Research on the Flow-Induced Stress Characteristics of Head-Cover Bolts of a Pump-Turbine during Turbine Start-Up
Abstract
:1. Introduction
2. Methodology of Flow-Induced Stress Analysis
3. Flow Field Simulation and Flow Characteristics
3.1. The Calculation Model and Boundary Conditions
3.2. Calibration of the Finite Volume Mesh
3.3. Results and Discussions
4. Flow-Induced Stress Analysis
4.1. The Calculation Model and Boundary Conditions
4.2. Mesh Sensitivity Analysis
4.3. Head-Cover Bolts Preloading and Fluid–Structure Coupling
5. Results and Discussions
5.1. Axial Hydraulic Thrust Force of the Head-Cover
5.2. Stress and Deformation Distribution of the Head-Cover
5.3. Stress Distribution of the Stay Ring
5.4. Stress Distribution of the Head-Cover Bolts
6. Conclusions
- The fluid flow and pressure distribution of the pump-turbine flow channel during turbine start-up have been analysed. The head-cover and head-cover bolts are excited by large hydraulic forces, which cause uneven stress distribution of the structures in the circumferential direction.
- As for the stress distribution of the head-cover bolts, the maximum stress occurs in the bolt with the least deformation. Due to the axisymmetric feature of the head-cover, the bolt positions with the maximum stress and with the maximum deformation differ by approximately 90 degrees in the circumferential direction.
- The maximum von Mises stress of the head-cover during turbine start-up is located in the connecting surface of the head-cover flange and a head-cover bolt. The maximum stress of the head-cover is around 249 MPa, which is below the yield stress 265 MPa of the head-cover material.
- The maximum von Mises stress of the stay ring during turbine start-up is in the fillet of the stay vane. The maximum stress of the stay ring is about 222 MPa, which is below the yield stress of 830 MPa of the stay ring material.
- The maximum von Mises stress of the head-cover bolts due to pretension force is located in the middle of each bolt. The maximum stress of the head-cover bolts is about 430 MPa, which is below the yield stress of 960 MPa of the bolt material.
- The maximum von Mises stress of the head-cover bolts during turbine start-up appears in the fillet of the bolts closed to the head-cover outer flange. The maximum stress of the head-cover bolts is about 377 MPa, which is below the yield stress of 960 MPa of the bolt material.
- During turbine start-up, the maximum stress of the head-cover bolts and the head-cover follow the same trend. At a certain time, the maximum stress of the head-cover bolts is always higher than the stress of the head-cover. Additionally, the maximum stress of the guide vane is less than the one of the head-cover bolts and the head-cover.
- It can be seen that the design of stationary structures and head-cover bolts are safe during turbine start-up which is a very challenging operation condition for the PT unit. The design, simulation methods, and conclusions in this investigation can be used as a good reference for evaluating the flow-induced stress characteristics of head-cover bolts of similar hydraulic pump-turbine units.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Abbreviations
CFD | computational fluid dynamics |
FEM | finite element method |
FSC | fluid–structure coupling |
FVM | finite volume method |
PSPS | pumped-storage power station |
PT | pump-turbine |
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Spiral Case | Stay Vane | Guide Vane | Runner | Crown Chamber | Band Chamber | Pressure-Balance Pipe | Draft Tube | Total | |
---|---|---|---|---|---|---|---|---|---|
Element number | 57,796 | 103,493 | 593,210 | 3,417,050 | 531,518 | 422,700 | 53,113 | 86,041 | 5,264,921 |
Head-Cover Bolt | Head-Cover | Stay Ring | |
---|---|---|---|
Material | 34CrNi3Mo | Q345C | Cr13Ni5Mo |
Density (kg·m−3) | 7850 | 7850 | 7850 |
Elastic modulus (MPa) | 2.1 × 105 | 2.1 × 105 | 2.1 × 105 |
Poisson’s ratio | 0.3 | 0.3 | 0.3 |
Tightening force (kN) | 4196 | - | - |
Yield stress (MPa) | 960 | 265 | 830 |
Ultimate stress (MPa) | 1100 | 450 | 980 |
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Wang, Z.; Yang, J.; Wang, W.; Qu, J.; Huang, X.; Zhao, W. Research on the Flow-Induced Stress Characteristics of Head-Cover Bolts of a Pump-Turbine during Turbine Start-Up. Energies 2022, 15, 1832. https://doi.org/10.3390/en15051832
Wang Z, Yang J, Wang W, Qu J, Huang X, Zhao W. Research on the Flow-Induced Stress Characteristics of Head-Cover Bolts of a Pump-Turbine during Turbine Start-Up. Energies. 2022; 15(5):1832. https://doi.org/10.3390/en15051832
Chicago/Turabian StyleWang, Zhengwei, Juwei Yang, Wei Wang, Jie Qu, Xingxing Huang, and Weiqiang Zhao. 2022. "Research on the Flow-Induced Stress Characteristics of Head-Cover Bolts of a Pump-Turbine during Turbine Start-Up" Energies 15, no. 5: 1832. https://doi.org/10.3390/en15051832