﻿ 大尺度双体船机舱通风系统的数值模拟分析和优化设计
 舰船科学技术  2020, Vol. 42 Issue (1): 75-79 PDF

Numerical simulation and optimization design of the cabin ventilation of the large-scale catamaran
GUO Ang, WANG Bo, SHEN Gao-zhan, ZHOU Xin-tao, WU Xian, GUO Yang-yang, WANG Hai-ning
China Ship Scientific Research Center, Wuxi 214082, China
Abstract: Because of the technical characteristics such as big depth and width, low radiation noise, strict weight and size requirements of the large-scale catamaran, cabin ventilation system is too long, the return air resistance is high, and the piping system is difficult to arrange, which is likely to cause serious wind uneven, excessive temperature and pressure. Taking the design of the world's larges 6000T catamaran as an example, this paper used CFD technology to carry out numerical simulation analysis of its ventilation system, and found that its airflow had many problems in speed, temperature and pressure; This paper further proposed a specific plan, which was to increase the main deck duct branch, increase the bottom cabin exhaust ducts and deck exhaust air openings, and selected the typical section before and after optimization to analyze the airflow, and verified the correctness of the plan. The plan meet the requirements of regulations, and had low cost and convenient construction, which had certain reference value for the design of large-scale catamaran ventilation system.
Key words: catamaran     CFD     airflow     numerical simulation     cabin ventilation
0 引　言

1 机舱通风系统的物理模型

 图 1 机舱主要设备和风管布置 Fig. 1 Main equipment and duct layout in the cabin

1）忽略对舱室热环境和气流组织影响较小的小功率油/水泵、管系、电缆和配电箱，对外形复杂的机电设备采用规则化处理；

2）忽略对热环境影响较小、但对网格质量和计算精度产生较大不利影响的烟管。

 图 2 机舱物理模型 Fig. 2 Cabin physical model
2 数学模型及边界条件 2.1 数学模型的建立

1）流体为不可压缩理想气体，流态为稳态流动过程；

2）除了主风机进气、烟囱和主机排气，门窗处于正常使用状态时的关闭状态，舱内密封良好，无漏气现象；

3）舱壁采用A-60级绝热材料包覆，无凝水或传热现象，作为绝热壁处理。

2.2 边界条件的设置

3 模拟过程和结果分析

 图 3 截面速度场图 Fig. 3 The distribution of air velocity field

 图 5 Y1=0 m截面压力场图 Fig. 5 The distribution of air pressure field Y1=0 m

 图 4 截面温度场图 Fig. 4 The distribution of air temperature field

1）主甲板区域。机舱后端风速约为0.2 m/s，此处为人员主通道区域，风速太小不满足人员舒适度的要求；左舷和右舷的主机之间温度适宜，但风速为13 m/s，较高的风速及由此产生的噪声问题不利于人员作业和全船辐射噪声的控制；两舷后侧为燃油舱、分油机、燃油泵及其油管所在区域，此处风速过小，边角处有涡流产生，会造成油雾汇集而不能正常排出，增大了火灾风险；锅炉、热井和焚烧炉作为热源，附近约48 ℃，温度较高不利于电子设备的长期使用和人员操作，同时不满足海船规范对于机舱温度的要求（45 ℃）；烟囱处温度和流速较高，但循环后的热风流经烟囱直接排向舱外，且人员通常不会到达该处，因此不作严格要求。

2）支柱体和湿甲板区域.。气相组织不均衡，速度梯度较大，但此处仅放置供水设备和冷水机组，且设备所在位置温度和流场尚可，因此其通风效果可以接受；在作为排风通道的上下梯道口处流场梯度大、风速过大（约15 m/s），气流将会因此产生较大的动压和噪声。

3）潜体区域。泵浦区域温度达到45 ℃，尾端风速太小，接近于一个大区域的流动死区，从速度场分析来看是因为进风口和出风口（上下梯道）距离太近，出现了明显的气流短路。

4）舱内压力较高，底舱静压达到310 Pa，大大高于人体舒适度对于压力范围的要求（±100 Pa），且会造成片体脱险通道防火门以及通向室外的风雨密门的人工开闭困难，不利于日常进出，给人员逃生到来极大安全隐患，同时过高的压力会引起送风机运行偏离其标准流量-压力工况，从而造成实际进风量大大减少。

4 通风系统的优化方案

 图 6 优化后机舱物理模型 Fig. 6 Cabin physical model after optimization

 图 7 截面速度场图 Fig. 7 The distribution of air velocity field

 图 9 Y1=0 m截面压力场图 Fig. 9 The distribution of air pressure field Y1=0 m

 图 8 截面温度场图 Fig. 8 The distribution of air temperature field

1）由于过流风量的增加，重点区域环境温度明显降低：锅炉、热井和焚烧炉附近温度降低至41 ℃，潜体泵浦区域温度降低至40 ℃。

2）流场梯度明显减小，气流有效行程增加，主甲板后端主通道风速增加到3 m/s，主机之间的风速降低至8 m/s；机舱尾部气流扰动增加，避免了气流死区和旋涡现象，保证了油雾的有效排出；上下梯道口风速降低至8 m/s。

3）舱内压力过高的现象得到明显改善，潜体降低至100 Pa。这是因为增加了片体抽风管路和甲板开孔，排风得到了有效的分流；同时由于排风背压的降低，送风机风量将会进一步增加。

5 结　语

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