Pub Date : 2021-05-01DOI: 10.13052/IJFP1439-9776.2214
Zoufiné Lauer-Baré, E. Gaertig, John L Krebs, C. Arndt, Christian Sleziona, André Gensel
The proper modelling of fluid flow through annular gaps is of great interest in leakage calculations for many applications in fluid power technology. However, while detailed numerical simulations are certainly possible, they are very time consuming, in various cases prone to numerical instabilities and may not even include all physically relevant effects. This is an issue especially in system simulations, where a large set of computations is needed in order to prepare the lookup-tables for the required input fields. In this work, an analytical approximation for the shear force, which is induced by viscous flow between two eccentric cylinders, is presented. This relation, and its derivation, mimics and enhances the well-known Piercy-relation for the corresponding volume flow that is utilized in state-of-the-art system simulation tools. To determine its range of validity, the analytical relation for the shear force is compared to 3D-simulations. Additionally, an application of this approximation for creating digital twins of hydraulic valves is also discussed in this work.
{"title":"A Note on Leakage Jet Forces: Application in the Modelling of Digital Twins of Hydraulic Valves","authors":"Zoufiné Lauer-Baré, E. Gaertig, John L Krebs, C. Arndt, Christian Sleziona, André Gensel","doi":"10.13052/IJFP1439-9776.2214","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2214","url":null,"abstract":"The proper modelling of fluid flow through annular gaps is of great interest in leakage calculations for many applications in fluid power technology. However, while detailed numerical simulations are certainly possible, they are very time consuming, in various cases prone to numerical instabilities and may not even include all physically relevant effects. This is an issue especially in system simulations, where a large set of computations is needed in order to prepare the lookup-tables for the required input fields. In this work, an analytical approximation for the shear force, which is induced by viscous flow between two eccentric cylinders, is presented. This relation, and its derivation, mimics and enhances the well-known Piercy-relation for the corresponding volume flow that is utilized in state-of-the-art system simulation tools. To determine its range of validity, the analytical relation for the shear force is compared to 3D-simulations. Additionally, an application of this approximation for creating digital twins of hydraulic valves is also discussed in this work.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":"113–146-113–146"},"PeriodicalIF":0.8,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47627428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-01DOI: 10.13052/IJFP1439-9776.2213
W. Rampen, D. Dumnov, Jamie Taylor, Henry Dodson, J. Hutcheson, N. Caldwell
In 1984 a hydrostatic wind-turbine transmission with ‘secondary control’ was proposed by Stephen Salter using the, then only conceptual, Digital Displacement® (DD) principle for controlling the flow of the primary, rotor-driven, ring-cam pump. This transmission ‘could achieve the correct ratio of tip-speed to wind-speed in conjunction with true synchronous generation’. In the following years DD machines were progressively developed. To start with they were relatively small in capacity but the power ratings were systematically increased, until it seemed that a high-power hydrostatic wind-turbine transmission might indeed be feasible. In 2006, Artemis Intelligent Power (Artemis), a company that had been formed from Salter's original university team, began working on a megawatt-scale, hydrostatic, wind-turbine transmission based on new pump and motor designs. In 2011 Artemis completed a 1.5 MW transmission and dynamometer test-rig. This was one of the largest hydraulic transmissions ever made and, with a shaft-to-shaft efficiency of 93%, one of the most efficient. Using secondary control to respond rapidly to gusting wind and to instantaneous grid faults, it was also the most controllable. This paper discusses the design of the transmission and test-rig and presents the results of steady-state efficiency tests. Subsequent papers will describe systematic experimental work to account for the various energy losses and to develop a comprehensive simulation model of the DD wind-transmission.
