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.

Micro Surface Shaping for the High-Pressure Operation of Piston Machines With Water as a Working Fluid

2015 ◽  
Author(s):  
Meike H. Ernst ◽  
Monika Ivantysynova
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Working Fluid ◽  
Hydraulic Systems ◽  
Machinery Construction ◽  
Pressure Buildup ◽  
Piston Cylinder ◽  
Low Viscosity ◽  
Load Carrying ◽  
Surface Shaping

Oil is the main working fluid used in the hydraulics industry today — but water is nonflammable, environmentally friendly and cheap: it is the better choice of working fluid for hydraulic systems. However, there is one caveat. Water’s extremely low viscosity undermines its ability to carry load. In forest machinery, construction machinery, and aircraft systems, today’s hydraulic circuits have high operating pressures, with typical values between 300 and 420 bar. These high pressures create the need for high load-carrying abilities in the fluid films of the tribological interfaces of pumps and motors. The most challenging of these interfaces is the piston-cylinder interface of swashplate type piston machines, because the fluid must balance the entire piston side load created in this design. The low viscosity of the water turns preventing metal-to-metal contact into quite a challenge. Fortunately, an understanding of how pressure builds and shifts about in these piston-cylinder lubrication interfaces, coupled with some clever micro surface shaping, can allow engineers to drastically increase the load-carrying ability of water. As part of this research, numerous different micro surface shaping design ideas have been simulated using a highly advanced non-isothermal multi-physics model developed at the Maha Fluid Power Research Center. The model calculates leakage, power losses, film thickness and pressure buildup in the piston-cylinder interface over the course of one shaft revolution. The results allow for the comparison of different surface shapes, such as axial sine waves along the piston, or a barrel-shaped piston profile. This paper elucidates the effect of those surface profiles on pressure buildup, leakage, and torque loss in the piston-cylinder interface of an axial piston pump running at high pressure with water as the lubricant.

scholarly journals Tailoring the Bore Surfaces of Water Hydraulic Axial Piston Machines to Piston Tilt and Deformation

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5997
Author(s):  
Meike Ernst ◽  
Andrea Vacca ◽  
Monika Ivantysynova ◽  
Georg Enevoldsen
Keyword(s):  
Experimental Testing ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Surface Shape ◽  
Working Fluid ◽  
Total Efficiency ◽  
Positive Displacement ◽  
Piston Cylinder ◽  
Low Viscosity ◽  
Axial Piston

A novel virtual prototyping algorithm has been developed to design one of the most critical lubricating interfaces in axial piston machines of the swash plate type—the piston–cylinder interface—for operation with water as the working fluid. Due to its low viscosity, the use of water as a lubricant can cause solid friction and wear in these machines at challenging operating conditions. The prototyping algorithm compensates for this by tailoring the shape of the bore surface that guides the motion of each piston in this type of positive displacement machine to conform with the piston surface, taking into account both the piston’s tilt and its deformation. Shaping these surfaces in this manner can render the interface more conducive to generating hydrodynamic pressure buildup that raises its load-carrying capacity. The present work first outlines the structure of the proposed algorithm, then presents a case study in which it is employed to design a bore surface shape for use with two prototypes, one virtual and one physical—both modified versions of a 444 cc commercial axial piston pump. Experimental testing of the physical prototype shows it to achieve a significantly higher maximum total efficiency than the stock unit.

Thermo-elastohydrodynamic simulation of the piston-cylinder contact in high-pressure pumps at 3000 bar

2019 ◽  
Vol 71 (5) ◽  
pp. 702-705
Author(s):  
Ömer Özdemir ◽  
Felix Fischer ◽  
Adrian Rienäcker ◽  
Katharina Schmitz
Keyword(s):  
High Pressure ◽  
Thermal Stresses ◽  
Test Bench ◽  
High Pressures ◽  
Elastohydrodynamic Lubrication ◽  
Simulation Method ◽  
Pressure Effects ◽  
High Pressure Pump ◽  
Content Type ◽  
Piston Cylinder

Purpose The purpose of this paper is to show these effects in an abstracted micro gap test bench. Because of stronger emission laws, the ambition to raise the rail pressure in common-rail systems from the current 2500 bar to 3000 bar is a given. The pressure increase will allow fine atomization of fuel and therefore more efficient combustion. But within the technical system of the high-pressure pump, stronger thermal stresses of the piston–cylinder contact are expected. A pressure drop from such a high level causes high temperature gradients due to energy dissipation. Design/methodology/approach For a detailed examination, the critical piston–cylinder contact has been investigated in an abstracted test bench with a flat parallel gap and an equivalent thermo-elastohydrodynamic simulation model. Findings The simulation results show good accordance to the measurements of pressures, temperatures and leakages for pressures up to 3000 bar. Comparison with elastohydrodynamic lubrication results outlines the need to consider temperature and pressure effects viscosity and solid deformation for the simulation and design of tribological contacts at high pressures. Originality/value This paper describes a simulation method with high accuracy to investigate tribological contacts considering temperature effects on solid structures and the fluid film. The thermo-elastohydrodynamic lubrication simulation method is valid not only for piston–cylinder contacts in high-pressure pumps but also for journal bearings in combustion engines.

