0
Research Papers: Flows in Complex Systems

Mechanism of the S-Shaped Characteristics and the Runaway Instability of Pump-Turbines

[+] Author and Article Information
Linsheng Xia

State Key Laboratory of Water Resources and
Hydropower Engineering Science,
Wuhan University,
Wuhan 430072, China
e-mail: xialinsheng@whu.edu.cn

Yongguang Cheng

State Key Laboratory of Water Resources and
Hydropower Engineering Science,
Wuhan University,
Wuhan 430072, China
e-mail: ygcheng@whu.edu.cn

Jianfeng You

State Key Laboratory of Water Resources and
Hydropower Engineering Science,
Wuhan University,
Wuhan 430072, China
e-mail: youjf@whu.edu.cn

Xiaoxi Zhang

State Key Laboratory of Water Resources and
Hydropower Engineering Science,
Wuhan University,
Wuhan 430072, China
e-mail: zhangxiaoxi@whu.edu.cn

Jiandong Yang

State Key Laboratory of Water Resources and
Hydropower Engineering Science,
Wuhan University,
Wuhan 430072, China
e-mail: jdyang@whu.edu.cn

Zhongdong Qian

State Key Laboratory of Water Resources and
Hydropower Engineering Science,
Wuhan University,
Wuhan 430072, China
e-mail: zdqian@whu.edu.cn

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received October 6, 2015; final manuscript received October 11, 2016; published online December 7, 2016. Assoc. Editor: Kwang-Yong Kim.

J. Fluids Eng 139(3), 031101 (Dec 07, 2016) (14 pages) Paper No: FE-15-1721; doi: 10.1115/1.4035026 History: Received October 06, 2015; Revised October 11, 2016

Understanding the formation mechanism of the S-shaped characteristics (SSCs) and the relationship between flow structures and the runaway instability (RI) is the prerequisite for optimizing runner design to promote operational reliability and flexibility. In this study, a new turbine equation is derived to reveal the prime cause of the SSCs, and the influence of geometric parameters on the SSCs is analyzed. Moreover, the flow patterns in three model turbines of different specific-speeds are simulated by unsteady Computational fluid dynamics (CFD), and the correlation between inverse flow vortex structures (IFVSs) and the RI in the SSCs region is identified. Theoretical analysis shows that the turbine equation can theoretically predict the change trend of the first quadrant SSCs curves of the pump-turbines; the flow losses caused by small blade inlet angle, instead of the diameter ratio, are the primary cause of the SSCs. The numerical simulation results reveal that the IFVSs at the hub side of the runner inlet are the origin of the RI; when operating points are far away from the best efficiency point (BEP), the IFVS locations change regularly. For large guide vane openings (GVOs), the IFVSs first incept at the shroud side, and then translate to the hub side, and further back to the midspan, when the discharge decreases. The inception points (IPs) of the SSCs correspond to the onset of the IFVSs at the hub side, which are in advance of the zero-torque operating points (ZTOPs); therefore, the ZTOPs are located in the positive slope region, leading to RI. For small GVOs, however, the IFVSs only locate at the midspan; the IPs of the SSCs, having no definite correlation with the IFVSs, are coincided with or are below the ZTOPs, because the ZTOPs are in the negative slope region and RI disappears. It is also found that the IPs of SSCs are the turning points of the predominant states between the turbine effect and pump effect. These results are valuable for design and optimization of pump-turbine runners.

