• Title, Summary, Keyword: Cylinder contact

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Influence of Groove Location on Lubrication Characteristics of the Piston and Cylinder in a Linear Compressor (그루브 위치가 리니어 압축기용 피스톤과 실린더의 윤활특성에 미치는 영향)

  • Jeon, W.J.;Son, S.I.;Lee, H.;Kim, J.W.;Kim, K.W.
    • Tribology and Lubricants
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    • v.32 no.1
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    • pp.24-31
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    • 2016
  • In this paper hydrodynamic lubrication analysis is carried out to investigate the effects of groove location on the lubrication performance of a piston and cylinder system in a linear compressor. The rectangle shaped grooves having a constant groove depth and width are applied on the lubrication area of the piston. The Universal Reynolds equation is used to calculate the oil film pressure, and the Elrod algorithm with the finite different method is used to solve the governing equation. The JFO boundary condition is applied to predict cavitation regions. Transient analysis for different locations of the grooves on the piston is carried out using the typical operating condition of the linear compressor in order to estimate the variations of frictional power losses and minimum film thicknesses. When the grooves are applied on the lubrication area, both the frictional power loss and the minimum film thickness decrease. The frictional power loss can be reduced effectively, while maintaining a minimum film thickness to enable the piston operation without direct contact with the cylinder surface, by means of choosing a proper location of the grooves. The optimum location of the grooves to improve a lubrication performance depends on the operation condition or the system requirements specification.

Experimental Study on the Friction Characteristics of Pin-Bush Bearing Metals for Diesel Engine (디젤엔진용 핀부시 베어링 소재의 마찰특성에 관한 실험적 연구)

  • Kim, Chung-Kyun;Kim, Kyung-Seob
    • Tribology and Lubricants
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    • v.25 no.6
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    • pp.409-413
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    • 2009
  • This paper presents the hardness and friction characteristics of pb-free pin-bush bearing metal, which is manufactured by a centrifugal casting technology. A bronze metal with a high hardness and low friction properties is usually used for Diesel engine pin-bush bearing and high pressure cylinder. Pb-free metal for pin-bush bearings shows a little high hardness of 120 Hv compared with that of a conventional Pb bearing metal of 100~110 Hv. In general, the friction coefficient of pin-bush bearings is affected by a rotating speed and a load for various rubbing contact modes. But a contact load is more influential parameter when the contact rubbing mode transits from a mixed lubrication to a dry friction contact. The experimental result shows that the friction coefficient is more unstable at the dry contact mode compared with that of other two rubbing modes such as oil film contact and mixed friction conditions.

Measurement of Pressure-Rise at No-Load in 800kV Model Interrupter (800kV 차단부의 무부하 압력상승 측정)

  • Chang, K.C.;Song, K.D.;Chung, J.K.;Song, W.P.;Kim, J.B.;Park, K.Y.;Shin, Y.J.
    • Proceedings of the KIEE Conference
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    • pp.475-478
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    • 1995
  • The variations of cold gas properties such as density, pressure, temperature and velocity which are dependent each other are closely related with the dielectric recovery of an interrupter. So, the pressure-rises at no-load in the puffer cylinder and in front of fixed arcing contact of 800kV model interrupter were measured experimentally using pressure transducers of strain gage type and semiconducting type, respectively. The maximum value of pressure-rise in the puffer cylinder increased almost linearly from 7.6 bar at the minimum operated pressure to 9.7 bar at the maximum operated pressure, while the pressure-rise in front of fixed arcing contact was independent with the operated pressure. The measured values will be utilized in verifying the self-developed cold flow analysis program and as an input of commercialized CFD program package.

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Two-Dimensional Finite Element Analysis of Hot Radial Forging (열간반경단조의 2차원 유한요소해석)

  • 박치용;조종래;양동열
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1166-1180
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    • 1990
  • The study is concerned with the two-dimensional thermo-viscoplastic finite element analysis for radial forging as an incremental forging process. The deformation and temperature distribution of the workpiece during radial forging are studied. The analysis of deformation and the analysis of heat transfer are carried out for simple upsetting of cylinder by decoupling the above two analyses. A method of treatment for heat transfer through the contact region between the die and the workpiece is suggested, in which remeshing of the die elements is not necessary. Radial forging of a mild steel cylinder at the elevated temperature is subjected to the decoupled finite element analysis as well as to the experiment. The computed results in deformation, load and temperature distribution are found to be in good agreement with the experimental observations. As an example of viscoplastic decoupled analysis of hot radial forging, forging of a square section into a circular section is treated. The stresses, strains, strain rates and temperature distribution are computed by superposing material properties as the workpiece is rotated and forged incrementally. It was been thus shown that proposed method of analysis can be effectively applied to the hot radial forging processes.

A Study on Air-tightness of High Pressure Liquid Hydrogen Pumping System at the Low Temperature (액체수소용 초저온 고압 피스톤 펌프의 기밀성 향상에 관한 기초연구)

  • Lee, Jonggoo;Lee, Jongmin;Lee, Jongtai
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.4
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    • pp.302-310
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    • 2013
  • As an initial step to develop a liquid hydrogen pump of piston type operated under cryogenic and high pressure, leakage and piston head shape for the piston pump were discussed with temperature and pressure. As the results, the leakage depended on correlation among density, viscosity, clearance area by the low temperature. In order to reduce the leakage, it was found that the air-tightness can be improved by minimizing contact surface between piston and cylinder, and also increasing pressure in-cylinder can reduce piston clearance. Among the proposed piston shapes, D type piston shape had the most air-tightness. D type piston had smaller contact surface than other piston shape and easier expansion of cup shape by pressure. The leakage of D type piston shape was found about 7%, compared with A type piston shape. But it was required that analyze about vapor lock by friction and wear resistance.

