A case study of the fluid structure interaction of a Francis turbine

Müller, Corinna; Staubli, Thomas; Baumann, Reto; Casartelli, Ernesto

doi:10.1088/1755-1315/22/3/032053

Cited by 6 publications

(4 citation statements)

References 1 publication

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“…Several authors have published mode shapes of actual Francis and pump turbine runners with different spesific speeds. [23,10,8] The overall trend seems to be that low head runners have more radial motion on the runner band near the outlet, while high head runners have larger disc like mode shapes. These runners may thus be affected differently by the walls.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on the effect off near walls on the eigen frequency of a low specific speed francis runner

Østby¹,

Sivertsen²,

Billdal³

et al. 2019

Mechanical Systems and Signal Processing

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The importance to correctly predict the natural frequency of a turbine runner have been demonstrated several times. It is now common practice to include the added mass effect of the surrounding water when calculating the natural frequencies. In this paper the added mass effect of water on a simplified low specific speed francis turbine runner is experimentally investigated. Three cases are investigated. 1: The runner hanging in air. 2: The runner hanging in a tank of water. 3: The runner installed into the turbine housing. The measurements reveal a frequency reduction of about 40% when the runner is hanging in water. Installing the runner into the turbine housing does not significantly change the natural frequency of the main blade modes. Modes which vibrate heavily on the outside of the runner are visible in the water tank but becomes dampened when installed into the turbine housing.

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Section: Introductionmentioning

confidence: 99%

Experimental investigation on the effect off near walls on the eigen frequency of a low specific speed francis runner

Østby¹,

Sivertsen²,

Billdal³

et al. 2019

Mechanical Systems and Signal Processing

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“…The effect water has on the eigenmodes of the runner was often underestimated. Methods to predict and correct these eigenfrequencies with the effect of surrounding water using vibro-acoustic FEA are now considered mature and well established in the field [3,4,5]. A common explanation to the waters effect on the eigenfrequency, is it acting as an added mass on the runners' motion [6,5].…”

Section: Introductionmentioning

confidence: 99%

On the topic of added mass and acoustics in High Head Francis Runners

Østby¹,

Knutsen

Billdal³

2022

IOP Conf. Ser.: Earth Environ. Sci.

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Methods used to calculate the eigenmodes and eigenfrequencies of a Francis runner with the added mass from water are well established and have been verified by several experiments. The common explanation of the water’s role is the added mass it brings to the runners structural eigenmodes and thereby reducing the eigenfrequencies. In this paper we calculate the first eigenfrequency of the runner from the acoustic properties of the runner channel and compare the result with full FEA calculations. Using this method we show that the local speed of sound for the water in the channel can be as low as 200m/s and that the density of the runner is not necessarily an important parameter for the first eigenfrequency with some Nodal Diameters of High Head Runners.

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“…Wang et al 25 used a tubular turbine as an example to analyze the stress concentration at the connection between the leading edge of the blade and hub. Müller et al 26 used fluid dynamics and finite element analysis to evaluate hydraulic pump-turbines and showed that the external excitation frequency is much lower than the modal vibration frequency of the runner, which does not cause resonance. Morissette et al 27 used experimental values and 1.5–dimensional interaction values from numerical simulations to compare the stress and strain distributions of the runner under the no-load state of the Francis turbine and estimated the fatigue distribution under arbitrary load.…”

Section: Introductionmentioning

confidence: 99%

Investigation on runner resonance and fatigue life of a high–head pump–turbine

Duan

Ning

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part C:

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The structural stability and fatigue of the runner of a high-head pump-turbine was explored by conducting a numerical simulation of the entire flow passage under different working conditions. A two-way fluid-structure interaction calculation method was used, which captured the values for 5.75 fn, 9 fn, 13 fn, 18 fn, and 20 fn ( fn is rotational frequency) in pressure fluctuation. The resonance of the runner was compared with the results of the modal analysis. The rain flow and damage accumulation methods were used to predict the fatigue life. The study found that the 13 fn pressure fluctuation of the fluid in the flow passage of the pump-turbine is the primary cause of the resonance of the runner blade. The main frequency of vibration is the third natural frequency of the runner. The vibration form is up and down along the Z–axis, and there are some high-order resonances. The most vulnerable part of the entire runner is located at the T-shaped connection between the blade inlet edge and the runner crown and bottom ring. The excitation force under the small flow condition is more complicated than that under the large flow condition, which is more likely to cause fatigue damage to the runner. In addition, the damage extent of the high-stress amplitude to the runner is obviously greater than the influence of the number of stress cycles, accounting for approximately 60% of the total damage. The research results can provide a reference for the operational stability and life prediction of a high-head pump-turbine runner.

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A case study of the fluid structure interaction of a Francis turbine

Cited by 6 publications

References 1 publication

Experimental investigation on the effect off near walls on the eigen frequency of a low specific speed francis runner

Experimental investigation on the effect off near walls on the eigen frequency of a low specific speed francis runner

On the topic of added mass and acoustics in High Head Francis Runners

Investigation on runner resonance and fatigue life of a high–head pump–turbine

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