• Title/Summary/Keyword: vibration reduction plane

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Transient Vibration Identification and Reduction of a Centrifugal Fan for a Wall-installed Air-conditioner (벽걸이에어컨의 원심홴에 대한 과도진동 규명 및 저감)

  • Kim, Minsung;Lim, Jonghyuk;Chung, Jintai
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.4
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    • pp.383-390
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    • 2016
  • In this paper, experiment and dynamics simulations were carried out to identify and reduce the out-of-plane vibration that occurs in a centrifugal fan of an air conditioner installed to a wall. In a wall-installed air conditioner, large space between a case and heat exchanger is often required for the fan to avoid the collision with the case and exchanger. This large space hinders the slim design of the air conditioner even if air conditioner market demands a slim air conditioner. In the present study, in order to determine the cause of the vibration in the centrifugal fan, the out-of-plane vibration and the physical properties were investigated, and the dynamic characteristics of the centrifugal fan were obtained by experiments. Based on these experiments, a dynamic simulation model was established to determine the cause of the out-of-plane vibration of the centrifugal fan. It was found that the main factor of out-of-plane vibration in the centrifugal fan is the axial misalignment between the centrifugal fan and the motor shaft.

The Vibration Characteristic of Large Main Steam Pipelines in Power Plant (발전소의 대형 주증기배관의 진동 특성)

  • Kim, Yeon-Whan;Lee, Hyun
    • Journal of KSNVE
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    • v.6 no.6
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    • pp.709-715
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    • 1996
  • In recent years, the piping vibration in many Power Plants is being increased by the aged generating facilities due to a long time use. Generally, the pressure fluctuations associated with the flow-induced excitations in this case are broadband in nature. Mainly, the dominant sources of vibration are a vortex-shedding, plane waves and boundary layer turbulence. The peak level of the spectrum is proportional to the dynamic head. A severe disturbance in pipeline results in the generation of intense broadband internal sound waves which can propagate through the piping system. The characteristic frequencies of operating loads of 20%, 57%, 70%, 100% are 4 - 6 Hz and coincide with the results from impact hammering test and FEM analysis. We chose the wire energy absorbing rope restraint as a vibration reduction method after reviewing the various conditions such as site, installing space and economic cost etc. After installation, the vibration level was reduced about 54% in velocity.

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Vibration Reduction of Vertical Pumps Used in the Power Plant Circulating Water System (발전소 순환수계통 수직펌프의 진동저감에 관한 연구)

  • Park, Hyeok;Yoo, Ho-Seon
    • Plant Journal
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    • v.9 no.1
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    • pp.43-49
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    • 2013
  • In this study, the natural frequency of the actual operating vertical pump in the P combined cycle power plant is measured and the cause of high vibration is determined by using fluid-structure coupled vibration theory. Choosing the vibration reduction plan suited for field conditions and using the numerical analysis verify effectiveness of the plan. The plan is applied to the actual pump and the empirical experiments are conducted.

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Active Noise Control Using Sensory Actuator (자기감응 액추에이터를 이용한 능동소음제어)

  • Go, Byeong-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.5
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    • pp.1573-1581
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    • 1996
  • This paper present as experimental demonstratio of DSP and a sensory actuator that is used to actively control sound transmission/radiation through a vibrating plate. A plane acoustic wave incident on a clamped, thin circular plate was used as a noise source, and a sensory actuator bounded to the plate was used to control and sense vibration of the plate. The sound transmission reduction problem was tranformed as a structural vibration control problem that actively control the structural vibration modes coupled to acoustic modes. The results show that the first structural vibration mode is controlled with a reduction of 78 percent in the displacement and velocity of the plate. This corresponds to a 13dB reduction in the acoustic response. These experimental results indicate that a sensory actuator bounded to the plate can be employed to attenuate the sound transmitted to radiated from the plate.

EDISON Co-rotational Plane Beam-Transient anlaysis를 이용한 Energy method방법의 충격량해석 및 타격중심 매개변수 연구

  • Kim, SangHyeok;Lee, SangGu;Shin, SangJoon
    • Proceeding of EDISON Challenge
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    • 2017.03a
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    • pp.194-203
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    • 2017
  • The center of percussion(COP) is the point of an extended massive object attached to a pivot where a perpendicular impact will produce no reactive shock at the pivot. COP is an important concept in the field of vibration and dynamics. In vibration, COP causes reduction of vibration and in dynamics, it brings about maximum speed of an object. Many studies about COP are still in progress. However most of the researches have typically focused on the method of mathematical and numerical anlalysis. In this paper, impact analysis was proved by the mechanical energy method using EDISON co-rotational plane beam transient analysis program. The result expressed in acceleration was the relative magnitude of the impulse, which was the indicator of COP. Then, these results were compared with the reference thesis results for exact consequences. Additionally, parametric study of COP was conducted.