Copyright © 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Nicolet, C. , Alligné, S. , Kawkabani, B. , Koutnik, J. , Simond, J. J. , and Avellan, F. , 2009, “ Stability Study of Francis Pump-Turbine at Runaway,” 3rd Meeting IAHR Workgroup on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Brno, Czech, Oct. 14–16.
Pejovic, S. , Zhang, Q. F. , Karney, B. , and Gajic, A. , 2011, “ Analysis of Pump-Turbine “S” Instability and Reverse Waterhammer Incidents in Hydropower Systems,” 4th International Meeting on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Belgrade, Serbia.
Staubli, T. , Senn, F. , and Sallaberger, M. , 2008, “ Instability of Pump-Turbines During Start-Up in the Turbine Mode,” Hydro2008, Ljubljana, Slovenia.
Zuo, Z. , Liu, S. , Sun, Y. , and Wu, Y. , 2015, “ Pressure Fluctuations in the Vaneless Space of High-Head Pump-Turbines—A Review,” Renewable Sustainable Energy Rev., 41, pp. 965–974. [CrossRef]
Zuo, Z. , Fan, H. , Liu, S. , and Wu, Y. , 2016, “ S-Shaped Characteristics on the Performance Curves of Pump-Turbines in Turbine Mode—A Review,” Renewable Sustainable Energy Rev., 60, pp. 836–851. [CrossRef]
Pettersen, K. , Nielsen, T. K. , and Billdal, J. T. , 2004, “ An Explanation to the Steep Speed-Flow Characteristics of Reversible Pump-Turbines,” 22nd IAHR Symposium on Hydraulic Machinery and Systems, Stockholm, Sweden.
Yang, W. , and Xiao, R. , 2014, “ Multiobjective Optimization Design of a Pump–Turbine Impeller Based on an Inverse Design Using a Combination Optimization Strategy,” ASME J. Fluids Eng., 136(1), p. 014501. [CrossRef]
Zhu, B. , Wang, X. , Tan, L. , Zhou, D. , Zhao, Y. , and Cao, S. , 2015, “ Optimization Design of a Reversible Pump-Turbine Runner With High Efficiency and Stability,” Renewable Energy, 81, pp. 366–376. [CrossRef]
Yin, J. , Wang, D. , Wei, X. , and Wang, L. , 2013, “ Hydraulic Improvement to Eliminate S-Shaped Curve in Pump-Turbine,” ASME J. Fluids Eng., 135(7), p. 071105. [CrossRef]
Olimstad, G. , Nielsen, T. , and Børresen, B. , 2012, “ Dependency on Runner Geometry for Reversible-Pump-Turbine Characteristics in Turbine Mode of Operation,” ASME J. Fluids Eng., 134(12), p. 121102. [CrossRef]
Olimstad, G. , Nielsen, T. K. , and Børresen, B. , 2012, “ Geometry Impact on Pump-Turbine Characteristics,” 14th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, Honolulu, HI, Feb. 27–Mar. 2.
Olimstad, G. , Nielsen, T. K. , and Børresen, B. , 2012, “ A Two Dimensional Model for Pump-Turbine Instability Investigations,” 14th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, Honolulu, HI, Feb. 27–Mar. 2.
Olimstad, G. , Børresen, B. , and Nielsen, T. , 2011, “ Design of a Reversible Pump-Turbine-With Purpose to Investigate Stability,” 4th International Meeting on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Belgrade, Serbia.
Olimstad, G. , Nielsen, T. , and Børresen, B. , 2012, “ Stability Limits of Reversible-Pump-Turbines in Turbine Mode of Operation and Measurements of Unstable Characteristics,” ASME J. Fluids Eng., 134(11), p. 111202. [CrossRef]
Kubota, T. , and Kushimoto, S. , 1978, “ Visual Observation of Internal Flow Through High-Head Pump-Turbine,” Fuji Electr. Rev., 26(4), pp. 609–620.
Zhang, S. Q. , Shi, Q. H. , and Zhang, K. W. , 2012, “ Flow Behavior Analysis of Reversible Pump-Turbine in “S” Characteristic Operating Zone,” 26th IAHR Symposium on Hydraulic Machinery and Systems, Beijing, China.
Wang, L. Q. , Yin, J. L. , Jiao, L. , and Wu, D. Z. , 2011, “ Numerical Investigation on the “S” Characteristics of a Reduced Pump-Turbine Model,” Sci. China Technol. Sci., 54(5), pp. 1259–1266. [CrossRef]
Choi, H. J. , Zullah, M. A. , Roh, H. W. , Ha, P. S. , Oh, S. Y. , and Lee, Y. H. , 2013, “ CFD Validation of Performance Improvement of a 500 kW Francis Turbine,” Renewable Energy, 54, pp. 111–123. [CrossRef]
Chen, D. , and Xie, H. , 2001, “ The Flow Patterns of Low Specific Speed Pump-Turbine in S-Shape Characteristic Region,” J. of Hydraulic Eng., 32(2), pp. 76–78.
Senoo, Y. , and Yamaguchi, M. , 1987, “ A Study on Unstable S-Shape Characteristic Curves of Pump-Turbines at No-Flow,” ASME J. Turbomach., 109(1), pp. 77–82. [CrossRef]
