• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.175-180
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• 1998

This paper describes evaluation of oxidation stability for diesel engine oils by Hot-tube oxidation tester at high temperature. Evaluation was rated by visual inspection of lacquer in capillary glass tube and TAN determination of used oil. Air, NO$_2$-air and SO$_2$-air mixed gases were used as oxidizing gas. One oil which has low oxidation stability is selected and reformulated by addition of some additives such as antioxidant, detergent and disperant to improve oxidation stability. As a results of reformulation, antioxidant and detergent was effective for improvement of high temperture oxidation stability on diesel engine oil.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제26회 추계학술대회
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• pp.100-109
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• 1997

Tappet is the part which consists of valve train system in Over Head Valve type diesel engine. The role of tappet is to open and close the intake/exhaust valve by rotating with cam. There are wear problems like scuffing or pitting in cam/tappet system because of the higher Hertzian contact stress and sliding wear characteristics between cam and tappet. In this paper, to find optimal materials combination in cam/tappet system, wear test and rig test were performed. $Si_3N_4$, chilled cast iron, sintered alloy were selected for tappet materials. As the result of test, it is found that $Si_3N_4$ tappet has the excellent wear properties.

• 항공우주시스템공학회지
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• 제17권5호
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• pp.11-18
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• 2023

The architecture of the Fuel Thermal Management System (FTMS) in a commercial aircraft engine was built to model and simulate the fuel system. The study shows the thermal interactions between the fuel and engine lubrication oil through the mission profile of a high bypass ratio, two-spool turbofan engine. Fuel temperature was monitored as it flowed through each sub-component of the fuel system during the mission. The heat load in the fuel system strongly depended on the fuel flow rate, and was significantly increased for the periods of cruise and descent with decrease of fuel flow rate, rather than for the periods of take-off. Due to the thermal interaction in the pump housing, the fuel temperature at the outlet of the low-pressure pump was increased (4.0, 9.2, and 30.0) % over the case without thermal interaction for take-off, cruise, and descent, respectively.

• Tribology and Lubricants
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• 제2권1호
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• pp.69-77
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• 1986

The motion of journal in a bearing is considered separately as rotation and translation, and then the equations of motion are derived. The bearing load capacities for these motions are calculated from the lubrication theory. The numeric integration of the equations of motion gives various journal orbit depending on force cycles and bearing parameters.

• 한국분무공학회지
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• 제10권4호
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• pp.8-15
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• 2005

The use of clean gaseous fuels for the purpose of high efficiency and low emission in automotive engines has tendency to increase in order to meet the reinforcing emission regulations and to efficiently utilize limited natural resources. Automotive companies developed and commercialized a LPG liquid injection system, which is mounted on LPLi(Liquid Phase LPG Injection) engines and vehicles based on this research trend. This research examines the biggest problem in LPLi engine, that is, the leakage characteristics of low viscosity LPG fuel according to the injector design variables. This study is also aimed to improve the performance of fuel-leakage in LPLi engine through the addition of a lubrication improver in HFRR(High Frequency Reciprocating Rig) facility. The needle displacement and the spring displacement of an LPLi injector are found to be already optimized. The possibility of a maximum of 70% leakage reduction compared to a conventional case, is verified when 1000ppm of a lubrication improvement material is added and 40% increase of a injector spring constant (K) is applied.

• 한국자동차공학회논문집
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• 제22권7호
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• pp.48-56
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• 2014

Engine oil is an oil used for lubrication of various internal combustion engines. The main function is to reduce wear on moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts. In engines, there are parts which move against each other. Otherwise, the friction wastes the useful power by converting the kinetic energy to heat. Those parts were worn away, which could lead to lower efficiency and degradation of the engine. It increases fuel consumption, decreases power output, and can induce the engine failure. This study was conducted to evaluate the relation between engine oil property changes and engine performance for the diesel engine. This test was performed by using 12L, 6 cylinder, heavy duty engines. Low SAPS 10W30 engine oil (two type engine oils) was used. Test procedure and method was in accordance with the modified CEC L-57-T97 (OM441LA) method. In this study, TAN, TBN, KV and metal components, engine power, blowby gas, A_F were presented to evaluate the relation with engine oil property changes and engine performance. TAN, TBN, KV and metal We found that the components were generally increased but engine performance did not change. This results mean that property changes did not affect on engine performance because those were not enough to affect engine performance.

• Tribology and Lubricants
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• 제34권4호
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• pp.146-159
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• 2018

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a four-strokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.143-150
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• 2007

Ring and cylinder bore wear may not be a problem in most current automotive engines. However, a small change in ring face and cylinder bore diameter can significantly affect the lubrication characteristics and ring axial motion. This in turn can cause to change inter-ring pressure, blow-by and oil consumption in an engine. Therefore, by predicting the wear of piston ring face and cylinder bore altogether, the changed ring end gap and the changed volume of gas reservoir can be calculated. Then the excessive oil consumption can be predicted. Here, the oil amount through top ring gap into combustion chamber is estimated as engine oil consumption. Furthermore, the wear theories of ring and cylinder bore are included. The changed oil consumption caused by the new end gap and the new volume of oil reservoir around second land, can be calculated at some engine running interval. Meanwhile, the wear amount and oil consumption occurred during engine durability cycle are compared with the calculated values. The wear data of rings and cylinder bore are obtained from three engines after engine durability test. The calculated wear data of each part are turn out to be around the band of averaged test values or a little below. It is shown that the important factor regarding oil consumption increasement is the wear of ring face.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.3-8
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• 1998

The industrial revolution in England was based on the manufacturing systems by the power of water mill and rapidly progressed by the innovation of steam engine. It is no exaggeration to say that today's civilization is realized by the development of various types of power machinery, namely fluid machinery and heat engine. The electric energy is converted mainly from thermal energy (mainly steam) of mineral oil, coal and nuclear fuel through generator connected with steam turbine which is a kind of power machinery. There are various types of power machinery as shown in Tables 1a and 1b. They are classified into two types by use. One is absorption type of fluid and/or thermal energy, for examples, windmill and heat engine. The other is provision type of the energies for examples, pump, compressor and propulsion. By flow type, they are also classified by two types, turbo type and positive-displacement type. The turbo type began from water mill and windmill and evolve to steam turbine and finally to gas turbine. The positive-displacement type started from reciprocating water pump and developed into steam engine and changed to reciprocating combustion engine. The pumps and motors used in oil hydraulic system for power control are also positive-displacement type.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.548-551
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• 2010

추력 150 lbf 급의 초소형 터보제트 엔진이 개발되었다. 본 엔진은 소형 무인항공기(UAV), 기만기, 대공망 제압용 유도무기 등 다양한 무기체계에 적용이 될 수 있도록 고성능, 소형, 저가로 설계되었으며, 시제엔진을 제작하여 지상 성능 시험 및 고도 시험을 수행하였다. 본 논문에서는 소형, 저가, 고효율 터보제트 엔진을 구성하는 각 엔진 구성품의 특징, 구조, 구성품 및 엔진 시험 결과 등에 대하여 기술하였다.