• Title, Summary, Keyword: Piston

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Numerical Analysis of the Piston Secondary Dynamics in Reciprocating Compressors

  • Kim, Tae-Jong
    • Journal of Mechanical Science and Technology
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    • v.17 no.3
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    • pp.350-356
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    • 2003
  • In this study, a numerical analysis for the piston secondary dynamics of small refrigeration reciprocating compressors is performed. In general, the length of cylinder in this class of compressors is shortened to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder wall is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the piston dynamics, the variation in bearing length of the piston and all corresponding forces and moments are considered in order to determine the piston trajectory, velocity and acceleration at each step. A Newton-Raphson procedure was employed in solving the secondary dynamic equations of the piston. The developed computer program can be used to calculate the entire piston trajectory and the lubrication characteristics as functions of crank angle under compressor running conditions. The results explored the effects of some design parameters and operating conditions on the stability of the piston, the oil leakage, and friction tosses.

Analysis of the Dynamic Behavior and Lubrication Characteristics of the Piston-Cylinder System in Reciprocating Compressors (왕복동형 압축기 피스톤-실린더계의 동적 거동 및 윤활특성 해석)

  • 김태종
    • Tribology and Lubricants
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    • v.18 no.4
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    • pp.291-298
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    • 2002
  • In this study, a numerical analysis f3r the piston secondary dynamics and lubrication characteristics of small refrigeration reciprocating compressors is presented. In general, the length of cylinder in this class of compressors is shortened to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder wall is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the piston dynamics, the change in bearing length of the piston and all corresponding forces and moments are considered in order to determine the piston trajectory, velocity and acceleration at each step. A Newton-Raphson procedure was employed in solving the secondary dynamic equations of the piston. The developed computer program can be used to calculate the entire piston trajectory and the hydrodynamic forces and moments as functions of crank angle under compressor running conditions. The results explored the effects of the radial clearance, lubricant viscosity, and pin location on the stability of the piston, the oil leakage, and friction losses.

A Study on the Effect of Piston Pin Offset on a Piston Motion and Kinetic Energy Loss (피스톤핀 옵셋이 피스톤운동과 운동에너지 손실에 미치는 영향에 관한 연구)

  • Han, D.J.;Choi, J.K.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.1 no.3
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    • pp.22-33
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    • 1993
  • A theoretical analysis of predicting the detailed motion of a piston-crank mechanism within piston-guide clearance is presented, and the analysis is applied to the piston motion in a gasoline engine. A piston movement program is developed to calculate the piston attitude relative to the bore, the piston to bore impact velocity and kinetic energy loss and the net transverse force acting on the piston. This paper presents the formulation of a set of differential equations governing the transverse and rotational motion of a piston. These equations of motion were solved by well established Runge-Kutta method. As a result of this study, it is possible to predict the effects of piston geometry and piston pin offset on a piston motion and kinetic energy loss.

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Analysis of the Effects of Bore Clearance Due to Skirt Profile Changes on the Piston Secondary Movements

  • Jang, Siyoul
    • KSTLE International Journal
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    • v.3 no.2
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    • pp.84-89
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    • 2002
  • Clearance movements of engine piston are very related to the piston impact to the engine block 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 magnitude to thrust side have better performance that has low side impact during the engine cycle.

A Lubrication Analysis between the Piston and Cylinder in Hydraulic Piston Pumps Part II : The Effect of Piston Reciprocating Motion (유압 피스톤 펌프의 피스톤과 실린더 사이의 윤활해석 (제2보 : 피스톤의 왕복운동에 의한 영향))

  • 박태조
    • Tribology and Lubricants
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    • v.17 no.6
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    • pp.435-440
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    • 2001
  • A numerical analysis between the piston and cylinder in hydraulic piston pumps under reciprocating motion is presented. A finite difference method and the Newton-Raphson method are used simultaneously to solve the Reynolds equation in the clearance and the equation of motion for the piston. The tapered piston showed stable behaviors regardless of their initial eccentric positions in the clearance, and the reciprocating speed affect highly on the piston end trajectories. Therefore, the numerical methods and results of present study can be used in the lubrication study of other piston-cylinder type fluid machineries.

