Influence of the Lubricant Thermo-Piezo-Viscous Property on Hydrostatic Bearings in Oil Hydraulics

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

2 Citations (Scopus)

Abstract

In fluid power machinery hydrostatic bearings are frequently used, and a first approximation approach to design is determination of a balance ratio by analytical calculations of the hydrostatic presure force. Usually this is performed assuming that the thermo-piezo-viscous property can be neglected. However, in applications as piston machines, where pressure in many cases exceeds 200 Bar, such assumption leads to considerable error in the valance ratio prediction, due to the piezo-viscous property of the lubricant. Furthermore, the thermo-viscosity relation also has a significant influence, which adds to the discrepancy of such simple design approach. In this paper the hydrostatic pressure force calculation is reviewed in terms of thermohydrodynamic (THD) lubrication theory, and simple analytical approximations of the hydrostatic pressure force, incorporating the piezo-viscous and thermo-viscous property of the lubricant, are presented. In order to investigate validity of the approximations a numerical THD model is developed. A comparison study of the numerical and analytical predictions is performed in order to validate the simple design approach. In addition, the assumptions that form the basis of these analytical approximations are explored in order to clarify the limits of application. In conclusion, it is found that the spatial gradient of the thermal field on the bearing surface is the significant factor in the thermo-viscous effect on the hydrostatic pressure profile, which leads to the conclusion that design engineers need to understand the thermodynamics of hydrostatic bearings, when using the conventional simple analytical approach, neglecting thermo-piezo-viscosity, in hydrostatic pressure force calculations.
Original languageEnglish
Title of host publicationProceedings of the 9th FPNI PhD Symposium on Fluid Power, 2016
Number of pages10
PublisherAmerican Society of Mechanical Engineers
Publication dateOct 2016
Article numberFPNI2016-1551
ISBN (Print)978-0-7918-5047-3
DOIs
Publication statusPublished - Oct 2016
Event9th FPNI Ph.D. Symposium on Fluid Power - Florianópolis, Brazil
Duration: 26 Oct 201628 Oct 2016

Conference

Conference9th FPNI Ph.D. Symposium on Fluid Power
CountryBrazil
CityFlorianópolis
Period26/10/201628/10/2016
SponsorFederal University of Santa Catarina (UFSC), Fluid Power Net International (FPNI)

Fingerprint

Hydrostatic bearings
Hydrostatic pressure
Lubricants
Hydraulics
Bearings (structural)
Viscosity
Pistons
Lubrication
Machinery
Numerical models
Thermodynamics
Engineers
Fluids
Oils

Keywords

  • Hydrostatics
  • Hydraulics
  • Lubricants
  • Bearings

Cite this

Johansen, P., Roemer, D. B., Andersen, T. O., & Pedersen, H. C. (2016). Influence of the Lubricant Thermo-Piezo-Viscous Property on Hydrostatic Bearings in Oil Hydraulics. In Proceedings of the 9th FPNI PhD Symposium on Fluid Power, 2016 [FPNI2016-1551] American Society of Mechanical Engineers. https://doi.org/10.1115/FPNI2016-1551
Johansen, Per ; Roemer, Daniel Beck ; Andersen, Torben O. ; Pedersen, Henrik Clemmensen. / Influence of the Lubricant Thermo-Piezo-Viscous Property on Hydrostatic Bearings in Oil Hydraulics. Proceedings of the 9th FPNI PhD Symposium on Fluid Power, 2016. American Society of Mechanical Engineers, 2016.
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abstract = "In fluid power machinery hydrostatic bearings are frequently used, and a first approximation approach to design is determination of a balance ratio by analytical calculations of the hydrostatic presure force. Usually this is performed assuming that the thermo-piezo-viscous property can be neglected. However, in applications as piston machines, where pressure in many cases exceeds 200 Bar, such assumption leads to considerable error in the valance ratio prediction, due to the piezo-viscous property of the lubricant. Furthermore, the thermo-viscosity relation also has a significant influence, which adds to the discrepancy of such simple design approach. In this paper the hydrostatic pressure force calculation is reviewed in terms of thermohydrodynamic (THD) lubrication theory, and simple analytical approximations of the hydrostatic pressure force, incorporating the piezo-viscous and thermo-viscous property of the lubricant, are presented. In order to investigate validity of the approximations a numerical THD model is developed. A comparison study of the numerical and analytical predictions is performed in order to validate the simple design approach. In addition, the assumptions that form the basis of these analytical approximations are explored in order to clarify the limits of application. In conclusion, it is found that the spatial gradient of the thermal field on the bearing surface is the significant factor in the thermo-viscous effect on the hydrostatic pressure profile, which leads to the conclusion that design engineers need to understand the thermodynamics of hydrostatic bearings, when using the conventional simple analytical approach, neglecting thermo-piezo-viscosity, in hydrostatic pressure force calculations.",
keywords = "Hydrostatics, Hydraulics, Lubricants, Bearings",
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Johansen, P, Roemer, DB, Andersen, TO & Pedersen, HC 2016, Influence of the Lubricant Thermo-Piezo-Viscous Property on Hydrostatic Bearings in Oil Hydraulics. in Proceedings of the 9th FPNI PhD Symposium on Fluid Power, 2016., FPNI2016-1551, American Society of Mechanical Engineers, 9th FPNI Ph.D. Symposium on Fluid Power, Florianópolis, Brazil, 26/10/2016. https://doi.org/10.1115/FPNI2016-1551

