﻿ 船舶双层底局部通风有害气体分布数值模拟研究
 舰船科学技术  2016, Vol. 38 Issue (5): 133-137 PDF

1. 中远集团培训中心, 山东 青岛 266071 ;
2. 青岛远洋船员职业学院, 山东 青岛 266071 ;
3. 重庆交通大学 交通运输学院, 重庆 400074 ;
4. 大连海事大学 船机修造工程交通运输行业重点实验室, 辽宁 大连 116026

Numerical simulation analysis of the harmful gas distribution in ship's double bottom cell with auxiliary ventilation
XU Kun-lun1,2, SHENG Jin-lu3,4
1. COSCO Group Training Center, Qingdao 266071, China ;
2. Qingdao Ocean Shipping Mariners College, Qingdao 266071, China ;
3. College of Traffic and Transportation, Chongqing Jiaotong University, Chongqing 400074, China ;
4. Laboratory of Ship-Machinery Maintenance and Manufacture for Ministry of Transportation, Dalian Maritime University, Dalian 116026, China
Abstract: A commercial CFD software Fluent is used to simulate the airflow and harmful gas distribution in ship's double bottom cell with forcing auxiliary ventilation during carbon dioxide gas welding, the mathematical model for simulation of harmful gas diffusion is established. The distribution pattern of CO2 and CO in a certain amount of ventilation is obtained using species source term, the simulation results fit the model experiment data well. The dangerous areas in welding could be obtained the harmful gas distribution under different ventilation conditions, that provides the basic theory for avoiding CO2 accumulation and CO poisoning.
Key words: numerical simulation     double bottom     ventilation     harmful gas     source term
0 引 言

1 双层底局部通风实验模型和模拟条件 1.1 双层底局部通风实验模型

 图 1 船舶双层底分段结构图 Fig. 1 Structure block of the double bottom cell

1.2 模拟条件

2 有害气体扩散数值模拟 2.1 几何模型的建立

 图 2 双层底局部通风的三维几何模型 Fig. 2 Three dimensional geometric model of double bottom with auxiliary ventilation
2.2 数学模型及边界条件

 $\quad\quad\quad\quad\quad\quad\frac{{\partial \rho u}}{{\partial x}} + \frac{{\partial \rho v}}{{\partial y}} + \frac{{\partial \rho w}}{{\partial z}} = {S_m}\text{，}$ (1)

 \begin{aligned} & \frac{{\partial \left( {\rho uu} \right)}}{{\partial x}} + \frac{{\partial (\rho uv)}}{{\partial y}} + \frac{{\partial (\rho uw)}}{{\partial z}} = \\ & \frac{\partial }{{\partial x}}({\mu _{eff}}\frac{{\partial u}}{{\partial x}}) + \frac{\partial }{{\partial y}}({\mu _{eff}}\frac{{\partial u}}{{\partial y}}) + \frac{\partial }{{\partial z}}({\mu _{eff}}\frac{{\partial u}}{{\partial z}}) - \frac{{\partial p}}{{\partial x}}\text{，}\end{aligned} (2)
 \begin{aligned} & \frac{{\partial \left( {\rho vu} \right)}}{{\partial x}} + \frac{{\partial (\rho vv)}}{{\partial y}} + \frac{{\partial (\rho vw)}}{{\partial z}} = \frac{\partial }{{\partial x}}({\mu _{eff}}\frac{{\partial v}}{{\partial x}}) + \\ & \frac{\partial }{{\partial y}}({\mu _{eff}}\frac{{\partial v}}{{\partial y}}) + \frac{\partial }{{\partial z}}({\mu _{eff}}\frac{{\partial v}}{{\partial z}}) - \frac{{\partial p}}{{\partial y}} - \left( {\rho - {\rho _0}} \right)g + {F_{\rm{y}}}\text{，} \end{aligned} (3)
 \begin{aligned} \frac{{\partial \left( {\rho wu} \right)}}{{\partial x}} + &\frac{{\partial (\rho wv)}}{{\partial y}} + \frac{{\partial (\rho ww)}}{{\partial z}} = \frac{\partial }{{\partial x}}({\mu _{eff}}\frac{{\partial w}}{{\partial x}}) + \\ & \frac{\partial }{{\partial y}}({\mu _{eff}}\frac{{\partial w}}{{\partial y}}) + \frac{\partial }{{\partial z}}({\mu _{eff}}\frac{{\partial w}}{{\partial z}}) - \frac{{\partial p}}{{\partial z}}\text{，} \end{aligned} (4)

 \begin{aligned} \frac{{\partial \left( {\rho {c_s}u} \right)}}{{\partial x}} + &\frac{{\partial (\rho {c_s}v)}}{{\partial y}} + \frac{{\partial (\rho {c_s}w)}}{{\partial z}} = \frac{\partial }{{\partial x}}({D_s}\frac{{\partial \rho {c_s}}}{{\partial x}}) + \\ & \frac{\partial }{{\partial y}}({D_s}\frac{{\partial \rho {c_s}}}{{\partial y}}) + \frac{\partial }{{\partial z}}({D_s}\frac{{\partial \rho {c_s}}}{{\partial z}}) + {S_s}\text{；} \end{aligned} (5)

