scholarly journals Wind turbine main-bearing lubrication – Part 1: An introductory review of elastohydrodynamic lubrication theory

2021 ◽  
Author(s):  
Edward Hart ◽  
Elisha de Mello ◽  
Rob Dwyer-Joyce
Keyword(s):  
Wind Turbine ◽  
Elastohydrodynamic Lubrication ◽  
Lubrication Theory ◽  
Complex Field ◽  
Dynamic Effects ◽  
Grease Lubrication ◽  
Main Bearing ◽  
Gear Teeth ◽  
Accessible Form ◽  
Introductory Review

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.

The Multi-Objective Optimization for Cycloidal Gear Drive Based on the Elastohydrodynamic Lubrication Theory

2012 ◽  
Vol 591-593 ◽  
pp. 697-703 ◽  
Author(s):  
Xue Yi Qian
Keyword(s):  
Particle Swarm Optimization ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Lubrication Theory ◽  
Multi Objective Optimization ◽  
Swarm Optimization ◽  
Gear Teeth ◽  
Multi Objective ◽  
Gear Drive ◽  
Minimum Film Thickness

For improving the designed quality of the cycloidal gear planetary drive, the paper derives a calculation formula of the minimum film thickness, which is between cycloidal gear teeth, based on elastohydrodynamic lubrication theory and gear geometry. A mathematical model for constrained multi-objective optimization is established and the model satisfies three constrains:maximize minimum film thickness between gear teeth( minimize the reciprocal ), minimize average value of m points’s absolute error value on active section that is between the tooth curves of positive shift optimal combination and tooth curves of rotated angle’s modification, minimize the total volume of gear drive. The paper abandons traditional designed method of the multi-objective optimization , improves two-objective particle swarm optimization and offers a new designed model for constrained three-objective optimization. The example is analyzed and the optimization program is complied using Matlab. The optimization’s process and result shows that the method of improved constrained multi-objective particle swarm optimization could effectively improve the products’ synthesize economical and technical indexes.

scholarly journals Wind turbine main-bearing lubrication – Part 2: Simulation based results for a double-row spherical roller main-bearing in a 1.5 MW wind turbine

2021 ◽  
Author(s):  
Edward Hart ◽  
Elisha de Mello ◽  
Rob Dwyer-Joyce
Keyword(s):  
Film Thickness ◽  
Wind Turbine ◽  
Elastohydrodynamic Lubrication ◽  
Rate Of Change ◽  
Hertzian Contact ◽  
Main Bearing ◽  
Double Row ◽  
Contact Patch ◽  
Wind Speeds ◽  
Operational Life

Abstract. This paper is the second in a two-part study on lubrication in wind turbine main-bearings. Where “Part 1” provided an introductory review of elastohydrodynamic lubrication theory, this paper will apply those ideas to investigate lubrication in the double-row spherical roller main-bearing of a 1.5 MW wind turbine. Lubrication is investigated across a “contact conditions dataset” generated by inputting processed loads, obtained from aeroelastic simulations, into a Hertzian contact model of the main-bearing. From the Hertzian model is extracted values of roller load and contact patch dimensions, along with the time rate-of-change of contact patch dimensions. Also included in the dataset are additional environmental and operational variable values (e.g. wind speeds and shaft rotational speeds). A suitable formula for estimating film thickness within this particular bearing is then identified. Using lubricant properties of a commercially available wind turbine grease, specifically marketed for use in main-bearings, an analysis of film thickness across the generated dataset is undertaken. The analysis includes consideration of effects relating to starvation, grease thickener interactions and possible dynamic EHL effects. Results show that the modelled main-bearing would be expected to operate under mixed lubrication conditions for a non-negligible proportion of its operational life, indicating that further work is required to better understand lubrication in this context and implications for main-bearing damage and operational lifetimes. Key sensitivities and uncertainties within the analysis are discussed, along with recommendations for future work.

scholarly journals Analysis of Wind-Turbine Main Bearing Loads Due to Constant Yaw Misalignments over a 20 Years Timespan

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1768 ◽  
Author(s):  
Martin Cardaun ◽  
Björn Roscher ◽  
Ralf Schelenz ◽  
Georg Jacobs
Keyword(s):  
Wind Turbine ◽  
Wind Farms ◽  
Wake Flow ◽  
Energy Output ◽  
Main Bearing ◽  
Load Distributions ◽  
Wind Speed Distribution ◽  
Bearing Loads ◽  
Compact Design ◽  
Multi Body

