• Tribology and Lubricants
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• 제31권3호
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• pp.86-94
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• 2015

We perform lacquer formation experiments with various combinations of marine fuel oils and lubricant oils. We also investigate the influences of base number (BN) in lubricant oil and sulfur content in fuel oil. A dissolution test with 10% dilute sulfuric acid and pull-off force test are accomplished to distinguish whether the residual layers are lacquering or not. The lacquering layers are dissolved by dilute sulfuric acid and have a strong pull-off force. Moreover, the calcium content detected in the residual layers is compared by energy dispersive x-ray spectroscopy (EDS). More calcium is detected in the lacquer layers than in other residual layers. Distillate fuels containing low sulfur levels are more prone to lacquering when mixed with lubricant oil with a high BN. On the other hand, residual fuels with a high sulfur content do not form lacquer. We investigate the effect of mixture volume ratio. The mixture with higher fuel oil content is more prone to generate lacquer. These experiments indicate that a lubricant with an appropriate BN should be used to prevent lacquer forming on the surfaces such as cylinder liners depending on the sulfur content of fuel oil.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.105-113
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• 2000

In order to clarify the final process of oil consumption, the distribution and flow of oil through each ring were visualized by induced fluorescence method. Motoring and firing test were performed in a single cylinder research engine with transparent cylinder liner. The appropriate calibration techniques were used to solve the unstability of induced light intensity as well as to know the relation of the oil film thickness and output signal. Oil behavior was also observed at dynamic state by high speed CCD camera. By analyzing the oil film thickness converted from the photographed image, it was observed that the main route of oil transport through each ring is the end gap under the usual operating condition, low engine speed and low load condition. Oil film thickness is observed to be irregular and tend to move in a body horizontally at a given piston land. And it is also found that oil flows through oil ring gap so quickly that it can be observed in a single cycle, but it flows so slowly through top and 2nd compression rings that it takes quite a long time to detect the flow.

• 한국가스학회지
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• 제16권2호
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• pp.18-24
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• 2012

본 연구는 Type II 가스실린터의 20,000 회 피로시험과 파열시험시 음향방출시험을 병행하여 용기의 손상정도를 평가하고자 하였으며, 실험에 사용된 용기는 결함 크기가 $3mm{\times}3mm{\times}50mm$ (폭${\times}$깊이${\times}$길이)이고 결함 방향이 용기의 종방향 및 횡방향인 인공결함용기와 건전한 용기 등 세 종류이다. 피로시험시 발생된 음향방출신호는 종방향결함의 경우 전체 신호 중 결함에서 발생된 이벤트의 비율이 50 % 이상이며, 음향방출신호의 위치표정도 매우 정확하게 일치하였다. 또한 파열시험에서는 인공결함용기가 결함 위치에서 에상파열압력보다 낮은 압력으로 파열될거라는 예상과는 달리 인공결함용기의 파열압력은 건전한 용기와 큰 차이가 없었으며, 단지 종방향 인공결함용기의 경우 파열위치가 결함 위치와 근접하게 발생하였다. 이는 종방향 결함의 길이만큼 복합재료의 두께가 얇아지는 효과로 나타나게 되어 금속라이너의 피로반복시 결함 발생과 성장위치에 영향을 미친 것으로 판단된다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.427-428
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• 2002

Clearance movements of engine piston are regarded very important because they cause impact vibrations as well as many tribological problems. Some of the major parameters that influence these kinds of performances are piston profiles, piston offsets and clearance magnitudes. In our study. computational investigation is performed about the piston movements in the clearance between piston and cylinder liner by changing the skirt profiles and piston offsets. Our results show that curved profile and more offset to thrust side have better performance with low side impact during the engine cycle.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.648-651
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• 2009

