• 대한기계학회논문집
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• 제7권4호
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• pp.469-476
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• 1983

The effects of oil supply conditions on the static and dynamic properties of journal bearings supporting high speed rotors were investigated. The initially unknown hydrostatic pressure in oil pockets were determined by iteration with the aid of the equation of oil flow balance for given oil supply pressure and flow coefficients of oil inlet. For the calculation of dynamic characteristics, the dynamic changes of pressure in lubricating gaps and oil pockets were linearised with a perturbation method.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.387-392
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• 2008

In order to improve the efficiency of the main transformer in a tilting train, the optimal operation of a cooling system is necessary. For the development of the optimal control algorithm of a cooling system, the mathematical model of a main transformer cooling system was developed. This includes the dynamic model of a main transformer, an oil pump, an oil cooler and a blower. The system algorithm of a cooling system, which consists of the temperature setpoint algorithm and the temperature control algorithm, was developed. Optimal oil temperatures of the inlet and the outlet of the main transformer were obtained by considering the total electric power consumption of the system. The oil inlet temperature was controlled by the blower and the oil outlet temperature was controlled by the oil pump. A simulation program was developed by using the mathematical model and the system algorithm. Simulation results showed that the system algorithm developed from this study may be effectively used to control the main transformer cooling system in a tilting train.

• Tribology and Lubricants
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• 제13권2호
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• pp.46-51
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• 1997

Crosshead bearings in two-stroke marine diesel engines are operated under severe conditions of lubrication because the load on the bearing is unidirectional and the sliding speed is very low and oscillatory. In this paper, the motion of journal in a bearing is investigated using the lubrication theory. Several locus paths are presented to show the effects of oil groove size, bearing clearance and oil inlet pressure. It is found that the minimum film thickness is affected by the oil groove and bearing clearance, and the oil groove is an important design factor.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2179-2186
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• 2005

The lubrication modes of line contact between the vane and the camring in an oil hydraulic vane pump have been investigated. First, variations of the radial acting force of a vane were calculated from previously measured results of the dynamic internal pressure in four chambers surrounding a vane. Next, distinctions of the lubrication modes were made using Hooke's chart, which represents an improvement over Johnson's chart. Finally, the influence of boundary conditions in the lubrication region on fluid film lubrication was examined by calculating film pressure distributions. The results show that the lubrication modes of the vane tip are a rigid-variable viscosity region. This region discharges pressure higher than 7 MPa, and exerts a great influence on oil film pressure in the large arc section due to the Piezo-viscous effect.

• 한국기계가공학회지
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• 제20권10호
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• pp.56-62
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• 2021

In this study, a cavitation occurrence in a piston-pump inlet was investigated by simulating the pressure distribution, according to the inlet shape of a variable-displacement swash-plate piston pump that supplies high-pressure oil to control the hydraulic system of a marine engine. Two types of pump inlets with different shapes were cast into impression models, and the models were reverse-engineered by 3D scanning. Then, the hydraulic-pressure distribution was analyzed through finite-element analysis. The results of the analysis confirmed that cavitation occurs more easily in the inlet with a steeper slope during pump operation because the inlet pressure on the valve plate is lower than that of the other pump with a gentler inlet slope.

• 설비공학논문집
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• 제27권3호
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• pp.146-151
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• 2015

The heat transfer performance of heating medium oil fluidized bed heat exchanger was measured. The operation variables were air flow rate, air inlet temperature, moisture content, water flow rate and water inlet temperature. The outside heat transfer coefficient was determined from the heat exchanger experiment and its experimental correlation was determined as a function of air velocity and viscosity of heating medium oil. Effect of viscosity was well agreed with the previous studies. Errors of the correlation equation was less than about 10% for outside heat transfer coefficient developed in this study when compared with the measured value. Hot water with the temperature greater than $77^{\circ}C$ could be produced by using the heating medium oil fluidized bed heat exchanger.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1990년도 추계학술발표회논문집
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• pp.53-56
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• 1990

When oil flows and rubs against various materials in transformer, electrostatic charges are separated at the interface of the oil and the solid material. Using simplified model transformer, authors investigated the basic characteristics of the streaming electrifica-tion which is caused by forced oil circulation. As the result of the study, it was concluded that the electrostatic charge distribution on test pipe of the transformer showed larger leakage current at the inlet and the outlet.

• Tribology and Lubricants
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• 제9권2호
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• pp.22-28
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• 1993

The experimental investigation on the inlet pressure of a large tilting pad journal bearing is studied. The continuous distribution of the film pressure and film thickness are measured along with the shaft speed and bearing load for various flow rates. Considerably large inlet pressure is observed at the entrance of each pad, especially lower pads. The inlet pressure increases with the increase of shaft speed as well as bearing load, but it is almost independent on the folw rate and the oil supply temperature. Because of the inlet pressure, the upper pads always keep up slight wedge film shape which are almost parallel to the journal surface, and spragging is not observed in the upper pads with no preload.

• 설비공학논문집
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• 제15권1호
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• pp.25-31
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• 2003

This paper addresses an oil supply enhancement device to resolve a shortage of oil supply or no oil supply at all encountered at low speed operation for a variable speed reciprocating compressor used for household refrigerators. The oil supply enhancement device comprises a moving cylinder attached to the lower end of crankshaft and two of fluid diodes, each one at the inlet and outlet of the cylinder. Up-and-down movement of the cylinder against the lower end of the crankshaft together with the functioning of the two fluid diodes produces net oil flow from oil reservoir to inside the crankshaft. The experiment on the test bench has shown that enough oil supply into the oil feeding hole cu be made by using this device even at low speed range. Some analytical study has also been carried out to under-stand its oil supply mechanism.

• 한국해양환경ㆍ에너지학회지
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• 제4권2호
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• pp.52-60
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• 2001

갈수록 강화되고 있는 해양오염 기준에 맞추어 유성 빌지 배출시 포함된 기름의 함유량을 제어하기 위한 방법 중의 하나로 중력 분리 방식의 유수분리기가 개발되어왔다. 중력분리 방식 중 분리판식 유수관리기는 고비중을 가진 다량의 농후유를 처리하는데 있어서 효과적이기 때문에, 현재 IMO 기준인 15ppm에 부합하는 필터여과방식의 보완장치로서 사용이 가능하다. 이 논고의 목적은 분리판의 배열에 따른 유수분리 효율에 대해 검토하는 것이다. 유량, 유입유분농도 그리고 분리판 사이의 간격 등을 포함한 여러 가지 운용상의 변수가 있는 유성혼합물에 대한 효율적인 처리를 알아보기 위해 실험적 연구를 수행하였다. 실험결과 얻은 결론에서 격리판 사이의 간격이 분리효율에 지대한 영향을 미치고 있음을 알 수 있었고, 가장 좋은 분리 효율은 분리판과 내통 사이 간격과의 비율(H/Ci)이 2일 때 유입유분농도가 낮고 유량이 작은 경우에 얻어졌다.