Influence of pressure distribution in the gap of piston-cylinder unit and properties of working fluid PES-3 on characteristics of high pressure piston-cylinder unit

2020 ◽  
pp. 38-42
Author(s):  
A. E. Aslanyan
Keyword(s):  
Mathematical Model ◽  
High Pressure ◽  
Pressure Distribution ◽  
Pressure Range ◽  
Pressure Change ◽  
Working Fluid ◽  
Research Results ◽  
Piston Cylinder ◽  
Pressure Distributions ◽  
The Mathematical Model

A simulation of the use of PES-3 liquid in a high-pressure piston-cylinder units was performed, and the parameters of the piston-cylinder units were determined in the article. The equations of the mathematical model describing the pressure change in the gap between the piston and the cylinder are given. As a result of the calculations, the pressure distributions in the gap between the piston and the cylinder are determined at under piston pressures less than 1.6 GPa. The profiles of the gaps between the deformed piston and cylinder at different under piston pressures are calculated. The dependences of the speed of lowering the piston and the effective gap on the under piston pressure at different gaps of the undeformed piston-cylinder unit are obtained. The research results can be used in the design of piston cylinder units operating on PES-3 liquid in the pressure range of 0.01–1.6 GPa.

scholarly journals Determination of basal hydraulic systems based on subglacial high-pressure pump experiments

2005 ◽  
Vol 40 ◽  
pp. 37-42 ◽  
Author(s):  
Gaute Lappegard ◽  
Jack Kohler
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Water Pressure ◽  
Drainage System ◽  
Load Cell ◽  
Low Flow ◽  
Hydraulic Systems ◽  
High Pressure Pump ◽  
Pressure Transducers ◽  
Fast Flow

AbstractWe have conducted short-term pump experiments with pump pressures exceeding ice overburden to study the seasonality of the subglacial hydraulic system of Engabreen, Norway. Data were collected from load cells installed flush with the ice–bedrock interface and pressure transducers installed in boreholes leading from bedrock tunnels underneath the glacier to the ice–bedrock interface. The water-pressure recordings, seen in relation with the load-cell record, show the existence of hydraulically connected vs unconnected bed areas. Monitored boreholes have been used to inject water at high pressures. Each experiment led to the growth of a high-pressure water cavity whose spatial extent could be inferred from load-cell and pressure transducer records. Post-pump pressures were low after summer pump tests and close to ice-overburden level after winter pump experiments. We conclude that drainage takes place in a fast-flow, low-pressure, channel-based drainage system during summer, and a low-flow, high-pressure, linked-cavity drainage system during winter.

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 Development of portable filtration unit with self-diagnostics for industrial use

2021 ◽  
Author(s):  
Nejc Novak ◽  
Rok Jelovčan ◽  
Franc Majdič
Keyword(s):  
High Pressures ◽  
High Flow ◽  
Operating Conditions ◽  
Main Topic ◽  
Hydraulic Fluid ◽  
Hydraulic Systems ◽  
Work Process ◽  
Flow Rates ◽  
Industrial Use ◽  
Filtration Unit

It is well known that contamination of fluids shortens the life of hydraulic systems. Sometimes the necessary operating conditions (high pressures and high flow rates) make adequate filtration in the suction, working, or return lines through the filter difficult because it would interfere with the work process. A high cleanliness of the oil can be achieved with a so-called "bypass" filtration, which is part of the whole hydraulic device with its own circuit. Another way to ensure fluid cleanliness is to filter the hydraulic fluid with a portable filtration unit, which is the main topic of this paper. The fluid is pumped from the reservoir of the main hydraulic device, through the portable filtration unit and returned to the reservoir. In this way it is possible to clean the hydraulic oil without the need for costly and unnecessary "bypass" hydraulic components for filtration.

scholarly journals Study on Oil Film Characteristics of Piston-Cylinder Pair of Ultra-High Pressure Axial Piston Pump

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 68 ◽  
Author(s):  
Jin Zhang ◽  
Baolei Liu ◽  
Ruiqi LÜ ◽  
Qifan Yang ◽  
Qimei Dai
Keyword(s):  
High Pressure ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Film Pressure ◽  
Oil Film ◽  
Ultra High Pressure ◽  
Piston Cylinder ◽  
The Mathematical Model ◽  
Axial Piston ◽  
Oil Film Pressure

The piston-cylinder pair is the key friction pairs in the piston pump. Its performance determines the volume efficiency of piston pump. With the increase of load pressure, the leakage at the clearance of piston-cylinder pair will also increase. In order to reduce leakage, the clearance of the piston-cylinder pair of the ultra-high pressure piston pump is smaller than that of the medium-high pressure piston pump. In order to explore whether the piston will stuck in the narrow gap, it is necessary to study the oil film characteristics of the piston-cylinder pair under the condition of ultra-high pressure, so as to provide a theoretical basis for the optimal design of the piston-cylinder pair of ultra-high pressure axial piston pump. In this paper, an ultra-high pressure axial piston pump is taken as the research object, and its structural characteristics are analyzed. The mathematical model of the oil film thickness of the piston-cylinder pair is established by using the cosine theorem in the cross section of the piston. The finite volume method is used to discretize the Reynolds equation of the oil film of the piston-cylinder pair, and the over relaxation iteration method is used to solve the discrete equations, and the mathematical model of the oil film pressure of the piston-cylinder pair is obtained. The mathematical model of oil film thickness and pressure field of piston-cylinder pair is solved by programming. The dynamic change process of oil film thickness and pressure field of the plunger pair of the ultra-high pressure axial piston pump under the load of 20 MPa and 70 MPa is obtained. Under the two conditions, the thinnest area of the oil film reaches 3 μm and 2 μm dangerous area respectively; the oil film pressure reaches 20 MPa and 70 MPa respectively when the swashplate rotates 10° and continues to increase with the increase of swashplate rotation angle. When the rotation angle reaches 90°, the oil film pressure also reaches the maximum value, but there is no pressure spike phenomenon. The oil film pressure characteristics of ultra-high pressure axial piston pump under conventional and ultra-high pressure conditions were obtained by modification and experimentation.

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