Fluid Force Moment on the Backshroud of a Francis Turbine Runner in Precession Motion

Song, Bingwei; Horiguchi, Hironori; Nishiyama, Yumeto; Hata, Shinichiro; Ma, Zeyu; Tsujimoto, Yoshinobu

doi:10.1115/1.4001618

Cited by 3 publications

(3 citation statements)

References 4 publications

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“…The angular velocity ratio Ω/ω was varied from -1.2 to 1.2. For the detailed experimental facility and the measurement of the fluid force moments, refer to [10,11]. Figure 4 shows the normalized whirl moments m n_W ≡M n_W /(ρπR T…”

Section: Outline Of Experimentsmentioning

confidence: 99%

“…In order to study the rotordynamic problem of the Francis turbine runner as reported in [6], the authors have measured the rotordynamic force moments on a whirling and precessing disk simulating the backshroud of a Francis turbine runner, respectively [10,11]. In [10], it was shown by a simplified vibration analysis that the moment on the rotor caused by the whirl can cause whirl instability through structural coupling for the case of an overhung rotor.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the relative importance of whirl and precession moments is examined. The rotordynamic moment coefficients were determined from the fluid force moments measured in [10] and [11]. The stability analysis of a cantilevered rotor is carried out by using a lumped parameter model.…”

Section: Introductionmentioning

confidence: 99%

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Rotordynamic Instabilities Caused by the Fluid Force Moments on the Backshroud of a Francis Turbine Runner

Song¹,

Horiguchi²,

Ma³

et al. 2010

International Journal of Fluid Machinery and Systems

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Severe flexural vibration of the rotor shaft of a Francis turbine runner was experienced in the past. It was shown that the vibration was caused by the fluid forces and moments on the backshroud of the runner associated with the leakage flow through the back chamber. The aim of the present paper is to study the self-excited rotor vibration caused by the fluid force moments on the backshroud of a Francis turbine runner. The rotor vibration includes two fundamental motions, one is a whirling motion which only has a linear displacement and the other is a precession motion which only has an angular displacement. Accordingly, two types of fluid force moment are exerted on the rotor, the moment due to whirl and the moment due to precession. The main focus of the present paper is to clarify the contribution of each moment to the self-excited vibration of an overhung rotor. The runner was modeled by a disk and the whirl and the precession moments on the backshroud of the runner caused by the leakage flow were evaluated from the results of model tests conducted before. A lumped parameter model of a cantilevered rotor was used for the vibration analysis. By examining the frequency, the damping rate, the amplitude ratio of lateral and angular displacements for the cases with longer and shorter overhung rotor, it was found that the precession moment is more important for smaller overhung rotors and the whirl moment is more important for larger overhung rotors, although both types of moment due to the leakage flow can cause self-excited vibration of an overhung rotor.

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Section: Outline Of Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Rotordynamic Instabilities Caused by the Fluid Force Moments on the Backshroud of a Francis Turbine Runner

Song¹,

Horiguchi²,

Ma³

et al. 2010

International Journal of Fluid Machinery and Systems

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Rotordynamics of Turbopumps and Hydroturbines

Tsujimoto

2017

Cavitation Instabilities and Rotordynamic Effects in Turbopumps and Hydroturbines

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Moment Whirl due to Leakage Flow in the Back Shroud Clearance of a Rotor

Tsujimoto

Ma²,

Song³

et al. 2010

International Journal of Fluid Machinery and Systems

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Recent studies on the moment whirl due to leakage flow in the back shroud clearance of hydro-turbine runners or centrifugal pump impellers are summarized. First, destabilizing effect of leakage flow is discussed for lateral vibrations using simplified models. Then it is extended to the case of whirling motion of an overhung rotor and the criterion for the instability is obtained. The fluid moment caused by a leakage clearance flow between a rotating disk and a stationary casing was obtained by model tests under whirling and precession motion of the disk. It is shown that the whirl moment always destabilizes the whirl motion of the overhung rotor while the precession moment destabilizes the precession only when the precession speed is less than half the rotor speed. Then vibration analyses considering both whirl and precession are made by using the hydrodynamic moments determined by the model tests. For larger overhung rotors, the whirl moment is more important and cause whirl instability at all rotor speed. On the other hand, for smaller overhung rotors, the precession moment is more important and cancels the destabilizing effect of the whirl moment.

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Fluid Force Moment on the Backshroud of a Francis Turbine Runner in Precession Motion

Cited by 3 publications

References 4 publications

Rotordynamic Instabilities Caused by the Fluid Force Moments on the Backshroud of a Francis Turbine Runner

Rotordynamic Instabilities Caused by the Fluid Force Moments on the Backshroud of a Francis Turbine Runner

Rotordynamics of Turbopumps and Hydroturbines

Moment Whirl due to Leakage Flow in the Back Shroud Clearance of a Rotor

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