Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection
Labyrinth seals are not usually included in the numerical models of hydraulic machinery to simplify the geometric modeling, and thereby reduce the calculation burden. However, this simplification affects the numerical results, especially in the load rejection process, because disc friction losses, v...
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MDPI AG
2019-02-01
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| Series: | Energies |
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| Online Access: | https://www.mdpi.com/1996-1073/12/4/716 |
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| author | Daqing Zhou Huixiang Chen Jie Zhang Shengwen Jiang Jia Gui Chunxia Yang An Yu |
| author_facet | Daqing Zhou Huixiang Chen Jie Zhang Shengwen Jiang Jia Gui Chunxia Yang An Yu |
| author_sort | Daqing Zhou |
| collection | DOAJ |
| description | Labyrinth seals are not usually included in the numerical models of hydraulic machinery to simplify the geometric modeling, and thereby reduce the calculation burden. However, this simplification affects the numerical results, especially in the load rejection process, because disc friction losses, volume losses, and pressure fluctuations in the seal ring (SR) clearance passage are neglected. This paper addresses the issue by considering all of the geometrical details of labyrinth seals when conducting multiscale flow simulations of a high head Francis turbine under a transient load rejection condition using the commercial software code. A comparison of the numerical results that were obtained with the experimental testing data indicates that the calculated values of both torque and mass discharge rate are 8.65% and 5% slightly less than the corresponding values that were obtained from experimental model testing, respectively. The obtained pressure fluctuations of the Francis turbine in the vaneless zone and the draft tube appear to more closely match with the experimental test data when including SR clearance. Moreover, the flow rates through SR clearance passages were very small, but the pressure fluctuations among them were significantly enhanced under the minimal load condition. The numerical model with SR clearance can more accurately reflect the fact that the water thrust on the runner only fluctuates from 800 N to 575 N during the load rejection process, even though the water thrust on the blades varies from −220 N to 1200 N. Therefore, multiscale flow study is of great significance in understanding the effect of clearance flow on the load rejection process in the Francis turbine. |
| first_indexed | 2024-04-13T06:07:16Z |
| format | Article |
| id | doaj.art-af2ccb1a66b8452285fe3a07753581a9 |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-04-13T06:07:16Z |
| publishDate | 2019-02-01 |
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| series | Energies |
| spelling | doaj.art-af2ccb1a66b8452285fe3a07753581a92022-12-22T02:59:13ZengMDPI AGEnergies1996-10732019-02-0112471610.3390/en12040716en12040716Numerical Study on Flow Characteristics in a Francis Turbine during Load RejectionDaqing Zhou0Huixiang Chen1Jie Zhang2Shengwen Jiang3Jia Gui4Chunxia Yang5An Yu6College of Energy and Electrical Engineering, Hohai University, Nanjing 210098, ChinaCollege of Energy and Electrical Engineering, Hohai University, Nanjing 210098, ChinaShanghai Investigation, Design & Research Institute Corporation Limited, Shanghai 200434, ChinaCollege of Energy and Electrical Engineering, Hohai University, Nanjing 210098, ChinaCollege of Energy and Electrical Engineering, Hohai University, Nanjing 210098, ChinaCollege of Energy and Electrical Engineering, Hohai University, Nanjing 210098, ChinaCollege of Energy and Electrical Engineering, Hohai University, Nanjing 210098, ChinaLabyrinth seals are not usually included in the numerical models of hydraulic machinery to simplify the geometric modeling, and thereby reduce the calculation burden. However, this simplification affects the numerical results, especially in the load rejection process, because disc friction losses, volume losses, and pressure fluctuations in the seal ring (SR) clearance passage are neglected. This paper addresses the issue by considering all of the geometrical details of labyrinth seals when conducting multiscale flow simulations of a high head Francis turbine under a transient load rejection condition using the commercial software code. A comparison of the numerical results that were obtained with the experimental testing data indicates that the calculated values of both torque and mass discharge rate are 8.65% and 5% slightly less than the corresponding values that were obtained from experimental model testing, respectively. The obtained pressure fluctuations of the Francis turbine in the vaneless zone and the draft tube appear to more closely match with the experimental test data when including SR clearance. Moreover, the flow rates through SR clearance passages were very small, but the pressure fluctuations among them were significantly enhanced under the minimal load condition. The numerical model with SR clearance can more accurately reflect the fact that the water thrust on the runner only fluctuates from 800 N to 575 N during the load rejection process, even though the water thrust on the blades varies from −220 N to 1200 N. Therefore, multiscale flow study is of great significance in understanding the effect of clearance flow on the load rejection process in the Francis turbine.https://www.mdpi.com/1996-1073/12/4/716Francis turbinelabyrinth sealsmultiscaleleakage flowtransient process |
| spellingShingle | Daqing Zhou Huixiang Chen Jie Zhang Shengwen Jiang Jia Gui Chunxia Yang An Yu Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection Energies Francis turbine labyrinth seals multiscale leakage flow transient process |
| title | Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection |
| title_full | Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection |
| title_fullStr | Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection |
| title_full_unstemmed | Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection |
| title_short | Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection |
| title_sort | numerical study on flow characteristics in a francis turbine during load rejection |
| topic | Francis turbine labyrinth seals multiscale leakage flow transient process |
| url | https://www.mdpi.com/1996-1073/12/4/716 |
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