大型燃煤电站汽轮机排汽通道结构优化研究

doi:10.12096/j.2096-4528.pgt.21067

摘要/Abstract

摘要：

针对河北某电厂600 MW湿冷机组，运用ANSYS Fluent软件对汽轮机排汽通道流场进行数值模拟。研究发现：在原设计下，由于排汽缸轴向排汽及凝汽器接颈存在扩散角，排汽通道内出现了较大的低速漩涡区域，对凝汽器换热性能具有负面作用，而给水泵汽轮机排汽对低速漩涡区域具有一定的补充作用，能够一定程度上改善流场。针对这种现象，通过设计导流结构，对排汽通道流场进行了优化，结果表明：经过流场优化后，机组排汽在主凝结区最上层管束平面处的流速均匀性得到了显著提升，从而有利于提高凝汽器换热系数、降低机组背压、提升机组发电效率。

关键词: 燃煤电站, 汽轮机, 排汽通道, 流场

Abstract:

For a 600 MW wet-cooled unit of a power plant in Hebei province, ANSYS Fluent software was used to numerically simulate the flow field of the steam turbine exhaust passage. It was found that under the original design, due to the axial exhaust steam of the exhaust cylinder and the diffusion angle of the condenser neck, a large low-speed vortex area appeared in the exhaust steam passage, which had a negative effect on the heat transfer performance of the condenser. The exhaust steam of the feed water pump steam turbine had a certain supplementary effect on the low-speed vortex area and could improve the flow field to a certain extent. Aiming at this phenomenon, the exhaust passage flow field was optimized through the design of diversion structures. The results show that after optimizing the flow field, the crew exhaust steam condensed in the main area of the upper tube bundle planar velocity uniformity has been significantly increased, which is benefit to improve the condenser heat transfer coefficient, reduce the unit back pressure, and promote the efficiency of generating units.

Key words: coal-fired power plants, steam turbine, exhaust steam passage, flow field

中图分类号:

TK05

王玉亭, 陈彦奇, 徐钢, 陈衡. 大型燃煤电站汽轮机排汽通道结构优化研究[J]. 发电技术, 2021, 42(4): 464-472.

Yuting WANG, Yanqi CHEN, Gang XU, Heng CHEN. Study on Structure Optimization of Exhaust Steam Passage of Steam Turbine in Large Coal-fired Power Station[J]. Power Generation Technology, 2021, 42(4): 464-472.

图/表 18

表1 排汽缸几何结构

Tab. 1 Exhaust hood geometry mm

内缸		内导流环		外缸		外导流环
直径	高度	直径	高度	直径	高度	直径	高度
3 260	7 721	8 90	7 721	3 454	7 721	4 657	7 721

表2 凝汽器接颈内构件结构

Tab. 2 Internal component structure of condenser throat mm

低压加热器		给水泵汽轮机排汽口		减温减压装置进汽口		最上层管束平面
直径	高度	直径	高度	直径	高度	高度
1 860	1 920	2 100	1 945	820	1 920	-850

表3 凝汽器接颈几何结构

Tab. 3 Condenser throat geometry

进口尺寸/mm	高度/mm	出口尺寸/mm	扩散角/(°)
6 680×7 580	4 622	10 892×7 580	62.5

图1 原排汽通道物理模型

Fig.1 Physical model of original exhaust steam passage

图2 原排汽通道网格划分

Fig.2 Grid division of original exhaust passage

图3 蒸汽流速对传热系数的影响

Fig.3 Effect of steam velocity on heat transfer coefficient

图4 原模型接颈出口及最上层管束平面速度云图对比

Fig.4 Comparison of plane velocity of original model throat outlet and uppermost tube bundle

图5 原排汽通道流线图

Fig.5 Flow diagram of original exhaust passage

图6 无给水泵汽轮机排汽情况下最上层管束平面速度云图

Fig.6 Plane velocity cloud image of the topmost tube bundle in the case of steam turbine exhaust without feed pump

图7 加入抽汽管道情况下最上层管束平面速度云图

Fig.7 Plane velocity cloud image of the topmost tube bundle with the addition of the extraction pipe

图8 优化方案示意图

Fig.8 Schematic diagram of optimization scheme

图9 优化方案最上层管束平面速度云图

Fig.9 Planar velocity cloud image of the uppermost tube bundle in the optimization scheme

表4 优化前后流场特性指标对比

Tab. 4 Comparison of flow field characteristic indexes before and after optimization

参数	原结构	优化方案
静压恢复系数	0.216	0.176
总压损失系数	0.502	0.593
均匀性系数	0.607	0.705

表5 阀门全开工况与额定工况排汽量对比

Tab. 5 Comparison of exhaust volume between valve in full open condition and rated condition

工况	给水泵汽轮机排汽量/(t/h)	主汽排汽量/(t/h)
阀门全开工况	65.167	1 109.332
额定工况	69	1 153.9

图10 阀门全开工况下导流板受力云图

Fig.10 Force cloud image of guide plate under fully open valve condition

表6 导流板在各温度下的许用应力

Tab. 6 Allowable stresses of guide plate at various temperatures

温度/℃	≤20	100	150	200
许用应力/MPa	113	113	113	105

图11 工程中的给水泵汽轮机导流板

Fig.11 Deflector of feedwater pump steam turbine in engineering

图12 导流板支撑结构

Fig.12 Support structure of deflector

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