Measurement of fluid film thickness on the valve plate in oil hydraulic axial piston pumps (I)-bearing pad effects-

2003 ◽  
Vol 17 (2) ◽  
pp. 246-253 ◽  
Author(s):  
Jong Ki Kim ◽  
Jae-Youn Jung
Keyword(s):  
Film Thickness ◽  
Valve Plate ◽  
Fluid Film ◽  
Axial Piston Pumps ◽  
Fluid Film Thickness ◽  
Axial Piston

scholarly journals Study of the influence of slipper parameters on the power efficiency of axial piston pumps

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401880146 ◽  
Author(s):  
Gaston Haidak ◽  
Dongyun Wang ◽  
E Shiju ◽  
Jun Liu
Keyword(s):  
Mathematical Model ◽  
Film Thickness ◽  
Power Loss ◽  
Power Efficiency ◽  
Fluid Film ◽  
Total Power ◽  
Axial Piston Pumps ◽  
Swash Plate ◽  
Fluid Film Thickness ◽  
Axial Piston

This article presents the influence and impact of the gap between the outer and the inner diameter of the slipper on the performance of axial piston pumps. For this, a mathematical model establishing and evaluating the quantities involved in the total power loss is established. Four slippers having a different values of the ratio between their diameters are considered; for which the study and the simulation concerning the fluid film thickness, the forces, the flow and the total power loss between the slipper and the swash plate are developed and compared. After the analysis of all these parameters for different slippers, the results of the simulation show that for each slipper, there are values of the optimum fluid film thickness for which the pump has the minimum in terms of power loss between the slipper and the swash plate. And after the comparison, the favourable ratio between the diameters of the slipper for good lubrication is given. The accuracy between the mathematical model and simulation results is checked, and a discussion is made. Finally, a conclusion based on the results of the lost power is made.

Surface Deformations Enable High Pressure Operation of Axial Piston Pumps

2011 ◽  
Author(s):  
Matteo Pelosi ◽  
Monika Ivantysynova
Keyword(s):  
Film Thickness ◽  
Material Properties ◽  
Fluid Film ◽  
Cylinder Block ◽  
Steel Cylinder ◽  
Elastic Deformations ◽  
Piston Cylinder ◽  
Fluid Film Thickness ◽  
The Impact ◽  
Axial Piston

In this paper, a fully coupled fluid-structure interaction and thermal numerical model developed by the authors is used to demonstrate the impact of surface elastic deformations on the piston/cylinder fluid film thickness and on the overall axial piston pump rotating kit performance. The piston/cylinder interface is one of the most critical lubricating interfaces of axial piston machines. This interface fulfills simultaneously a bearing and sealing function under oscillating load conditions in a purely hydrodynamic regime. It represents one of the main sources of energy dissipation and it is therefore a key design element, determining axial piston machine efficiency. In the past years, the research group of the authors studied the impact of advanced micro surface design and fluid film thickness micro alteration in the piston/cylinder interface through extensive simulations and experiments. However, the numerical models used did not include the influence of surface elastic deformations, heat transfer and therefore material properties on the piston/cylinder interface behavior. Hence, the aim of this paper is to show the alterations on fluid film thickness and on the consequent coupled physical parameters due to the solid boundaries pressure and thermal surface elastic deformations. A simulation study considering two different material properties for the cylinder bores is performed, where a steel cylinder block and a steel cylinder block with brass bushings are separately studied. Piston/cylinder gap pressure field and coupled gap surface elastic deformations due to pressure and thermal loading are shown for the different materials. The impact of the different materials behavior on lubricating interface performance is discussed.

A partial lubrication model between valve plate and cylinder block in axial piston pumps

2015 ◽  
Vol 229 (17) ◽  
pp. 3201-3217 ◽  
Author(s):  
Lei Han ◽  
Shaoping Wang ◽  
Chao Zhang
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Multiple Scales ◽  
Valve Plate ◽  
Cylinder Block ◽  
Height Distribution ◽  
Axial Piston Pumps ◽  
Surface Profiles ◽  
Axial Piston ◽  
Lubrication Conditions

Axial piston hydraulic pumps are commonly used in aircraft, which makes analysis of their lubrication conditions of significant importance. Oil film between valve plate and cylinder block plays an most important role in pump lubrication. This paper proposes a partial lubrication model of the contact surfaces between valve plate and cylinder block in axial piston pumps for predicting film thickness. The asperity curvature at multiple scales and height distribution are obtained by analyzing actual contact surface profiles, then the separating pressure of asperities is estimated by the Hertz theory and the fluid separating pressure is calculated by Reynolds equation. Experimental results indicate that this model can predict film thickness accurately.