{"title":"A Digital Displacement Hydrostatic Wind-turbine Transmission","authors":"W. Rampen, D. Dumnov, Jamie Taylor, Henry Dodson, J. Hutcheson, N. Caldwell","doi":"10.13052/IJFP1439-9776.2213","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2213","url":null,"abstract":"In 1984 a hydrostatic wind-turbine transmission with ‘secondary control’ was proposed by Stephen Salter using the, then only conceptual, Digital Displacement® (DD) principle for controlling the flow of the primary, rotor-driven, ring-cam pump. This transmission ‘could achieve the correct ratio of tip-speed to wind-speed in conjunction with true synchronous generation’. \u0000In the following years DD machines were progressively developed. To start with they were relatively small in capacity but the power ratings were systematically increased, until it seemed that a high-power hydrostatic wind-turbine transmission might indeed be feasible. In 2006, Artemis Intelligent Power (Artemis), a company that had been formed from Salter's original university team, began working on a megawatt-scale, hydrostatic, wind-turbine transmission based on new pump and motor designs. In 2011 Artemis completed a 1.5 MW transmission and dynamometer test-rig. This was one of the largest hydraulic transmissions ever made and, with a shaft-to-shaft efficiency of 93%, one of the most efficient. Using secondary control to respond rapidly to gusting wind and to instantaneous grid faults, it was also the most controllable. This paper discusses the design of the transmission and test-rig and presents the results of steady-state efficiency tests. Subsequent papers will describe systematic experimental work to account for the various energy losses and to develop a comprehensive simulation model of the DD wind-transmission.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":"87–112-87–112"},"PeriodicalIF":0.8,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44429836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-01DOI: 10.13052/IJFP1439-9776.2212
G. Grossschmidt, M. Harf
Model-based simulation of a hydraulic closed-loop rotary transmission with automatic control of hydraulic pump and hydraulic motor is considered in the paper. The approach is based on multi-pole modelling and intelligent simulation. In the paper the functional scheme of the transmission is proposed and multi-pole models of components are introduced. Mathematical multi-pole models of components for steady state conditions and for dynamic transient responses are presented. A high-level graphical environment CoCoVila (compiler compiler for visual languages) is used as a tool for describing models and performing simulations. Object-oriented multi-pole models, visual programming environment, automatic program synthesis and distributed computing are as original approach in simulation of fluid power systems.
{"title":"Model-based Simulation of a Hydraulic Closed-loop Rotary Transmission with Automatic Control","authors":"G. Grossschmidt, M. Harf","doi":"10.13052/IJFP1439-9776.2212","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2212","url":null,"abstract":"Model-based simulation of a hydraulic closed-loop rotary transmission with automatic control of hydraulic pump and hydraulic motor is considered in the paper. The approach is based on multi-pole modelling and intelligent simulation. In the paper the functional scheme of the transmission is proposed and multi-pole models of components are introduced. Mathematical multi-pole models of components for steady state conditions and for dynamic transient responses are presented. A high-level graphical environment CoCoVila (compiler compiler for visual languages) is used as a tool for describing models and performing simulations. Object-oriented multi-pole models, visual programming environment, automatic program synthesis and distributed computing are as original approach in simulation of fluid power systems.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":"45–86-45–86"},"PeriodicalIF":0.8,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44151833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-06DOI: 10.13052/IJFP1439-9776.2133
Michael D. Banas
Plastics are used more and more in hydraulic systems. The chemical properties of the plastics favour the use of working fluids alternative to mineral oil, e.g. water. The conditions in the manufacturing process, e.g. injection moulding, limit the achievement of high working pressures in the hydraulic elements. Internal leakage reduces the efficiency of the hydraulic pump with plastic gears. The article presents the results of internal leakage tests of a water-supplied hydraulic pump. Gears made of various materials (PPS+GF40 and PEEK) have been used in the research, made by two methods: injection moulding and machining. A simplified mathematical model of the dependence of leakages on pressure and rotational speed has been developed. The influence of the materials and manufacturing methods used on the pump operation is discussed.
