• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.201-211
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• 2001

The influence of aerated oil on high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of aerated oil in fluid-film bearing. Convection to the walls, mixing with supply oil and re-circulating oil, and some degree of journal misalignment are considered. The considered Parameters for the study of bubbly lubrication are oil aeration level, air bubble size, shaft misalignment and shaft speed. The results show that deliberate oil aeration can more clearly bring on the increasing load capacity under high-speed operation of plain journal hearing than previous normal speed operation. And the load capacity may be increased more by oil aeration under the conditions of shaft misalignment and the increasing speed.

• 환경정책연구
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• 제14권2호
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• pp.133-148
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• 2015

폐유의 발생량에 비해 폐유 정제업체수가 크게 증가하여 폐유의 물량이 부족하고, 수거경쟁으로 인해 과도한 비용이 투입되고 있으며, 질이 나쁜 폐유를 함께 수거해 정제하고 있어 환경오염의 가능성이 높다. 과도한 비용으로 인한 정제유의 가격 상승은 소비자에게 부담을 주고 있다. 이러한 상황을 해결하기 위해 폐유 재활용 활성화 방안을 제시하였다. 재활용 활성화 방안 첫 번째로 부족한 폐유 물량 확보를 위한 폐유 수입은 선진국으로부터 가능하다. 수입국의 국제공인기관에서 품질검사를 실시한 후 국내에 반입 시 석유품질관리원에서 이중으로 검사를 실시하여야 하여 철저한 관리가 필요하다. 폐유 정제 비용 중 큰 비율을 차지하는 수분 및 침전물 품질기준의 완화를 고려하였으나, 이 경우 침전물의 함량이 높아져 환경적으로 문제가 될 수 있기 때문에, 영향이 적은 수분을 따로 측정하여 기준을 완화하고 침전물의 기준은 2%로 유지하였다. 마지막으로 폐유를 난방기 연료로 사용하는 경우가 있어 환경오염의 가능성이 있으며, 적절한 관리가 요구된다. 폐유난방기 사용은 품질이 우수한 자동차용 폐윤활유를 연료로 사용하고, 대기오염방지장치가 포함되어 있다면 사용가능하다. 폐기물 발생자 처리원칙에 부합되고, 품질이 우수한 폐유를 수거과정과 처리과정을 통해 투입되는 비용을 절감할 수 있다.

• KSTLE International Journal
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• 제7권2호
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• pp.35-44
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• 2006

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure, then the friction and load of journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• Tribology and Lubricants
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• 제23권5호
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• pp.207-218
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• 2007

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure distribution, then the friction in a journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• 펄프종이기술
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• 제46권1호
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• pp.18-28
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• 2014

Renewable Portfolio Standards(RPS) is a regulation that requires a renewable energy generated from eco-friendly energy sources such as biomass, wind, solar, and geothermal. The RPS mechanism generally is an obligatory policy that places on electricity supply companies to produce a designated fraction of their electricity from renewable energies. The domestic companies to supply electricity largely rely on wood pellets in order to implement the RPS in spite of undesirable situation of lack of wood resources in Korea. This means that the electricity supply companies in Korea must explore new biomass as an alternative to wood. Palm kernel shell (PKS) and empty fruit bunch (EFB) as oil palm wastes can be used as raw materials used for making pellets after their thermochemical treatment like torrefaction. Torrefaction is a pretreatment process which serves to improve the properties including heating value and energy densification of these oil palm wastes through a mild pyrolysis at temperature typically ranging between 200 and $300^{\circ}C$ in the absence of oxygen under atmospheric pressure. Torrefaction of oil palms wastes at above $200^{\circ}C$ contributed to the increase of fixed carbon with the decrease of volatile matters, leading to the improvement of their calorific values over 20.9 MJ/kg (=5,000 kcal/kg) up to 25.1 MJ/kg (=6,000 kcal/kg). In particular, EFB sensitively responded to torrefaction because of its physical properties like fiber bundles, compared to PKS and hardwood chips. In conclusion, torrefaction treatment of PKS and EFB can greatly contribute to the implement of RPS of the electricity supply companies in Korea through the increased co-firing biomass with coal.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.111-112
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• 2002

The influence of aerated oil on a high-speed proceeding bearing is examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing including the live surface tension of aerated oil. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil aeration level, air bubble size and shaft speed. The results show that, if the live surface tension is considered, the effect of air bubbles on the bearing load capacity is reduced due to temperature engagement comparing with that under the condition of a constant surface tension.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.24-27
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• 2002

The environmental problems by using coolant demanded the new cooling methods. As one of them, the studies on the finding with compressed cold air and oil mist have been done. The cooling method using compressed cold air was effective through going down the temperature of compressed air supplied below $-25^{\circ}$ and increasing the amount of compressed cold air, but had not enough cooling effect due to the low performance of lubrication. Therefore, the cooling methods using oil mist newly were suggested. This method can satisfy both cooling effect and lubrication with only small amount of coolant, also have the benefit in the point of decreasing the environmental pollution. This paper focused on analyzing the grinding characteristics of the cooling method using oil mist. The grinding test according to compressed cold air, oil mist spray pressure and oil mist supply direction were done.

• 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.

• Tribology and Lubricants
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• 제17권4호
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• pp.321-334
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• 2001

The influence of aerated oil on high-speed journal bearing Is examined by thermohydrodynamic lubrication theory to lubrication with mixtures of a Newtonian liquid and an ideal gas. For this purpose, analytical models for viscosity and density of aerated oil in fluid-film bearing are applied. Convection to the walls, mixing with supply oil and re-circulating oil, and some degree of journal misalignment are considered. The results show that deliberate oil aeration can increase the load capacity of high-speed plain Journal bearing. And the load capacity is increased more by oil aeration under the conditions of shaft misalignment and higher speed.

• 한국지하수토양환경학회지:지하수토양환경
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• 제8권1호
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• pp.75-80
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• 2003

해수 중에는 연안 조간대의 저서생물의 생존에 필수적인 용존산소와 영양염이 풍부하게 내포되어 있기 때문에 해수의 토양침투는 저서생물의 생존과 밀접한 관련을 맺고 있다. 그러나 유출된 기름이 조간대에 표착하게 되면 해수의 침투가 차단되어 생물에게 많은 피해를 유발시킬 것이다. 또한 유출된 기름의 토양 침투에 관한 정보는 생태계 영향을 최소화하고 처리를 위한 대책수립의 단서로서 매우 중요하다. 본 연구에서는 유출된 기름의 침투 거동을 파악하고 침투된 기름의 해수 침투 차단을 검토하는 것을 목적으로 하여 연구를 수행하였다. 점도가 낮은 원유가 C중유보다 침투 깊이가 약 2배 깊었으며, 유출된 기름의 침투 깊이는 조간대에 표착된 기름의 양에 따라 영향을 받는 것을 알 수 있었다. 그리고 표착된 기름은 첫번째 조석에서 가장 급격한 침투거동을 보였으나, 두번째 조석변동부터는 급격한 침투 변화는 나타나지 않았다. 그리고 침투한 유분의 수직적 분포로부터 기름은 토양 표층 2cm에 집중적으로 분포하는 것을 알 수 있었다. 한편 해수의 침투량은 표착유의 양에 비례적으로 감소하였으며, C중유가 원유보다 약 1.7배 정도의 해수의 토양 침투량을 감소시키는 것을 알 수 있었다. 따라서, 침투한 기름의 처리는 가능한 빠른 시간내에 수행되어야 해수의 침투를 회복시켜 연안 조간대 생태계의 피해를 최소화 시킬 수 있다고 판단된다.