sjes-10042

Analysis of Fatigue Failure of Francis Turbine Runner at Derbendikhan Hydropower Station

Raza Abdulla Saeed [Irrigation Department – College of Engineering - University of Sulaimani]

Received : 06/02/2015
Accepted : 09/10/2016
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DOI Link: https://doi.org/10.17656/sjes.10042 

ABSTRACT

Fatigue failures in Francis turbine runner are frequently occurred in hydropower plants, causing unexpected plant downtime and considerable financial loss. Decades of operational experience have shown that turbine runners develop fatigue cracks in areas, where stress concentrations and material defects coincide. In Francis turbine runners, cracks tend to propagate from the transition of the welded T-joint between the blade and the band or crown. This type of turbine runner, which operate under a wide range of heads and outputs, are subjected to considerable dynamic forces which can lead to fatigue cracking. The magnitude of these forces is a function of the hydraulic pressure, the water velocity and the geometry of the stationary parts guiding the water into the runner.
This paper presents the water pressure and bending stresses for different operational conditions in a Francis runner of a Derbendikhan hydropower station. At the first step, the dynamic fluid calculation is used to determine the fluctuating water pressure on the blade of the runner. At the second step, for a period of operational nominal bending stress due to the fluctuating water pressure are determined. The result indicates that the hydropower plant was operated with the high fluctuating water pressure which is responsible for inducing bending stress response. The high bending stress on the blade is a probable reason for fatigue failure. Furthermore, the paper discusses the fatigue analysis of the runner. Typical results are presented and discussed.


KEYWORDS: Fatigue Failures, Francis Turbine Runner, Dynamic Fluid Calculation, Nominal Bending Stress.

REFERENCES

1- Huth, H. J., 2005, “Fatigue Design of Hydraulic Turbine Runners”, PhD thesis, University of Science and Technology , Department of Engineering Design and Materials, Trondheim, Norway.
2- Carpinteri A., Brighenti R., Huth H. J. and Vantadori S., 2004, “Fatigue growth of a surface crack in a welded T-joint”, Elsevier Science Ltd.
3- Härkegard G., Huth H. J. and Faanes S., 2000, “FEA-Based Fatigue Assessment Methodology for Hydraulic Turbine Runners”, Norwegian University of Science and Technology, Trondheim, Norway.
4- Farhat M., Avellan F. and Seidel U., 2002, “Pressure Fluctuation Measurements In Hydro Turbine Models”, The 9th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, Honolulu, Hawaii.
5- Avellan F., Etter S., Gummer J. H. and Seidel U., 2000, “Dynamic Pressure Measurements On A Model Turbine Runner And Their Use In Preventing Runner Fatigue Failure”, 20th IAHR Symposium, Charlotte, North Carolina, USA.
6- Saeed R. A., 2003, “An Investigation About Preventing the Mechanical Failures That Occur in Derbendikhan Power Station”, University of Sulaimani, Sulaimani, Iraq.
7- Ramamrutham S., 1985, "Hydraulic Machine", DHANPAT RAI & SONS, Delhi, India.
8- Humphreys A. E., 2004, "Influence of residual stress on the initiation of fatigue cracks at welded piping joints", Ph.D. dissertation. North Carolina State University.
9- Araujo M., 2002, "Non-Linear Kinematic Hardening Model for Multiaxial Cyclic Plasticity", Civil and Environmental Engineering, Louisianan State University (2002).
10- Apostolopoulos C. A. and Michalopoulos D., 2007, “Mechanical properties of reinforcing steel and fatigue behavior in corrosive environment”, Journal of Materials Engineering and Performance, 16(5), 559-566.


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