Abstract
This paper is the first in a two-part study on lubrication in wind turbine main-bearings. Elastohydrodynamic lubrication is a complex field, the formulas and results from which should not be applied blindly, but with proper awareness and consideration of their context, validity and limitations in any given case. The current paper, “Part 1”, therefore presents an introductory review of elastohydrodynamic lubrication theory in order to provide this necessary background and context in an accessible form, promoting cross-disciplinary understanding. Fundamental concepts, derivations and formulas are presented, followed by the more advanced topics of: starvation, dynamic effects, surface roughness interactions and grease lubrication. “Part 2” applies the presented material in order to analyse wind turbine main-bearing lubrication in the context of available film thickness formulas and related results from lubrication theory. Aside from the main-bearing, the material presented here is also applicable to other lubricated non-conformal contacts in wind turbines, including pitch and yaw bearings and gear-teeth.
Highlights
Wind turbine main-bearings have come under increased research scrutiny of late, due to higher than expected failures rates and failure mechanisms which are yet to be fully understood (Hart et al, 2019, 2020; Hart, 2020; Guo et al, 2021)
Complex elastohydrodynamic lubrication (EHL) problems are solved routinely, with experimental comparisons demonstrating the effectiveness of currently available models
It is understood that some of the simplifying assumptions applied in classical EHL, and still used today, must be challenged
Summary
Wind turbine main-bearings have come under increased research scrutiny of late, due to higher than expected failures rates and failure mechanisms which are yet to be fully understood (Hart et al, 2019, 2020; Hart, 2020; Guo et al, 2021). The lubricant and lubrication mechanisms acting within this component must be accounted for as part of any attempt to fully characterize and understand main-bearing internal operational conditions, failure mechanisms and reliability. This two-part study seeks to begin this process. This paper, “Part 1” of the main-bearing lubrication study, presents such an introductory review for the elastohydrodynamic lubrication of non-conformal (roller bearings, gear-teeth etc.) contacts.
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