저널 오정렬 및 수막두께의 축방향 단계변화의 복합영향을 고려한 수직펌프용 유체동압 저널베어링의 하중지지력 변화에 관한 연구

최문호 한국기계기술학회 2020 한국기계기술학회지 Vol.22 No.4

Load carrying capacity(LCC) can be reduced from its design value as a result of film thickness change when a journal is misaligned and some part of bearing is unintentionally translated. In this study, the numerical solution of the incompressible Reynolds equation was obtained by using the finite difference method and mass conservation algorithm (JFO boundary condition) with periodic pressure distribution in circumferential direction to analyze the change of LCC due to journal misalignment and step change of film thickness in axial direction for a journal bearing of vertical pumps. Smallest LCC in each eccentricity ratio is obtained as two angular positions are changed – an angular position where misalignment occurs, and another angular position where the axial step takes place while the degree of misalignment is fixed at 90%. Compared with the reaction force of plain journal bearing, the LCC reduced as much as 26.7% due to geometric effects of journal bearing at the eccentricity ratio of 0.9, while the step height is no higher than 0.1 times of bearing clearance.

〈기술논문〉 저널베어링 정비최적화를 통한 터빈설비 신뢰도 향상

이혁순(Hyuk Soon Lee),이병학,김오근 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

Turbine journal bearings are designed to support the weight of the rotors on a hydrodynamic oil film and to provide dynamic stability to the rotor system. The life time of journal bearings is infinite theoretically because the journal bearings are separated from the shaft journal by oil film. But poor design, assembly and operation can cause problems to the journal bearings. The FMEA results of the journal bearings refer that often maintenance of the journal bearings can cause failures and reduction of the bearing life. So, to maintain optimum bearing condition, it is necessary to provide a sufficient flow of clean oil to each bearing and optimize the journal bearings maintenance frequency.

타원형 저널베어링에 관한 실험적 연구

강병연(Byeong-Yeon Kang),류재몽(Jae-Mong Ryu),조영천(Young-Cheon Jo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.6

본 논문에서는 타원형 저널베어링의 안정성 향상을 목적으로 대칭 및 비대칭 오일 홈을 갖는 타원형 저널베어링의 운전특성을 연구하였다. 베어링은 운전 시 회전체와의 마찰력에 의해 금속온도가 상승하게 되며, 온도가 과도하게 상승하면 열적 피로를 유발하게 된다. 이러한 이유로 열적 피로는 저널베어링의 내구성에 큰 영향을 미치게 된다. 베어링의 열적 피로 예방과 안정성 향상을 위해 화이트 메탈의 두께가 얇고 간극비가 최적화 된 비대칭 오일 흠을 갖는 타원형 저널베어링을 개발하여, 실험을 통해 최대 금속온도가 2~3℃ 감소되는 결과를 도출하였고, 해석을 통해 실험 결과의 신뢰성을 확인하고 개선된 베어링의 운전특성이 향상되는 것을 확인하였다. This study has investigated operational characteristics of elliptical journal bearing with symmetrical and asymmetrical oil grooves. When the steam turbine is operated, metal temperature of bearing is increased due to friction force. Due to its intrinsic feature, the durability of journal bearing strongly depends on trends of thermal fatigue. To solve these problems, the bearing design improvements are needed. So it is suggested that the elliptical journal bearing includes the following features, thin white metal, optimum clearance and asymmetrical oil grooves. From the analysis of experimental results, it is concluded, advanced bearings(model A and model B) with thin white metal and without dovetails have increased yield strength and heat-resistance characteristics of white metal. By optimum clearance, maximum metal temperature decreases about 2~3℃ and then prevents thermal fatigue failure. Especially, advanced bearing with asymmetrical oil grooves is excellent for static and dynamic characteristics.

