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

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Bingwei Song ◽  
Hironori Horiguchi ◽  
Yumeto Nishiyama ◽  
Shinichiro Hata ◽  
Zhenyue Ma ◽  
...  
Keyword(s):  
Flow Model ◽  
Swirl Flow ◽  
Francis Turbine ◽  
Leakage Flow ◽  
Fluid Force ◽  
Disk Rotation ◽  
Leakage Flow Rate ◽  
Turbine Runner ◽  
Force Moment ◽  
Axial Clearance

The fundamental characteristics of rotordynamic fluid force moment on the backshroud of a Francis turbine runner in precession motion were studied using model tests and computations based on a bulk flow model. The runner is modeled by a disk positioned close to a casing with a small axial clearance. An inward leakage flow is produced by an external pump in the model test. The effects of the leakage flow rate, the preswirl velocity at the inlet of the clearance, and the axial clearance on the fluid force moment were examined. It was found that the fluid force moment encourages the precession motion at small forward precession angular velocity ratios and the region encouraging the precession motion is affected by the preswirl velocity. Through the comparisons of the fluid force moment with and without the rotation of the disk, it was found that the normal moment without the disk rotation did not have the effect to encourage the precession motion. Thus, the swirl flow due to disk rotation was found to be responsible for the encouragement of the precession motion.

Rotordynamic Moment on the Backshroud of a Francis Turbine Runner Under Whirling Motion

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Bingwei Song ◽  
Hironori Horiguchi ◽  
Zhenyue Ma ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Influence Factor ◽  
Small Region ◽  
Francis Turbine ◽  
Radial Clearance ◽  
Leakage Flow ◽  
Structural Coupling ◽  
Fluid Force ◽  
Whirling Motion ◽  
Turbine Runner ◽  
Force Moment

This paper addresses the rotordynamic instability of an overhung rotor caused by a hydrodynamic moment due to whirling motion through the structural coupling between whirl and precession modes. First, the possibility of instability is discussed based on a vibration model in which the hydrodynamic forces and moments are assumed to be smaller than structural forces with the structural coupling being represented by a structural influence factor. Then, the fundamental characteristics of rotordynamic moment on the backshroud of a Francis turbine runner under whirling motion were studied using model tests and numerical calculations. The runner is modeled by a disk positioned close to a casing with a small radial clearance at the outer periphery. The moment is caused by an inward leakage flow that is produced by an external pump in the model test. The experiments were designed to measure the rotordynamic fluid force moments under various leakage flow rates with various preswirl velocities and various axial clearances between the backshroud and casing. The computation was carried out based on a bulk flow model. It was found that the fluid force moment is generally destabilizing, except for a small region of positive whirling speed ratios.

Fluid Force Moment on a Centrifugal Impeller Shroud in Precessing Motion

1997 ◽  
Vol 119 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Yoshinobu Tsujimoto ◽  
Yoshiki Yoshida ◽  
Hideo Ohashi ◽  
Norihiro Teramoto ◽  
Shin Ishizaki
Keyword(s):  
Flow Model ◽  
Tangential Velocity ◽  
Inviscid Flow ◽  
Bulk Flow ◽  
Centrifugal Impeller ◽  
Shear Stresses ◽  
Leakage Flow ◽  
Fluid Force ◽  
Clearance Flow ◽  
Force Moment

Experimental results of fluid moment on a centrifugal impeller shroud in precessing motion are discussed based on the bulk flow model to elucidate the fundamental flow mechanism. It is shown that the backshroud/casing clearance flow and the destabilizing fluid force moment can be simulated by the bulk flow model fairly well if the measured behavior of the resistance is correctly incorporated in the model. From the calculations with and without steady and unsteady wall shear stresses, the unsteady component of the clearance flow is shown to be basically a two-dimensional inviscid flow induced by the change in the flow thickness. The effects of the leakage flow rate and the resistance at the leakage flow entry are discussed, paying attention to the steady tangential velocity of the leakage flow.

A Simple Leakage Flow Model Including Viscous Effect

2011 ◽  
Author(s):  
Yuping Qian ◽  
Jian Cui ◽  
Chaoqing Chen ◽  
Yifang Gong ◽  
Qiushi Li
Keyword(s):  
Flow Rate ◽  
Flow Model ◽  
Leakage Flow ◽  
Viscous Effect ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Factors Affecting ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Leakage Flow Rate

The tip leakage flow rate can be directly linked to the loss and stall margin. In this paper, key factors affecting the tip leakage flow rate are explained based on a simple leakage flow model including viscous effect. Based on the numerical results, the flow model is verified in a low speed compressor rotor, and finally a simplified one-dimensional tip blockage model is established based on the Khalid’s model, which may be helpful in the design of compressor.

