• Title/Summary/Keyword: Piston skirt

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The Effects of Surface Porfiles and Coatings on the Tribological Behaviors of the Surfaces of Piston Skirt (피스톤 스커트 표면의 트라이볼로지 거동에 미치는 표면형상과 코팅의 영향)

  • Cho, Dae-Hyun;Chung, Soon-Oh;Won, Young-Duck;Han, Man-Cheol;Lee, Young-Ze
    • Tribology and Lubricants
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    • v.24 no.3
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    • pp.122-128
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    • 2008
  • To reduce the friction losses and the wear amounts in the piston assembly two methods were proposed. One is the modification of surface profile of the skirt part. The surface coating is another method to protect the sliding surfaces. To modify the profile of the skirt surfaces the surfaces were ground to have three different shapes of profiles. Also, several coatings, such as graphite, TiN, and $MoS_2$, and DLC, were used to protect the surfaces of the piston skirts. The specimens of the skirt and the cylinder bores were tested with the reciprocating wear tester. SAE 5W40 engine oil was used in boundary lubrication regime. Among several coatings the graphite and DLC coatings were very effective to reduce the friction forces. Especially, DLC film represented much better tribological performances than the others. The friction coefficient of the graphite coating was the lowest, but the graphite coating was not effective to protect the surfaces.

Study on the Clearance Design for Low Side Impacts of Engine Piston

  • Cho, Joon-Haeng;Jang, Si-Youl
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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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.

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Friction Characteristics of Piston Assembly (II) -Experiment- (피스톤계 마찰 특성 (II) -실험적 연구-)

  • Cho, Myung-Rae;Ha, Kyoung-Pyo;Kim, Joong-Soo;Oh, Dae-Yoon;Han, Dong-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.1
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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.

A Study on Effect of Recirculated Exhaust Gas upon Wears of Piston and Piston Rings in Diesel Engines with Scrubber EGR System (스크러버형 EGR시스템 디젤기관의 피스톤 및 피스톤링 마모에 미치는 재순환 배기의 영향에 관한 연구)

  • 배명환;하정호
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.6
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    • pp.79-86
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    • 2000
  • The effects of recirculated exhaust gas on the wears of piston and piston rings were investigated by the experiment with a two-cylinder, four cycle, indirect injection diesel engine operating at an engine load of 75% and an engine speed of 1600 rpm. For the purpose of comparison between the wear rates of two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot contenets in exhaust emissions were removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors(A water injector has 144 nozzles of 1.0 mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out on the fuel injection timing fixed at 15.3$^{\circ}$ BTDC. It was found that the wear rate of piston skirt with EGR increased a little bit, but the piston head diameter increased, rather than decreased, owing to soot adhesion and erosion wear, and especially larger with EGR, and that the wear rates of the top and second piston ring(compression ring)thickness with EGR were more than twice the wear rate of top ring in case of no EGR, but the wear rate of oil rings thickness without EGR increased greater than that with EGR.

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A Study on the Coating Thickness Prediction of a Piston Skirt (피스톤 스커트의 코팅두께 예측에 관한 연구)

  • Chun, Sang-Myung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.2
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    • pp.84-91
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    • 2011
  • The purpose of this study is to find how to be formed the wet film thickness during the low friction coating process for a piston skirt with application to the theory of screen printing. In other words, the general expressions predicting the pressure under a blade and the volume of coating fluid passing through the blade edge are derived. Using these expressions, the coating thickness on a piston skirt during a sample blade coating process can be quantitatively assessed.

A Basic Study on Blade Coating Process of Piston Skirt by Applying the Technology of Screen Printing - Case Study (스크린 프린팅 기술을 적용한 피스톤 스커트의 브레이드 코팅공정에 관한 기초연구 - 사례연구)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.26 no.2
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    • pp.142-148
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    • 2010
  • The purpose of this study is to find how to be formed the wet film thickness during the low friction coating process for a piston skirt with application to the theory of screen printing. In other words, in this research, it is to derive the general expressions predicting the pressure under a blade and the volume of coating fluid passing through the blade edge. Using these expressions, it is to be approved that the current operation characteristics of a screen printing system to a sample blade coating process for low friction coating on a piston skirt can be quantitatively assessed.

