蜗壳轴向出流式低比转数水轮机设计与数值模拟
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摘要
基于流体机械设计理论和数值模拟分析方法,设计了一种新型低比转数水轮机,其不仅适用于小水电机组的更新完善,也可作为冷却塔风机的直接驱动装置。该水轮机采用蜗壳轴向出水方式,使其径向尺寸约为相似常规水轮机的1/2,除降低造价成本外,更有利于冷却塔内通风;为适应冷却塔内部结构,采用反击式环形叶片作功,在很大程度上降低了水轮机径向尺寸;对应水轮机转轮出水形式,环形尾水管进水模式将尾水接入对称布置的4个布水管,均匀出水结构在很大程度上改善了尾水管内流场,同时可使水轮机直接安装在中心基座上。数值模拟结果表明:蜗壳出口速度满足等速度矩定律,采用轴向出水方式的反击式水轮机的流场分布符合要求;水轮机预测效率约90%,各部分水力损失均较小。
Considering the trend of small hydropower towards low head,and reusing the water surplus head of cooling tower,a new type of turbine with small size,high efficiency and super low specific speed was proposed to be as direct drive for fan in large cooling tower or applied in small hydropower plants for generating electricity,which was designed and validated based on design theory of fluid mechanics and validation method of numerical simulations. Combining binary theory and spiral potential flow to design the flow streamline in volute,the new type volute adopted axial outlet to ensure the turbine radial dimension was about half compared with similar conventional turbines,this kind of structure was a great benefit to decrease manufacturing cost,which was more conducive to ventilation in cooling tower. The work of impact annular blades reduced the turbine specific speed to a large extent which adapted to the internal structure of the cooling tower,the tangent of runner blade was perpendicular to the runner axis.Corresponding to the runner outlet,draft tube was designed with annual inlet,the water flow through the four water distribution pipes in the draft tube which was propitious to improve flow field performance in draft tube,meanwhile,the turbine was able to mount on the central base directly with this structure.Theoretical calculation on hydraulic loss in each domain was given and it was compared with corresponding data that acquired from numerical calculations; the results showed that the hydraulic loss in each domain was relatively small, and differences between them were less than 5%. Numerical calculations were carried out with model which was built in Solidedge and meshed in ICEM,SST k-ω was used in all simulations to capture fluid details,while monitoring points were located on guide vane andrunner blade for obtaining pressure values. Numerical results showed that velocity at the volute outlet was consistent with constant velocity moment law and the flow field characteristics illustrated this model with good performance,and the predicting efficiency was around 90%.
Considering the trend of small hydropower towards low head,and reusing the water surplus head of cooling tower,a new type of turbine with small size,high efficiency and super low specific speed was proposed to be as direct drive for fan in large cooling tower or applied in small hydropower plants for generating electricity,which was designed and validated based on design theory of fluid mechanics and validation method of numerical simulations. Combining binary theory and spiral potential flow to design the flow streamline in volute,the new type volute adopted axial outlet to ensure the turbine radial dimension was about half compared with similar conventional turbines,this kind of structure was a great benefit to decrease manufacturing cost,which was more conducive to ventilation in cooling tower. The work of impact annular blades reduced the turbine specific speed to a large extent which adapted to the internal structure of the cooling tower,the tangent of runner blade was perpendicular to the runner axis.Corresponding to the runner outlet,draft tube was designed with annual inlet,the water flow through the four water distribution pipes in the draft tube which was propitious to improve flow field performance in draft tube,meanwhile,the turbine was able to mount on the central base directly with this structure.Theoretical calculation on hydraulic loss in each domain was given and it was compared with corresponding data that acquired from numerical calculations; the results showed that the hydraulic loss in each domain was relatively small, and differences between them were less than 5%. Numerical calculations were carried out with model which was built in Solidedge and meshed in ICEM,SST k-ω was used in all simulations to capture fluid details,while monitoring points were located on guide vane andrunner blade for obtaining pressure values. Numerical results showed that velocity at the volute outlet was consistent with constant velocity moment law and the flow field characteristics illustrated this model with good performance,and the predicting efficiency was around 90%.
引文
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2周波,王志成,周长西.水力通风冷却塔的发展与应用现状[J].工业用水与废水,2010,41(3):73-75.ZHOU Bo,WANG Zhicheng,ZHOU Changxi.Development and application of hydraulic draft cooling tower[J].Industrial Water and Waste Water,2010,41(3):73-75.(in Chinese)
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5张文俊.冷却塔水轮机特性理论分析与试验研究[D].郑州:华北水利水电学院,2011.ZHANG Wenjun.Theoretical analysis and experimental study on turbine characteristics of cooling tower[D].Zhengzhou:North China University of Water Resources and Electric Power,2011.(in Chinese)
6徐大荣,马志龙.双驱动冷却塔水轮机装置的研究[J].节能技术,2015,33(4):376-379.XU Darong,MA Zhilong.Research of the dual-drive turbine device for cooling tower[J].Energy Conservation Technology,2015,33(4):376-379.(in Chinese)
7 LI Y,ZHANG L,CHEN D.Study on characteristics of special turbine in hydrodynamic cooling tower[J].Research Journal of Applied Sciences Engineering&Technology,2012,4(21):4429-4431.