An Experimental Study on the Piston Slap Motion Measurement during Real Operation of an IDI DIESEL Engine. (간접분사식 디젤엔진의 실운전중 피스톤 Slap 운동측정에 관한 실험적 연구)

  • 박승일;김승수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.1 no.1
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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.

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A Lubrication Analysis between the Piston and Cylinder in Hydraulic Piston Pumps Part 1: The effect of piston shape (유압 피스톤 펌프의 피스톤과 실린더 사이의 윤활해석 (제1보:피스톤 형상에 의한 영향))

  • 박태조;전병수
    • Tribology and Lubricants
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    • v.14 no.1
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    • pp.64-69
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    • 1998
  • A numerical analysis is carried out to study the effect of piston shape on the lubrication characteristics between the cylinder and piston in hydraulic piston pumps. The results showed that the shape of piston affect significantly the pressure distribution in the clearance, the lateral force acting on the piston and leakage flow through the clearance. Partially tapered piston is more effective than any other piston shapes because it reduces the possibility of hydraulic locking and improves the volumetric efficiency of the pump.

Performance Comparison of Collecting Efficiencies to Various Types of Piston Oil Cooling Gallery (피스톤 오일 냉각 유로 형태에 따른 수집효율 성능 비교)

  • Lee, Jeong-Keun;Chun, Sang-Myung;Joo, Dae-Heon;Ryu, Kwan-Ho
    • Tribology and Lubricants
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    • v.26 no.1
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    • pp.21-30
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    • 2010
  • In this research, it is investigated the collecting efficiency of jet oil to several types of piston oil cooling gallery by using recently developed PCJ (piston cooling jet) rig tester. So it will be selected for a better design of piston oil cooling gallery. The collecting efficiencies at each type of piston cooling galleries are measured under conditions of a few piston positions, and several oil jet pressures and oil viscosities. Furthermore, the type of jet cone will be compared for a few jet pressure conditions. The selected type of piston oil cooling gallery is planned to be applied to the target engine which is now developing to satisfy the EURO VI emission regulation.

A Study on the Development of Aluminum Piston by Forging Process (알루미늄 단조 피스톤의 개발에 관한 연구)

  • Kim, Y.H.;Bae, W.B.;Kim, H.S.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.9
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    • pp.30-36
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    • 1997
  • In this study, the development of an aluminum forged piston was tried to substitute the cast piston, in which there were internal defects such as blow hole and shrink pipe. A gasoline engine piston was chosen as an example for developing the forged piston. Before aluminum forging, model, material (plasticine) test was carried out to investigate the forgeability and internal flow pattern of the forged piston at room temperature. From the result of model material test, an aluminum piston to be forged was redesigned. The aluminum pistion was forged in hot process. The quality of a forged piston was compared with that of a cast piston in the point of mechanical properties, internal defect and microstructure. It was proved that the forged piston was superior to the cast piston.

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The Study on Development of Performance in Cryogenic Piston Pump (초저온 피스톤 펌프의 성능 향상에 관한 연구)

  • Lee, Jongmin;Lee, Jonggoo;Lee, Kwangju;Lee, Jongtai
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.3
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    • pp.240-246
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    • 2014
  • In order to develop a universal cryogenic piston pump of small size for increasing utilization of liquid hydrogen, dynamic compression performance of piston pump were evaluated and improvements were also discussed for piston rod and piston tip. The cryogenic piston pump has crosshead structure and inclined cup shape piston tip. As the results, it was found that i) insulation of heat flow from piston-rod part is required for stable operation ii) improving the self-clearance adjustment effect of piston tip and reducing piston eccentricity were desirable to promote pumping pressure and operating range.