• Tribology and Lubricants
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• 제13권1호
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• pp.76-81
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• 1997

The lubrication characteristics of high-speed roller bearings at oil-starvation have been investigated empirically using the bearings employed in small industrial gas turbine engines. Testing was done by simulating the oil-starvation conditions in engines, such as stopping the oil-supply to the bearing during normal operating, starting without oil-supply at atmospheric temperature, and accelerating with oil-supply at atmospheric temperature. During testing, the temperature of bearing, the power consumption, and the rotating resistance of the bearing were measured. From this study, on the contrary to the ball bearing, it was found that the resistance of the bearing was higher at the regime of without oil-supply than that at the regime of with oil-supply, despite less power consumption.

• Tribology and Lubricants
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• 제13권1호
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• pp.70-75
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• 1997

The lubrication characteristics of high-speed ball bearings at oil-starvation have been investigated empirically using the bearings employed in small industrial gas turbine engines. For the close structural simulation, experiments carried our with bearing mounting supports of real engines, such as bearing housings and oil nozzle assemblies with squeeze film dampers. Thus the results of tests can be applied to the design and the development of gas turbine engines. Testing was done by simulating the oil-starvation conditions in engines, such as stopping the oil-supply to the bearing during normal operating, starting without oil-supply at atmospheric temperature, and accelerating with oil-supply at atmospheric temperature. From this study, the relative comparison of the frictional resistance and the resistance due to the bearing cavity oil was demonstrated visually, and the resistance due to the bearing cavity oil was dominant in the resistance of bearing at high speed.

• Tribology and Lubricants
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• 제15권3호
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• pp.233-239
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• 1999

Generally quantity of supply oil for piston ring lubrication in an internal combustion engine may be insufficient to fill the entire volume formed in the clearance between piston ring and cylinder liner. Thus oil starvation condition should be considered for the analysis of piston ring lubrication. In order to reasonably estimate amount of oil left on the cylinder liner, adequate boundary condition should be adapted for the analysis of ring pack lubrication. In this analysis of ring pack lubrication of an internal combustion engine, oil starvation and open-end boundary conditions are considered at inlet and outlet of piston rings. It is revealed that piston rings are operated under oil starvation in most operating cycle and the result with these conditions are quite different from that with fully-flooded assumption.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.232-239
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• 1999

Generally quantity of supply oil for piston ring lubrication in an internal combustion engine may be insufficient to fill the entire volume formed in the clearance between piston ring and cylinder liner. Thus oil starvation condition should be considered for the analysis of piston ring lubrication. In order to reasonably estimate amount of oil left on the cylinder liner, adequate boundary condition should be adapted for the analysis of ring pack lubrication. In this analysis of ring pack lubrication of an internal combustion engine, oil starvation and open-end boundary conditions are considered at inlet and outlet of piston rings. It is revealed that piston rings are operated under oil starvation in most operating cycle and the result with these conditions are quite different from that with fully-flooded assumption.

• Journal of Mechanical Science and Technology
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• 제14권9호
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• pp.928-934
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• 2000

This paper describes a method developed for the simulation of ring pack lubrication characteristic in an internal combustion engine. In general, the quantity of oil supply for piston ring lubrication may be insufficient in filling the entire volume formed at the interference between the piston ring and the cylinder liner. Thus the oil starvation condition should be considered in analyzing piston ring lubrication. In order to reasonably estimate the amount of oil left over on the cylinder liner, the flow rate at the posterior portion of the interface should be calculated with an adequate boundary condition that confirms flow continuity condition. In this analysis, oil starvation and open-end boundary conditions are considered at the inlet and outlet of the piston rings. The lubrication characteristic of each piston ring is obtained by an iterative method with sequential steps. It is revealed that piston rings are operated under oil starvation in most operating cycles and the result under these conditions are quite different from that with the fully-flooded assumption.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.358-364
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• 1998

Lubricational characteristics at the interface between the piston ring and the cylinder liner are considered in this paper. To verify that surface shape and operating conditions of the engine can affect the state of lubrication, the changes of the minimum film thickness and friction force are calculated with various conditions. Oil starvation and open-end boundary condition are used to determine computational boundaries as reported on previous paper for lubrication analysis for the piston ring. From this analysis, it can be found that lubricational characteristics are seriously affected by degree of oil starvation, surface shape and operating conditions.