터보 컴프레셔용 복합재료 틸팅 패드 저널 베어링의 오일 공급 중단 상황에서의 내구성 연구

최강영 ( Kang-yeong Choe ),정민혜 ( Min-hye Jung ),유준일 ( Jun-il You ),송승아 ( Seung-a Song ),김성수 ( Seong-su Kim ) 한국복합재료학회 2016 Composites research Vol.29 No.3

터보/컴프레셔(Turbo compressor)용 틸팅 패드 저널 베어링(Tilting pad journal bearing)은 고속, 고하중의 주축(Rotor)을 지지하는 역할을 하며, 화이트 메탈(White metal)이 대표적인 소재로 널리 사용되어왔다. 그러나 예기치 않은 윤활유 공급 중단 상황(Oil cut situation) 또는 베어링과 주축 사이에 유막(Oil film)이 제대로 형성되지 않을 경우, 기존의 화이트 메탈 베어링은 융착(Seizure) 현상에 의해 바로 정지하게 되고 주축에 심각한 손상을 유발한다. 이러한 융착 문제를 해결하기 위해 기존의 화이트 메탈에 비해 높은 비강성, 비강도 그리고 뛰어난 마찰 특성(Tribological characteristic)을 가지는 탄소섬유 강화 복합재료(Carbon fiber reinforced composite)가 틸팅 패드 저널 베어링에 사용될 수 있다. 본 연구에서는 고 내열성 탄소섬유/에폭시 복합재료 틸팅 패드 저널 베어링의 오일공급 중단 상황에서의 내구성에 대한 연구를 진행하였다. 이를 위해 상온 및 오일공급 중단상황의 고온에서 인장, 압축, 전단 등의 기초적인 복합재료 물성 실험을 진행하였고, 복합재료 틸팅 패드 저널 베어링에 있어 가장 중요한 물성인 층간 계면 강도를 측정하기 위해 Short Beam Shear 실험을 진행 하였다. 오일 공급 중단 상황에서 복합재료 틸팅 패드 저널 베어링의 파손(Failure) 가능성을 알아보기 위해 유한 요소 해석(Finite element analysis)을 진행함으로써 베어링 표면에 가해지는 최대 응력을 도출하였고, 해석 결과와 물성 시험으로부터 측정된 강도 값을 이용하여 Tsai-Wu Failure index를 계산하였다. 해석 결과를 검증하기 위해 산업용 테스트 벤치를 이용하여 탄소섬유/에폭시 복합재료로 제조된 틸팅 패드 저널 베어링의 오일 공급 중단 실험을 진행하였다. The tilting pad journal bearing for the turbo compressor application has a role to support high speed and heavy loading rotor. White metal has been widely used for the bearing material but the conventional bearing is immediately suspended and induces serious serious damage to the rotor under the unexpected oil cut situation or the insufficient oil film formation. The carbon fiber reinforced composite having high specific stiffness, specific strength and excellent tribological characteristics can solve these seizure problems. In this work, the study on the durability of high thermal resistance carbon fiber/epoxy composite tilting pad journal bearing under oil cut situation was conducted. The material properties of the composite materials including tensile, compressive and interlaminar properties were measured at room and high temperature of oil cut situation. To investigate the possibility of failure of composite tilting pad journal bearing under oil cut situation, the stress distribution of the composite bearing was analyzed via finite element analysis and the Tsai-Wu Failure index was calculated. To verify the failure analysis results, the oil cut tests for the composite tilting pad journal bearing were conducted using industrial test bench.

저널베어링의 이상상태 진단을 위한 데이텀 효용성 평가

전병철(Byungchul Jeon),정준하(Joonha Jung),윤병동(Byeng D. Youn),김연환(Yeon-Whan Kim),배용채(Yong-Chae Bae) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.8