8 ZHANG L,REN Y,LI Y,et al.Hydraulic characteristic of cooling tower francis turbine with different spiral casing and stay ring[J].Energy Procedia,2012,16:651-655.
9范小娟,郑源,毛秀丽.双动力源冷却塔设计研究[J].南水北调与水利科技,2014,12(5):199-201.FAN Xiaojuan,ZHENG Yuan,MAO Xiuli.Research and design of cooling tower with double power sources[J].South-to-North Water Transfers and Water Science&Technology,2014,12(5):199-201.(in Chinese)
10陈洋,周大庆,李玲玉,等.水动冷却塔直驱混流式水轮机转轮数值模拟优化[J].排灌机械工程学报,2014,32(7):600-605.CHEN Yang,ZHOU Daqing,LI Lingyu,et al.Numerical simulation and hydrodynamics optimization of direct-drive Francis turbine runner in cooling towers[J].Journal of Drainage and Irrigation Machinery Engineering,2014,32(7):600-605.(in Chinese)
11 MAO X,MONTE A D,BENINI E,et al.Numerical study on the internal flow field of a reversible turbine during continuous guide vane closing[J].Energies,2017,10(7):988.
12 CAVAZZINI G,COVI A,PAVESI G,et al.Analysis of the unstable behavior of a pump-turbine in turbine mode:fluid dynamical and spectral characterization of the S-shape characteristic[J].Journal of Fluids Engineering,2016,138(2):021105.
13 CHOI H J,ZULLAH M A,ROH H W,et al.CFD validation of performance improvement of a 500 k W Francis turbine[J].Renewable Energy,2013,54(6):111-123.
14 NICOLLE J,MORISSETTE J F,GIROUX A M.Transient CFD simulation of a Francis turbine startup[C]∥IOP Conference Series:Earth and Environmental Science,2012,15(6):062014.
15王旭,李萍,陈荣盛,等.水轮机椭圆蜗壳设计的CFD计算及试验分析[J].人民黄河,2016,38(1):109-111.WANG Xu,LI Ping,CHEN Rongsheng,et al.Oval section design of spiral case based on CFD and model test[J].Yellow River,2016,38(1):109-111.(in Chinese)
16毛秀丽,郑源,屈波,等.小型混流式水泵水轮机水力设计[J].南水北调与水利科技,2014,12(6):123-126.MAO Xiuli,ZHENG Yuan,QU Bo,et al.Hydraulic design of small mixed-flow reversible pump turbine[J].South-to-North Water Transfers and Water Science&Technology,2014,12(6):123-126.(in Chinese)
17 LUO W W,LEI Z,WANG H S,et al.Effects of high-pressure guide vane adjustment on 1+1/2 counter-rotating turbine[J].Journal of Aerospace Power,2011,26(12):2741-2748.
18 VELEZ C,CORONADO P,ALKURAN H,et al.Numerical computations of turbine blade aerodynamics;comparison of LES,SAS,SST,SA and k-ε[C]∥47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference&Exhibit,2013.
19任芸,刘厚林,舒敏骅,等.考虑旋转和曲率影响的SST k-ω湍流模型改进[J/OL].农业机械学报,2012,43(11):123-128.http:∥www.j-csam.org/jcsam/ch/reader/view_abstract.aspx?file_no=20121123&flag=1.DOI:10.6041/j.issn.1000-1298.2012.11.023.REN Y,LIU H L,SHU M H,et al.Improvement of SST k-ωturbulence model and numerical simulation in centrifugal pump[J/OL].Transactions of the Chinese Society for Agricultural Machinery,2012,43(11):123-128.(in Chinese)
20 https:∥www.cfd-online.com/Wiki/SST_k-omega_model.
21 ZHANG W,MA Z,YU Y C,et al.Applied new rotation correction k-ωSST model for turbulence simulation of centrifugal impeller in the rotating frame of reference[J].Journal of Hydrodynamics Ser B,2010,22(5):404-407.
22 BOI'C I.Determination of hydraulic losses in the flow passage between the guide vanes and runner of the Kaplan turbine[J].Journal of Hydraulic Research,2017,55(3):349-361.