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

2010 ◽  
Vol 3 (1) ◽  
pp. 67-79 ◽  
Author(s):  
Bingwei Song ◽  
Hironori Horiguchi ◽  
Zhenyue Ma ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Francis Turbine ◽  
Fluid Force ◽  
Turbine Runner

scholarly journals Measurements of the Flow in Backshroud/Casing Clearance of Precessing Centrifugal Impeller

1997 ◽  
Vol 3 (4) ◽  
pp. 259-268 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Yoshinobu Tsujimoto ◽  
Hideo Ohashi ◽  
Akira Saito ◽  
Shin Ishizaki
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Impeller ◽  
Leakage Flow ◽  
Pressure Measurements ◽  
Side Plate ◽  
Flow Measurements ◽  
Fluid Force ◽  
Unsteady Pressure ◽  
Impeller Outlet ◽  
Force Moment

Detailed flow measurements have been made to clarify the unsteady flow in the backshroud/ casing clearance of a precessing centrifugal impeller. The unsteady pressure was integrated to obtain the fluid force moment on the precessing impeller shroud for various precessing frequencies. It was shown that the fluid force moment can become rotordynamically destabilizing for small forward precessing motion as originally found by Ohashi et al. The effects of leakage flow in the backshroud/casing clearance and a gap between impeller side plate and casing at the impeller outlet are clearly shown, and the discussions are also made based on the unsteady velocity and pressure measurements.

scholarly journals Effect of the leakage flow in runner on flow characteristics of a Francis turbine model

2021 ◽  
Vol 774 (1) ◽  
pp. 012087
Author(s):  
S J Kim ◽  
Y S Choi ◽  
Y Cho ◽  
J W Choi ◽  
J J Hyun ◽  
...  
Keyword(s):  
Flow Characteristics ◽  
Francis Turbine ◽  
Leakage Flow ◽  
Turbine Model

scholarly journals Impact of Orifice-to-Pipe Diameter Ratio on Leakage Flow: An Experimental Study

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2189
Author(s):  
Tingchao Yu ◽  
Xiangqiu Zhang ◽  
Iran E. Lima Neto ◽  
Tuqiao Zhang ◽  
Yu Shao ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Pipe Wall ◽  
Pressure Head ◽  
Diameter Ratio ◽  
Pipe Diameter ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Different Shapes ◽  
Real Scale

The traditional orifice discharge formula used to estimate the flow rate through a leak opening at a pipe wall often produces inaccurate results. This paper reports an original experimental study in which the influence of orifice-to-pipe diameter ratio on leakage flow rate was investigated for several internal/external flow conditions and orifice holes with different shapes. The results revealed that orifice-to-pipe diameter ratio (or pipe wall curvature) indeed influenced the leakage flow, with the discharge coefficient ( C d ) presenting a wide variation (0.60–0.85). As the orifice-to-pipe diameter ratio decreased, the values of C d systematically decreased from about 12% to 3%. Overall, the values of C d also decreased with β (ratio of pressure head differential at the orifice to wall thickness), as observed in previous studies. On the other hand, orifice shape, main pipe flow velocity, and external medium (water or air) all had a secondary effect on C d . The results obtained in the present study not only demonstrated that orifice-to-pipe diameter ratio affects the outflow, but also that real scale pipes may exhibit a relevant deviation of C d from the classical range (0.61–0.67) reported in the literature.

Numerical Prediction of Critical Cavitation Performance in Hydraulic Turbines

2003 ◽  
Author(s):  
Sadao Kurosawa ◽  
Kiyoshi Matsumoto
Keyword(s):  
Flow Model ◽  
Flow Analysis ◽  
Prediction Method ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Two Phase ◽  
Cavitation Performance ◽  
Hydraulic Turbines ◽  
Critical Cavitation ◽  
Good Agreement

In this paper, numerical method for predicting critical cavitation performance in a hydraulic turbine is presented. The prediction method is based on unsteady cavitation flow analysis to use bubble two-phase flow model. The prediction of the critical cavitation performance was carried out for the aixal hydraulic turbine and the francis turbine as a typical examples. Results compared to the experiment showed a good agreement for the volume of cavity and the performance drop off and it was recognized that this method could be used as an engineering tool of a hydraulic turbine development.

The Strength Analysis of Francis Turbine Runner Based on the Fluid-Solid Coupling

2014 ◽  
Vol 709 ◽  
pp. 41-45
Author(s):  
Kan Kan ◽  
Yuan Zheng ◽  
Xin Zhang ◽  
Bin Sun ◽  
Hui Wen Liu
Keyword(s):  
Water Pressure ◽  
Eastern China ◽  
Static Stress ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Strength Analysis ◽  
Maximum Deformation ◽  
The North ◽  
North Eastern ◽  
Turbine Runner

This paper does unidirectional fluid-solid coupling calculation on the runner strength under three designed head loading conditions of a certain Francis turbine in the north-eastern China. The water pressure on the blade in the flow fields of different operating conditions is calculated by means of CFD software CFX. With the help of ansys workbench, the water pressure is loaded to the blade as structural load to conclude the static stress distribution and deformation of the runner under different operating conditions. The results show that the maximum static stress increases with the rise of the flow and appears near the influent side of the blade connected to the runner crown; the maximum deformation increases with the rise of the flow and appears on the band. The results provides effective basis for the structural design and safe operation of the Francis turbine.

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