• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.271-276
• /
• 2006

This paper shows the rotordynamic characteristics of a turbo-generator for a BOP of a fuel cell system. The rotor-bearing system consists of magnetic shaft and compressor-turbine shaft, and the two shafts are connected by spline coupling and supported by oil free air foil bearing. Preliminary design according to several parameter is considered in detail. Static and dynamic characteristics of the AFB are estimated by the soft elasto-hydrodynamic analysis technique and the perturbation method. The results of the natural frequencies, mode shape, and unbalance response analysis are presented.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
• /
• pp.272-277
• /
• 1997

The axial bearing using two ring type permanent magnets to support the weight of a flywheel is proposed to reduce the bearing loss in a flywheel energy storage , system. Two permanent magnet makes stable force in axial direction but unstable force in lateral direction. The lateral unstable stiffness is identified quantitatively using flux analysis, and then through the rotor dynamic analysis on a rigid flywheel system the unstable effects on the system by the stiffness is investigated.

• 소음진동
• /
• 제5권2호
• /
• pp.235-246
• /
• 1995

Experiment on the modal balancing of a flexible rotor supported on two kinds of fluid film bearings is performed to verify the modal balancing theory. The fluid film bearings are a tilting pad bearing and a two axial grooved journal bearing. One is inherently stable, but the other is not. The experimental result shows that the modal balancing method is effective for balancing of a high speed flexible rotor system. Besides, the critical speeds and mode shapes measured experimentally are in good coincidence with the results of rotordynamic analysis. Oil whip, which is the instability phenomenon due to fluid film force, is also observed during the experiment.

• 한국기계가공학회지
• /
• 제5권3호
• /
• pp.92-98
• /
• 2006

In this study, the behavior characteristics of a hydrostatic thrust bearing used in hydraulic equipment was analyzed using a commercial finite element program, ADINA. The solid domain was modeled with the fluid domain simultaneously to solve the fully coupled problem, because this is a problem where a fully coupled analysis is needed in order to model the fluid-structure interaction(FSI). The results such as bearing deformation, stress, film thickness and lifting bearing force were obtained through FSI analysis, and then they were compared with the results calculated from the classical method, a single step sequential analysis. It was found that the result difference between two analyses was increased according to the injection pressure. Therefore, in case of high pressure loading, it is desirable to conduct the FSI analysis to examine the deformation characteristics of a hydrostatic slipper bearing.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
• /
• pp.662-667
• /
• 2003

This paper presents a performance analysis of the 1st generation bump foil journal bearings for the micro gas turbine TG75. Static performances such as load capacity and attitude angle are estimated by using soft elasto-hydrodynamic analysis technique, and dynamic performances such as stiffness and damping coefficients are estimated by perturbation method. Rotordynamic analysis for TG75 is performed by using the bearing analysis results. TG75 rotor has 2 horizontal and vertical directional natural modes due to the bearing stiffness characteristics. TG75 rotor will be stably operated between the 1st bending mode at 33000cpm and the 2nd bending mode at 85500cpm. Unbalance response analysis results satisfy the API vibration criteria.

• 한국정밀공학회지
• /
• 제15권11호
• /
• pp.218-226
• /
• 1998

In this study a neural network based expert system designed to diagnose operating status of a rotating spindle system supported by ball bearings was introduced. In order to facilitate practical failure situations, five exemplary abnormal status was fabricated. Out of several possible data source locations, seven most effective spots were chosen and proven to be the most successful in predicting single and multiple abnormalities. Increased signal strength was measured around where abnormality was embedded. Signal mea-surement locations producing high prediction rate were also classified. Even though multiple abnormalities were hard to be decoupled into their individual causes, proposed diagnostic system was somewhat effective in predicting such cases under certain combination of sensor locations. Among several abnormal operating conditions, highest prediction rate can be expected when signal is spoiled by the failure or damage in outer race. Proposed diagnostic system was again proven to be the most effective system in analyzing and ranking the importance of data sources.

• 한국소음진동공학회논문집
• /
• 제12권12호
• /
• pp.929-934
• /
• 2002

This paper considers the vibration Problem of vehicle driveline which consists of two propeller shafts and the center bearing. The excessive vibration occurs at the center bearing when the vehicle starts to run. Using the kinematic constraints at the universal joint between two propeller shafts, we developed an one d.o.f model which describes the radial motion of the center bearing. We found out that the vibration occurs at the specific vehicle speed corresponding to the natural frequency of the model. Comparing the simulation results with test results we also show that the vibration at low vehicle speed is caused primarily by the feint angle and secondarily by the mis-aligned yoke flange rather than by the unbalance.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 추계학술대회논문집 II
• /
• pp.1026-1031
• /
• 2001

