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UV-Vis 분광분석에 의한 전기변압기 내 절연지 열화도 측정
공호성(Hosung Kong),한흥구(Hung-Gu Han) 한국트라이볼로지학회 2019 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.35 No.3
Insulated oil degradation produces charged by-products, such as acids and hydro-peroxides, which tend to reduce the insulating properties of the oil. In this study, UV-vis spectroscopy measurement technology is developed and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate its ability to monitor the degradation of electrical insulating paper. The degradation characteristics of the insulating paper are appropriately represented through various types of measurement methods, such as the Tan (delta) method, CO₂ gas production measurement, the titration method, and IR spectroscopy. The results are demonstrated to be well comparable to a change in the fluorescence emission ratio (FER), which is defined as the shift in fluorescence intensity in the measured wavelength range, and also to the chromatic ratio, which is defined as a color shift to longer wavelength ranges. The results also show that, by using UV-vis spectroscopy, it is possible to detect the degradation of the insulating paper. This study suggests that UV-vis spectroscopy can be applied as an alternative to high-performance liquid chromatography, which is the internationally recognized measurement technology for cellulose paper degradation. The FER detector is also verified to be useful as an effective condition-monitoring device for power transformers.
공호성(Hosung Kong),한흥구(Hung-Gu Han),김진욱(Jin Uk Kim),김경석(Kyoung Seok Kim),박종식(Jong Sik Park) 한국트라이볼로지학회 2019 한국윤활학회지(윤활학회지) Vol.35 No.2
This work aims to develop a dry lubricant for oilless bush, especially a solid lubricant, thereby creating a coating method with improved properties of anti-friction and load-carrying capacity without oil lubrication. In this work, spherical-shaped powders of thermosetting resin such as polyimide (PI) are mixed with a binder matrix obtained by mixing a fluorocarbon compound resin such as Polytetrafluoroethylene (PTFE) or Ethylene tetra fluoro ethylene (ETFE) with itself or with a non-fluorocarbon thermoplastic resin such as Polyether ether ketone (PEEK). And these dry lubricant mixtures are thickly coated (200-300 mm in the thickness) on the inner surface of the bush by using a wet-typed air-spray deposition method. It was found that the load-carrying capacity of the solid lubricant for excavator bush (60 mm in diameter) that operates under a high load condition (at 40 MPa) is greatly improved owing to the spherical-shaped powders of thermosetting resin. In addition, the coefficient of friction at the sliding surface is also reduced less than 0.1. Thick coating also lowers the contact stress at the edge of a bush that results in better tribological performances. The result suggests that the lubrication performance and durability life of the bush can be remarkably improved even without lubrication (oil or grease).
이슬점 응축 현상을 이용한 오일 내 수분함량 측정에 관한 실험적 연구
공호성(Hosung Kong),윤의성(Eui-Sung Yoon),한흥구(Hung-Gu Han),김학열(Hak Yeul Kim) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.39 No.-
Presence of water in the lubricating oils could be one of the first indicators of potentially expensive and possibly catastrophic failure of the machine as it may cause displace the oil films to prevent the lubrication function of the oil or chemically react with many oil additives resulting in the oil degradation. In order to detect water content quantitatively in lubricating oils many methods and sensors has been developed. Among these, capacitive sensors including sensitive layer, whose dielectric factor changes according to the water content absorbed in the layer, are proposed mainly in the market. But these sensors are not sensitive to a high water content. Besides, the absorbing layer soils in time. In this work. an evaporation of water moisture from oil into air volume above lubricant surface and condensation of water vapor at a cooling surface was used to measure water content quantitatively in an lubricating oil. Laboratory test results of a prototype sensor were presented. Test results showed that the proposed method could be avaliable to measure a low levels of oil moisture.
엔진 수트 측정 센서 표면에서의 흡착 오염 저감을 위한 실험적 연구 (Ⅰ)
김학열(Hak-Yal Kim),공호성(Hosung Kong),한흥구(Hung-Gu Han),윤의성(Eui-Sung Yoon),Kyung-Young Jhang 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.38 No.-
The adsorption of soot particles onto a sensor surface of the engine soot detector posses a critical problem in the measurement. In order to prevent the optical rod surface from soot contamination, various functional coatings and flow-induced cleaning were applied to the surface in this work. For surface coatings, various materials of self-assembled monolayers(SAM) such as OTS (octadecyltrichlorosilane), PFDTES (perfluorodecyltriethoxysilane) and PFDTMS (perfluorodecyltrimethoxysilane) were coated on the optical rod surface, which have different characteristics in both hydrophobicity and oleophobicity. These coatings were tested with soot content varying from 0% to 3wt% and oil temperature from 20 to 70℃. Test results showed that surface coatings were not effective for preventing the adsorption of soot particles on the surface of optical rod. It was thought that these coatings provided the surface with additional attractive surface forces. However, it was found that adsorption of soot particles onto a sensor surface was minimized by flow-induced cleaning. This effect was tested with varying the flow velocity.
엔진 수트 측정 센서 표면에서의 흡착 오명 저감을 위한 실험적 연구 (Ⅰ)
김학열(Hak-Yal Kim),공호성(Hosung Kong),한홍구(Hung-Gu Han),윤의성(Eui-Sung Yoon) 한국트라이볼로지학회 2004 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.20 No.6
The adsorption of soot particles onto a sensor surface of the engine soot detector posses a critical problem in the measurement. In order to prevent the optical rod surface from soot contamination, various functional coatings and flow-induced cleaning were applied to the surface in this work. For surface coatings, various materials of self-assembled monolayers (SAM) such as OTS (octadecyltrichlorosilane), PFDTES (perfluorodecyl-triethoxysilane) and PFDTMS (perfluorodecyltrimethoxysilane) were coated on the optical rod surface, which have different characteristics in both hydrophobicity and oleophobicity. These coatings were tested with soot content varying from 0% to 3 wt% and oil temperature from 20 to 70℃. Test results showed that surface coatings were not effective for preventing the adsorption of soot particles on the surface of optical rod. It was thought that these coatings provided the surface with additional attractive surface forces. However, it was found that adsorption of soot particles onto a sensor surface was minimized by flow-induced cleaning. This effect was tested with varying the flow velocity.