Material Combinations for the Piston-Cylinder Interface of Axial Piston Machines: A Simulation Study

2014 ◽  
Author(s):  
Daniel Mizell ◽  
Monika Ivantysynova
Keyword(s):  
Material Properties ◽  
High Pressures ◽  
Pump Operation ◽  
Axial Piston Pumps ◽  
Piston Cylinder ◽  
Manufacturing Complexity ◽  
Novel Material ◽  
Fluid Film Thickness ◽  
Axial Piston ◽  
Selection Of

Axial-piston pumps and motors which operate at high pressures (above 380 bar) typically incorporate a copper-alloy bushing paired with a steel piston. Manufacturers have a desire to eliminate such nonferrous heavy metals from their designs to reduce manufacturing complexity and cost. This paper explores possible alternatives to this material combination at high pressures. Simulations incorporating thermal and elastic material properties are computed using a Fluid Structure Thermal Interaction (FSTI) model. The results of simulation reveal how material properties interact to affect fluid film thickness and pressure generation during pump operation. An understanding of these phenomena points the way toward the selection of novel material combinations to improve the behavior of the piston/cylinder interface.

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.

Experimental Verification of Slipper Spinning Motion in Axial Piston Pumps

2017 ◽  
Author(s):  
Qun Chao ◽  
Junhui Zhang ◽  
Qiannan Wang ◽  
Bing Xu ◽  
Yuan Chen
Keyword(s):  
Experimental Verification ◽  
Experimental Investigations ◽  
Test Rig ◽  
Plate Interface ◽  
Pump Operation ◽  
Axial Piston Pumps ◽  
Swash Plate ◽  
Lubrication Characteristics ◽  
Spinning Speed ◽  
Axial Piston

As one of the micro motions of slipper in axial piston pumps, the slipper spinning motion has a significant effect on the lubrication characteristics of slipper/swash plate interface. However, no experimental investigations on the slipper spin were available in previous studies. The aim of this work is to design a novel test rig to measure the slipper spinning speed. A detailed description of this test rig will be given followed by a sample result of the slipper spinning motion. Also, a simulation model considering the slipper spin will be developed to investigate the effects of the spinning motion on the slipper performance. It can be concluded that the slipper spinning motion does exist during pump operation, which is helpful to prevent the slipper from further tilting motion.

scholarly journals A Numerical Study on Influence of Temperature on Lubricant Film Characteristics of the Piston/Cylinder Interface in Axial Piston Pumps

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1842 ◽  
Author(s):  
Yueheng Song ◽  
Jiming Ma ◽  
Shengkui Zeng
Keyword(s):  
Thermal Effect ◽  
Contact Time ◽  
Numerical Study ◽  
Lubricant Film ◽  
Piston Pump ◽  
Pump Efficiency ◽  
Axial Piston Pumps ◽  
Piston Cylinder ◽  
Film Characteristics ◽  
Axial Piston

The loss of kinetic energy of moving parts due to viscous friction of lubricant causes the reduction of piston pump efficiency. The viscosity of lubricant film is mainly affected by the thermal effect. In order to improve energy efficiency of piston pump, this research presents a numerical method to analyze the lubricant film characteristics in axial piston pumps, considering the thermal effect by the coupled multi-disciplinary model, which includes the fluid flow field expressed by Reynolds equation, temperature field expressed by energy equation and heat transfer equation, kinematics expressed by the motion equation. The velocity and temperature distributions of the gap flow of piston/cylinder interface in steady state are firstly numerically computed. Then the distributions are validated by the experiment. Finally, by changing the thermal boundary condition, the influence of thermal effect on the lubricant film, the eccentricity and the contact time between the piston and cylinder are analyzed. Results show that with the increase of temperature, the contact time increases in the form of a hyperbolic tangent function, which will reduce the efficiency of the axial piston pump. There is a critical temperature beyond which the contact time will increase rapidly, thus this temperature is the considered as a key point for the temperature design.

Research on wear prediction of piston/cylinder pair in axial piston pumps

Wear ◽  
2020 ◽  
Vol 456-457 ◽  
pp. 203338 ◽  
Author(s):  
Fei Lyu ◽  
Junhui Zhang ◽  
Guangming Sun ◽  
Bing Xu ◽  
Min Pan ◽  
...  
Keyword(s):  
Wear Prediction ◽  
Axial Piston Pumps ◽  
Piston Cylinder ◽  
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.

Experimental Studies on the Performance of Slipper Bearings Within Axial-Piston Pumps

2004 ◽  
Vol 126 (3) ◽  
pp. 511-518 ◽  
Author(s):  
Noah D. Manring ◽  
Chris L. Wray ◽  
Zhilin Dong
Keyword(s):  
Contact Point ◽  
Experimental Studies ◽  
Load Carrying Capacity ◽  
Deformation Characteristics ◽  
Axial Piston Pumps ◽  
Load Carrying ◽  
Overall Performance ◽  
Bearing Design ◽  
Fluid Film Thickness ◽  
Axial Piston

The objectives of this study are to experimentally investigate the performance characteristics of similar slipper bearings using different socket geometries. In this study, the lubrication equations for the bearing are derived based upon an assumption that the bearing deformations are small and that they may be modeled linearly. This study is based upon the hypothesis that variations in the socket geometry will impact the deformation characteristics of the bearing and thereby have an effect on the overall performance of the design. To test this hypothesis, bearings with different socket geometries are designed and tested and compared to the original bearing design with standard socket geometry. The experimental results are then used with the analytical results to numerically infer the minimum fluid-film thickness and the magnitude of deformation for the bearing. Conclusions are drawn from these results which indicate that socket geometry has a significant impact on the bearing performance and that both leakage and load-carrying capacity may be altered by adjusting the location of the contact point within the ball-and-socket joint relative to the center of the ball.

Cylinder Bore Micro-Surface Shaping for High Pressure Axial Piston Machine Operation Using Water as Hydraulic Fluid

2017 ◽  
Author(s):  
Meike H. Ernst ◽  
Monika Ivantysynova
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
High Heat ◽  
Surface Shape ◽  
Working Fluid ◽  
Hydraulic Fluid ◽  
Hydraulic Systems ◽  
Piston Cylinder ◽  
Axial Piston Machine ◽  
Axial Piston

Water as a working fluid in hydraulic systems: the benefits of this particular hydraulic fluid are both numerous and consequential, but its implementation remains nontrivial for certain key applications. One of these key applications is the axial piston machine of swashplate type, which counts among its selling points efficiency, the possibility of variable displacement, and the ability to function in high-pressure systems [1]. Water as a working fluid tends to mar that last point with its extremely low viscosity — and the high leakages and low load support that stand as effects of that fluid property in the context of tribological interfaces. However, water’s environmentally friendly, fire resistant nature is coupled with a high thermal conductivity and high heat capacity favorable for keeping hydraulic systems cool, as well as a high bulk modulus that cuts slack in the exact execution of machine motions [2]. That makes it worth implementing in hydraulic systems, even in the face of the aforementioned troubles. This paper investigates the effects of a surface shape that can be applied to the cylinder bores of axial piston machines with the goal of improving load support while keeping down leakage in the critical piston cylinder tribological interface of axial piston machines operating at high pressures with water as their hydraulic fluid.

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