Study on Structure Optimization of Exhaust Steam Passage of Steam Turbine in Large Coal-fired Power Station

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

Abstract

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

CLC Number:

TK05

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.

Figures/Tables 18

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

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

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

Fig.1 Physical model of original exhaust steam passage

Fig.2 Grid division of original exhaust passage

Fig.3 Effect of steam velocity on heat transfer coefficient

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

Fig.5 Flow diagram of original exhaust passage

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

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

Fig.8 Schematic diagram of optimization scheme

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

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

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

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

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

Fig.11 Deflector of feedwater pump steam turbine in engineering

Fig.12 Support structure of deflector

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