• Title/Summary/Keyword: Pressure and Rotating

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Determination of Eccentric Axis for Pump Control Valve Using the Characteristic Function (특성함수를 이용한 펌프 제어 밸브의 편심축 결정)

  • Shin, Myung-Seob;Yi, Sang-Il;Park, Gyung-Jin;Yoon, Joon-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.11 no.3
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    • pp.43-49
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    • 2008
  • The pump control valve is a butterfly valve that has an eccentric rotating axis. It is not only used as a butterfly valve to control the flow rate or pressure, but also as a check valve to prevent backward flow. A new design method of eccentric rotating axis is proposed to design the valve. The height of the rotating axis is determined through flow field analysis. A general purpose of computational fluid dynamics software system, Fluent is used to simulate the fluid flow. Flow field analysis is performed for various heights of the rotating axis and different opening angles of the valve. A characteristic function is defined for estimating the flow characteristics based on the results of flow field analysis. The characteristic function is defined in order to determine the height of the rotating axis. An optimization problem with a characteristic function is formulated to determine the amount of eccentricity. The height of the Totaling axis of the valve is determined through solving the optimization problem.

Pressure Drop Characteristics in a Coolant Passage With Turning Region and Rotation (냉각유로 내 곡관부 및 유로의 회전이 압력강하에 미치는 영향)

  • Kim, Kyung-Min;Cho, Hyung-Hee
    • The KSFM Journal of Fluid Machinery
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    • v.10 no.2 s.41
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    • pp.32-40
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    • 2007
  • The present study investigated local pressure drop in a rotating smooth square duct with turning region. The duct has a hydraulic diameter $(D_h)$ of 26.7mm and a divider wall of 6.0mm or $0.225D_h$. The distance between the tip of the divider and the outer wall of the duct is $1.0D_h$. The Reynolds number (Re) based on the hydraulic diameter is kept constant at 10,000, and the rotation number (Ro) is varied from 0.0 to 0.20. The pressure coefficient distribution $(C_p)$, the friction factor (f) and the thermal performance $({\eta})$ are presented on the leading, the trailing and the outer surfaces. It is found that the curvature of the $180^{\circ}-turn$ produces Dean vortices that cause the high pressure drop in the turning region. The duct rotation results in the pressure coefficient discrepancy between the leading and trailing surfaces. That is, the high pressure values appear on the trailing surface in the first-pass and on the leading and side surfaces in the second-pass. As the rotation number increases, the pressure discrepancy enlarges. In the fuming region, a pair of the Dean vortices in the stationary case transform into one large asymmetric vortex cell, and then the pressure drop characteristics also change.

Analysis for Lubrication between a Rotating Cylinder and a Translating Plate (회전하는 원통과 병진운동하는 평판사이의 윤활유동해석)

  • 정호열;정재택
    • Tribology and Lubricants
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    • v.18 no.6
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    • pp.411-417
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    • 2002
  • Two dimensional slow viscous flow between a rotating cylinder and a translating plate is investigated using Stokes' approximation. An exact formal expression of the stream function is obtained by using the bipolar cylinder coordinates and Fourier series expansion. From the stream function obtained, the streamline patterns are shown and the pressure distribution in the flow field is determined. By integrating the stress distributions on the cylinder, the farce and the moment exerted on the cylinder are calculated. The flow rate through the gap between the cylinder and the plate is also determined as a function of the distance between the cylinder and the plate. Special attention is directed to the case of very small distance between the cylinder and the plate concerned with the lubrication theory and the minimum pressure is calculated to explain a possible cavitation.

A Study on the Reduction of Flow Induced Acoustic Noise for a High-Speed Rotating Hexagonal Disk (고속회전 육각형 디스크의 유동기인 소음저감에 관한 연구)

  • Han, Ji-Min;Rhim, Yoon-Chul
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.168-171
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    • 2005
  • The present study describes the prediction of the flow induced noise level of a high-speed rotating hexagonal disk and proposes the way how to reduce it. Since a hexagonal disk, which is used in the laser printer and named a polygon mirror, has six sharp comers, there are low and high pressure regions on each of six edges when it rotates. Therefore, the Pressure difference generates three dimension flow field and causes aerodynamic noise. The Ffowcs-Williams and Hawkings(FWH) method is employed for the analysis. We have measured the sound pressure levels and compared them with the computational results. The calculated sound pressure levels agree well with the experimental results. We modified the shape of the edges of a hexagonal disk to reduce the noise level and confirm their effects through numerical computation.

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A Study on Reduction of Sound Noise Induced by Disk Rotation in Optical Disk Drives (광 디스크 드라이브의 공력소음 감소에 관한 연구)

  • 송인상;박건순;최학현;김수경;이승엽
    • Journal of KSNVE
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    • v.9 no.4
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    • pp.693-702
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    • 1999
  • We study the characteristics of airflow and sound noise induced by disk rotation in optical disk drives. The characteristics of airflow around a rotating disk surrounded by various tray structures are numerically investigated using a commercial CFD program and then compared with experimental results. Sound pressure and intensity caused by the fluid-structure interactions in the CD/DVD-ROM drive are measured, and the effect of the ariflow on the sound noise and disk vibration is discussed. In order to reduce airflow-induced noise and vibration around the rotating disk, tray geometry is modified. Both numerical and experimental studies implemented with different tray models show that the improved tray model alters the characteristics of the disk-induced airflow, causing the reduction of the airflow-induced sound level.