{"title":"Internal Leakages in a Water Hydraulic Pump with Gears From Plastic","authors":"Michael D. Banas","doi":"10.13052/IJFP1439-9776.2133","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2133","url":null,"abstract":"Plastics are used more and more in hydraulic systems. The chemical properties of the plastics favour the use of working fluids alternative to mineral oil, e.g. water. The conditions in the manufacturing process, e.g. injection moulding, limit the achievement of high working pressures in the hydraulic elements. Internal leakage reduces the efficiency of the hydraulic pump with plastic gears. The article presents the results of internal leakage tests of a water-supplied hydraulic pump. Gears made of various materials (PPS+GF40 and PEEK) have been used in the research, made by two methods: injection moulding and machining. A simplified mathematical model of the dependence of leakages on pressure and rotational speed has been developed. The influence of the materials and manufacturing methods used on the pump operation is discussed.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":"347–362-347–362"},"PeriodicalIF":0.8,"publicationDate":"2021-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47011870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-06DOI: 10.13052/IJFP1439-9776.2131
P. Noskievič, Melvin Alexis Lara de León
The paper deals with the control of the test rig for measurement of the stiffness of the spring. The test rig is equipped with integrated hydraulic actuator and multilayer control system with computer vision to automate the testing process and to increase the safety of the operating staff during the testing. The integrated hydraulic actuator allows to control the piston velocity and position and to produce the force needed for the spring compression and stiffness measurement. It has an integrated manifold with four proportional flow control valves connected as the full hydraulic resistance bridge. Each control valve is controlled separately using the input signal. That makes it possible to realize different connections and control strategies of the hydraulic cylinder using the different control algorithms. The hydraulic circuit was modelled and simulated, and the achieved simulation results are presented in the paper. The test rig is controlled using the microprocessor control system and is it equipped by different transducers – position transducer, pressure transducers and force transducer to be able to collect data important for the stiffness characteristic evaluation. The upper level of the control system is created by the vision control system. The goal of the implementation of the machine vision is to decrease the number of the manual operations done by the technician by the spring testing and to extend the automatic testing cycle of the automatic computer vision-controlled movement of the actuator at the beginning of the testing cycle and finally to increase the safety of the operating staff. The structure and functionality of the designed control system, experimentally obtained results and evaluated stiffness characteristic of the tested spring are presented in the following chapters.
{"title":"Control of the Test Rig for Spring Stiffness Measurement with Hydraulic Integrated Actuator and Computer Vision","authors":"P. Noskievič, Melvin Alexis Lara de León","doi":"10.13052/IJFP1439-9776.2131","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2131","url":null,"abstract":"The paper deals with the control of the test rig for measurement of the stiffness of the spring. The test rig is equipped with integrated hydraulic actuator and multilayer control system with computer vision to automate the testing process and to increase the safety of the operating staff during the testing. The integrated hydraulic actuator allows to control the piston velocity and position and to produce the force needed for the spring compression and stiffness measurement. It has an integrated manifold with four proportional flow control valves connected as the full hydraulic resistance bridge. Each control valve is controlled separately using the input signal. That makes it possible to realize different connections and control strategies of the hydraulic cylinder using the different control algorithms. The hydraulic circuit was modelled and simulated, and the achieved simulation results are presented in the paper. The test rig is controlled using the microprocessor control system and is it equipped by different transducers – position transducer, pressure transducers and force transducer to be able to collect data important for the stiffness characteristic evaluation. The upper level of the control system is created by the vision control system. The goal of the implementation of the machine vision is to decrease the number of the manual operations done by the technician by the spring testing and to extend the automatic testing cycle of the automatic computer vision-controlled movement of the actuator at the beginning of the testing cycle and finally to increase the safety of the operating staff. The structure and functionality of the designed control system, experimentally obtained results and evaluated stiffness characteristic of the tested spring are presented in the following chapters.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":"305–326-305–326"},"PeriodicalIF":0.8,"publicationDate":"2021-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44076111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-06DOI: 10.13052/IJFP1439-9776.2132
L. Ivanović, M. Matejic
Gerotor pumps are well known by a compact design, simple structure and low noise level, which makes them suitable for use in the automotive industry, and especially in hydraulic systems for engine lubrication. One of the main disadvantages of gerotor pumps is the inability to adjust to wear, which significantly reduces the pump efficiency. In order to mitigate the negative effect of the inevitable wear process, this paper presents a methodology for determining the optimal combination of trochoid gears design parameters for a defined aspect. An appropriate mathematical model has been developed to analyze the effect of changes in gear design parameters in relation to maximum contact stresses, pressure changes in gerotor pump chambers and wear rate proportional factor (WRPF). Verification of the developed models was performed by realizing physical pairs of gears and laboratory experiments with simulation of pump operating conditions. The results and conclusions presented in this paper, with an emphasis on the actual work processes, bring very important perspectives for the gerotor pumps design with improved performance.
