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.

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.

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.

An Analytical and Experimental Assessment of a Diffuser Flow Phenomenon as a Precursor to Stall

2012 ◽  
Author(s):  
James M. Sorokes ◽  
Jorge E. Pacheco ◽  
Clementine Vezier ◽  
Syed Fakhri
Keyword(s):  
Rotating Stall ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Diffuser Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses ◽  
Validation Testing ◽  
Lower Flow Rate

The paper describes an experimental and analytical study on the vaneless diffuser downstream of a high flow coefficient, high inlet relative Mach number centrifugal impeller. The diffuser flowfield exhibited a unique behavior in which the low momentum zone typically found along the shroud side of a centrifugal compressor diffuser suddenly shifted to the hub side of the diffuser just prior to the onset of diffuser rotating stall. The phenomenon was observed in the computational fluid dynamics (CFD) analyses conducted as well as in the experimental data obtained during stage validation testing. A review of the analytical and test results suggested that the phenomenon was at least partially attributable to the level of diffusion in the vaneless diffuser. Modifications made to reduce the diffusion rate were shown by CFD analysis to move the onset of the unusual shift of low momentum flow to a much lower flow rate. The modifications also increased the efficiency of the overall stage by 1.2%.

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

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.

The Rotordynamic Forces on an Open-Type Centrifugal Compressor Impeller in Whirling Motion

1999 ◽  
Vol 121 (2) ◽  
pp. 259-265 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Yoshinobu Tsujimoto ◽  
Nobuhiro Ishii ◽  
Hideo Ohashi ◽  
Fumitaka Kano
Keyword(s):  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Speed Ratio ◽  
Fluid Force ◽  
Open Type ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Compressor Impeller ◽  
Whirl Speed ◽  
Rotordynamic Forces

In recent years, increasing interest has been given to the rotordynamic forces on impellers, from the view point of the shaft vibration analysis. Previous experimental and analytical results have shown that the fluid-induced forces on closed-type (with shroud) centrifugal impellers in whirling motion contribute substantially to the potential destabilization of subsynchronous shaft vibrations. However, to date nothing is known of the rotordynamic forces on open-type (without shroud) centrifugal impellers. This paper examines the rotordynamic fluid forces on an open-type centrifugal compressor impeller in whirling motion. For an open-type impeller, the variation of the tip clearance due to the whirling motion is the main contribute to the rotordynamic forces. Experiments were performed to investigate the rotordynamic forces by direct measurements using a force balance device, and indirectly from the unsteady pressure on the casing wall over a range of whirl speed ratio (Ω/ω) for several flow rates. In this paper, the following results were obtained: (1) Destabilizing forces occur at small positive whirl speed ratio (0 ≤ Ω/ω ≤ 0.3) throughout the flow range of normal operation; (2) At smaller flow rate with inlet backflow, the magnitude of the fluid force changes dramatically at a whirl speed ratio close to Ω/ω = 0.8, resulting in destabilizing rotordynamic forces. From the measurement of unsteady inlet pressure, it was shown that the drastic changes in the fluid force are related to the coupling of the whirling motion with a rotating flow instability, similar to “rotating stall”; (3) The forces estimated from the unsteady pressure distribution on the casing wall and those estimated from the pressure difference across the impeller blades were compared with the results from the direct fluid force measurements. The direct fluid forces correlate better with the forces due to the pressure distribution on the casing wall.

Theoretical Analysis of Fluid Forces on an Open-Type Centrifugal Impeller in Whirling Motion

2002 ◽  
Vol 124 (2) ◽  
pp. 342-347 ◽  
Author(s):  
Akira Hiwata ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Theoretical Analysis ◽  
Temporal Change ◽  
Centrifugal Impeller ◽  
Shaft Speed ◽  
Open Type ◽  
Tip Leakage ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Minor Contribution ◽  
Unsteady Fluid

For turbomachines operating at supercritical shaft speed, it is important to understand the characteristics of unsteady fluid forces on the impeller that occur due to shaft vibration. The present paper treats the forces on an open-type centrifugal impeller in whirling motion using unsteady potential flow theory. The whirling forces obtained agree reasonably with experimental results and show a destabilizing region at small positive whirl. It was found that the destabilizing force is due to the forces on the hub caused by temporal change in the thickness of the flow channel, with minor contribution of tip leakage on the destabilization.

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