• 한국자동차공학회논문집
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• 제11권2호
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• pp.75-82
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• 2003

DME is a good alternative fuel to reduce the smoke remarkably when used in a diesel engine, while problems concerned with low lubricity and high compressibility exist. In the present study, single cylinder DI diesel engine was operated with neat DME and DME blended fuels which are DME-diesel blended fuel and DME-propane blended fuel. The results showed that the power of the neat DME and DME blended fuels was the same as that of pure diesel oil, and the specific energy consumption slightly increased. In addition, smoke emission was considerably reduced with the increase of DME content up to zero level, but NOx emission was slightly increased.

• 한국세라믹학회지
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• 제32권9호
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• pp.1027-1032
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• 1995

SiC had been widely applied for mechanical sealing as a sealing material. SiC sintering is commonly made of reaction sintering, presureless sintering, and hot isostatic pressing (HIP) sintering. In this investigation, however, clay bonded sintering was used to avoide any complications of the special sintering methods as mentioned above. In order to prevent harmful SiC oxidation in the clay bonded sintering, clay and frit were used to form the SiC oxidation protecting layer and graphite was added to provide high solid lubricity. As a result, the material with 6% clay (clay 5.4% and frit 0.6%) and 2~4% graphite (45 mesh) sintered at 140$0^{\circ}C$ for 3 hours, showed the following physical properties; porosity 6%, static friction coefficient 0.15, kinematic coefficient 0.1,. and specific wear rate 4.8$\times$10-8 $\textrm{mm}^2$kgf-1. On the other hand, the flexural strength was 900kgf/$\textrm{cm}^2$. This tribological characteristic properties were similar to those of the reaction sintered SiC except the flexural strength.

• 대한안전경영과학회지
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• 제4권2호
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• pp.237-249
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• 2002

A cutting fluid can improve machining quality and tool life by maintaining the tool toughness and by providing a lubrication effect to reduce the friction between the chip and tool interface. Although liquid nitrogen as an environmentally safe coolant has been widely recognized in cryogenic machining, its function as a lubricant is plausible due to its chemical inertness, physical volatility and low viscosity. Since a reduced friction is a direct witness of the lubrication effect from a tribological viewpoint, this paper presents an evaluation of the apparent friction coefficient on the tool-chip interface in cryogenic cutting operations to prove and characterize the lubricity of LN2 in cryogenic machining. The mathematical approaches have been formulated to derive the normal and frictional forces on the tool-chip interface for the oblique cutting tests.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2001년도 춘계학술대회 발표논문집
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• pp.91-94
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• 2001

Powder Metallurgy method have been used to fabricate TiC base composite with ferrous binder. TiC base composite has versatile hardness and is usable as sintered, or after heat treatment as required by the given applications. Smooth, round TiC grains impart high wear resistance and lubricity as well known characteristics of this composite. Annealed composite can be formed by conventional machining and be hardened up to 70 H$\_$R/C in vacuum. The optimizing fabrication process enables this composite to improve mechanical properties in heat, wear and corrosion environments. This study has examine the relationship between fabrication condition and mechanical property in TiC-Cr-Mo-Fe Composite.

• 한국응용과학기술학회지
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• 제34권4호
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• pp.866-873
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• 2017

산업이 발전함에 따라 전 세계적으로 환경오염에 대한 문제가 대두되고 있으며, 자동차 배출가스 규제도 점점 강화되고 있다. 하지만, 배출가스는 단순한 자동차만의 문제가 아닌 연료물성성분에 따른 영향도 받는 것으로 알려져 있으며, 특히, 디젤엔진의 경우 CRDI 엔진이 개발 및 상용화되면서 고성능 엔진은 고성능 연료를 필요로 하고, 그 중 대표적인 것이 연료의 윤활성으로 밝혀진바, 이에 본 연구에서는 연료물성변화가 자동차 주요부품 및 배출가스에 미치는 영향을 확인하고자 하였다. 윤활성이 취약한 연료($651{\mu}m$/품질기준 $400{\mu}m$이하)를 차량에 사용하여 고압펌프 및 인젝터, 매연저감장치 등의 파손이 발생하며, 매연 및 배출가스, 연비가 악화되는 것을 확인하였다. 또한, 파손된 매연저감장치(DPF)를 확인한 결과 철분성분이 다량 검출되었으며 이는 연료에 철분성분이 많이 함유되어 있어, 배출가스에 영향을 미쳐 매연저감장치(DPF)의 처리능력을 초과한 입자상물질의 배출로 인한 파손으로 추정 및 확인하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.349-350
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• 2002