2周波,王志成,周长西.水力通风冷却塔的发展与应用现状[J].工业用水与废水,2010,41(3):73-75.ZHOU Bo,WANG Zhicheng,ZHOU Changxi.Development and application of hydraulic draft cooling tower[J].Industrial Water and Waste Water,2010,41(3):73-75.(in Chinese)
3张丽敏,郑源,张成华,等.用于冷却塔的超低比转数混流式水轮机设计[J].农业机械学报,2010,41(增刊):39-42.ZHANG Limin,ZHENG Yuan,ZHANG Chenghua,et al.Study on the Francis turbine with super low specific speed applied in cooling tower[J].Transactions of the Chinese Society for Agricultural Machinery,2010,41(Supp.):39-42.(in Chinese)
4李延频,南海鹏,陈德新.冷却塔专用水轮机的工作特性与选型[J].水力发电学报,2011,30(1):175-179.LI Yanpin,NAN Haipeng,CHEN Dexin.Performance and type selection of special hydraulic turbine in cooling tower[J].Journal of Hydroelectric Engineering,2011,30(1):175-179.(in Chinese)
5张文俊.冷却塔水轮机特性理论分析与试验研究[D].郑州:华北水利水电学院,2011.ZHANG Wenjun.Theoretical analysis and experimental study on turbine characteristics of cooling tower[D].Zhengzhou:North China University of Water Resources and Electric Power,2011.(in Chinese)
6徐大荣,马志龙.双驱动冷却塔水轮机装置的研究[J].节能技术,2015,33(4):376-379.XU Darong,MA Zhilong.Research of the dual-drive turbine device for cooling tower[J].Energy Conservation Technology,2015,33(4):376-379.(in Chinese)
7 LI Y,ZHANG L,CHEN D.Study on characteristics of special turbine in hydrodynamic cooling tower[J].Research Journal of Applied Sciences Engineering&Technology,2012,4(21):4429-4431.
8 ZHANG L,REN Y,LI Y,et al.Hydraulic characteristic of cooling tower francis turbine with different spiral casing and stay ring[J].Energy Procedia,2012,16:651-655.
9范小娟,郑源,毛秀丽.双动力源冷却塔设计研究[J].南水北调与水利科技,2014,12(5):199-201.FAN Xiaojuan,ZHENG Yuan,MAO Xiuli.Research and design of cooling tower with double power sources[J].South-to-North Water Transfers and Water Science&Technology,2014,12(5):199-201.(in Chinese)
10陈洋,周大庆,李玲玉,等.水动冷却塔直驱混流式水轮机转轮数值模拟优化[J].排灌机械工程学报,2014,32(7):600-605.CHEN Yang,ZHOU Daqing,LI Lingyu,et al.Numerical simulation and hydrodynamics optimization of direct-drive Francis turbine runner in cooling towers[J].Journal of Drainage and Irrigation Machinery Engineering,2014,32(7):600-605.(in Chinese)
11 MAO X,MONTE A D,BENINI E,et al.Numerical study on the internal flow field of a reversible turbine during continuous guide vane closing[J].Energies,2017,10(7):988.
12 CAVAZZINI G,COVI A,PAVESI G,et al.Analysis of the unstable behavior of a pump-turbine in turbine mode:fluid dynamical and spectral characterization of the S-shape characteristic[J].Journal of Fluids Engineering,2016,138(2):021105.
13 CHOI H J,ZULLAH M A,ROH H W,et al.CFD validation of performance improvement of a 500 k W Francis turbine[J].Renewable Energy,2013,54(6):111-123.
14 NICOLLE J,MORISSETTE J F,GIROUX A M.Transient CFD simulation of a Francis turbine startup[C]∥IOP Conference Series:Earth and Environmental Science,2012,15(6):062014.
15王旭,李萍,陈荣盛,等.水轮机椭圆蜗壳设计的CFD计算及试验分析[J].人民黄河,2016,38(1):109-111.WANG Xu,LI Ping,CHEN Rongsheng,et al.Oval section design of spiral case based on CFD and model test[J].Yellow River,2016,38(1):109-111.(in Chinese)
16毛秀丽,郑源,屈波,等.小型混流式水泵水轮机水力设计[J].南水北调与水利科技,2014,12(6):123-126.MAO Xiuli,ZHENG Yuan,QU Bo,et al.Hydraulic design of small mixed-flow reversible pump turbine[J].South-to-North Water Transfers and Water Science&Technology,2014,12(6):123-126.(in Chinese)
17 LUO W W,LEI Z,WANG H S,et al.Effects of high-pressure guide vane adjustment on 1+1/2 counter-rotating turbine[J].Journal of Aerospace Power,2011,26(12):2741-2748.
18 VELEZ C,CORONADO P,ALKURAN H,et al.Numerical computations of turbine blade aerodynamics;comparison of LES,SAS,SST,SA and k-ε[C]∥47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference&Exhibit,2013.
19任芸,刘厚林,舒敏骅,等.考虑旋转和曲率影响的SST k-ω湍流模型改进[J/OL].农业机械学报,2012,43(11):123-128.http:∥www.j-csam.org/jcsam/ch/reader/view_abstract.aspx?file_no=20121123&flag=1.DOI:10.6041/j.issn.1000-1298.2012.11.023.REN Y,LIU H L,SHU M H,et al.Improvement of SST k-ωturbulence model and numerical simulation in centrifugal pump[J/OL].Transactions of the Chinese Society for Agricultural Machinery,2012,43(11):123-128.(in Chinese)
20 https:∥www.cfd-online.com/Wiki/SST_k-omega_model.
21 ZHANG W,MA Z,YU Y C,et al.Applied new rotation correction k-ωSST model for turbulence simulation of centrifugal impeller in the rotating frame of reference[J].Journal of Hydrodynamics Ser B,2010,22(5):404-407.
22 BOI'C I.Determination of hydraulic losses in the flow passage between the guide vanes and runner of the Kaplan turbine[J].Journal of Hydraulic Research,2017,55(3):349-361.