Calculation of Mixed Lubrication at Piston Ring and Cylinder Liner Interface

  • Cho, Myung-Rae;Park, Jae-Kwon;Han, Dong-Chul
    • Journal of Mechanical Science and Technology
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    • v.15 no.7
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    • pp.859-865
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    • 2001
  • This paper reports on the theoretical analysis of mixed lubrication for the piston ring. The analytical model is presented by using the average flow and asperity contact model. The cyclic variations of the nominal minimum oil film thickness are obtained by numerical iterative method. The total friction is calculated by using the hydrodynamic and asperity contact theory. The effect of the roughness height, pattern, and engine speed on the nominal minimum film thickness, friction force, ad frictional power losses are investigated. As the roughness height increases, the nominal oil film thickness and total friction force increase. Also, the effect of the surface roughness on the boundary friction is dominant at low engine speed and high asperity height. The longitudinal roughness pattern shows lower mean oil film pressure and thinner oil film thickness compared to the case of the isotropic and transverse roughness patterns.

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Analysis of Piston Seal in High-Speed Pneumatic Cylinders (고속 공기압 실린더의 피스톤 실 특성 해석)

  • Zhang, Z.J.;Kim, D.T.;Han, S.S.
    • 유공압시스템학회:학술대회논문집
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    • pp.99-104
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    • 2010
  • Nonlinear seal friction in pneumatic cylinders can impede the performance of pneumatic systems designed for high precision positioning with favorable high speed actuation. The behaviour of an elastomeric piston seal in high speed pneumatic cylinders is analysed by nonlinear finite element analysis using ABAQUS. The contact pressures, stress and strain distributions and frictional forces of the piston seal are simulated with variation of interference fits, supply pressures, friction coefficients and piston rod velocities. The nonlinear finite element model of the piston seal is used to predict deformation of a seal, friction force and contact pressure distributions.

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Performance Analysis of Urethane Packing in the Hydraulic Breaker by a Finite Element Method (유한요소해석을 이용한 유압브레이커용 우레탄 패킹의 성능분석)

  • Shin, Hyun Woo;Hong, Jong Woo;Choi, Yi Kwang
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.2
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    • pp.139-147
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    • 2016
  • Performances of urethane packing in the hydraulic breaker were analyzed using a finite element method. Because of high temperature and high pressure in the hydraulic breaker, it is better to use urethane rather than rubber as a packing material. We obtained the physical properties of urethane at elevated temperature by the tensile test. We analyzed buffer seal and U-packing maintaining the pressure and preventing oil leakage. Deformation, stress distribution, contact length, contact pressure of packing at each pressure step were obtained using finite element analysis. As the temperature increases, stress and contact force tend to decrease at low pressure. As the gap between piston and cylinder increases, contact length and contact forces decrease. Consequently, it is possible to design the packing section using these analyses, and construct a system to predict the possibility of oil leakage in the hydraulic breaker.

Instability of Plunging Breaking Wave Impact on Inclined Cylinder (경사진 실린더에 작용하는 플런징 쇄파 충격력의 불안정성 고찰)

  • Hong, Key-Yong;Shin, Seung-Ho
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.10 no.4
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    • pp.187-192
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    • 2007
  • Impact on cylindrical surface caused by plunging breaking waves is investigated experimentally. The breaking waves are generated in a wave flume by decreasing the wave maker frequencies linearly and focusing the generated wave components at one specific location. The breaking wave packets are based on constant wave steepness spectrum. Three inclination angles of cylinder are applied to examine the effect of contact angle between cylinder and front surface of breaking waves. Also, the effect of cylinder diameter on pressure distribution and its peak value is investigated by adopting three cylinders with different diameters. The longitudinal location of cylinder is slightly moved in eight different points to find out a probable maximum value of impact pressure. The pressures and total force on cylinder surface are measured by piezo-electric pressure sensors and 3-components load cell with 30kHz sampling rate. The variation of peak impact pressures and forces is analyzed in terms of cylinder diameter, inclination angle and location. Also, the pressure distribution on cylindrical surface is examined. The cylinder location and surface position are more important parameters that govern the magnitude and shape of peak pressures, while the cylinder diameter and inclined angle are relatively insignificant. In a certain conditions, the impact phenomenon becomes very unstable which results in a large variation of measured valves in repeated runs.

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A Study on Slamming Impact Pressure (슬래밍 충격 압력에 대한 연구)

  • Park, Jun-Soo;Oh, Seung-Hoon;Kwon, Sun-Hong;Chung, Jang-Young
    • Journal of Ocean Engineering and Technology
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    • v.23 no.1
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    • pp.67-73
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    • 2009
  • This study presents the results of a slamming experiment using a pneumatic cylinder. The employment of the pneumatic cylinder showed a relatively good repeatability when the results were compared with those of other slamming devices. The experiment was done for various incident angles. An air pocket was believed to cause a reduction in the magnitude of the impact pressure with an incident angle of $0^{\circ}$ for the water entry. A high speed camera was used in an attempt to locate the time of the contact between the bottom of the specimen and the free surface. It seemed that the maximum pressure occurred before the water contacted the bottom of the specimen.