In this paper. the dynamic characteristics of a super high-speed tilting-pad air bearing(TPGB) used in a turbo expander with high expansion ratio are analyzed. The dynamic behavior and stability of a rotary system supported by two journal air bearings are investigated numerically. The transient response of the shaft is obtained by simultaneously solving the equation of motion of the shaft and the dynamic Reynolds equation. The stiffness and damping coefficients of the bearing are calculated from the loading coefficients of the bearing are calculated from the loading capacity. shaft velocity and displacement by using a curve fitting method. The natural frequencies of the 1st and 2nd rigid modes can be calculated from these coefficients. The theoretical method of a rigid rotor system is verified by experimentsut.

• 한국산학기술학회논문지
• /
• 제18권12호
• /
• pp.106-111
• /
• 2017

본 연구에서는 해양구조물의 상부(top side) 구조물을 설치할 때 필요한 장치인 LMU(Leg Mating Unit)의 강성을 구조해석을 통하여 검토하였다. 이것은 구조물의 지지 점에 장착되어 설치 시 충격을 흡수하고 안정적으로 구조물을 지지하는 데 사용된다. LMU는 가운데가 비어있는 원통형 구조로서 수직 하중을 지지하기 위해서 일래스토머릭 베어링(Elastomeric Bearing, 이하 EB)과 철판을 여러 층으로 적층한다. EB의 강성은 기본적으로 베어링의 크기에 영향을 받지만, 동일한 크기에서도 내부 보강판의 적층 수에 따라 강성이 변하게 된다. 일반적으로 보강판과 압축 강성 사이의 관계를 분석하여 적합한 설계를 한다. EB의 강성은 변위를 제어하면서 반력을 산출하는 방식으로 분석을 한다. 먼저 보강판의 크기와 압축 강성 관계를 검토하고, 보강판의 적층 수와 압축 강성 관계를 검토한다. LMU는 장착되는 지점마다 다른 하중이 요구된다. 해석을 통해 각 지점에서 동일한 변형이 발생하도록 압축 강성을 다르게 설계하는 것이 목표이다. 본 연구의 유한요소해석을 위하여 상용 프로그램인 ANSYS를 이용하였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.96-96
• /
• 2012

복합분자펌프는 기존의 터보분자펌프 turbine blade에 spiral grooved를 추가하여 초고진공(10-8Pa)에서 저진공(330Pa)까지 넓은 압력범위에서 사용할 수 있고 이 펌프를 사용함으로서 완전 oil free한 진공시스템을 만들 수 있는 특징을 가지고 있다. 특히, 회전체를 비접촉으로 지지하는 자기베어링 방식을 적용함으로써, 진동은 극히 작고 베어링수명은 길면서 중저진공에 대한 배기속도가 크고 임의의 방향으로 접속이 가능하여 반도체 및 디스플레이 제조 공정과 같은 첨단산업의 다양한 분야에 쉽게 적용되고 있으며, 그 적용 분야와 시장은 계속 성장하고 있다. 고 진공과 배기 속도의 달성을 위해서, 고속으로 이동하는 격면과 기체분자를 충돌시켜, 기체 분자를 원하는 방향으로 유도하는 작동원리를 가지고 있다. 특히 공기분자의 밀도가 매우 낮은 희박가스 상태에서 고속 회전하는 blade로 공기분자를 쳐내면서 작동됨으로써 날개의 상하 압력차에 의한 공기력보다도 날개의 고속회전이 매우 중요시되고 압력으로는 10-1 Pa 이하의 분자영역에서 그 성능을 최고로 발휘할 수 있다. 이러한 복합 펌프의 주요 장점은 다음과 같다. 1. 10-8 Pa (10-10 torr) ~ 10 Pa (1 torr) 까지 넓은 영역에서 배기가 가능하다. 2. 탄화수계의 대하여 높은 압축특성을 가지고 있고, 윤활유를 사용하지 않으므로 얻을 수 있는 진공상태가 고청정하다(oil free). 3. 정밀 5축제어 자기베어링으로 완전히 부상하여 회전함으로서 마모가 없고 진동이 최소화하였을 뿐 만 아니라, 또한 운전음도 거의 없다. 4. 설치조건에 제한이 없고 고장이 거의 없다. 특히 복합분자펌프는 탄화수소화합물이 없는 진공을 생성시키면서 구성요소가 간단한 반면 폭넓은 진공대역을 충족하기 때문에 산업계와 연구계의 주요 첨단 분야에서 광범위하게 사용되고 있으며, 최근 반도체 및 디스플레이, 바이오엔지니어링 등의 발전으로 적용분야가 넓어지고 있다.