탄소섬유강화플라스틱(CFRP:Carbon Fiber Reinforced Plastic)용기의 외부에 화재가 발생할 경우 함침된 수지(Resin)가 탄화되면서 자체 강도가 약화되고 충전된 가스가 외부 온도 상승에 따라 압력 상승이 발생하여 용기의 폭발로 이어지는 사고가 발생할 개연성이 높다. 화염 노출조건에서 복합재료 용기의 폭발을 방지하기 위하여 용기용 밸브에 내장된 온도감응식 압력안전장치(TPRD:Thermally activated Pressure Relief Device) 작동 성능을 검증하기 위한 방법으로 화염실험(Bonfire test)를 실시하고 있으나, 개방 공간에서 실시되는 이 실험은 표면 온도 변화가 매우 크게 발생하여 실험에 대한 재현성(Reproducibility)에 의문이 제기되고 있다. 따라서, 표면 온도를 일정하게 유지하기 위한 실험 방법의 개선이 필요하다. 본 연구에서는 경유+heptane을 이용한 전체 화염에 노출되는 경우와, 천연가스를 이용한 단일화염에 노출되는 경우의 실험 결과 비교를 통하여 화염 노출 표면 온도를 일정하게 유지하기 위한 가열 방법의 타당성을 검토하였다. 또한, 복합재료 라이너(Liner)의 온도 변화 비교를 통하여 집중화염 노출 조건에서 열전달 특성을 알아보았다.

• Tribology and Lubricants
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• 제14권3호
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• pp.51-58
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• 1998

This paper considers analysis of the lubrication between the piston ring and the cylinder liner. Piston ring lubrication analysis considering oil transport is important because oil consumption is an essential factor to design the piston assembly. To develop the lubrication analysis program for the piston ring, oil continuity condition and open-end boundary assumption are used for computational boundaries. Results show that oil continuity can be almost satisfied at any crank angle in and out of the piston ring clearance. Therefore the amount of oil consumption and the dynamic behavior of ring pack can be estimated using this algorithm. And it can be known that the effective width may be smaller than the full width of the piston ring, so oil starvation condition should be considered for the lubrication analysis of the piston ring.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.41-49
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• 1993

Piston slap is one of the major sources of noise in a 4-cycle diesel engine. Piston slap is not only one of major source mounted near the top and bottom of the piston thrust and antithrust skirts. Effects of engine speed, load and coolant temperature on piston motion were investigated. The measured piston motion showed 6 slapes per cycle resulting from the change of side force. Major piston slap timing was retarded as engine speeds became higher. The increase of engine load made large piston transverse movement toward thrust side of cylinder block. Piston transverse movement was due to reduced piston-liner clearance at higher coolant temperature.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.115-122
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• 1999

A friction tester to measure friction force generated at the interface between the piston ring and the cylinder liner was developed. Modified piston ring is bar-shaped and 100mm long. Surface of the modified piston ring is machined by the profile grinding machine to be formed as a shape of an arc of a circle. Measured data are treated as mean effective friction force and power loss. From this test it can be confirmed that friction force is deeply affected by surface shape of the piston ring and viscosity of supplied oil. Friction force is deeply affected by surface shape of the piston ring and viscosity of supplied oil. Friction force is decreased and power loss is increased with increasing velocity. And it is known that region of mixed lubrication is broader than estimated with theoretical analysis. it is expected that this tester can be used as the optimization tool of the surface shape of the piston ring at the first stage of development of the piston rings.

• 한국자동차공학회논문집
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• 제2권3호
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• pp.94-104
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• 1994

In order to improve engine performance and its reliability it is very important to find the friction force between piston-ring assembly and cylinder wall in engine operating conditions. A new system was developed for the piston-ring assembly friction force measurement. This system had a relatively high fundamental frequency at 884 Hz and a fine resolution of 0.5N in friction force measurement. Comparing with existing floating liner systems this systems required small installation space and at the same time alleviated the system noise problem induced by the thrust and slap impulse forces.

• KSTLE International Journal
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• 제1권2호
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• pp.83-90
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• 2000

The surface roughness between a piston ring pack and a cylinder liner directly affects the fuel economy, the oil consumption, and the emission of the engine so that it is very important to clarify the surface roughness effects on the lubrication characteristics. The friction characteristics of the piston ring during engine operations are known to as mixed lubrication experimentally. In this study to simulate the effects of the surface roughness of the piston ring pack on the lubrication characteristics, the mixed lubrication analysis of piston rings was performed using the simplified average Reynolds equation. From the results the surface roughness was found be considerably affects minimum oil film thickness as well as FMEP(Friction Mean Effective Pressure). Especially, the oil ring was the most sensitive on the surface roughness.