The influence of various factors on piston friction (피스턴마찰에 미치는 각 인자의 영향)

  • 이종태;이성열
    • Journal of the korean Society of Automotive Engineers
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    • v.5 no.1
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    • pp.45-53
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    • 1983
  • There exist many kinds of frictions in internal combustion engine such as piston ring and skirt, cam and tappet, bearing friction etc. Among them, the frictions between piston ring, skirt and cylinder are particular. These frictions for motoring test are differ from that of firing test even though the temperature of cooling water and lubricating oil keep identically. The frictions for firing test are increased due to combustion pressure and products. The precise calculation of the friction is difficult. But we can assume that the friction is governed by the viscosity of lubricating oil and gas pressure of cylinder. And the viscosity of lubricating oil is dependant on gas temperature of cylinder, so the piston friction may be governed by gas pressure and temperature of cylinder. In this treatise, we propose the method of evaluating piston friction under the condition of constant engine speed, and we analyzed the behaviours and influence of factors concerned with the piston friction for output correction when the inlet pressure and temperature were varied. The main results are as follows: 1) The behaviours on the inlet conditions for the contact force of the piston rings and the viscosity of the lubricating oil concerned with piston friction are found. 2) The essential point the these behaviours is dependant on the cyclic variation following to the inlet conditions. 3) According to our analysis, It was observed that the viscosity of lubricating oil is more effective than the contact force to the piston rings.

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Analysis of the Characteristics of the Low Friction Pad Type Piston (패드식 피스톤의 특성 해석에 관한 연구)

  • 김청균;김희붕
    • Tribology and Lubricants
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    • v.9 no.2
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    • pp.70-78
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    • 1993
  • Using the finite element method, the film pressure, the transverse force and the firction torque which are distributed over the pad surface of low-friction piston skirt are calculated in order to investigate the dynamic characteristics of the piston. The results indicate that the frictional torque for the low-friction piston pad may increase 3% efficiency in comparison th the conventional one.

Friction Power Loss Reduction for a Marine Diesel Engine Piston (박용엔진 피스톤 스커트 프로파일 변경에 의한 마찰손실(FMEP) 저감 연구)

  • An, Sung Chan;Lee, Sang Don;Son, Jung Ho;Cho, Yong Joo
    • Tribology and Lubricants
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    • v.32 no.4
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    • pp.132-139
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    • 2016
  • The piston of a marine diesel engine works under severe conditions, including a combustion pressure of over 180 bar, high thermal load, and high speed. Therefore, the analyses of the fatigue strength, thermal load, clamping (bolting) system and lubrication performance are important in achieving a robust piston design. Designing the surface profile and the skirt ovality carefully is important to prevent severe wear and reduce frictional loss for engine efficiency. This study performs flexible multi-body dynamic and elasto-hydrodynamic (EHD) analyses using AVL/EXCITE/PU are performed to evaluate tribological characteristics. The numerical techniques employed to perform the EHD analysis are as follows: (1) averaged Reynolds equation considering the surface roughness; (2) Greenwood_Tripp model considering the solid_to_solid contact using the statistical values of the summit roughness; and (3) flow factor considering the surface topology. This study also compares two cases of skirt shapes with minimum oil film thickness, peak oil film pressure, asperity contact pressure, wear rate using the Archard model and friction power loss (i.e., frictional loss mean effective pressure (FMEP)). Accordingly, the study compares the calculated wear pattern with the field test result of the piston operating for 12,000h to verify the quantitative integrity of the numerical analysis. The results show that the selected profile and the piston skirt ovality reduce friction power loss and peak oil film pressure by 7% and 57%, respectively. They also increase the minimum oil film thickness by 34%.

An Experimental Study on the Measurement of the Instantaneous Surface Temperature of the Piston of the DI Mono Cylinder Diesel Engine (직분식 단기통 디젤기관 피스톤의 순간온도 측정에 관한 실험적 연구)

  • 이재순;이현구;강태경;이응래;정인곤;안병태
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.1
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    • pp.196-204
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    • 1998
  • For the experimental measurement of instantaneous surface temperature of the piston of the DI mono cylinder diesel engine, the instantaneous temperature proves, data acquisition system, and grass-hopper type linkage system were developed. The instantaneous temperatures on the piston bowl, crown, lands and skirt were measured and analyzed, and the following conclusions were derived ; (i) The crank angle for the maximum instantaneous temperature during one cycle varies and moves back and forth by the measuring positions and engine speeds. (ii) The engine speeds, the positions of the measuring points and the cooling water temperature had an effect on the instantaneous temperature amplitude. (iii) The instantaneous temperature suing phenomena appeared on the temperature profiles of the piston crown, top and second land of ring, but on the temperature profiles of the parts of the third land of the fing and skirt, they didn't appear, (iv) The isothermal lines in the piston were acquired through the operation of the finite elements method using the measured temperatures as the boundary conditions.

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