Abstract
This work aims to study the tribological performance of the water-lubricated journal bearings by developing an EHL model considering non-Gaussian roughness and cavitation. An elastohydrodynamic lubrication (EHL) model is established by solving the Reynolds equation, elastic deformation and film thickness equations in a coupling manner by using the finite difference method with a successive over-relaxation scheme. The non-Gaussian flow factors and cavitation factors are incorporated in the Reynolds equation to tackle the roughness and non-Gaussian roughness effects. The result shows that the coefficient of friction increases with an increase in skewness. A significantly increase in the minimum film thickness is observed for a surface having high negative skewness. The friction coefficient decreases with an increase in the L/D ratio.
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Abbreviations
- WLJB :
-
Water-lubricated journal bearing
- SOR :
-
Successive over relaxation
- CoF :
-
Friction coefficient
- EHL:
-
Elastohydrodynamic lubrication
- S sk :
-
Skewness
- S ku :
-
Kurtosis
- N r :
-
Speed of the shaft, RPM
- C :
-
Radial clearance, µm
- ε :
-
Eccentricity ratio, e/C
- D :
-
Bearing diameter, mm
- T :
-
Bushing thickness, mm
- W t :
-
Tangential load, N
- W r :
-
Radial load, N
- W :
-
Total load, N
- \(\overline{h}\) :
-
Dimensionless film thickness, \({h \mathord{\left/ {\vphantom {h C}} \right. \kern-0pt} C}\)
- \(h\) :
-
Water film thickness, µm
- \(\theta\) :
-
Circumferential angle in radian
- \(\varphi\) :
-
Attitude angle (radian)
- \(\overline{z}\) :
-
Dimensionless z-coordinate, \({z \mathord{\left/ {\vphantom {z {\left( {{L \mathord{\left/ {\vphantom {L 2}} \right. \kern-0pt} 2}} \right)}}} \right. \kern-0pt} {\left( {{L \mathord{\left/ {\vphantom {L 2}} \right. \kern-0pt} 2}} \right)}}\)
- S q :
-
Composite root mean square (RMS) roughness, µm
- R :
-
Bearing radius, mm
- L :
-
Length of the shaft, mm
- U :
-
Surface speed of the shaft, m/s
- p hyd :
-
Hydrodynamic pressure
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Appendix A
Appendix A
1.1 Brief description of topography parameters
1.1.1 Root mean square (RMS) roughness (S q )
For a discrete residual surface, z (xi, yi), the statistical expression for determining RMS roughness is given in Eq. A1.
1.1.2 Skewness (S sk )
The skewness measures the asymmetry of surface deviation from the mean plane. Positive skewness represents a greater number of roughness peaks than valleys from the mean plane of a rough surface. At the same time, negative skewness represents a higher number of valleys than roughness peaks. For a discrete residual surface, z (xi, yi), the statistical expression for determining skewness (Ssk), is given in Eq. A2.
where M and N are total number of sampling points within the measured area
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Prajapati, D.K., Katiyar, J.K. & Prakash, C. Determination of friction coefficient for water-lubricated journal bearing considering rough surface EHL contacts. Int J Interact Des Manuf (2023). https://doi.org/10.1007/s12008-023-01466-7
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DOI: https://doi.org/10.1007/s12008-023-01466-7