Piston-Ring Lubrication Problems for Refrigeration Compressors Considering Combined Effects of Supply Oil Quantity and Surface Roughness

1996 ◽  
Vol 118 (2) ◽  
pp. 286-291 ◽  
Author(s):  
H. Nakai ◽  
N. Ino ◽  
H. Hashimoto
Keyword(s):  
Surface Roughness ◽  
Friction Force ◽  
Piston Ring ◽  
Reynolds Equation ◽  
Numerical Procedure ◽  
Cylinder Wall ◽  
Combined Effects ◽  
One Dimensional ◽  
Modified Reynolds Equation ◽  
Piston Ring Lubrication

Reciprocating-type compressors are widely used for refrigeration systems, and an understanding of piston-ring lubrication in the compressor is vital for designers in reducing the energy losses due to friction because a substantial portion of friction in the compressors is attributable to the piston-ring assembly. This study aimed at developing a one-dimensional analysis for lubrication between the piston-ring and cylinder of refrigeration compressors considering the combined effects of supply oil quantity and surface roughness on piston-ring face and cylinder wall. In the theoretical model, the piston-ring is treated as a one-dimensional dynamically loaded bearing with combined sliding and squeezing motion. The one-dimensional modified Reynolds equation based on the average flow model by Patir and Cheng is used as a governing equation. In the analysis of the modified Reynolds equation, two-types of inlet boundary conditions, flooded condition and starvation condition, are applied at the leading edge according to the supply oil quantity, and the Reynolds boundary condition is applied at the trailing edge. A numerical procedure is then developed to estimate the cyclic variation of minimum film thickness, inlet and outlet positions of lubrication film and friction force, and the combined effects of supply oil quantity and surface roughness height are examined for a typical refrigeration compressor. It is clarified from the numerical results that the supply oil quantity and surface roughness affect significantly the friction force of the piston-ring for refrigeration compressors.

Effects of Film Temperature on Piston-Ring Lubrication for Refrigeration Compressors Considering Surface Roughness

1998 ◽  
Vol 120 (2) ◽  
pp. 252-258 ◽  
Author(s):  
H. Nakai ◽  
N. Ino ◽  
H. Hashimoto
Keyword(s):  
Surface Roughness ◽  
Piston Ring ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Leading Edge ◽  
Combined Effects ◽  
Oil Film ◽  
One Dimensional ◽  
The One ◽  
Piston Ring Lubrication

This paper describes a theoretical model for piston-ring lubrication considering the combined effects of surface roughness and oil film temperature variation for refrigeration compressors. In the model, the piston-ring is treated as a one-dimensional dynamically loaded bearing with combined sliding and squeezing motion. The one-dimensional modified Reynolds equation, based on the average flow model by Patir and Cheng, is used to determine the pressure distribution, and the one-dimensional energy equation, considering the heat generated due to contact of asperities, is applied to calculate the oil film temperature distribution. In the analysis of the modified Reynolds equation, the flooded condition and Reynolds condition are employed at the leading edge and trailing edge of piston-ring, respectively. On the other hand, in the analysis of the modified energy equation, a constant temperature equivalent to the cylinder wall temperature is assumed at the leading edge. From numerical results of the minimum film thickness, pressure and temperature distributions and friction force, the combined effects of surface roughness and oil film temperature variation on these lubrication characteristics are clarified.

Numerical study of influences of hard particles in lubricant on tribological performances of the piston ring

2007 ◽  
Vol 221 (3) ◽  
pp. 361-372 ◽  
Author(s):  
F M Meng ◽  
Y Y Zhang ◽  
Y Z Hu ◽  
H Wang
Keyword(s):  
Friction Force ◽  
Contact Stress ◽  
Piston Ring ◽  
Reynolds Equation ◽  
Numerical Study ◽  
Cylinder Wall ◽  
Finite Element Program ◽  
Hard Particles ◽  
Element Program ◽  
Maximum Contact

Influences of hard particles lying in the lubrication region between piston ring face and cylinder wall, including the effects of a non-contact particle and contact particle, on tribological performances of the piston ringwere numerically analysed. A modified Reynolds equation incorporating a non-contact particle effect was presented. The total friction force, deformation, and contact stress of the ring, with a non-contact particle and contact particle consideration, were solved separately by using finite-element program code of the authors and software ANSYS 5.7. The numerical results show that obvious changes in the total friction force and deformation of the ring can occur, if the diameter and height across the film thickness of a non-contact particle and axial velocity difference between the non-contact particle and ring are considered. The maximum contact stress of the ring is obviously affected by the contact particle's interfering time and velocity, and hardness value of the plastically deformed particle.