{"title":"Improving Gerotor Pump Performance Trough Design, Modeling and Simulation","authors":"L. Ivanović, M. Matejic","doi":"10.13052/IJFP1439-9776.2132","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2132","url":null,"abstract":"Gerotor pumps are well known by a compact design, simple structure and low noise level, which makes them suitable for use in the automotive industry, and especially in hydraulic systems for engine lubrication. One of the main disadvantages of gerotor pumps is the inability to adjust to wear, which significantly reduces the pump efficiency. In order to mitigate the negative effect of the inevitable wear process, this paper presents a methodology for determining the optimal combination of trochoid gears design parameters for a defined aspect. An appropriate mathematical model has been developed to analyze the effect of changes in gear design parameters in relation to maximum contact stresses, pressure changes in gerotor pump chambers and wear rate proportional factor (WRPF). Verification of the developed models was performed by realizing physical pairs of gears and laboratory experiments with simulation of pump operating conditions. The results and conclusions presented in this paper, with an emphasis on the actual work processes, bring very important perspectives for the gerotor pumps design with improved performance.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48812252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-06DOI: 10.13052/IJFP1439-9776.2134
U. Warzyńska, T. Siwulski
A pressure pulsation phenomenon in positive displacement machinery and resulting from that noise and vibration problems are well-known and still unsolved issues. The article concerns modeling pressure pulsation dampers used for fluid machinery, in particular in gas systems. The currently used mathematical models based on the plane wave theory are verified in the special laboratory conditions with no flow and no wave reflections at the system outlet. The use of a compressor as an excitation source significantly influences the characteristics of a damper installed in a system. In this study, a measurement of common type dampers transmission loss characteristics with the use of pressure transducers is proposed. The article discusses the influence of boundary conditions in analytical models based on the plane wave theory on the accuracy of dampers characteristics. Basing on the measurements results some improvements in the analytical model are proposed.
{"title":"Influence of Boundary Conditions on the Accuracy of Pulsation Dampers Characteristics in Analytical Models","authors":"U. Warzyńska, T. Siwulski","doi":"10.13052/IJFP1439-9776.2134","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2134","url":null,"abstract":"A pressure pulsation phenomenon in positive displacement machinery and resulting from that noise and vibration problems are well-known and still unsolved issues. The article concerns modeling pressure pulsation dampers used for fluid machinery, in particular in gas systems. The currently used mathematical models based on the plane wave theory are verified in the special laboratory conditions with no flow and no wave reflections at the system outlet. The use of a compressor as an excitation source significantly influences the characteristics of a damper installed in a system. In this study, a measurement of common type dampers transmission loss characteristics with the use of pressure transducers is proposed. The article discusses the influence of boundary conditions in analytical models based on the plane wave theory on the accuracy of dampers characteristics. Basing on the measurements results some improvements in the analytical model are proposed.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41981875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-06DOI: 10.13052/IJFP1439-9776.2135
R. Rituraj, R. Scheidl
Spools in hydraulic valves are prone to sticking caused by unbalanced lateral forces due to geometric imperfections of their sealing lands. This sticking problem can be related to the stability of the coaxial spool position. Numerical methods are commonly used to study this behaviour. However, since several parameters can influence the spool stability, parametric studies become significantly computationally expensive and graphical analysis of the numerical results in multidimensional parameter space becomes difficult. To overcome this difficulty, in this work, an analytical approach for studying the stability characteristics of the spool valve is presented. A Rayleigh-Ritz method is used for solving the Reynolds equation in an approximate way in order to determine an analytical expression for the lateral force on the sealing lands. This analytical expression allows stability analysis of the spool via analytical means which finally results in the expression of critical axial velocity which demarcates the regions of stable behaviour. Simplicity of the expression allows an immediate insight into the role of design parameters in the stability of the spool. To verify the analytical model, a numerical model for spool dynamics is developed in this work and the numerical results are found to match the analytical model in terms of the stability behaviour of the spool.
