的温度得到有效降低。

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