RNG $k - \varepsilon$ 方程：

 \begin{aligned} \frac{{\partial \left( {\rho ku} \right)}}{{\partial x}} + &\frac{{\partial (\rho kv)}}{{\partial y}} + \frac{{\partial (\rho kw)}}{{\partial z}} = \frac{\partial }{{\partial x}}({\alpha _k}{\mu _{eff}}\frac{{\partial k}}{{\partial x}}) + \\ & \frac{\partial }{{\partial y}}({\alpha _k}{\mu _{eff}}\frac{{\partial k}}{{\partial y}}) + \frac{\partial }{{\partial z}}({\alpha _k}{\mu _{eff}}\frac{{\partial k}}{{\partial z}})\!\! +\!\! {G_k} - \rho \varepsilon \text{，} \end{aligned} (6)
 \begin{aligned} \frac{{\partial \left( {\rho \varepsilon u} \right)}}{{\partial x}} + &\frac{{\partial (\rho \varepsilon v)}}{{\partial y}} + \frac{{\partial (\rho \varepsilon w)}}{{\partial z}} = \\ & \frac{\partial }{{\partial x}}({\alpha _\varepsilon }{\mu _{eff}}\frac{{\partial \varepsilon }}{{\partial x}}) + \frac{\partial }{{\partial y}}({\alpha _\varepsilon }{\mu _{eff}}\frac{{\partial \varepsilon }}{{\partial y}}) + \\ & \frac{\partial }{{\partial z}}({\alpha _\varepsilon }{\mu _{eff}}\frac{{\partial \varepsilon }}{{\partial z}}) + \frac{\varepsilon }{k}\left( {C_{1\varepsilon }^*{G_k} - {C_{2\varepsilon }}\rho \varepsilon } \right)\text{，} \end{aligned} (7)

 \begin{aligned} \frac{{\partial \left( {\rho uT} \right)}}{{\partial x}} + &\frac{{\partial (\rho vT)}}{{\partial y}} + \frac{{\partial (\rho wT)}}{{\partial z}} = \frac{\partial }{{\partial x}}(\frac{{k}}{{{c_p}}}\frac{{\partial T}}{{\partial x}}) + \\ & \frac{\partial }{{\partial y}}(\frac{{k}}{{{c_p}}}\frac{{\partial T}}{{\partial y}}) + \frac{\partial }{{\partial z}}(\frac{{k}}{{{c_p}}}\frac{{\partial T}}{{\partial z}}) + {S_T}\text{。} \end{aligned} (8)

1）壁面边界条件：将巷道壁面处理为无滑移固体壁面；

2）速度入口边界条件：舱室中的风流可认为是不可压缩流体，设置风筒出口边界为速度入口边界条件，指定速度大小为风筒出口的平均流速，方向垂直于风筒出口边界，风速为 5 m/s；

3）出口边界条件为出流：人孔出口断面风流的流动是完全发展的，设置为出流边界条件；

4）源项：将焊接区域设置为流体区域，分别设置 CO2 和 CO 两种组分的质量源项、动量源项及能量源项。

3 数值模拟结果分析 3.1 风流流场分析

 图 3 双层底轴向风流流场分布z=1.2 m Fig. 3 Distribution of stream line on section along axis z=1.2 m

3.2 有害气体分布

 图 4 双层底轴向CO2浓度分布z=1.2 m Fig. 4 Distribution of Co2 concentration on section z=1.2 m

 图 5 双层底轴向CO浓度分布z=1.2 m Fig. 5 Distribution of CO concentration on section z=1.2 m

 图 6 舱室横切面CO浓度分布y=0.6 m Fig. 6 Distribution of CO concentration on section y=0.6 m

 图 7 舱室横断面CO浓度分布x = 0.3 m Fig. 7 Distribution of CO concentration on section x=0.3 m

3.3 数据对比

4 结 语

1）双层底内部在焊接作业区上方出现涡流，不利于有毒有害气体的排出，在舱室顶部也出现涡流，容易造成有毒有害气体的集聚。

2）利用设置源项的方法通过组分输运方程可以得出双层底二氧化碳气体保护焊接作业时有害气体的浓度分布情况，经数据对比数值模拟结果与实验结果基本一致。

3）风筒位于舱室底部距离焊接作业地点 1.2 m 处，风速为 5 m/s 的情况下，舱室顶部不会造成 CO2 的集聚，而在焊点正上方 CO2 浓度超过 1%，作业人员头部在此区域内有发生中毒窒息的可能性。