저널베어링은 회전하는 축과 베어링 지지부 사이에 유막을 형성하여 회전체를 지지하는 구조물이며, 고속 및 고하중 조건에서도 안정적이기 때문에 발전소와 같은 대형 시스템에 널리 사용되고 있다. 본 연구에서는 저널베어링 시스템의 신뢰성을 확보하기 위한 감독학습 기반의 상태진단 알고리즘을 연구하였다. 기존에는 진동신호 특성인자들의 정의에 대한 연구가 주로 진행되었으나, 본 연구에서는 정의된 특성인자의 추출단위인 데이텀의 적용 기준에 대한 연구가 수행되었다. 데이텀의 효용성 평가를 통해 저널베어링 회전체 특성인자의 추출기준은 시간영역에서 1 회전, 주파수영역에서 60 회전 기준이 타당하다는 결론을 도출하였다. Journal bearings support rotors using fluid film between the rotor and the stator. Generally, journal bearings are used in large rotor systems such as turbines in a power plant, because even in high-speed and load conditions, journal bearing systems run in a stable condition. To enhance the reliability of journal-bearing systems, in this paper, we study health-diagnosis algorithms that are based on the supervised learning method. Specifically, this paper focused on defining the unit of features, while other previous papers have focused on defining various features of vibration signals. We evaluate the features of various lengths or units on the separable ability basis. From our results, we find that one cycle datum in the time-domain and 60 cycle datum in the frequency domain are the optimal datum units for real-time journal-bearing diagnosis systems.

프로세스 압축기 틸팅패드 저널베어링의 비정상 고온거동 트러블슈팅

이안성(An Sung Lee),이운실(Woonsil Lee),최동훈(Dong-Hoon Choi) 한국트라이볼로지학회 2017 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.33 No.2

A DE-side LBP tilting pad journal bearing of a 1-stage overhung heat-pump compressor in a propylene process exhibited abnormal high-temperature behavior. Its temperature had been relatively high at 78 °C from the beginning of operation. In 2014, after three years of operation, it increased suddenly and reached 103 °C. Installing a varnish removal equipment and others managed to stabilize the temperature at 95 °C. We undertook a troubleshooting approach for reviewing the comprehensive status and integrity of the temperature design of the bearing. We performed lubrication and heat-balance analysis, based on the design engineering data and documents supplied by the OEM. For the base design data of DE-side TPJB, evaluating the effects of key design variables on bearing metal temperature showed that firstly, increasing the bearing clearance and supply oil flow-rate, and next, changing the oil type, and finally, increasing the machined pad clearance and offset, are more effective in reducing the bearing metal temperature. Furthermore, a clarification meeting with the OEM revealed that an incorrect decision had been made to decrease the bearing clearance to eliminate the SSV harshness issue, while not maintaining a sufficient oil flow-rate. We conducted a detailed retrofit design analysis, wherein we increased the oil flow-rate and bearing clearance by decreasing the preload. We predicted that the bearing temperature would decrease to 63 °C from 75.7 °C even at the rerate condition. Finally, after installing and operating a retrofit replacement bearing in 2015, the bearing temperature stabilized at a low temperature of 65 °C. Currently (January. 2017), two year later, the bearing metal temperature remains at 65 °C. Therefore, we can conclude that the abnormal high-temperature behavior of the bearing has been resolved completely.

열변형으로 인한 틸팅패드 저널베어링의 예압 변화

서준호(Junho Suh),황철호(Cheolho Hwang) 한국트라이볼로지학회 2016 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.32 No.1

This paper focuses on the thermal deformation induced preload change in the tilting pad journal bearing, using a three-dimensional (3D) thermo-hydro-dynamic (THD) approach. Preload is considered as a critical factor in designing the tilting pad journal bearing. The initial preload measured under nil external load and nil thermal gradient is influenced by two factors, namely, the thermal deformation and elastic deformation. Thermal deformation is due to a temperature distribution in the bearing pads, whereas the elastic deformation is due to fluid forces acting on the pads. This study focuses on the changes induced in preload and film clearance due to thermal deformation. The generalized Reynolds equation is used to evaluate the force of the fluid and the 3D energy equation is used to calculate the temperature of the lubricant. The abovementioned equations are combined by establishing a relationship between viscosity and temperature. The heat transfer within the bearing pads, the lubricant, and the spinning journal is calculated using the heat flux boundary condition. The 3D Finite Element Method (FEM) is used in modeling the (1) heat conduction in the spinning journal and bearing pads, (2) thermal gradient induced thermal distortion of the spinning journal and pads, and (3) viscous shearing, and heat conduction and convection in a thin film. This evaluation method has an increased fidelity, and it can prove to be a cost-effective tool that can be used by designers to predict the dynamic behavior of a bearing.