Analysis of Tribological Performance of Piston Ring Lubrication

2011 ◽  
Author(s):  
Yibin Guo ◽  
Wanyou Li ◽  
Dequan Zou ◽  
Xiqun Lu ◽  
Tao He
Keyword(s):  
Film Thickness ◽  
Friction Force ◽  
Power Loss ◽  
Piston Ring ◽  
Design Parameters ◽  
Oil Film ◽  
Starved Lubrication ◽  
Piston Ring Lubrication ◽  
Cylinder Bore ◽  
Lubrication Conditions

In this paper a mixed lubrication model considering lubricant supply conditions on cylinder bore has been developed for the piston ring lubrication. The numerical procedures of both fully flooded and starved lubrication were included in the model. The lubrication equations and boundary conditions at the end of strokes were discussed in detail. The effects of piston ring design parameters, such as ring face profile and ring tension, on oil film thickness, friction force and power loss under fully flooded and starved lubrication conditions due to available lubricant supply on cylinder bore were studied. The simulation results show that the oil available in the inlet region of the oil film is important to the piston ring friction power loss. With different ring face crown heights and tensions, the changes of oil film thickness and friction force were apparent under fully flooded lubrication, but almost no changes were found under starved lubrication except at the end of a stroke. In addition, the oil film thickness and friction force were affected evidently by the ring face profile offsets under both fully flooded and starved lubrication conditions, and the offset towards the combustion chamber made a large contribution to forming thicker oil film during the expansion stroke. So under different lubricant supply conditions on the cylinder bore, the ring profile and tension need to be adjusted to reduce the friction and power loss. Moreover, the effects of lubricant viscosity, surface composite roughness, and engine operating speed on friction force and power loss were also discussed.

Effects of Surface Roughness and Additives in Lubrication: Generalized Reynolds Equation and its Application to Elastohydrodynamic Film

1987 ◽  
Vol 201 (1) ◽  
pp. 1-9 ◽  
Author(s):  
P Sinha ◽  
J S Kennedy ◽  
C M Rodkiewicz ◽  
P Chandra ◽  
R Sharma ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Molecular Size ◽  
One Dimensional ◽  
Theoretical Investigations ◽  
Minimum Film Thickness ◽  
Porous Matrices ◽  
The Mean ◽  
Generalized Reynolds Equation

To study the effects of surface roughness and additives in lubrication, a generalized form of Reynolds equation is derived by taking into account the roughness interaction zones adjacent to the moving rough surfaces as sparsely porous matrices and purely hydrodynamic film of micropolar fluid characterizing the lubricant with additives. A particular, one-dimensional form of this equation is used to study these effects on the elastohydrodynamic (EHD) minimum film thickness at the inlet, between two rough rollers. It is shown that for the low permeability of the roughness zone, the EHD film thickness increases as the mean height of the asperities increases, whereas for the high permeability it decreases. The EHD film thickness is also found to increase with the concentration of the additives and the molecular size of the particles. These results are in conformity at least qualitatively, with various experimental and theoretical investigations, cited in the paper.

Surface Roughness Effects in High-Speed Hydrodynamic Journal Bearings

1997 ◽  
Vol 119 (4) ◽  
pp. 776-780 ◽  
Author(s):  
H. Hashimoto
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Reynolds Equation ◽  
Computation Time ◽  
Experimental Results ◽  
Roughness Effects ◽  
Modified Reynolds Equation ◽  
Nonlinear Simultaneous Equations ◽  
Theoretical Results ◽  
Good Agreement

This paper describes an applicability of modified Reynolds equation considering the combined effects of turbulence and surface roughness, which was derived by Hashimoto and Wada (1989), to high-speed journal bearing analysis by comparing the theoretical results with experimental ones. In the numerical analysis of modified Reynolds equation, the nonlinear simultaneous equations for the turbulent correction coefficients are greatly simplified to save computation time with a satisfactory accuracy under the assumption that the shear flow is superior to the pressure flow in the lubricant films. The numerical results of Sommerfeld number and attitude angle are compared with the experimental results to confirm the applicability of the modified Reynolds equation in the case of two types of bearings with different relative roughness heights. Good agreement was obtained between theoretical and experimental results.

Numerical Simulation of Piston Ring Lubrication with Multi-Grade Oil

2014 ◽  
Vol 595 ◽  
pp. 83-90
Author(s):  
A. Mohamad Salaheldin ◽  
Qun Zheng ◽  
Xi Qun Lu ◽  
Yi Bin Guo ◽  
Jing Zhi Zhu
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Piston Ring ◽  
Reynolds Equation ◽  
Viscosity Index ◽  
Power Losses ◽  
Oil Characteristics ◽  
Simulation Results ◽  
Viscosity Index Improvers ◽  
Piston Ring Lubrication

The present work mainly focuses on study the piston ring lubrication parameters, and the influence of viscosity index improvers onthese parameters. Mathematical model has been developed using average Reynolds equation considering fully flooded inlet condition. The oil characteristics used in the modeling is enhanced by a series of polyacrylates viscosity index improvers, in order to indicate the effect of them on the oil film thickness, friction force, and hydrodynamic power losses. The simulation results help to explain the mechanism of action of viscosity index improvers in the oil during running conditions.

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