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Simulation of turbulent flow of turbine passage with uniform rotating velocity of guide vane

  • Wang, Wen-Quan;Yan, Yan
    • Coupled systems mechanics
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    • v.7 no.4
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    • pp.421-440
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    • 2018
  • In this study, a computational method for wall shear stress combined with an implicit direct-forcing immersed boundary method is presented. Near the immersed boundaries, the sub-grid stress is determined by a wall model in which the wall shear stress is directly calculated from the Lagrangian force on the immersed boundary. A coupling mathematical model of the transition process for a model Francis turbine comprising turbulent flow and rotating rigid guide vanes is established. The spatiotemporal distributions of pressure, velocity, vorticity and turbulent quantity are gained with the transient process; the drag and lift coefficients as well as other forces (moments) are also obtained as functions of the attack angle. At the same time, analysis is conducted of the characteristics of pressure pulsation, velocity stripes and vortex structure at some key parts of flowing passage. The coupling relations among the turbulent flow, the dynamical force (moment) response of blade and the rotating of guide vane are also obtained.

Effect of Axial Spacing between the Components on the Performance of a Counter Rotating Turbine

  • Subbarao, Rayapati;Govardhan, Mukka
    • International Journal of Fluid Machinery and Systems
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    • v.6 no.4
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    • pp.170-176
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    • 2013
  • Counter Rotating Turbine (CRT) is an axial turbine with a nozzle followed by a rotor and another rotor that rotates in the opposite direction of the first one. Axial spacing between blade rows plays major role in its performance. Present work involves computationally studying the performance and flow field of CRT with axial spacing of 10, 30 and 70% for different mass flow rates. The turbine components are modeled for all the three spacing. Velocity, pressure, entropy and Mach number distributions across turbine stage are analyzed. Effect of spacing on losses and performance in case of stage, Rotor1 and Rotor2 are elaborated. Results confirm that an optimum axial spacing between turbine components can be obtained for the improved performance of CRT.

A Study on the ]Reduction of Flow induced Acoustic Noise for a High-speed Rotating Hexagonal Disk (고속회전 육각형 디스크의 유동기인 소음저감에 관한 연구)

  • Han Ji-Min;Rhim Yoon-Chul
    • 정보저장시스템학회:학술대회논문집
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    • 2005.10a
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    • pp.71-74
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    • 2005
  • The present study describes the prediction of the flow induced noise level of a high-speed rotating hexagonal disk and proposes the way how to reduce it. Since a hexagonal disk, which is used in the laser printer and named a Polygon mirror, has six sharp corners, there are low and high pressure regions on each of six edges when it rotates. Therefore, the pressure difference generates three dimension flow field and causes aerodynamic noise. The Ffowcs-Williams and Hawkings (FWH) method is employed for the analysis. We have measured the sound pressure levels and compared them with the computational results. The calculated sound pressure levels agree well with the experimental results. We modified the shape of the edges of a hexagonal disk to reduce the noise level and confirm their effects through numerical computation.

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Analysis for Lubrication between Two Close Rotating Cylinders (근접하여 회전하는 두 원통 사이의 윤활유동해석)

  • 이승재;정호열;정재택
    • Tribology and Lubricants
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    • v.17 no.5
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    • pp.391-398
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    • 2001
  • Two dimensional slow viscous flow around two counter-rotating equal cylinders is investigated based on Stokes'approximation. An exact formal expression of the stream function is obtained by using the bipolar cylinder coordinates and Fourier series expansion. From the stream function obtained, the streamline patterns around the cylinders are shown and the pressure distribution in the flow field is determined. By integrating the stress distributions on the cylinder, the force and the moment exerted on the cylinder are calculated. The flow rate through the gap between the two cylinders is also determined as the distance between two cylinders varies. Special attention is directed to the case of very small distance between two cylinders concerned with the lubrication theory and the minimum pressure is calculated to explain a possible cavitation.

Structural Integrity Evaluation for the Reactor Coolant Pump Shaft Seal Assembly (원자로냉각재펌프 축밀봉장치에 대한 구조적 건전성 평가)

  • Kim, Minsu;Kim, Minchul;Kim, Oaksug;Chung, Sungho
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.13 no.2
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    • pp.44-50
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    • 2017
  • The shaft seal of the reactor coolant pump is installed on the upper side of the rotating shaft of the pump to seal the reactor coolant from flowing out between the rotating shaft and the non-rotating parts. In this study, the loading conditions for the normal operation and faulted conditions are identified and structural integrity evaluation is performed using the finite element stress analysis for the sealing apparatus of the APR 1400 reactor coolant pump. It is confirmed that the stress analysis results satisfy the design criteria at all loading conditions.