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Viscoelastic Damping Treatment Analysis and Aeroelasticity for Vibration Reductions of a Hingeless Composite Helicopter Rotor System (무힌지 복합재 헬리콥터 로터 시스템의 진동 저감을 위한 점탄성 감쇠처리 해석 및 공탄성 연구)

  • Hwang, Ho-Yon
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.15 no.3
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    • pp.6-14
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    • 2007
  • In this research, vibration reduction and aeroelastic stability of a composite hingeless rotor hub flexure with viscoelastic constrained layer damping treatment(CLDT) were investigated. The composite flexures with viscoelastic CLDT were applied to hingeless rotor system to improve the in-plane stability of the lead-lag motion causing resonance. The modal test was performed and dynamic properties(natural frequency and loss factor) were acquired. Also, complex eigenvalue analysis(SOLlO7) in the NASTRAN structural analysis module was performed and compared with results of the modal test. To insure aeroelastic stability, damping ratio analyses of the hingeless rotor system with CLDT were accomplished at hovering condition due to collective pitch angle changes. Satisfactory results of increasing structural damping and stability were obtained.

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Static and Dynamic Instability Characteristics of Thin Plate like Beam with Internal Flaw Subjected to In-plane Harmonic Load

  • R, Rahul.;Datta, P.K.
    • International Journal of Aeronautical and Space Sciences
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    • v.14 no.1
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    • pp.19-29
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    • 2013
  • This paper deals with the study of buckling, vibration, and parametric instability characteristics in a damaged cross-ply and angle-ply laminated plate like beam under in-plane harmonic loading, using the finite element approach. Damage is modelled using an anisotropic damage formulation, based on the concept of reduction in stiffness. The effect of damage on free vibration and buckling characteristics of a thin plate like beam has been studied. It has been observed that damage shows a strong orthogonality and in general deteriorates the static and dynamic characteristics. For the harmonic type of loading, analysis was carried out on a thin plate like beam by solving the governing differential equation which is of Mathieu-Hill type, using the method of multiple scales (MMS). The effects of damage and its location on dynamic stability characteristics have been presented. The results indicate that, compared to the undamaged plate like beam, heavily damaged beams show steeper deviations in simple and combination resonance characteristics.

Active Controll of Flow Noise Sources of Flat Plate Using Piezo Film (피에조 필름을 이용한 평판에서의 유동유기 소음원의 능동제어)

  • Shin, Seung-Yeol;Song, Woo-Seog;Lee, Seung-Bae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.924-927
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    • 2004
  • Measurements of fluctuating wall pressures were made with a linear array of 16 piezo-electric transducers beneath a fully-developed turbulent boundary layer. The piezoelectric bimorph actuator applied in this experiment has bonding structures of each polarity to make out-of-plane displacements rather than in-plane ones by using piezoelectric effect To specify the boundary layer characteristics at the location where the actuation was applied, the wall friction coefficients and $Re_\theta$ were measured by using the CPM method. The actuating frequency for the bimorph film was determined according to the priori bursting frequency from boundary layer parameters. The reduction of convecting energies in wave-number space was clearly observed at the specified actuating frequencies.

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Target-free vision-based approach for vibration measurement and damage identification of truss bridges

  • Dong Tan;Zhenghao Ding;Jun Li;Hong Hao
    • Smart Structures and Systems
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    • v.31 no.4
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    • pp.421-436
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    • 2023
  • This paper presents a vibration displacement measurement and damage identification method for a space truss structure from its vibration videos. Features from Accelerated Segment Test (FAST) algorithm is combined with adaptive threshold strategy to detect the feature points of high quality within the Region of Interest (ROI), around each node of the truss structure. Then these points are tracked by Kanade-Lucas-Tomasi (KLT) algorithm along the video frame sequences to obtain the vibration displacement time histories. For some cases with the image plane not parallel to the truss structural plane, the scale factors cannot be applied directly. Therefore, these videos are processed with homography transformation. After scale factor adaptation, tracking results are expressed in physical units and compared with ground truth data. The main operational frequencies and the corresponding mode shapes are identified by using Subspace Stochastic Identification (SSI) from the obtained vibration displacement responses and compared with ground truth data. Structural damages are quantified by elemental stiffness reductions. A Bayesian inference-based objective function is constructed based on natural frequencies to identify the damage by model updating. The Success-History based Adaptive Differential Evolution with Linear Population Size Reduction (L-SHADE) is applied to minimise the objective function by tuning the damage parameter of each element. The locations and severities of damage in each case are then identified. The accuracy and effectiveness are verified by comparison of the identified results with the ground truth data.

A Study on the Transient Motion Analysis for the Liquid Balinced Washing Machine (액체밸런서를 고려한 세탁기의 과도응답 특성에 관한 연구)

  • 이동익;오재응
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.1
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    • pp.1-13
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    • 1995
  • In order to investigate the effect of liquid balancer in washing machine, we identify the vibration characteristics of suspension system of washing machine and formulate the 4 D. O. F. system dynamic equations. As the washing machine rotates higher speed, it is emphasized to reduce the ecentric force due to unbalanced mass. Nowadays, the most effective cancelling method of eccentric force is known as the usage of liquid balancer. To determine the liquid distribution in liquid balancer, the fluid statics is considered. The system dynamic equations are solved by Runge-Kutta method and represent the good characteristics of real washing machine in X-Y plane. The accuracy of the numerical solution was examined by experiments. The simulation results show that the unbalanced mass has so much influence on vibration magnitude and the rotating shape of spin-basket. But the effect of mass reduction due to the dehydration of the spin-basket has little influence on transient vibration.