• Tribology and Lubricants
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• 제14권4호
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• pp.108-113
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• 1998

In order to investigate the characteristics of top ring groove deposit formation in diesel engine, engine test and simulation test were performed. From component analysis of used oils sampled from actual running engines, soot content in engine oil was selected as a main parameter for evaluating oil degradation. Deposit formation is highly related to soot content in lubricating oils. And high soot content oil accelerates deposit formation even in low temperature region below 26$0^{\circ}C$. In low temperature region below 26$0^{\circ}C$, deposit formation rate is mainly affected by top ring groove temperature. However, in high temperature region above 26$0^{\circ}C$, deposit formation rate is affected by soot content as well as top ring groove temperature. Therefore, soot content as well as top ring groove temperature should be kept a certain level in order to prevent troubles due to carbon deposit formation.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.100-106
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• 1998

The wide open throttle performance and piston temperatures were measured by the change of fuel : gasoline and liquefied petroleum gas(LPG). Bench test method was developed and experimented to study the effect of temperature on the formation of carbon deposit. The bench test results were confirmed by measuring the piston temperature and observing the deposit production rate at an actual engine running condition. Results show that if the fuel of spark ignition engine is changed from gasoline to LPG, the output power decreases about 10% and the piston temperatures increase about 40~55$^{\circ}C$. In actual engine tests, because of this temperature increase, it was observed that the quantity of carbon deposit in the top ring groove increased in a big degree. Consuquently, it is known that the fing sticking may occur if the gasoline engine was rebuilt to LPG fuelled engine. Therefore, in order to preserve the durability of LPG fuelled engine, it is necessary to lower the piston temperature by hardware modificationor to reduce the carbon deposit by the improvement of engine oil.

• 한국산학기술학회논문지
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• 제11권12호
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• pp.4685-4690
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• 2010

E-EGR Valve 고장의 원인이 되는 내부 퇴적물 축적을 최소화하기 위한 새로운 Valve 형상을 제안하고자 한다. 전산유체 해석을 통하여 다양한 형상에 대하여 유속과 유량을 관찰하였으며, 밸브 상부에 라운드를 추가한 Valve 디자인 변형을 통하여 유량손실 없이 Valve 내의 유속을 약 10% 향상시킬 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.234-238
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• 2002

Lubricating oil supply system is an essential instrument for safe turbine operation. A lubricating condition may cause the abnormal vibration of turbine. In this paper we have discussed the abnormal vibration of turbine due to lubricating oil. Dusts of the air usually attach to end of the oil deflector and contact particles of the bearing oil. Dusts which were contacted particles of the bearing oil were changed into carbon deposit because of high temperature. therefore, carbon deposits occur abnormal vibration of the turbine when they contact a rotor. So, we have solved this problems through the various maintenance.

• 오토저널
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• 제10권6호
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• pp.48-53
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• 1988

In a previous report, the properties of vegetable oils as diesel fuel substitutes were investigated and the basic load performance of a diesel engine was examined using vegetable oil. The results show that despite of the long term chain hydrocarbon structure and large droplet size due to high viscosity, vegetable oils have good basic performance and exhaust emissions, however they cause serious problems as carbon deposit buildup, they have poor durability, and also poor thermal efficiency. In this paper, the startability and engine durability with long term operation was tested by physical methods for reducing viscosity when vegetable oil was used as compared against diesel fuel. The results obtained in this investigation may be stated as follows; (1) There is no problem in startability when vegetable oil was used as diesel fuel substitutes as far as fuel temperature is higher than 30.deg. C (2) The carbon deposits were most extensive at lower loads and lower engine speeds, and deposit buildup more heavily on the cooler parts of the combustion chamber wall. (3) Blends with 25% diesel fuel and 20v-% ethanol are effective in reducing the carbon deposit buildups. (4) Significant improvement in carbon deposit and piston ring stick can be obtained by heating fuel(200.deg.).

• Tribology and Lubricants
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• 제13권4호
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• pp.33-39
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• 1997

In order to establish a new temperature criterion to prevent the pistons from ring sticking due to deposit formation, bench test and engine test were performed. The effects of oil degradation and temperature on deposit formation was studied by a modified panel coking test. Oil degradation was analyzed by FTIR. Oil oxidation and nitration were selected as a factors to evaluate oil degradation. Bench test results show that oil oxidation is more effective to the deposit formation than oil nitration. And the temperature increase accelerates deposit formation and deposit formation increase rapidly above 26$0^{\circ}C$. Especially, in case of degraded oil, the deposit formation increases so rapidly that ring sticking can occur. The effect of piston temperature on the deposit formation was confirmed by engine test.