The friction and wear behaviors of fluorine-containing compounds such as perfluoropolyethers (PFPE), phosphazenes (X-1P), ionic liquids as lubricants for steel/seel, steel/ceramic, ceramic/ceramic were investigated using a SRV tester and a one-way reciprocating friction tester both in ball-on-disc configuration. It was found that the three fluorine-containing lubricants could reduce friction coefficient and wear volume effectively. The effectiveness of the three lubricants in reducing wear volume could be ranked as ionic liquids>X-1P>PFPE. Tests also showed that aryloxyphosphazene with polar substituent as a lubricant of steel/steel pair gave low wear, while aryloxyphosphazene with nonpolar group on the phenyl pendant led to high wear. The morphology and the tribo-chemical reaction of the worn surfaces were analyzed with a scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). XPS analyses illustrated the formation of iron fluoride in steel/steel system with the lubrication of both phosphazenes and ionic liquids.

• 공업화학
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• 제21권6호
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• pp.653-658
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• 2010

바이오디젤은 기존석유디젤을 대체할 수 있는 친환경적인 연료로 알려져 있다. 하지만 원료물질이 대부분 가격이 높은 식량자원을 이용한다는 단점을 지니고 있다. 본 연구에서는 음식쓰레기로 생긴 오리기름을 전처리 한 후, 염기촉매를 이용하여 전이에스테르화 반응을 통해 바이오디젤을 합성하였다. 합성되어진 바이오디젤의 대표적 연료특성으로 밀도, 동점도, 저온특성, 윤활성, 세탄가를 분석한 결과, 국내에서 동절기 외에는 충분히 석유대체연료로 사용 가능하다는 결과를 얻었다.

• Tribology and Lubricants
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• 제28권1호
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• pp.33-37
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• 2012

Automotive wheel bearing grease helps to reduce stresses and prevent wear of wheel bearings. But it is easily contaminated by water and other contaminants. Previously, our research group reported the change of grease physical properties such as dropping point, work penetration and oxidation work stability, water washout characteristics, leakage tendency, oil separation, evaporation loss and rust protection by water contamination. In this paper, we analyzed the physical characteristics of grease such as lubricity, viscosity and total acid number to investigate the mechanism of thickener decomposition. In water contaminated grease, the total acid number and wear scar were increased, the viscosity was decreased due to the decomposition of lithium complex thickener.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.89-95
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• 2020

The main scope of this paper is to see if the conventional pump can be properly used for a specific fuel, Di-methyl Ether (DME) despite of its low lubricity and high reactivity in the experimental conditions. A wobble plate type fuel pump was connected to the common rail to verify that the pump could deliver the fuel at the required pressure and resultantly DME could be used as fuel without modifying the original pump. At each required pressure (30 Mpa, 35 Mpa, 40 Mpa, 45 Mpa, and 50 Mpa), the pump met the pressure required by the common rail. In addition, pump performance experiments tended to follow the usual performance curve while the flow rate decreased as the pressure increased. The maximum flow rate of the pump was 470 kg/h at 30 Mpa and all measurements were taken with keeping DME temperature below 60℃.

• 융복합기술연구소 논문집
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• 제3권1호
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• pp.15-18
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• 2013

The next generation alternative fuel of diesel, DME (Dimethyl Ether) discharges particulate matter hardly due to chemical structural as oxygen-fuel so it has the eco-friendly property. Despite these advantages, the DME has the technical difficulties to apply to the diesel engine because of a low calorific value, viscosity and compressibility effects. From this point of view, we performed experimental studies on improved reliability of DME common-rail vehicle and lubricity enhancement of DME fuel for empirical distribution of eco-friendly DME fuel. Also we analyzed solubility of lubrication enhancer according to a drop in temperature, try to secure reliability about core parts of DME vehicle by applying lubrication enhancer in the DME common-rail vehicle.