4）在焊点正上方区域内 CO 浓度高达 100 ppm 以上，已经远远超出安全限值，可能会造成人员中毒，在距离舱壁 0.2 m 以外的区域 CO 浓度逐渐降低；距离舱壁 0.3 m 处作业人员头部所在位置上的 CO 浓度在 50 ppm 以下，而在舱室顶部区域出现 CO 集聚现象，最高浓度达 60 ppm。

 [1] 宋永伦. 我国造船焊接生产环境与安全的思考[J]. 电焊机 , 2007, 37 (6) :92–97. SONG Yong-lun. Thought of manufacture environment and safety of shipbuilding welding[J]. Electric Welding Machine , 2007, 37 (6) :92–97. [2] 蔡治平, 徐宗古, 施介宽, 等. 大型船体装焊车间焊接烟尘扩散模式理论探讨[J]. 东华大学学报(自然科学版) , 2003, 29 (2) :27–312. CAI Zhi-ping, XU Zong-gu, SHI Jie-kuan, et al. Theoretical study on diffusion model of welding dust in large-scale assembling-welding workshop[J]. Journal of Donghua University (Natural Science Edition) , 2003, 29 (2) :27–312. [3] 桑丽群. 焊接污染及其防治措施的研究进展[J]. 能源环境保护 , 2008, 22 (1) :18–201. SANG Li-qun. Study on the pollution and countermeasures of welding[J]. Energy Environmental Protection , 2008, 22 (1) :18–201. [4] 郑振太, 单平, 罗震, 等. CO2气体保护焊温度场的数值模拟[J]. 天津大学学报 , 2007, 40 (2) :234–2389. ZHENG Zhen-tai, SHAN Ping, LUO Zhen, et al. Numerical simulation of CO2 arc welding temperature field[J]. Journal of Tianjin University , 2007, 40 (2) :234–2389. [5] 贾雪峰, 刘东, 刘传聚, 等. 某封闭焊接车间的置换通风模拟研究[J]. 暖通空调 , 2010, 40 (2) :76–801. JIA Xue-feng, LIU Dong, LIU Chuan-ju, et al. Simulation of displacement ventilation in a large-space closed welding work-shop[J]. Heating Ventilating &Air Conditioning HV &AC , 2010, 40 (2) :76–801. [6] 夏胜全, 区智明, 孙晓明, 等. CO2气体保护焊电弧温度场和流场建模与分析[J]. 焊接学报 , 2013, 34 (11) :97–1002. XIA Sheng-quan, OU Zhi-ming, SUN Xiao-ming. Numerical simulation of temperature and flow field of CO2 gas shielded arc[J]. Transactions of the China Welding Institution , 2013, 34 (11) :97–1002. [7] 戚顺顺, 陈书锦, 朱文琪, 等. 焊接半封闭现场有害气体分布特点研究[J]. 环境科学与技术 , 2013, 36 (6L) :100–1034. QI Shun-shun, CHEN Shu-jin, ZHU Wen-qi, et al. Study on the characteristics of harmful gas distribution of welding semi-closed field[J]. Environmental Science &Technology , 2013, 36 (6L) :100–1034. [8] 陈建平. 船舶密闭舱室热工作业温度变化及通风计算的仿真分析[J]. 船海工程 , 2010, 39 (3) :60–62. CHEN Jian-ping. Simulation of the temperature changing and ventilation in ship's closed- in compartment[J]. Ship &Ocean Engineering , 2010, 39 (3) :60–62. [9] 张博思, 陆守香. 机械通风对船舶机舱火灾烟气控制的影响分析[J]. 船海工程 , 2013, 42 (4) :28–30. ZHANG Bo-si, LU Shou-xiang. Analysis of the influence of mechanical ventilation on smoke control during the ship engine room fire[J]. Ship &Ocean Engineering , 2013, 42 (4) :28–30. [10] 杨志青, 王志国, 仲晨华, 等. 舰船内部通道的火灾烟气蔓延模拟及防火设计[J]. 船海工程 , 2003 (4) :1–3. YANG Zhi-qing, WANG Zhi-guo, ZHONG Chen-hua, et al. Stimulation of fire in the passage of the warship and its fire-proofing design[J]. Ship &Ocean Engineering , 2003 (4) :1–3. [11] Fluent Inc., Fluent 6.1 user's guide[Z]. USA:Fluent Inc., 2003.