경사조건을 고려한 대용량 추진 전동기용 베어링 개발에 대한 연구

오승태(Seung Tae Oh),최진우(Jin Woo Choi),강병희(Byeng Hi Kang),김진(Jin Kim),최성필(Seong Pil Choi),빈재구(Jae Goo Bin) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.2

본 논문에서는 상용 회전체 동역학 해석 툴을 이용하여 경사 운전조건을 고려한 대용량 추진 전동기용 베어링 개발에 상사적 설계 방법과 실험적 방법을 적용하였다. 개발된 베어링은 전기적으로 절연이 되어있으며 각 연결부는 2~4mm 의 에폭시 절연판을 연결하여 낮은 열전도 특성을 가지도록 하였다. 본 연구에서는 기존의 저속운전에서 야기되는 베어링 손상 문제를 해결하기 위해 원활한 유막이 생성될 수 있도록 고안한 정압 윤활장치를 적용하여 우수한 윤활특성을 확보하였다. 또한 대형 중량물에 대한 유지보수를 고려하여 반분할 방식의 조립구조를 적용하였다. 본 논문은 고부하, 저속 운전의 추진 전동기 분야에 사용되는 미끄럼 베어링의 주요 핵심설계요소를 언급하였다. 게다가, 시험벤치상에서 다양한 경사조건을 통해 실링부의 오일누유 현상을 확인하였다. In this study, bearings were developed for a high-power propulsion motor operating in inclined operation conditions through a simulation and similitude-experimental methods using commercial rotating machinery dynamics analysis software. The developed journal bearing is electrically insulated and has low thermal conductivity because each part is connected with 2-4 -mm-thick epoxy plates. To realize an appropriate oil thickness, an oil lift system is adopted, and a half separated structure is applied to ensure the feasibility of maintaining very heavy components. This study discusses some of the key design aspects of sleeve bearing design for high-torque and low-speed propulsion motor applications. Furthermore, the conditions of variable slope tests are examined to prevent oil leakage from the bearing lip seal on the test rig.

Two roller machine을 이용한 저널베어링 윤활시험기 개발

이상돈(Sangdon Lee),김명환(Myounghwan Kim),김태완(Taewan Kim),조용주(Yongjoo Cho) 한국트라이볼로지학회 2008 한국트라이볼로지학회 학술대회 Vol.2008 No.6

In a scuffing failure of a journal and a bearing, we needs an analysis of mechanism and technology of failure prediction because serious situations could be caused by scuffing failure. Accordingly, as constructing the rig of journals and bearings, we are going to get data by using it in a scuffing experiment and the various experiments of journal and bearing. In this study, methods for using the pull-up resistor and the contact resistor concept were introduced as the monitoring technology.

저널베어링의 윤활상태 판별 기법에 관한 연구

김명환(MyungHwan Kim),이상돈(SangDon Lee),조용주(YongJoo Cho) 한국트라이볼로지학회 2009 한국윤활학회지(윤활학회지) Vol.25 No.1

A journal bearing is used in a hydrodynamic lubrication state, but it becomes a boundary lubrication state that asperity of a contact part touch each other when pressure is too high and an enough oil film is not formed by viscosity change due to lubricating oil temperature. At this time, abrasion due to contact between a journal and a bearing is unavoidable, and scuffing damage that the journal adheres to the bearing occurs if the process is repeated. Damage of the journal bearing is an important problem because it gives huge damage to a machine and can generate large accidents such as economic loss and human life damage. In this study, method for using the pull-up resistor concept was introduced as the monitoring technology. This monitoring system is important to enhance reliability of the engine.