Numerical Study on the Dynamic Behavior of a Francis Turbine Runner Model with a Crack

Zhang, Ming; Zhang, Xingfang; Zhao, Weiqiang

doi:10.20944/preprints201805.0032.v1

Cited by 4 publications

(4 citation statements)

References 22 publications

(60 reference statements)

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“…For instance, domestic projects such as the Yantan and Xiaolangdi Hydropower Stations have exhibited abnormal vibrations under full-load conditions, with some stations even unable to sustain long-term operation under these conditions [1][2][3]. Prolonged self-excited or excessive vibrations in hydroelectric units can lead to component deformation, loosening, or even fracturing, thereby posing a threat to the safety of the entire unit and the power station [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Testing and Numerical Analysis of Abnormal Pressure Pulsations in Francis Turbines

Jia,

Zeng,

Liu

et al. 2024

Energies

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During the flood season, Francis turbines often operate under low-head and full-load conditions, frequently experiencing significant pressure pulsations, posing potential threats to the safe and stable operation of the units. However, the factors contributing to substantial pressure pulsations in Francis turbines are multifaceted. This paper focuses on a mixed-flow hydroelectric generating unit at a specific hydropower station. Field tests were conducted to investigate abnormal vibrations and hydraulic pressure pulsations under low-head and full-load conditions. Utilizing the Navier–Stokes equations and the RNG k-ε turbulence model, the unsteady flow field within the turbine under these conditions was calculated. The results indicate that the abnormal pressure pulsations detected in the bladeless zone between the wicket gates and the turbine inlet are due to operational points deviating from the normal operating range of the turbine. When water flows at a large inflow angle, striking the turbine blade heads, it leads to significant flow separation and vortex formation at the back of the blade inlet edges, causing severe vibrations in the hydroelectric generating unit. These findings provide a basis and assurance for the safe and stable operation of the power station.

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Section: Introductionmentioning

confidence: 99%

Testing and Numerical Analysis of Abnormal Pressure Pulsations in Francis Turbines

Jia,

Zeng,

Liu

et al. 2024

Energies

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“…In recent years, the design of the Francis turbine runner has had good achievements in the hydraulic design but still exists defects in the rigidity and stiffness of the structural part. At present, during the operation of medium and low head Francis turbines, problems such as runner blade cracks [1], [2], draft tube lining steel plate tearing, and unit resonance [3], affect the safe and stable operation of the unit, manufacturing, installation and other factors [4]. In order to avoid local stress concentration, some early manufacturers used finite element calculation or empirical calculation methods to design individual parts and parts of hydro-generator units, so as to avoid damage to individual parts of the unit due to stress concentration.…”

Section: Introductionmentioning

confidence: 99%

Strength Evaluation of the Flow Passage Stationary Structures of a Large Francis Turbine Unit

Jiang,

Xiao,

Zhao

et al. 2024

J. Phys.: Conf. Ser.

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The multifield design and multifield coupling performance of the Francis turbine unit is a topic that needs to be studied deeply. In this paper, the strength evaluation of the stationary structures of the flow passage of a large Francis turbine unit under extreme conditions has been performed based on the fluid-structure coupling theory. The calculated stationary structures include the spiral casing, bottom ring, and head cover. The pressure load applied on the structures is 1.5 times the maximum head of the unit. The results show that there is stress concentration in the spiral casing, and the weld length with equivalent stress greater than 345 MPa reaches 800 mm; the maximum stress at the rib plate of the head cover reaches 357 MPa, which is greater than the yield limit 345MPa. Based on the evaluation results, the local and overall defects of the unit design can be found. The suggested strength evaluation methodology can provide references for the optimization of the unit and a theoretical basis for the operation of the unit.

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“…Stress measurement at site is an effective way to obtain the stress characteristics of runner, then to detect potential operational risks [9]. The difficulty for site measurement is the location of the runner while it rotates in the water, so the measurement sensors must sustain the shock of water and the data acquisition device must rotates together with the turbine [10] [11]. Stress measurement is carried out on a Francis prototype turbine in this paper.…”

Section: Introductionmentioning

confidence: 99%

Stress measurement of runner blade for a Francis prototype turbine

Cao,

Dodge,

Zhou

et al. 2024

J. Phys.: Conf. Ser.

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Fatigue crack on the runner blade is one of the severe threats to the operation safety of prototype turbine. Several factor, such as limited operation range, may lead to fatigue cracking commonly observed on Francis turbine. Several cases show that fatigue crack may reduce the working life of runner. The high stress during operation is one of main reasons to produce cracks. Hydraulic design, manufacture quality, deviation of operation condition and resonance may cause high stress on the runner blade. Because static and dynamic stress cannot be predicted with absolute certainty for all operating conditions, the most effective way to obtain the actual stress level of the blade is site measurement. In this paper, stress measurement is carried out on a Francis prototype turbine. Measurement results show that high static stress appears at a load range near full load, and high dynamic stress appears at lower loads. Finally, some practicable suggestions are proposed to reduce the stress of runner blade.

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Numerical Study on the Dynamic Behavior of a Francis Turbine Runner Model with a Crack

Cited by 4 publications

References 22 publications

Testing and Numerical Analysis of Abnormal Pressure Pulsations in Francis Turbines

Testing and Numerical Analysis of Abnormal Pressure Pulsations in Francis Turbines

Strength Evaluation of the Flow Passage Stationary Structures of a Large Francis Turbine Unit

Stress measurement of runner blade for a Francis prototype turbine

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