The Effects of Casing Geometry and Flow Instability on Rotordynamic Fluid Forces on a Closed Type Centrifugal Impeller in Whirling Motion

2011 ◽  
Author(s):  
Shinichiro Hata ◽  
Julien Richert ◽  
Yumeto Nishiyama ◽  
Hironori Horiguchi ◽  
Yoshinobu Tujimoto
Keyword(s):  
Flow Instability ◽  
Rotating Stall ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Speed Ratio ◽  
Suction Surface ◽  
Flow Rates ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Closed Type

The rotordynamic fluid forces on a closed type centrifugal impeller in whirling motion were measured with a vaneless diffuser at various flow rates for three types of casing, with the casing/impeller shroud clearance of 2[mm], 5[mm], and 5[mm] with seven radial grooves to break the flow swirl. The rotordynamic fluid forces are destabilizing within small positive whirl speed ratio Ω/ω, where Ω and ω are a whirling speed and a rotational speed of the shaft, respectively. The radial grooves were effective to reduce the fluid forces and the destabilizing region due to the reduction of the circumferential velocity of the clearance flow. At low flow rates, the fluid forces increased at Ω/ω, ≈ 0.7. By the measurement of unsteady pressure on the casing wall and the CFD analysis of flow field in the pump, it was found that the large fluid forces at Ω/ω ≈ 0.7 were caused by the rotating stall of the impeller. The rotating stall was caused by the backflow along the suction surface of the main blade due to the separation vortices near the middle of the chord.

Effects of Seal Geometry on Dynamic Impeller Fluid Forces and Moments

2003 ◽  
Vol 125 (5) ◽  
pp. 786-795 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Yoshinobu Tsujimoto ◽  
Goh Morimoto ◽  
Hiroki Nishida ◽  
Shigeki Morii
Keyword(s):  
Force Sensor ◽  
Rotating Stall ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Face Seal ◽  
Vaneless Diffuser ◽  
Fluid Force ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Force Moment

This paper reports an experimental investigation of the rotordynamic fluid force and moment on a centrifugal impeller with three types of wear-ring seals; i.e., a face seal and two types of toothed seals. The impeller is equipped with a vaneless diffuser. Rotordynamic fluid forces and moments on the impeller in whirling motion were measured directly by using four-axis force sensor. Unsteady pressures were measured at several locations in the diffuser. It was found that, (1) at low flow rate, the fluid force and fluid force moment become maximum at a certain whirling speed caused by a coupling between the whirl motion and vaneless diffuser rotating stall and (2) the seal geometry with axial seal affects the direction of the coupled fluid force relative to the direction of eccentricity through the change in the unsteady leakage flow due to the whirl.

Lateral Fluid Forces on Whirling Centrifugal Impeller (1st Report: Theory)

1987 ◽  
Vol 109 (2) ◽  
pp. 94-99 ◽  
Author(s):  
H. Shoji ◽  
H. Ohashi
Keyword(s):  
Potential Flow ◽  
Guide Vane ◽  
Flow Theory ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Flow Rates ◽  
Guide Vanes ◽  
Fluid Forces ◽  
Damping Effect ◽  
Whirling Motion

Lateral fluid forces acting on a rotating centrifugal impeller in whirling motion are analyzed using unsteady potential flow theory. Impellers operating in diffusers with and without vanes are modeled and the fluid forces calculated for different whirl speeds and flow rates. The influences of these parameters are clarified by parametric calculations. The results for whirling impellers operating in vaneless diffusers show that the fluid forces exert a damping effect on the rotor whirling motion at all operating conditions. The results for impellers operating in vaned diffusers or guide vanes show that the time averaged values of fluid forces remain almost unchanged, while there are significant instantaneous fluctuations due to the impeller/guide vane interactions.

scholarly journals The Effect of Casing Geometry on Rotordynamic Fluid Forces on a Closed Type Centrifugal Impeller in Whirling Motion

2011 ◽  
Vol 4 (2) ◽  
pp. 217-222 ◽  
Author(s):  
Julien Richert ◽  
Yumeto Nishiyama ◽  
Shinichiro Hata ◽  
Hironori Horiguchi ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Centrifugal Impeller ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Closed Type

Mechanism of the Occurrence of Rotordynamic Fluid Forces on a Closed Type Centrifugal Impeller in Whirling Motion

