• 대한기계학회논문집A
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• 제27권6호
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• pp.857-863
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• 2003

In rotating machinery, unbalance and misalignment are major concerns in vibration. Unbalance can be eliminated by balancing procedure to some degree. but little work has been done on the vibrations that occur in a misaligned rotor system. Currently, no generalized theoretical model based on a rotor system with flexible coupling is available to describe the vibrations caused by misalignment. As a part of systematic investigation on the misalignment, first of all, the study on flexible coupling with misalignment should be preceded. In this study, the geometry and reaction force and moment of a gear coupling with misalignment was investigated, also the theoretical model of a gear coupling with misalignment was presented by using the relationship between geometry and moment of gear coupling. It is expected that the proposed procedure can be applied to derive the theoretical model of other couplings.

• Journal of Advanced Marine Engineering and Technology
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• 제30권8호
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• pp.885-893
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• 2006

A dynamic model of turbo air compressor having multi-helical gear pairs is developed by transfer matrix method. The model accounts for the shaft and bearing flexibilities, gyroscopic effects and the force couplings among the transverse, torsion, and axial motions due to gearing. The program which can be used to analyze and predict the vibrational characteristics by the mass unbalance of the rotors and gear transmission error of turbo compressor is developed with this system model We expect this developed program to contribute the reduction of the vibration/noise on turbo compressor in the field of both design and manufacturing and can be used as a basic sub-program for CAD/CAM of low-noised gear teeth also.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.43-48
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• 2006

This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system. Under the combination operation of single & three phase load, voltage unbalance will be generated and current unbalance will be more severe by the dropped voltage quality. All power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. Moors may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration.

• 연구논문집
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• 통권31호
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• pp.65-75
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• 2001

A dynamic model of pump having one step gearbox and two step gearbox is developed by the lumped parameter method. The model accounts for shafts, ball bearings and journal bearings flexibilities, gyroscopic effects and the force couplings among the transverse and torsion motions due to gearing. Excitation forces of pump having one step gearbox and two step gearbox are considered as the mass unbalance of the rotors and gear transmission error which comes from the modified tooth surface. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors and the transmitted errors of the gearing are considered, shows that there are no critical speeds at the operating speeds. One step and two step gearboxes are manufactured and are estimated for vibration/noise, lubrication and performance.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.39-40
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• 2006

Diesel power plant(DPP) with the medium speed diesel engine is operated under the very severe condition in aspect of load and operating time as compared with the marine diesel generator set. So, minimized vibration level have to be insured for the more stable operation of engine and generator. The vibration of generator set mainly comes from the resonance between the rigid modes by resilient mount or distortion modes by structural stiffness and the excitation forces of engine. Then, avoidance of resonance with structural modification is generally well known. In this paper, the first order vibration in non-resonance range and local vibration modes were investigated by impact test, response/ODS(operational deflection shape) measurement and 3D finite element analysis for the additional reduction of vibration. The proposed countermeasures were actually applied and their final effects were verified through the in-situ measurement.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.110-115
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• 2014

The nuclear power plant was launched by Kori unit 1 in 1978 years. Currently, 23 nuclear power plants have been operating in Korea since 1978 years. The localization was completed for most of the reactor facility from Hanbit(Youngkwang) unit 3&4. However, RCP(Reactor Coolant Pump) and MMIS(Man Machine Interface System) is an important technology that has been excluded from the scope of the technical transfer has been dependent on a specific overseas vendor. Recent success in RCP development through co-operation with government and industries. Developed RCP will be applied to Shin-Hanul unit 1&2 nuclear power plants. The RCP operates in high speed and high pressure condition and only rotating component in the NSSS(Nuclear Steam Supply System). Therefore, the problem of vibration has arisen caused by the hydraulic forces of the working fluid. These forces can influence on the stability characteristics for entire RCS(Reactor Coolant System) loop, and can act as significant destabilizing forces. In this study, vibration evaluation of the pump shaft of development RCP estimated under normal operation and over speed conditions. In order to predict the vibration characteristics and dynamic behavior, modal analysis, critical speed analysis and unbalance response spectrum analysis were performed.