Hasmatuchi, V. , Roth, S. , Botero, F. , Avellan, F. , and Farhat, M. , 2010, “ High-Speed Flow Visualization in a Pump-Turbine Under Off-Design Operating Conditions,” IOP Conference Series: Earth and Environmental Science, 12(1), p. 012059.
Hasmatuchi, V. , Farhat, M. , Roth, S. , Botero, F. , and Avellan, F. , 2011, “ Experimental Evidence of Rotating Stall in a Pump-Turbine at Off-Design Conditions in Generating Mode,” ASME J. Fluids Eng., 133(5), p. 051104. [CrossRef]
Widmer, C. , Staubli, T. , and Ledergerber, N. , 2011, “ Unstable Characteristics and Rotating Stall in Turbine Brake Operation of Pump-Turbines,” ASME J. Fluids Eng., 133(4), p. 041101. [CrossRef]
Staubli, T. , Widmer, C. , Tresch, T. , and Sallaberger, M. , 2010, “ Starting Pump-Turbines With Unstable Characteristics,” Hydro, Lisbon, Portugal.
Gentner, C. , Sallaberger, M. , Widmer, C. , Braun, O. , and Staubli, T. , 2012, “ Numerical and Experimental Analysis of Instability Phenomena in Pump-Turbines,” IOP Conf. Ser.: Earth Environ. Sci., Beijing, China.
Gentner, C. , Sallaberger, M. , Widmer, C. , Bobach, B. J. , and Jaberg, H. , 2014, “ Comprehensive Experimental and Numerical Analysis of Instability Phenomena in Pump-Turbines,” 27th IAHR Symposium on Hydraulic Machinery and Systems, Montreal, Canada.
Guggenberger, M. , Senn, F. , Schiffer, J. , Jaberg, H. , Gentner, C. , Sallaberger, M. , and Widmer, C. , 2014, “ Experimental Investigation of the Turbine Instability of a Pump-Turbine During Synchronization,” IOP Conf. Ser.: Earth Environ. Sci., Montreal, Canada.
Martin, C. S. , 2000, “ Instability of Pump-Turbines With S-Shaped Characteristics,” 20th IAHR Symposium on Hydraulic Machinery and Systems, Charlotte, NC.
Martin, C. S. , 1986, “ Stability of Pump-Turbines During Transient Operation,” 5th International Conference on Pressure Surges, BHRA, Hanover, Germany.
Dörfler, P. K. , Engineer, A. J. , Pendse, R. N. , Huvet, P. , and Brahme, M. V. , 1998, “ Stable Operation Achieved on a Single-Stage Reversible Pump-Turbine Showing Instability at No-Load,” 19th IAHR Symposium on Hydraulic Machinery and Cavitation, Singapore.
Klemm, D. , 1982, Stabilizing the Characteristics of a Pump-Turbine in the Range Between Turbine Part-Load and Reverse Pump Operation, Voith Research and Construction, Heidenheim an der Brenz, Germany, p. 28.
Yin, J. L. , 2012, Study on the Internal Flow and Optimal Design of Pump-Turbine in the “S” Zone, Ph.D. dissertation, Zhejiang University, Hangzhou, Zhejiang, China.
Zhang, Z. , and Titzschkau, M. , 2012, “ Self-Validated Calculation of Characteristics of a Francis Turbine and the Mechanism of the S-Shape Operational Instability,” 26th IAHR Symposium on Hydraulic Machinery and Systems, Beijing, China.
IEC, 2008, “ Hydraulic Turbines, Storage Pumps and Pump-Turbines-Rehabilitation and Performance Improvement,” International Electrotechnical Commission, Geneva, Switzerland, Standard No. IEC 62256.
Ida, T. , 1989, “ Analysis of Scale Effects on Performance Characteristics of Hydraulic Turbines—Part 1: Scale Formulae of Hydraulic Performance and Loss Distribution Coefficients in Model Francis Turbines and Pump-Turbines,” J. Hydraul. Res., 27(6), pp. 809–831. [CrossRef]
Ida, T. , 1995, “ New Formulae for Scaling-Up Hydraulic Efficiency of Hydraulic Turbines,” J. Hydraul. Res., 33(2), pp. 147–162. [CrossRef]
Nielsen, T. K. , and Olimstad, G. , 2010, “ Dynamic Behaviour of Reversible Pump-Turbines in Turbine Mode of Operation,” 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machine, Honolulu, HI.
Zeng, W. , Yang, J. , and Guo, W. , 2015, “ Runaway Instability of Pump-Turbines in S-Shaped Regions Considering Water Compressibility,” ASME J. Fluids Eng., 137(5), p. 051401. [CrossRef]
Nicolle, J. , Giroux, A. M. , and Morissette, J. F. , 2014, “ CFD Configurations for Hydraulic Turbine Startup,” IOP Conference Series: Earth and Environmental Science, Montreal, Canada.
Menter, F. R. , and Egorov, Y. , 2010, “ The Scale-Adaptive Simulation Method for Unsteady Turbulent Flow Predictions—Part 1: Theory and Model Description,” Flow Turbul. Combust., 85(1), pp. 113–138. [CrossRef]
Trivedi, C. , Cervantes, M. J. , Gandhi, B. K. , and Dahlhaug, O. G. , 2013, “ Experimental and Numerical Studies for a High Head Francis Turbine at Several Operating Points,” ASME J. Fluids Eng., 135(11), p. 111102. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