Influence of the Lubricant Thermo-Piezo-Viscous Property on Hydrostatic Bearings in Oil Hydraulics. / Johansen, Per; Roemer, Daniel Beck; Andersen, Torben O.; Pedersen, Henrik Clemmensen.

Proceedings of the 9th FPNI PhD Symposium on Fluid Power, 2016. American Society of Mechanical Engineers, 2016. FPNI2016-1551.

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

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AU - Johansen, Per

AU - Roemer, Daniel Beck

AU - Andersen, Torben O.

AU - Pedersen, Henrik Clemmensen

PY - 2016/10

Y1 - 2016/10

N2 - In fluid power machinery hydrostatic bearings are frequently used, and a first approximation approach to design is determination of a balance ratio by analytical calculations of the hydrostatic presure force. Usually this is performed assuming that the thermo-piezo-viscous property can be neglected. However, in applications as piston machines, where pressure in many cases exceeds 200 Bar, such assumption leads to considerable error in the valance ratio prediction, due to the piezo-viscous property of the lubricant. Furthermore, the thermo-viscosity relation also has a significant influence, which adds to the discrepancy of such simple design approach. In this paper the hydrostatic pressure force calculation is reviewed in terms of thermohydrodynamic (THD) lubrication theory, and simple analytical approximations of the hydrostatic pressure force, incorporating the piezo-viscous and thermo-viscous property of the lubricant, are presented. In order to investigate validity of the approximations a numerical THD model is developed. A comparison study of the numerical and analytical predictions is performed in order to validate the simple design approach. In addition, the assumptions that form the basis of these analytical approximations are explored in order to clarify the limits of application. In conclusion, it is found that the spatial gradient of the thermal field on the bearing surface is the significant factor in the thermo-viscous effect on the hydrostatic pressure profile, which leads to the conclusion that design engineers need to understand the thermodynamics of hydrostatic bearings, when using the conventional simple analytical approach, neglecting thermo-piezo-viscosity, in hydrostatic pressure force calculations.

AB - In fluid power machinery hydrostatic bearings are frequently used, and a first approximation approach to design is determination of a balance ratio by analytical calculations of the hydrostatic presure force. Usually this is performed assuming that the thermo-piezo-viscous property can be neglected. However, in applications as piston machines, where pressure in many cases exceeds 200 Bar, such assumption leads to considerable error in the valance ratio prediction, due to the piezo-viscous property of the lubricant. Furthermore, the thermo-viscosity relation also has a significant influence, which adds to the discrepancy of such simple design approach. In this paper the hydrostatic pressure force calculation is reviewed in terms of thermohydrodynamic (THD) lubrication theory, and simple analytical approximations of the hydrostatic pressure force, incorporating the piezo-viscous and thermo-viscous property of the lubricant, are presented. In order to investigate validity of the approximations a numerical THD model is developed. A comparison study of the numerical and analytical predictions is performed in order to validate the simple design approach. In addition, the assumptions that form the basis of these analytical approximations are explored in order to clarify the limits of application. In conclusion, it is found that the spatial gradient of the thermal field on the bearing surface is the significant factor in the thermo-viscous effect on the hydrostatic pressure profile, which leads to the conclusion that design engineers need to understand the thermodynamics of hydrostatic bearings, when using the conventional simple analytical approach, neglecting thermo-piezo-viscosity, in hydrostatic pressure force calculations.

KW - Hydrostatics

KW - Hydraulics

KW - Lubricants

KW - Bearings

U2 - 10.1115/FPNI2016-1551

DO - 10.1115/FPNI2016-1551

M3 - Article in proceeding

SN - 978-0-7918-5047-3

BT - Proceedings of the 9th FPNI PhD Symposium on Fluid Power, 2016

PB - American Society of Mechanical Engineers

ER -

Johansen P, Roemer DB, Andersen TO, Pedersen HC. Influence of the Lubricant Thermo-Piezo-Viscous Property on Hydrostatic Bearings in Oil Hydraulics. In Proceedings of the 9th FPNI PhD Symposium on Fluid Power, 2016. American Society of Mechanical Engineers. 2016. FPNI2016-1551 https://doi.org/10.1115/FPNI2016-1551