• 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.

• Tribology and Lubricants
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• 제1권1호
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• pp.46-58
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• 1985

피스톤링과 실린더벽 사이의 윤활이 왕복운동을 하며 동하중을 받는 포물선형의 슬라이드 베어링의 유체 윤활로 보고 전개하였다. 싸이클 상의 유막 두께의 변화, 윤활유 운반과 마찰력을 계산하는 과정이 개략적으로 설명되었고, 이들 성능 특성들에 대한 링 높이, 링 앞면 곡률반경과 링의 비대칭의 영향을 고찰하였다. 단독링에 대한 해석결과를 조금 더 복잡한 링 팩에 대해 확대 적용하였다. 링의 부하가 되는 링 주위의 압력들은 실험적으로 또는 가스 흐름 해석으로부터 얻을 수 있는데 본 연구에서는 후자를 택하였다. 링팩에서의 유체 연속 및 윤활유 부족에 따른 수치 해석에 주안점을 두었다.

• Tribology and Lubricants
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• 제18권2호
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• pp.133-137
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• 2002

This paper reports on the effect of fuel additive friction modifier on the engine friction and fuel consumption. The test of engine friction and fuel consumption is performed for the each oils and fuels. The TFA4724 friction modifier is added in test oil and fuel. The test results show that total engine friction is a decrease of 0.7-2.0% compared with base fuel, and fuel consumption is improved by 0.3%. The amount of friction reduction corresponds to that of boundary friction loss term in ring-pack friction losses. From the results, it is thought that the additive friction modifier in the fuel is effective to reduce the boundary friction in ring-pack.

• Tribology and Lubricants
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• 제22권3호
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• pp.155-163
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• 2006

Ring, groove and cylinder bore wear may not be a problem in most current automotive engines. However, a small change in ring face, groove geometry and cylinder bore diameter can significantly affect the lubrication characteristics and ring axial motion. This in turn can cause to change inter-ring pressure, blowby and oil consumption in an engine. Therefore, by predicting the wear of piston ring face, ring groove 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. Being based on the calculation of gas flow amount by the theory of piston ring dynamics and gas flow, and the calculation of oil film thickness and friction force by the analysis of piston ring lubrication, the calculation theory of oil amount through top ring gap into combustion chamber will be set. This is estimated as engine oil consumption. Furthermore, the wear theories of ring, groove and cylinder bore are included. Then the each amount of wear is to be obtained. 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. Next, the calculated amount of oil consumption and wear are compared with the guideline of each part's wear and oil consumption. So, the timing of part repair and engine life cycle can be predicted in advance without performing engine durability test. The wear data of rings, grooves and cylinder bore are obtained from three engines before and 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.

• 대한기계학회논문집A
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• 제27권1호
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• pp.88-93
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• 2003

The aim of this paper is to investigate the friction characteristics of piston assembly, which composed of ring pack and piston skirt. The friction force of piston assembly was measured by using the movable liner in the single cylinder engine, and the various parameters were tested. The friction force was suddenly increased at the expansion stroke due to higher cylinder pressure. The viscous friction was dominant at the mid stroke, but the boundary friction was dominant at the top and bottom dead centers. Through the experiment, we could validate previous theoretical study, and confirm that th e radial clearance and ring tension were very effective to reduce friction loss of piston assembly.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.1333-1334
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• 2011

• 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.

• 항공우주시스템공학회지
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• 제10권3호
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• pp.52-58
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• 2016

The elastomeric O-ring is the most-commonly-used seal due to its excellent sealing capacity, and its availability in various costs and sizes; furthermore, its importance has lasted over a long duration. However, a dearth of research exists in Korea regarding the elastomeric O-ring and the corresponding techniques. The constituent parts of elastomeric rubber are important; to determine their properties, the uni-axial tension and equi-biaxial tension need to be tested. Also, the non-linear analysis method reduces the design cost. An O-ring failure causes leaks and vibration. In this paper, foreign objects are used to affect an O-ring and its performance so that all angles of the O-ring design can be considered. This paper presents a solution for the O-ring-failure problem using a finite-element analysis.

• 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.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.238-249
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• 1995

The gas pressure acting on the rings in internal combustion engine influences the friction and wear characteristics. Inter-ring pressure variation during engine operation results from cylinder gas flow through a piston-ring pack. The flow passages consist of ring end gaps and clearances between the ring and the piston groove. The gas flow in the clearance between the ring and the groove is directly affected by the axial motion of the ring in the groove. In this paper the asperity contact force is newly considered in the prediction of the clearence between the ring and the groove surface. This term must be taken into account physically in case that the clearance get narrow rather than asperity height between the ring and the groove surface. Finally, comparisons of calculated inter-ring gas pressures based on the analytical method are made with the measured ones. The agereement was found to be good below midium engine speed, 3000rpm. In order to obtain accurate analytical results to the extend of high rpm range, it is recommended to include oil ring motion as well as top and second ring in analytical model.