{"title":"Stability Analysis of Spools with Imperfect Sealing Gap Geometries","authors":"R. Rituraj, R. Scheidl","doi":"10.13052/IJFP1439-9776.2135","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2135","url":null,"abstract":"Spools in hydraulic valves are prone to sticking caused by unbalanced lateral forces due to geometric imperfections of their sealing lands. This sticking problem can be related to the stability of the coaxial spool position. Numerical methods are commonly used to study this behaviour. However, since several parameters can influence the spool stability, parametric studies become significantly computationally expensive and graphical analysis of the numerical results in multidimensional parameter space becomes difficult. \u0000To overcome this difficulty, in this work, an analytical approach for studying the stability characteristics of the spool valve is presented. A Rayleigh-Ritz method is used for solving the Reynolds equation in an approximate way in order to determine an analytical expression for the lateral force on the sealing lands. This analytical expression allows stability analysis of the spool via analytical means which finally results in the expression of critical axial velocity which demarcates the regions of stable behaviour. Simplicity of the expression allows an immediate insight into the role of design parameters in the stability of the spool. To verify the analytical model, a numerical model for spool dynamics is developed in this work and the numerical results are found to match the analytical model in terms of the stability behaviour of the spool.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48567313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.13052/ijfp1439-9776.2234
Sven Osterland, L. Müller, J. Weber
This article gives experimentally evidence that cavitation erosion in hydraulic components like valves and pumps is caused by vapour cavitation not gas or pseudo cavitation. In fact, the free air content which is released by vapour and gas cavitation reduces the erosion significantly. In order to clearly separate the different cavitation types, a test rig with a specially designed reservoir with integrated degassing capability is presented. As flow geometry a valve model with realistic dimensions and under realistic operating conditions was used, which ensures very high transferability of the results to the reality of hydraulic components in practical applications and typical operating conditions. A total of 4 five-hour long tests are performed and analysed. The quantification of the cavitation erosion is determined by the mass loss of the copper samples. The experimental results show a 4.4–5.1 times higher mass loss in tests with air-free oil compared to tests with air-saturated or oversaturated hydraulic oil. The experimental fact that air-free hydraulic oil causes significantly more cavitation erosion than normal (saturated) hydraulic oil, and its implications are discussed. The conclusion can be drawn, that further developments of hydraulic components and systems towards the use of air-free oil or increasing power densities will be disproportionately challenged by cavitation erosion.
{"title":"Influence of Air Dissolved in Hydraulic Oil on Cavitation Erosion","authors":"Sven Osterland, L. Müller, J. Weber","doi":"10.13052/ijfp1439-9776.2234","DOIUrl":"https://doi.org/10.13052/ijfp1439-9776.2234","url":null,"abstract":"This article gives experimentally evidence that cavitation erosion in hydraulic components like valves and pumps is caused by vapour cavitation not gas or pseudo cavitation. In fact, the free air content which is released by vapour and gas cavitation reduces the erosion significantly. In order to clearly separate the different cavitation types, a test rig with a specially designed reservoir with integrated degassing capability is presented. As flow geometry a valve model with realistic dimensions and under realistic operating conditions was used, which ensures very high transferability of the results to the reality of hydraulic components in practical applications and typical operating conditions. A total of 4 five-hour long tests are performed and analysed. The quantification of the cavitation erosion is determined by the mass loss of the copper samples. The experimental results show a 4.4–5.1 times higher mass loss in tests with air-free oil compared to tests with air-saturated or oversaturated hydraulic oil. The experimental fact that air-free hydraulic oil causes significantly more cavitation erosion than normal (saturated) hydraulic oil, and its implications are discussed. The conclusion can be drawn, that further developments of hydraulic components and systems towards the use of air-free oil or increasing power densities will be disproportionately challenged by cavitation erosion.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66116676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-04DOI: 10.13052/IJFP1439-9776.2125
V. Donkov, T. Andersen, M. Linjama, M. Ebbesen
This paper analyses the current state of the art in linear actuation with digital hydraulics. Based on the differences in their aims the paper partitions the area into four actuation concepts – parallel valve solutions, single switching valve solutions, multi-chamber cylinders, and multi-pressure cylinders. The concepts are evaluated based on accuracy and smoothness of motion, switching load, reliability, efficiency and the number of components required.
{"title":"Digital Hydraulic Technology for Linear Actuation: A State of the Art Review","authors":"V. Donkov, T. Andersen, M. Linjama, M. Ebbesen","doi":"10.13052/IJFP1439-9776.2125","DOIUrl":"https://doi.org/10.13052/IJFP1439-9776.2125","url":null,"abstract":"This paper analyses the current state of the art in linear actuation with digital hydraulics. Based on the differences in their aims the paper partitions the area into four actuation concepts – parallel valve solutions, single switching valve solutions, multi-chamber cylinders, and multi-pressure cylinders. The concepts are evaluated based on accuracy and smoothness of motion, switching load, reliability, efficiency and the number of components required.","PeriodicalId":13977,"journal":{"name":"International Journal of Fluid Power","volume":"1 1","pages":"263–304-263–304"},"PeriodicalIF":0.8,"publicationDate":"2020-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46555636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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