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.

scholarly journals Rotordynamic Fluid Force Moments on an Open-type Centrifugal Compressor Impeller in Precessing Motion

2001 ◽  
Vol 7 (4) ◽  
pp. 237-251 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Yoshinobu Tsujimoto ◽  
Daizo Yokoyama ◽  
Hideo Ohashi ◽  
Fumitaka Kano
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Design Flow ◽  
Tip Clearance ◽  
Speed Ratio ◽  
Fluid Force ◽  
Open Type ◽  
Unsteady Pressure ◽  
Fluid Forces ◽  
Compressor Impeller

In recent years, increasing interest has been given to the rotordynamic fluid forces on impellers, from the view point of the shaft vibration analysis. Previous experimental and analytical results have shown that the fluid-induced forces and moments on closed type pump impellers contribute substantially to the potential destabilization of subsynchronous shaft vibrations. However, to date few papers are known of the rotordynamic fluid forces on open-type centrifugal impellers. This paper reports about experimental investigations of the rotordynamic fluid force moments on an open-type centrifugal compressor impeller in precessing motion. For open-type impellers, the variations of the tip clearance and the clearance between the back shroud and casing due to the precessing motion contribute to the rotordynamic fluid force moments. Experiments were conducted to measure the rotordynamic fluid force moments directly using the 4-axis sensor, and the unsteady pressure on the front and back casing wall. In this paper, following results are obtained: (1) The fluid force moment becomes destabilizing in the region of negative precessing speed ratio(-0.3<Ω/ω<0), at the design flow rate; (2) At reduced flow rate, the destabilizing fluid force moments occurred at small positive precessing speed ratio(0.2<Ω/ω<0.4); (3) From the comparison of direct measured fluid force moments with those estimated from the unsteady pressure measured on the front and back casing walls, it was found that the destabilizing moments in the backward precession are mainly caused by the fluid forces on the front surface of the present impeller, where there is large clearance between the back shroud and casing.

scholarly journals Flow Simulation And Performance Analysis Of Centrifugal Compressor Using Cfd_Tool

2021 ◽  
Vol 23 (11) ◽  
pp. 693-703
Author(s):  
Tesfaye Barza ◽  
◽  
G. Lakshmikanth ◽  
Keyword(s):  
Performance Analysis ◽  
Pressure Distribution ◽  
Turbulence Model ◽  
Centrifugal Compressor ◽  
Flow Simulation ◽  
Internal Flow ◽  
Design System ◽  
Turbulent Fluid Flow ◽  
Compressor Impeller ◽  
And Performance

This paper is concerned the flow simulation and performance analysis of the Centrifugal Compressor Using CFD – Tool. The complex internal flow of centrifugal compressor can be well analyzed, and the unique design system needs to be developed. It should be early to use the interface and also flexible for input and output. A 3-D flow simulation of turbulent – fluid flow is presented to visualize the flow pattern in-terms of velocity, streamline and pressure distribution on the blade surface are graphically interpreted. The standard K- e turbulence model and the simple model algorithm were chosen for turbulence model and pressure distribution well determined. The simulation was steady Heat transfer and moving reference frame was used to consider the impeller interaction under high resolution. Furthermore, A computational Fluid Dynamics (CFD) 3-D simulation is done to analyze the impeller head and efficiency required of centrifugal compressor. The impeller is rotated for a constant revolution and mass flow rate, in this study initially the geometry of centrifugal compressor impeller is created by an ANSYS Vista CCD, and the Blade modeller done by Bladegen, Finally, CFD analysis was performed in ANSYS CFX using the ANSYS Turbo grid meshing tool. According to the analysis, as the number of impeller blades increases, so does the value of the head and power imparted, as well as the impeller’s efficiency.

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.

Non-Axisymmetric Flows and Rotordynamic Forces in an Eccentric Shrouded Centrifugal Compressor—Part 2: Analysis

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Jieun Song ◽  
Seung Jin Song
Keyword(s):  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Axisymmetric Flow ◽  
Mass Conservation ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
New Model ◽  
Flow Coupling ◽  
Order Of Magnitude ◽  
Rotordynamic Forces

AbstractAn integrated analytical model to predict non-axisymmetric flow fields and rotordynamic forces in a shrouded centrifugal compressor has been newly developed and validated. The model is composed of coupled, conservation law-based, bulk-flow submodels, and the model takes into account the flow coupling among the blades, labyrinth seals, and shroud cavity. Thus, the model predicts the entire flow field in the shrouded compressor when given compressor geometry, operating conditions, and eccentricity. When compared against the experimental data from part 1, the new model accurately predicts the evolution of the pressure perturbations along the shroud and labyrinth seal cavities as well as the corresponding rotordynamic stiffness coefficients. For the test compressor, the cross-coupled stiffness rotordynamic excitation is positive; the contribution of the shroud is the highest; the contribution of the seals is less than but on the same order of magnitude as that of the shroud; and contribution of impeller blades is insignificant. The new model also enables insight into the physical mechanism for pressure perturbation development. The labyrinth seal pressure distribution becomes non-axisymmetric to satisfy mass conservation in the seal cavity, and this non-axisymmetry, in turn, serves as the influential boundary condition for the pressure distribution in the shroud cavity. Therefore, for accurate flow and rotordynamic force predictions, it is important to model the flow coupling among the components (e.g., impeller, shroud, labyrinth seal, etc.), which determines the non-axisymmetric boundary conditions for the components.