Velocity triangles at the runner inlet and outlet

Grahic Jump Location
Fig. 2

Diagram for the formation of the S-shaped characteristic curve

Grahic Jump Location
Fig. 3

Speed-discharge characteristics by the theoretical turbine equations: (a) pumping effect neglected (Eq. (8)) and (b) pumping effect considered (Eq. (10))

Grahic Jump Location
Fig. 4

Comparisons between the predicted and measured characteristics: (a) BQ, (b) XJ, (c) BLH, and (d) SBY

Grahic Jump Location
Fig. 5

Loss coefficients for different turbines

Grahic Jump Location
Fig. 6

Influence of the inlet blade angle β1b

Grahic Jump Location
Fig. 7

Influence of the diameter ratio D1/D2

Grahic Jump Location
Fig. 8

Computational domain and grid: (a) geometry and (b) grid

Grahic Jump Location
Fig. 9

Grid dependency test at normal operating points for the three turbine models

Grahic Jump Location
Fig. 10

Characteristic curves of model 1 for GVO 24 deg: (a) n11Q11 and (b) n11T11

Grahic Jump Location
Fig. 11

Characteristic curves and flow behavior of model 2 for GVO 20 deg: (a) speed-discharge characteristics and (b) average flow rate distributions along the spanwise at the runner inlet

Grahic Jump Location
Fig. 12

Characteristic curves and flow behavior of model 1 for GVO 6 deg: (a) speed-discharge characteristics and (b) average flow rate distributions along the spanwise at the runner inlet

Grahic Jump Location
Fig. 13

Characteristic curves and flow behavior of model 2 for GVO 6 deg: (a) speed-discharge characteristics and (b) average flow rate distributions along the spanwise at the runner inlet

Grahic Jump Location
Fig. 14

Characteristic curves and flow behavior of model 3 for GVO 20 deg: (a) speed-discharge characteristics and (b) average flow rate distributions along the spanwise at the runner inlet

Grahic Jump Location
Fig. 16

Flow vortex structures at the runner inlet of model 1 for GVO 24 deg: (a) separations emerging Q11 = 0.167 m3/s, (b) inverse flow at shroud side Q11 = 0.139 m3/s, (c) inverse flow at hub side Q11 = 0.094 m3/s, and (d) inverse flow at midspan Q11 = 0.023 m3/s

Grahic Jump Location
Fig. 17

Flow vortex structures at the runner inlet of model 1 for GVO 6 deg

Grahic Jump Location
Fig. 18

Variations of the pressure coefficients along the streamwise of model 1 for GVO24 deg: (a) total pressure coefficient Ctp, (b) partial enlarged view of Ctp, (c) static pressure coefficient Csp, and (d) kinetic pressure coefficient Ckp

Grahic Jump Location
Fig. 19

Variations of the pressure coefficients along the streamwise of model 1 for GVO 6 deg: (a) total pressure coefficient Ctp, (b) partial enlarged view of Ctp, (c) static pressure coefficient Csp, and (d) kinetic pressure coefficient Ckp

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In