The compact design of modern wind farms means that turbines are located in the wake over a certain amount of time. This leads to reduced power and increased loads on the turbine in the wake. Currently, research has been dedicated to reduce or avoid these effects. One approach is wake-steering, where a yaw misalignment is introduced in the upstream wind turbine. Due to the intentional misalignment of upstream turbines, their wake flow can be forced around the downstream turbines, thus increasing park energy output. Such a control scheme reduces the turbulence seen by the downstream turbine but introduces additional load variation to the turbine that is misaligned. Within the scope of this investigation, a generic multi body simulation model is simulated for various yaw misalignments. The time series of the calculated loads are combined with the wind speed distribution of a reference site over 20 years to investigate the effects of yaw misalignments on the turbines main bearing loads. It is shown that damage equivalent loads increase with yaw misalignment within the range considered. Especially the vertical in-plane force, bending and tilt moment acting on the main bearing are sensitive to yaw misalignments. Furthermore, it is found that the change of load due to yaw misalignments is not symmetrical. The results of this investigation are a primary step and can be further combined with distributions of yaw misalignments for a study regarding specific load distributions and load cycles.

scholarly journals Comparison of Electrical and Vibration Analysis Methods for Mechanical Fault Monitoring in Wind Turbine Drivetrains

2019 ◽  
Vol 9 (1) ◽  
pp. 2-7
Author(s):  
P Granjon ◽  
P D Longhitano ◽  
A Singh
Keyword(s):  
Wind Turbine ◽  
Vibration Analysis ◽  
Wind Farm ◽  
Electromechanical System ◽  
Main Bearing ◽  
Monitoring Method ◽  
Fault Monitoring ◽  
Three Phase ◽  
Mechanical Faults ◽  
Electrical Generator

Mechanical faults occurring in drivetrains are traditionally monitored through vibration analysis and, more rarely, by analysing electrical quantities measured on the electromechanical system involved. However, a monitoring method that is able to take into account all of the information contained in three-phase electrical quantities was recently proposed. The goal of this paper is to compare this threephase electrical approach with the usual vibration-based method in terms of its capability to detect mechanical faults in drivetrains. In this context, a 2 MW geared wind turbine operating in an industrial wind farm was equipped with accelerometers near the main bearing and electrical sensors on the stator of the electrical generator for several months. During this period, an important mechanical fault occurred in the main bearing of the system. The evolution of the fault indicators computed by the two previous approaches were compared throughout this period of time. All of the indicators behaved similarly and showed the development of an inner bearing fault in the main bearing. This demonstrated that a mechanical fault occurring in a drivetrain can be monitored and detected by analysing electrical quantities, even if the fault is located some distance from the electrical generator.

scholarly journals Multibody dynamic modelling of a direct wind turbine drive train

2019 ◽  
Vol 44 (5) ◽  
pp. 519-547
Author(s):  
Saeed Asadi ◽  
Håkan Johansson
Keyword(s):  
Wind Turbine ◽  
Measurement Data ◽  
Dynamic Modelling ◽  
Simulation Software ◽  
Operating Conditions ◽  
Drive Train ◽  
Operational Experience ◽  
Main Bearing ◽  
Wide Range ◽  
Turbine Drive

Wind turbines normally have a long operational lifetime and experience a wide range of operating conditions. A representative set of these conditions is considered as part of a design process, as codified in standards. However, operational experience shows that failures occur more frequently than expected, the costlier of these including failures in the main bearings and gearbox. As modern turbines are equipped with sophisticated online systems, an important task is to evaluate the drive train dynamics from online measurement data. In particular, internal forces leading to fatigue can only be determined indirectly from other locations’ sensors. In this contribution, a direct wind turbine drive train is modelled using the floating frame of reference formulation for a flexible multibody dynamics system. The purpose is to evaluate drive train response based on blade root forces and bedplate motions. The dynamic response is evaluated in terms of main shaft deformation and main bearing forces under different wind conditions. The model was found to correspond well to a commercial wind turbine system simulation software (ViDyn).

Study on the Influence of Non-Newtonian Characteristics on Robots for Medical Application

2010 ◽  
Vol 29-32 ◽  
pp. 857-861
Author(s):  
Jian Ping Liu ◽  
Xin Yi Zhang ◽  
Qing Xuan Jia
Keyword(s):  
Film Thickness ◽  
Elastic Deformation ◽  
Reynolds Equation ◽  
Traction Force ◽  
Elastohydrodynamic Lubrication ◽  
Medical Application ◽  
Lubrication Theory ◽  
Newtonian Model

Considering lumen elastic deformation, Reynolds equation is deduced based on non-Newtonian model in this paper. Traction force and hydrodynamic mucus film thickness are calculated according to elastohydrodynamic lubrication theory. Compared with results based on Newtonian model and experiments, analysis based on non-Newtonian model reflects practical condition well. Lumen elastic deformation has some influence on traction force and mucus film thickness.

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