• Korean Chemical Engineering Research
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• 제45권6호
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• pp.547-553
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• 2007

FER, MFI, MOR, BEA 제올라이트 촉매에서 n-옥탄의 분해반응을 양성자 분해반응(protolytic cracking mechanism) 기구로 해석하여 제올라이트의 세공구조가 생성물 분포와 활성저하에 미치는 영향을 고찰하였다. 세공이 작으면 분해반응이 많이 진행되어 $C_3$와 $C_3{^=}$가 주로 생성되나, 세공이 큰 제올라이트에서는 초기 생성물인 $C_4$와 $C_4{^=}$가 주로 생성된다. MFI 제올라이트에서는 탄소 침적이 억제되어 활성저하가 느리나, FER 제올라이트에서는 탄소가 많이 침적되어 촉매 활성이 빠르게 저하되었다. BEA 제올라이트에서는 탄소가 많이 침적되어도 활성저하가 느리나, MOR 제올라이트에서는 탄소가 조금만 침적되어도 활성저하가 빨랐다. n-옥탄 분해반응의 기구를 단순화하고 탄소 침적에 의한 세공 차폐 정도를 활성저하와 연관지어 반응시간에 따른 전환율 저하 과정을 모사하였다.

• Corrosion Science and Technology
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• 제4권3호
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• pp.75-80
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• 2005

This work dealt with the evaluation of galvanic corrosion rate in a corrosion cell having annular gap of 0.5 mm between carbon steel 1018 and alloy 600 as a function of temperature and boron concentration. Temperature and boron concentration were ranged from 110 to 300 $^{\circ}C$ and 2000~10000 ppm, respectively. After the operating temperature of the corrosion cell where the electrolyte was injected was attained at setting temperature, galvanic coupling was made and at the same time galvanic current was measured. The galvanic corrosion rate decreased with time, which was described by corrosion product such as protective film as well as boric acid deposit formed on the carbon steel with time. From the galvanic current obtained as a function of temperature and boron concentration, it was found that the galvanic corrosion rate decreased with temperaturewhilethe corrosionrate increasedwith boronconcentration. The experimental resultsobtained from galvanic corrosion measurement were explained by adhesive property of corrosion product such as protective film, boric acid deposit formed on the carbon steel wall and dehydration of boric acid to be slightlysolubleboric acid phase.Moreoverthe galvaniccorrosionrate calculatedusing initialgalvaniccoupling current instead of steady state coupling current was remarked, which could give us relatively closer galvanic corrosion rate to real pressurized water reactor.

• 한국재료학회지
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• 제18권5호
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• pp.253-258
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• 2008

A simple method to deposit carbon nanotube films uniformly on large area substrates using an arc discharge method is reported in this paper. The arc discharge method was modified to deposit carbon nanotube films in situ on the substrates. The substrates were scanned several times over the arcing point for a uniform film thickness. Deposition was carried out under variable dc bias conditions at 600 torr of $H_2$ gas. The thickness uniformity of the single-wall carbon nanotube films as characterized by a four-point probe was within 30% deviation. The morphology and crystal quality of the single-wall carbon nanotube film were also characterized by field emission scanning electron microscopy and Raman spectroscopy.

• 한국표면공학회지
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• 제37권2호
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• pp.80-85
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• 2004

Chromium-carbon (Cr-C) and chromium-carbon-phosphorus (Cr-C-P) alloy deposits using trivalent chromium sulfate baths containing potassium formate were prepared to study their current efficiency, hardness change and phase transformations behavior with heat treatment, respectively. The current efficiencies of Cr-C and Cr-C-P alloy deposits increase with increasing current density in the range of 15-35 A/dm$^2$. Carbon content of Cr-C and phosphorous of Cr-C-P layers decreases with increasing current density, whereas, the carbon content of Cr-C-P layer is almost constant with the current density. Cr-C deposit shows crystallization at $400^{\circ}C$ and has (Cr+Cr$_{ 23}$$C_{6}$) phases at $800^{\circ}C$. Cr-C-P deposit shows crystallization at $600^{\circ}C$ and has (Cr+Cr$_{23}$ $C_{6}$$+Cr_3$P) phases at $800^{\circ}C$. The hardness of Cr-C and Cr-C-P deposits after heating treatment for one hour increase up to Hv 1640 and Hv 1540 and decrease about Hv 820 and Hv 1270 with increasing annealing temperature in the range of $400～^{\circ}C$, respectively. The hardness change with annealing is due to the order of occurring of chromium crystallization, precipitation hardening effect, softening and grain growth with temperature. Less decrease of hardness of Cr-C-P deposit after annealing above $700^{\circ}C$ is related to continuous precipitation of $Cr_{23}$ $C_{6}$ and $Cr_3$P phases which retard grain growth at the temperature.