• Tribology and Lubricants
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• 제23권5호
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• pp.219-227
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• 2007

The dynamic performance of air foil bearings relies on a coupling between a thin air film and an elastic foil structure. A number of successful analytical techniques to predict dynamic performance have been developed. However, the evaluation of its dynamic characteristic is still not enough because of the mechanical complexity of the foil structure and strong nonlinear behavior of friction force. This work presents a nonlinear transient analysis method to predict dynamic performance of foil bearings. In this method, time dependent Reynolds equation is used to calculate pressure distribution and a finite element method is used to model the bump foil structure. The analysis is treated with a direct implicit integration technique that can handle nonlinear problems and the stick-slip algorithm is used to consider friction force. Using this method the response to the mass unbalance excitation is investigated for various design parameters and operating conditions. The results of analysis show that foil bearing is very effective on the restriction of vibration at the resonance frequency compared to the rigid surface bearings and the effectiveness depends on the operating conditions, static load and a amount of mass unbalance. In addition, there exist optimum values of friction coefficient, bump foil stiffness and number of circumferential slit with regards to minimizing dynamic response at the resonance frequency. These optimum values are system dependent.

• 한국소음진동공학회논문집
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• 제17권5호
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• pp.415-426
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• 2007

링크모션 펀치프레스는 많은 링크들이 서로 연결되어 있으며 각각의 링크는 고속에서 구속 운동을 수행한다. 그 결과 동적 불평형 힘과 모멘트가 프레스의 메인프레임으로 전달되며 원하지 않는 진동을 수반한다. 이로 인하여 생산성과 정확한 스탬핑 작업의 저하를 초래한다. 이 논문은 기구학 및 동역학 분석에 기초하여 링크모션 펀치프레스의 다이나믹 언발란스를 저감하는 효과적인 방법을 제시한다. 그리고 디자인 변화가 필요할 때마다 메커니즘의 모델 구성을 자동화하기 위한 디자인 변수 방식을 소개한다. 질량, 질량관성모멘트, 질량중심 등의 링크들의 관성 성질을 얻기 위하여 3차원 캐드 소프트웨어를 활용하였다. 메커니즘의 기구학적, 동역학적 거동에 주요한 영향을 미치는 일부 링크들의 디자인을 변화시킬 때 얻을 수 있는 다양한 조합에 대하여 동역학 시뮬레이션을 수행하였다.

• 한국소음진동공학회논문집
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• 제18권8호
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• pp.879-885
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• 2008

A rotordynamic analysis was performed with a decant-type centrifuge, which is a kind of industrial centrifuge. The system is composed of screw rotor, bowl rotor, driving motors, gear box, and support rolling element bearings. These rotors have a rated speed of 4300 rpm, and were modeled utilizing a rotordynamic FE method for analysis, which was verified through 3-D FE analysis. Design goals are to achieve wide separation margins of lateral critical speeds, and favorable unbalance responses of the rotor in the operating range. Then, a complex analysis rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds and mode shapes, whirl natural frequencies, and unbalance responses under various balance grade. As a result of analysis, the rotordynamic analysis performed by separating a screw rotor and bowl rotor may cause an error in predicting critical speed of entire system. Therefore, the rotordynamic analysis of a coupled rotor combining a screw and bowl rotor must be performed in order to more accurately estimate dynamic characteristics of the decanter-type centrifuge as presented in this paper. Also, rolling element bearings with suitable stiffness should be selected to keep enough separation margin. In addition, in establishing balance grade of a screw and bowl rotor, ISO G2.5 balance grade is more recommended than ISO G6.3, in particular balancing correction of a screw rotor based on ISO G2.5 grade is strongly recommended.

• Journal of Advanced Marine Engineering and Technology
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• 제36권8호
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• pp.1043-1049
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• 2012

다단의 기어와 이를 구동하고 지지하는 축 및 베어링으로 구성되는 슬래그 분쇄장치(Briquetting M/C) 용 감속기를 개발하기 위하여, AGMA 규격에 의한 치차의 굽힘강도와 면압강도의 해석과 케이스의 구조해석을 포함한 정적설계를 수행하고, 감속기의 불평형 질량, 기어의 맞물림 전달오차에 의한 기진력을 고려한 동적설계를 하였다. 진동해석 결과 감속기의 운전속도 범위 내에 위험속도가 없는 것을 확인하였다.