• Title/Summary/Keyword: Centrifugal forces

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Dynamic Characteristics of the Double Volute Double Suction Centrifugal Pump Using Measured Vibration Data (진동응답 측정에 의한 이중 벌류트형 양흡입 원심펌프의 동적특성)

  • 최복록;박진무
    • Journal of KSNVE
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    • v.10 no.3
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    • pp.500-507
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    • 2000
  • Dynamic forces due to mechanical and hydraulic related causes are always exerted on operating turbomachinery such as centrifugal pumps. To ensure the safety and the reliability of the pump. the magnitudes of the vibration must be kept within an acceptable limit. The focus of this paper is on the identification of the vibration behavior and the quantitative analysis of the hydraulic excitation forces. As the structure becomes more complex finite element analysis is essential to accurately predict the vibration characteristics and the excitation forces, This paper presents an experimental and analytical technique to find and solve to vibration problems in double volute double suction centrifugal pump. Measured vibration data due to the dynamic forces are presented and individual causes are identified, finally excitation forces of the pump are inversely estimated at each frequency on operating conditions.

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Hydraulic Force and Impeller Evaluation of a Centrifugal Heart Pump

  • Timms, D.L;Tan, A.C.C;Pearcy, M-J;Mcneil, K;Galbraith, A
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.2
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    • pp.376-381
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    • 2004
  • A rig was constructed to test the performance characteristics and compare the hydraulic forces exerted on a centrifugal type artificial heart impeller. A conventional shaft. seal and bearing system. while driven by a small electric motor. supported the impeller which was separated from the pump casing by a six degree of freedom force transducer (JR3 Ine). Radial (x. y) and axial (z) hydraulic forces were recorded and compared. At physiological operating conditions. the results indicate that the double entry/exit centrifugal pump encounters a smaller radial force and significantly reduced axial thrust. These experimental results are valuable in the design of a magnetic bearing system to suspend the impeller of a centrifugal artificial heart pump. This experimental technique may also be applied to evaluate the required capacity and predict the lifetime of contact bearings in marine pumps.

Numerical Analysis on the Low Momentum Fluid Flow Characteristics in Centrifugal Pump Impeller (원심 펌프 회전차 내부의 저 운동량 유동특성에 관한 수치적 연구)

  • 김세진;김동원;김윤제
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • 1999.05a
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    • pp.151-157
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    • 1999
  • In this study, tile characteristics of three dimensional flow fields in centrifugal flump impeller are investigated by numerically. Detailed analysis and understanding of flow field in centrifugal pump are very important to predict performance of components. The three dimensional viscous fluid flow in centrifugal pump is distingushed isentropic process region from irreversible process region by wall shear effect, secondary flow, centrifugal and Coriolis forces, variation of boudary layers. Development of low momentum region by viscous fluid flow in the centrifugal impeller causes stall and blockage which is irreversible process region, and resulting in decrease of the performance and efficiency of centrifugal pump. Especially, the result is that Coriolis and centrifugal forces are most powerful factors which are increasing the irreversible region.

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A Study on the Hydraulic Excitation Forces Using Transfer Function and Operational Measured Data for the Centrifugal Pump (전달함수와 진동응답 측정에 의한 원심펌프에서의 유체력 특성에 관한 연구)

  • Choi, Bok-Lok;Park, Jin-Moo;Kim, Kwang-Eun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.8 s.179
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    • pp.1931-1939
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    • 2000
  • Operating excitation forces of the linear vibratory system are normally determined by direct measurement techniques using load cells, strain gauges, etc. But, hydraulic forces of the rotating turbomachinery such as centrifugal pumps are exerted on an impeller due to asymmety of the flow by the interaction between pump impeller and volute. So, investigations of wide range of hydraulic designs and geometric deviations are difficult by direct method. This paper presents a hybrid approach for fourier transformed operational excitation forces, which uses pseudo-inverse matrix of the transfer matrix for the system and the measured vibrational data with standard installed pump. The determination of the transfer function matrix is based on a linear rotor/stationary system and steady state harmonic response in finite element analysis. And, vibrational data is collected in both vertical and horizontal directions at inboard and outboard bearing housings. The results of the process may be enhanced by making acceleration measurements at many more locations than there are forces to be determined.

A Comparison of Separated and Combined Winding Concepts for Bearingless Centrifugal Pumps

  • Raggl, Klaus;Nussbaumer, Thomas;Kolar, Johann W.
    • Journal of Power Electronics
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    • v.9 no.2
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    • pp.243-258
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    • 2009
  • Bearingless centrifugal pump systems are employed in the semiconductor, pharmaceutical and medical industries due to their facility for pumping high purity fluids without particle contamination. Two types of forces have to be generated by the stator units, namely bearing forces for achieving magnetic levitation, and drive forces for producing the needed pump torque. The generation of these forces requires bearing and drive windings, which can be realized as separate bearing and drive coils or as identical, combined coils on the stator claws. In this paper, a detailed comparison between these two winding concepts is undertaken, whereby the copper losses, the power electronics losses, and the achievable pump output pressure are evaluated for both concepts. For each criterion a ratio of improvement is calculated analytically which allows evaluation of the performance of the two winding concepts for any given pump operating point and design. Finally, also practical features such as control complexity, cabling effort and manufacturability are discussed and measurements on prototype systems are carried out to validate the considerations.