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.

Development of Experimental Active Magnetic Bearing Device for Measurement of Mechanical Seal Reaction Force Acting on Rotor

2018 ◽  
Author(s):  
Hiroki Manabe ◽  
Shota Yabui ◽  
Hideyuki Inoue ◽  
Tsuyoshi Inoue
Keyword(s):  
Force Measurement ◽  
Reaction Force ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Mechanical Seal ◽  
Rotating Shaft ◽  
Fluid Force ◽  
Fluid Forces ◽  
Whirling Motion ◽  
Measurement And Evaluation

In turbomachinery, seals are used to prevent fluid leakage. At seal part, rotordynamic fluid force (RD fluid force), which causes whirling motion of rotor, is generated. Under certain conditions, the RD fluid force may contribute to instability of the machine. There are several cases that the whirling is accompanied by eccentricity due to the influence of gravity, or the whirling orbit becomes elliptical due to the influence of the bearing support anisotropy. In these cases, mathematical modeling of the RD fluid forces becomes increasingly complex. As a result, the RD fluid force measurement is more preferable. To improve the measurement and evaluation technology of the RD fluid force, a method to arbitrarily control whirling of the orbit is required. In this paper, RD fluid force measurement by controlling the shape of the orbit using an active magnetic bearing (AMB) is proposed. A contact type mechanical seal is used as a test specimen. When the rotating shaft is whirling, the RD fluid force due to hydrodynamics lubrication and the frictional force due to contact occur on the sliding surface. The resultant force of these forces is taken as the reaction force of mechanical seal and the measurement is performed. The measured reaction force of the mechanical seal is compared with simulation results and the validity of the proposed measurement method is confirmed.

scholarly journals Rotordynamic Forces on Open-type Centrifugal Impeller in Whirling Motion.

1997 ◽  
Vol 63 (615) ◽  
pp. 3609-3616
Author(s):  
Nobuhiro ISHII ◽  
Daizo YOKOYAMA ◽  
Yoshiki YOSHIDA ◽  
Yoshinobu TSUJIMOTO ◽  
Hideo OHASHI ◽  
...  
Keyword(s):  
Centrifugal Impeller ◽  
Open Type ◽  
Whirling Motion ◽  
Rotordynamic Forces

Non-Axisymmetric Flows and Rotordynamic Forces in an Eccentric Shrouded Centrifugal Compressor: Part 2 — Analysis

2019 ◽  
Author(s):  
Jieun Song ◽  
Seung Jin Song
Keyword(s):  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Axisymmetric Flow ◽  
Mass Conservation ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
New Model ◽  
Order Of Magnitude ◽  
Entire Flow ◽  
Rotordynamic Forces

Abstract An integrated analytical model to predict non-axisymmetric flow fields and rotordynamic forces in a shrouded centrifugal compressor has been newly developed and validated. The model is composed of coupled, conservation law-based, bulk-flow sub-models, and the model takes into account the flow coupling among the blades, labyrinth seals, and shroud cavity. Thus, the model predicts the entire flow field in the shrouded compressor when given compressor geometry, operating conditions, and eccentricity. When compared against the experimental data from Part 1, the new model accurately predicts the evolution of the pressure perturbations along the shroud and labyrinth seal cavities as well as the corresponding rotordynamic stiffness coefficients. For the test compressor, the cross stiffness rotordynamic excitation is positive — the contribution of the shroud is the highest; the contribution of the seals is less than but on the same order of magnitude as that of the shroud; and contribution of impeller blades is insignificant. For accurate flow and rotordynamic force predictions, it is critical to model the coupling among the components (e.g., impeller, shroud, labyrinth seal, etc.) which determines the non-axisymmetric boundary conditions for the components. The new model also enables insight into the physical mechanism for pressure perturbation development. The labyrinth seal pressure distribution becomes non-axisymmetric to satisfy mass conservation in the seal cavity, and this non-axisymmetry, in turn, serves as the influential boundary condition for the pressure distribution in the shroud cavity.

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.

A Novel Quasi 3-D Design Method for Centrifugal Compressor Meridional Plane

2010 ◽  
Author(s):  
Mahdi Nili-Ahmadabadi ◽  
Mohammad Durali ◽  
Ali Hajilouy-Benisi
Keyword(s):  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Design Method ◽  
Navier Stokes ◽  
Meridional Plane ◽  
3D Analysis ◽  
3D Design ◽  
Design Algorithm ◽  
Compressor Impeller ◽  
The Difference

This paper is concerned with a quasi-3D design method for centrifugal compressor impeller in the meridional plane. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a quasi-3D analysis code. The Euler equation is solved on the meridional plane for a numerical domain of which some unknown boundaries (hub and shroud) are iteratively modified under the BSA until a prescribed pressure distribution is reached. In BSA, the unknown walls are composed of a set of virtual balls that move freely along the specified directions called spines. The difference between target and current pressure distribution causes to deform flexible boundary at each modification step. In order to validate the quasi-3D analysis code, an existing compressor is investigated by some experiments in which several static pressure points on the shroud, the flow parameters at the compressor inlet and outlet are measured. Comparison of the quasi-3D analysis results with experimental results shows good agreement. Also, a full 3D Navier-Stokes code is used to analyze the existing and designed compressor numerically. The results show that the momentum decrease near the shroud wall in the existing compressor is removed by hub-shroud modification resulting an improvement in performance by 0.6 percent.

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