2019 ◽  
Vol 12 (4) ◽  
pp. 380-387
Author(s):  
Hironori Horiguchi ◽  
Shinichiro Hata ◽  
Yutaro Wada ◽  
Julien Richert ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Centrifugal Impeller ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Closed Type

J1030102 Mechanism of an Occurrence of Rotordynamic Fluid Forces on a Closed Type Centrifugal Impeller in Whirling Motion

2015 ◽  
Vol 2015 (0) ◽  
pp. _J1030102--_J1030102-
Author(s):  
Hironori HORIGUCHI ◽  
Shinichiro HATA ◽  
Julien Richert ◽  
Yutaro WADA ◽  
Yoshinobu TSUJIMOTO
Keyword(s):  
Centrifugal Impeller ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Closed Type

Research on Failure of Semi-Open Centrifugal Impeller Under Aerodynamic Load

2017 ◽  
Author(s):  
Xudong Chen ◽  
Shengli Xu ◽  
Xiaofang Wang ◽  
Wenying Ju ◽  
Shuhua Yang ◽  
...  
Keyword(s):  
Dynamic Stress ◽  
Leading Edge ◽  
Rotation Frequency ◽  
Rotating Stall ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Aerodynamic Load ◽  
Material Damping ◽  
Flow Rates ◽  
Aerodynamic Damping

The designs of centrifugal compressors are pushed towards higher pressure ratios, higher mass flow rates, and wider operating conditions. As the change of the actual condition, compressors often operate at low flow rates. There are some important unstable flow conditions at low flow rates such as rotating stall. The exciting forces may cause blade resonance and high dynamic stress level. High cycle fatigue failure is one of the main damage form of compressor impellers. Therefore, the dynamic stress prediction of impeller is an important part of compressor design and failure analysis. This paper is concerned with the prediction of dynamic stress of an actual damaged semi-open centrifugal impellers under unsteady aerodynamic load using a full nonlinear damping model which includes material and aerodynamic damping. Material damping is predicted based on an empirical equation and expressed as a function of stress amplitude. Aerodynamic damping is predicted through unidirectional fluid-structure interaction analysis. In this paper, the aerodynamic damping of the semi-open centrifugal impeller with various vibration amplitudes, modes and operation conditions is estimated. The numerical result indicates that, the material damping increases with the increasing stress amplitude while the aerodynamic damping is independent of the blade vibratory amplitude for a given blade mode. A nonlinear total damping model is then proposed, including both material and aerodynamic damping. The contribution of material damping plays an important part in total damping estimation as well as the aerodynamic damping. With this model, a procedure for dynamic stress estimation is proposed. Aerodynamic load on the surface of the impeller obtained by transient CFD calculation and the load in frequency domain obtained by Fast Fourier Transformation (FFT). Comparing normal condition with low flow condition, the main frequencies of the aerodynamic load are basically coincident and the load amplitude increases significantly under low flow rate. The main frequencies at the leading edge of blades are 4 times, 5 times and 6 times rotation frequency. They may be caused by rotating stall and excite the impeller. As the load of 5 times rotation frequency is maximum, harmonic analysis is performed to estimate the dynamic stress of the semi-open centrifugal compressor blades under the load. The result shows that the resonance stress at the leading edge of the blade under low flow condition is 22 times up on the stress under normal condition. The result of fatigue strength assessment shows that fatigue damage may occur at the leading edge of blades and it is consistent with the actual damaged position of the impeller. Therefore, fatigue damage is likely to happen under low flow rate condition. It is necessary to consider the situation carefully during the design of compressors.

scholarly journals Laser Velocimeter Measurements in the Stator of an Automotive Torque Converter

2000 ◽  
Vol 6 (6) ◽  
pp. 417-431 ◽  
Author(s):  
Steven B. Ainley ◽  
Ronald D. Flack
Keyword(s):  
Secondary Flow ◽  
Mass Flow ◽  
Torque Converter ◽  
Speed Ratio ◽  
Pressure Side ◽  
Suction Surface ◽  
General Direction ◽  
Flow Rates ◽  
Pressure Surface ◽  
Mass Flow Rates

