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.

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.

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.

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.

Heat Transfer and Thermal Elastic Deformation Analysis on the Piston/Cylinder Interface of Axial Piston Machines

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Matteo Pelosi ◽  
Monika Ivantysynova
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Elastic Deformation ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Fluid Film ◽  
Design Elements ◽  
Piston Cylinder ◽  
Viscous Shear ◽  
Axial Piston

The piston/cylinder interface of swash plate–type axial piston machines represents one of the most critical design elements for this type of pump and motor. Oscillating pressures and inertia forces acting on the piston lead to its micro-motion, which generates an oscillating fluid film with a dynamically changing pressure distribution. Operating under oscillating high load conditions, the fluid film between the piston and cylinder has simultaneously to bear the external load and to seal the high pressure regions of the machine. The fluid film interface physical behavior is characterized by an elasto-hydrodynamic lubrication regime. Additionally, the piston reciprocating motion causes fluid film viscous shear, which contributes to a significant heat generation. Therefore, to fully comprehend the piston/cylinder interface fluid film behavior, the influences of heat transfer to the solid boundaries and the consequent solid boundaries’ thermal elastic deformation cannot be neglected. In fact, the mechanical bodies’ complex temperature distribution represents the boundary for nonisothermal fluid film flow calculations. Furthermore, the solids-induced thermal elastic deformation directly affects the fluid film thickness. To analyze the piston/cylinder interface behavior, considering the fluid-structure interaction and thermal problems, the authors developed a fully coupled simulation model. The algorithm couples different numerical domains and techniques to consider all the described physical phenomena. In this paper, the authors present in detail the computational approach implemented to study the heat transfer and thermal elastic deformation phenomena. Simulation results for the piston/cylinder interface of an existing hydrostatic unit are discussed, considering different operating conditions and focusing on the influence of the thermal aspect. Model validation is provided, comparing fluid film boundary temperature distribution predictions with measurements taken on a special test bench.

Rheological Behaviors of Pressure-Driven Radial Flow

2007 ◽  
Author(s):  
Z. Xie ◽  
Q. Zou ◽  
D. Yao
Keyword(s):  
Film Thickness ◽  
Radial Flow ◽  
Practical Interest ◽  
Fluid Film ◽  
Fluid Viscosity ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Shear Dependent Viscosity ◽  
Fluid Film Thickness ◽  
Pressure Driven

The characteristics of fluid flows confined within microscale space are of theoretical and practical interest [1]. Such flow includes the thin lubrication films, the liquid flow between biological cells, and the flow of polymer melts in a micro-injection molding machines, etc. A pressure-driven radial flow microrheometry (PDRFM) is used to characterize high-shear microscale fluids. The shear-dependent viscosity of the pressure-driven radial flow is modeled to investigate the possible size effect on the fluid viscosity. In the modeling, the surface shear rate and surface shear stress at the edge of the radial flow are expressed in terms of three measurable parameters, i.e. the flow rate, the loading force, and the fluid film thickness. By decreasing the fluid film thickness to microscale level, this model can be used to study the microscale effect of any homogeneous fluids. The analysis has been verified by using CFD simulations as digital testing platforms. Furthermore, the preliminary experimental results of Newtonian and non-Newtonian flows also proved the rheological modeling.

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