• Tribology and Lubricants
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• 제14권3호
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• pp.51-58
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• 1998

This paper considers analysis of the lubrication between the piston ring and the cylinder liner. Piston ring lubrication analysis considering oil transport is important because oil consumption is an essential factor to design the piston assembly. To develop the lubrication analysis program for the piston ring, oil continuity condition and open-end boundary assumption are used for computational boundaries. Results show that oil continuity can be almost satisfied at any crank angle in and out of the piston ring clearance. Therefore the amount of oil consumption and the dynamic behavior of ring pack can be estimated using this algorithm. And it can be known that the effective width may be smaller than the full width of the piston ring, so oil starvation condition should be considered for the lubrication analysis of the piston ring.

• 한국양식학회지
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• 제7권1호
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• pp.63-76
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• 1994

사료의 n-3HUFA 함량이 $1.6\%$ 이상 함유되도록 조절한 3종의 실험 사료로 43g 전후의 조피볼락을 19주간 사육 실험한 후, 136g전후의 어체를 45일간 절식시켜 사료 지질원에 따른 조피볼락의 성장 및 체성분의 변화와 절식시 체내 대사를 조사하였다. 증중율, 사료 효율, 단백질 축적 효율 및 지질 축적 효율 모두 사료 지질원에 따른 유의차가 없었다$(P\geq0.05)$ 간과 등 근육의 총지질 중의 지방산은 사료 지질원의 조성비에 영향을 받아, monoene산은 우지 첨가구에, n-6계 지방산 (18:2n-6, 22:4n-6)들은 대두유 첨가구에, n-3계 지방산 (20 : 5n-3, 22 : 6n-3)들은 오징어 간유 단독 첨가구에 상대적으로 더 높게 조성되어 있었다. 전 어체 및 등 근육의 일반 성분은 실험구별로 차이가 없었으며, 간 중량비 및 내장 중량비도 차이가 없었다. 간과 내장의 수분 함량은 오징어 간유 구가 타 실험구에 비해 높았으며, 간지질 함량은 우지 첨가구가 가장 높았다. 간 중량비 및 내장 중량비는 모두 절식기간 중에 전체적으로 감소하였으며, 오징어 간유 구가 타 실험구에 비해 그 감소폭이 컸다. 절식 15일까지는 근육 단백질과 지질이 감소하였고, 그 후부터는 간의 글리코겐 함량이 감소하였으며, 내장 지질은 절식 기간 중 계속 감소하는 현상을 보여 절식 중에 이용되는 에너지원의 형태와 시기가 다르게 나타났다. 혈청 성분은 지질원에 따라 절식 기간별로 이동되는 형태가 약간 다르게 나타나기는 하였으나, 절식 기간이 길어짐에 따라 점차 그 차이는 없었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.244-251
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• 1998

This paper presents case studies on the oil related failures in automotive engines. In this study, engine oils play an important roles as a friction reducing matehals and should be supplied to a tribological machine elements sufficiently. The starvation or depletion of a lubricant may seriously produce the tribological failures on the rubbing parts of the engine.

• 신재생에너지
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• 제19권4호
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• pp.27-34
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• 2023

In this study, microalgal oil was extracted from Nannochloropsis oceanica cultured in an open raceway pond and converted into biodiesel using a solid acid catalyst. Microalgal oil was extracted from two types of microalgae with and without nitrogen starvation using the KOH-solvent extraction method and the fatty acid content and oil extraction yield from each microalgae were compared. The fatty acid content of N. oceanica was 184.8 mg/g cell under basic conditions, and the oil content increased to 340.1 mg/g under nitrogen starvation conditions. Oil extraction yields were 90.8 and 95.4% in the first extraction, and increased to 97.5 and 98.8% after the second extraction. Microalgal oil extracted by KOH-solvent extraction was yellow in color and had reduced viscosity due to chlorophyll removal. In biodiesel conversion using the catalyst SO₄^2-/HZSM-5, solvent-extracted oil showed a FAME content of 4.8%, while KOH-solvent-extracted oil showed a FAME content of 90.4%. Solid acid catalyst application has been made easier by removal of chlorophyll from microalgal oil. The FAME content increased to 96.6% upon distillation, and the oxidation stability increased to 11.07 h with addition of rapeseed biodiesel and 1,000 ppm butylated hydroxyanisole.