Developing a systematic approach to the analysis of time‐varying main bearing loads for wind turbines

Abstract

This paper considers the time-varying loads experienced by wind turbine main bearings. Radial load trajectories based on simulated data indicate that 'looped' structures, in the form of repeating changes in radial load magnitudes and directions that form elliptical patterns, are present, which have not been described before in the literature. In order to allow these identified structures to be described and studied, an automated method for identification and parameterisation of these loops is presented, along with preliminary results from applications on simulated data. In order to assess the relative importance and potential impacts of these identified structures on bearing rollers, an internal load model for double-row spherical roller bearings is also developed. Results indicate that identified loops in radial main bearing applied loads lead to significant fluctuations in bearing roller loads, even within normally unloaded regions. These findings motivate further study with respect to the identified load structures and their impacts on wind turbine main bearing internal loading and failures. The methods developed in this paper provide the basis for a systematic approach and necessary tools for this future work.

Constructing fast and representative analytical models of wind turbine main bearings

“…MBs are becoming recognised as an important component for which failures need to be better understood and reliability improved (Keller et al, 2016;Hart et al, 2020). MB failure rates have been reported as being as high as 30 % (Hart et al, 2019) across a 20-year lifetime, with some wind farms having reported MBs failing in less than 6 years (Sethuraman et al, 2015). Recent work which has demonstrated important and unusual load behaviours in wind turbine MBs (Hart et al, 2019;Hart, 2020) implements simplified analytical representations of the drivetrain.…”

“…MB failure rates have been reported as being as high as 30 % (Hart et al, 2019) across a 20-year lifetime, with some wind farms having reported MBs failing in less than 6 years (Sethuraman et al, 2015). Recent work which has demonstrated important and unusual load behaviours in wind turbine MBs (Hart et al, 2019;Hart, 2020) implements simplified analytical representations of the drivetrain. Such representations are necessary if this type of analysis is to be performed across large numbers of load cases, incorporated into fleet-wide modelling, or into industry standard simulation software (e.g.…”

“…In addition to the analyses outlined above, work has also been undertaken in which simple drivetrain representations are used to study general characteristics of MB loads and their relationship to the incident wind field (Hart et al, 2019;Hart, 2020), with the current paper building directly on these. The first of these (Hart et al, 2019) considered load characteristics for different possible drivetrain configurations and demonstrated sensitivities to both wind field characteristics and drivetrain set-up. More recently, work was undertaken in which repeating structures in time-varying MB loading were identified and characterised, with impacts on the loading experienced by bearing rolling elements also studied.…”

“…Analytic model for single-main-bearing set-up in one plane. The full model consists of two such representations, one in each of the horizontal and vertical planes (Hart et al, 2019). the accuracy of these models given their inherent simplifying assumptions and the existence of different load reaction behaviours for different bearing types.…”

“…These accuracy considerations form the focus of the current paper. The single-MB model and turbulent wind field simulations from Hart et al (2019) are used here. As such, both are described below in more detail.…”