Improving the Volumetric Efficiency of the Axial Piston Pump

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Shu Wang
Keyword(s):  
Operating Conditions ◽  
Volumetric Efficiency ◽  
Valve Plate ◽  
Piston Pump ◽  
Efficient Design ◽  
Axial Piston Pumps ◽  
Definition Of ◽  
Engineering Practices ◽  
First Time ◽  
Axial Piston

The volumetric efficiency is one of the most important aspects of system performance in the design of axial piston pumps. From the standpoint of engineering practices, the geometric complexities of the valve plate (VP) and its multiple interactions with pump dynamics pose difficult obstacles for optimization of the design. This research uses the significant concept of pressure carryover to develop the mathematical relationship between the geometry of the valve plate and the volumetric efficiency of the piston pump. For the first time, the resulting expression presents the theoretical considerations of the fluid operating conditions, the efficiency of axial piston pumps, and the valve plate designs. New terminology, such as discrepancy of pressure carryover (DPC) and carryover cross-porting (CoCp), is introduced to explain the fundamental principles. The important results derived from this study can provide clear recommendations for the definition of the geometries required to achieve an efficient design, especially for the valve plate timings. The theoretical results are validated by simulations and experiments conducted by testing multiple valve plates under various operating conditions.

Performance Analysis of a Nonrecessed Hybrid Conical Journal Bearing Compensated With Capillary Restrictors

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Prashant G. Khakse ◽  
Vikas M. Phalle ◽  
S. S. Mantha
Keyword(s):  
Performance Analysis ◽  
Film Thickness ◽  
Journal Bearing ◽  
Fluid Film ◽  
Load Parameter ◽  
Radial Load ◽  
Wide Range ◽  
Bearing Stiffness ◽  
Fluid Film Thickness ◽  
Film Stiffness

The present paper deals with the performance analysis of a nonrecessed hole-entry hydrostatic/hybrid conical journal bearing with capillary restrictors. Finite element method has been used for solving the modified Reynolds equation governing the flow of lubricant in the clearance space of journal and bearing. The hole-entry hybrid conical journal bearing performance characteristics have been depicted for a wide range of radial load parameter (W¯r  = 0.25–1.5) with uniform distribution of holes at an angle of 30 deg in the circumferential direction. The numerically simulated results have been presented in terms of maximum fluid film pressure, minimum fluid film thickness, lubricant flow rate, direct fluid film stiffness coefficients, direct fluid film damping coefficients, and stability threshold speed. However, the proposed investigation of nonrecess hole-entry hybrid conical journal bearing shows important performance for bearing stiffness and minimum fluid film thickness at variable radial load and at given operating speed.

Lubrication Analysis of the Thrust Bearing in the Valve Plate of a Swash-Plate Type Axial Piston

2011 ◽  
Author(s):  
J. H. Shin ◽  
H. E. Kim ◽  
K. W. Kim
Keyword(s):  
Thrust Bearing ◽  
Valve Plate ◽  
Time Dependent ◽  
Fluid Film ◽  
Simulation Tool ◽  
Film Pressure ◽  
Swash Plate ◽  
Cylinder Barrel ◽  
Axial Piston ◽  
Plate Type

This application study of a swash-plate type axial piston pump was concerned about the hydrostatic lubrication characteristics of cylinder barrel and valve plate which are main rotating body and its opposite moving part respectively. A computer simulation was implemented to assess thrust bearing and mechanical sealing functions of the fluid film between cylinder barrel and valve plate. A new algorithm was developed to facilitate simultaneous calculations of dynamic cylinder pressure, 3 degree-of-freedom barrel motions considering inertia effect, and fluid film pressure assuming full fluid film lubrication regime. Using the simulation tool, force and moment balancing of cylinder barrel which is a key issue of piston pump design was analyzed. Time dependent fluid film pressure and thickness distributions for several given balance ratios were calculated. This analysis helps to decide appropriate balance ratio in the valve and cylinder barrel. Oil leakage flow and friction torque in the fluid film between cylinder barrel and valve plate were calculated as well and discussed in the viewpoint of energy loss. The results show that film thickness in plain surface is not high enough to bear the barrel and reduce power loss and that surface waviness which exists in actual sliding surfaces can have a positive effect on it. This simulation tool could also predict time dependent barrel motions due to simultaneous calculation algorithm. It has been known that cylinder barrel rotates with oscillation. Therefore average clearance, tilt angle, and azimuth angle were calculated for each time step and the results were discussed.

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