The flow field in the stator of a clear torque converter was studied using laser velocimetry. Five planes in the stator were studied at a speed ratio of 0.800 and three planes were studied at a speed ratio of 0.065. Data complements previously available pump and turbine data. Flow in the stator inlet plane is highly non-uniform due to the complicated flow exiting the turbine. At the 0.800 speed ratio, separation regions are located in the 1/4 and mid-planes in the corepressure corner region. In the 3/4 and exit planes, separation regions are located in the shellsuction corner. In the inlet plane a region of high velocities is located along the shell near the pressure side for a speed ratio of 0.800. The high velocity region migrated to the shell-suction corner and suction side in the 1/4 and mid-planes. The overall velocity field for the speed ratio of 0.065 changes significantly from the inlet plane to the mid-plane. The velocity magnitude generally decreases from the suction to the pressure side of the inlet plane and the general direction of the tangential velocity is from pressure-to-suction surface. At the speed ratio of 0.065 a strong secondary flow in the inlet from suction surface to pressure surface was seen. However, at the high speed ratio a moderate secondary flow in the inlet from pressure surface to suction surface was observed. Mass flow rates at the different planes are within the experimental uncertainty and also within the uncertainty of pump and turbine mass flow rates. The flow in the stator inlet plane are significantly influenced by the turbine relative blade position. The turbine influence on the mid-plane data is significantly less than on the inlet plane data. The influence of the pump blade position on the stator exit plane is small.

Lateral Fluid Forces on Whirling Centrifugal Impeller (2nd Report: Experiment in Vaneless Diffuser)

1987 ◽  
Vol 109 (2) ◽  
pp. 100-106 ◽  
Author(s):  
H. Ohashi ◽  
H. Shoji
Keyword(s):  
Orbital Motion ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Fluid Forces ◽  
Damping Effect ◽  
Whirling Motion ◽  
Stiffness Matrices ◽  
Whirl Speed

Fluid forces acting on a rotating centrifugal impeller in whirling motion are studied experimentally. A two-dimensional impeller installed in a parallel walled vaneless diffuser was forced on a circular orbital motion at various positive and negative whirl speeds. The measurements show that the fluid forces exert a damping effect on the rotor at most operating conditions, but excite positive whirl when the impeller operates at a partial discharge and rotates at speeds more than twice the whirl speed. The test results were compared with those calculated by the theory described in the 1st Report. The characteristics of whirling fluid forces are examined from both the measurements and calculations. The measured fluid forces are expressed in terms of mass, damping, and stiffness matrices.

scholarly journals The Influence of Flow Rate on the Wake in a Centrifugal Impeller

1982 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Flow Rate ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Stagnation Pressure ◽  
Centrifugal Impeller ◽  
Suction Surface ◽  
Cross Sectional ◽  
Flow Rates ◽  
Pressure Losses ◽  
Compressor Impeller

Three-dimensional flows and their influence on the stagnation pressure losses in a centrifugal compressor impeller have been studied. All 3 mutally perpendicular components of relative velocity and stagnation pressure on 5 cross-sectional planes, between the inlet and outlet of a 1 m dia shrouded impeller running at 500 rpm were measured. Comparisons were made between results for a flow rate corresponding to nearly zero incidence angle and two other flows, with increased and reduced flow rates. These detailed measurements show how the position of separation of the shroud boundary layer moved downstream and the wake’s size decreased, as the flow rate was increased. The wake’s location, at the outlet of the impeller, was also observed to move from the suction surface at the lowest flow rate, to the shroud at higher flow rates.

Suppression of Self-Excited Flow Instability in a Radial Diffuser Using Rough Surfaces

2006 ◽  
Author(s):  
Saad A. Ahemd ◽  
Hayder Salem
Keyword(s):  
Flow Rate ◽  
Smooth Surface ◽  
Flow Instability ◽  
Rough Surfaces ◽  
Flow Coefficient ◽  
Flow Instabilities ◽  
Low Flow ◽  
Flow Rates ◽  
Flow Limit ◽  
Stable Operating

Flow instabilities in a compression system at low flow rates set the flow limit of the stable operating range. Experiments to investigate the feasibility of controlling the stall in the radial diffuser of a low speed centrifugal compressor were carried out. The technique was very simple and involved using rough surfaces (i.e., sand papers) attached to the diffuser shroud. The results showed that the flow instability in the diffuser (stall) was delayed to a lower flow coefficient (the mass flow rate could be reduced to 70% of its value with the smooth surface) when the rough surfaces were positioned on the diffuser shroud.

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