Hydrodynamic forces of impeller shroud and wear-ring seal on centrifugal pump (고성능 원심펌프에서 임펠러 시라우드 및 마모 시일의 유체가진력 해석)

  • Ha, Tae-Woong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.1
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    • pp.102-110
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    • 1998
  • The analysis of lateral hydrodynamic forces in the leakage path between a shrouded pump impeller through wear-ring seal and its housing is presented. Governing equations are derived based on Bulk-flow and Hirs' turbulent lubrication model. By using a perturbation analysis and a numerical integration method, governing equations are solved to yield leakage and rotordynamic coefficients of force developed by the impeller shroud and wear-ring seal. The variation of rotordynamic coefficients of pump impeller shroud and wear-ring seal is analyzed as parameters of rotor speed, pressure difference, shroud clearance, wear-ring seal clearance, and circumferential velocity at the entrance of impeller shroud for a typical multi-stage centrifugal pump.

Measurement of Inward Turbulent Flows in a Rotating with Square Cross-Section $90^{\circ}$ Duct (회전하는 정사각단면 $90^{\circ}$ 곡덕트 내 내향 난류유동 측정)

  • Kim, Dong-Chul;Chun, Kun-Ho;Choi, Young-Don
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.627-632
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    • 2000
  • Developing turbulent flows in a rotating 90 degree bend with square cross-section were measured by a hot-wire anemometer. The six orientation hot-wire technique was applied to measured the distributions of 3 mean velocities and 6 Reynolds stress components. Effects of Coriolis and centrifugal forces caused by the curvature and rotation of bend on the mean motion and turbulence structures were experimentally investigated Productive addition of Coriolis and centrifugal forces to the outward radial direction in the entrance region of bend increases the secondary flow intensity according to the rotational speeds. However, after 45 degree of bend, centrifugal force due to the rotation of bend may promote the break down of counter rotating vortex pair into multi-cellular pattern, thereby decreasing the production rate of turbulence energy and Reynolds stresses.

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Sensitivity Analysis of the Zigzag Switch under Acceleration and Centrifugal Forces (가속력과 원심력을 받는 지그잭 스위치의 민감도 해석)

  • 김경환
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.11a
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    • pp.1067-1072
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    • 1996
  • Sensitivity analysis of the cylindrical zigzag cams under acceleration and centrifugal forces is performed. A Lagrangian method is used to determine the mechanism constant of zigzag track, And the equation of motion for cylindrical zigzag cam under rectangular pulse is derived by the governing equations of a single spring mass system. The ratio of the drive force tn resisting force is derived by angular acceleration, centrifugal force and setback force on the operation of the munition. The theoretical sensitivity curves for 3 models are analyzed. And experiments for 3 models are conducted to check safe and functional zone. Zigzag cam types can be satisfied all major design requirements for switch system of munition.

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Effect of crystal and crucible rotations on the mass transfer in magnetohydrodynamic Czochralski crystal growth of silicon (자기장이 가하여진 초크랄스키 실리콘 단결정 성장에서 질량전달에 미치는 성장결정과 도가니의 회전효과)

  • 김창녕
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.7 no.4
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    • pp.536-547
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    • 1997
  • For various angular velocities of crucible and crystal, the characteristics of melt flows, temperatures and concentrations of oxygen are numerically studied in the Czochralski furnace with a uniform axial magnetic field. Buoyancy effect due to the heating of crucible wall and thermocapillary effect due to the temperature gradient at the free surface, can be differentiably suppressed by the centrifugal forces due to the rotations of the crucible and crystal. The most important factor which yields the centrifugal forces is the rotation velocity of the crucible, that influences the fields of velocities, temperatures and concentrations. In the case that the crucible rotation velocity is not high, the rotations of the crystal gives rise to the centrifugal forces effectively.

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Analysis of the three-dimensional Steady Flow through A Multi-blade Centrifugal Fan (다익송풍기 내부 3차원 정상유동의 수치해석)

  • Seo, Seoung-Jin;Chen, Xi;Kim, Kwang-Yong;Kang, Shin-Hyoung
    • The KSFM Journal of Fluid Machinery
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    • v.3 no.1 s.6
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    • pp.19-27
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    • 2000
  • A numerical study is presented for analysis of three-dimensional incompressible turbulent flows in a multi-blade centrifugal fan. Reynolds-averaged Navier-Stokes equations with a standard $k-{\espilon}$ turbulence model are discretized with finite volume approximations. The computational area is divided into three blocks; inlet core, impeller and scroll parts, which are linked by a multi-block method. The flow inside of the fan is regarded as steady flow, and the mathematical models for the impeller forces were established from a cascade theory and measured data. Empirical coefficients are obtained comparing between computational and experimental results for the case without scroll, and are employed to simulate the flow through the impeller with scroll. In comparisons with experimental data, the validity of the mathematical models for the impeller forces was examined. The characteristics of the flow in the scroll were also discussed.

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