System dynamic modelling applied to wind turbine bearings

Presented in Warsaw at EWEC 2010

By Rut Heemskerk/ SKF Technology Centre Wind,

Thierry Adane/SKF France & Reiner Wagner/SKF Germany

2010-04-23

www.skf.com

2010-04-23 © SKF Group

Presentation outline

Product development process:

=>Design for Six Sigma

=>Advanced modelling tools

Practical examples

=> SKF quiet running bearing for wind turbine generator

=> SKF NautilusTM bearing for wind turbine main shafts

Learning from experience

2010-04-23 © SKF Group

SKF

sim

ulatio

n

toolb

ox

Orpheus

The multi-party development process to improve performance and efficiency

Developmentcenters

Manufacturingcenters

Wind turbineapplication

Applicationengineers

DfSS

Condition monitoring

Customer

2010-04-23 © SKF Group

DfSS methodologye.g. HOQ DFMEA DOE …..

€

Research Design Prototype Production CustomerCost

to A

ch

ieve Q

uality

Targ

et

Defect Prevention

Reduce variation

Interconnection of DfSS and Six Sigma methodologies & tools

Problems are hard to foresee,

easy to fix

Problems are easy to see,costly to fix

DMAIC

2010-04-23 © SKF Group

Wind turbine generator system to components

Sub system generator

Sub sub system bearing

Wind turbine system

Components& design rules

Internal geometryGreaseCage Rolling elements,Material…

SKF simulation toolbox

Orpheus

Optimization & solving loop

Cascade approach to make the link between the WT system demands and the requirements on component design and specifications

2010-04-23 © SKF Group

Advanced tools to serve development

Multi body tools like SKF Orpheus and SKF BEAST are simulating the bearing and its surrounding, including

– Detailed bearing models

– Flexible shafts

– Flexible housings

– Flexible planet stage gears

– Flexible bearing rings Real time loading input data Unique bearing model

– Considering contacts between all the components

– Full flexible model

– EHL model

2010-04-23 © SKF Group

Practical example of

SKF quiet running bearing

for wind turbine generator

2010-04-23 © SKF Group

Noise typeRepetitive impact noise

High tone noise

Clacking

Hooting/whistling

Low frequency noise

Rumbling

Found in application field

Noise mapping in wind turbine generator

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SKF BEAST

Understanding of noise phenomena

•Approach- Analyse noise occurring in the

application- Simulate noise phenomena in

MBS- Reproduce noise phenomena

on test rig- Compare simulation models

with test results- Optimise bearing design for

minimum noise & vibration- Verify improvements by tests- Supply prototype to generator- Analyse noise of prototype

bearingin generator

•Advantages- Reliable model to optimize- Less prototyping to target a

solution- Positive footprint on

environment

LOOP application- testing-components

Wind Turbine Generator SKF Test Rig

2010-04-23 © SKF Group

Detail on interaction modelling / DfSS

Bearing component

s design

Application

influence

Robust design against noise &

vibration

Bearing noise & vibration level in application

Parameters of influence

Response surface under equations

Control of variation

Noise mapping

Desig

n

para

mete

rsOperating conditions

ac_ir

ac_

or

29282726252423222120

29

28

27

26

25

24

23

22

21

20

oscOR 0,5275Gac 17,5oscIR 0,5275RotSpeed 5050misa 0

Hold Values

> – – – – – < 4

4 55 66 77 88 9

9

shockma

Contour Plot of shockma vs ac_or; ac_ ir

Noise level

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conventional cage design

optimised cage designfor the application

Detail on noise modelling

WTG operating conditions Amplitude of the impact power ball/cage (recorded over several

rotations)

Back & forth motion

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Rela

tive v

ibra

tion level

Conv.

cag

e

Desig

n va

r. C

Fina

l des

ign

optim

ised

M

cage

• Significant reduction of the average vibration & noise level (10x)

• Spread of the vibration & noise reduced

=> Impact of cage design on noise & vibration generation identified, and optimised cage design developed and tested

Comparison of test results

Desig

n va

r. A

Desig

n va

r. B

2010-04-23 © SKF Group

Practical example

NautilusTM bearing for

wind turbine main shaft

2010-04-23 © SKF Group

NautilusTM bearing

Application functionality and features

Able to carry all rotor loads by one single unit

Compact drive train with reduced weight and high torsional stiffness

Designed to work under preload conditions

Needs

Relative large diameter

Large pressure angle to be handled

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Problems of large size bearings in operation

EFFECTS

Deflection of the roller-raceway contact is relative low (but stiffness is high) Deflection of the bearing rings in the application is large

=>advanced calculation necessary!! =>„Standard“ cages are in a sliding contact with rollers and/or rings.CONSEQUENCES

Deflection of the bearing rings generate: - high sliding forces and friction - misguiding of the rollers - high operation temperature and wear, resulting in life reduction

Friction vs Deflection

0

0,5

1

1,5

2

2,5

3

0 1 2 3 4 5 6Deflection

Fric

tio

n

Cage clearanceconsumed

Bearing/housing deformation…and the effect on the cage (twisting, compression)

Impact on friction

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Reducing high bearing friction by modelling

SKF catalogue friction model:• Gives quite precise results on catalogue bearings but does not consider the cage influence and is not applicable to non-standard bearings.

Consistent usage of the process loops and the modelling leads to the following design:

Segmented cage

One-piece cage

Full dynamic simulation model:• Is needed to come to an accurate result on bearing friction moment with an optimized cage design

Modelling of bearing friction torque with a 3D flexible model has identified:• The source of highest friction when

bearing operates as in application

• A robust method to develop a solution to overcome any inconvenience

• A bearing design with features going beyond initial expectations

=> An innovative segmented cage with low friction and negligible wear

2010-04-23 © SKF Group

Validation on test rig requires less prototypes

The model, including friction, has been verified on a SKF large size bearing test rig

A reference case for friction prediction based on new calculation models has been established,

Reduced prototyping requirements

Measured lifetime is more than 5 timesthe calculated lifetime L10h

Function of the bearing has been provenin real applications

0

20

40

60

80

100

0 5 10 15 20 25 30 35 40 45

Stribeck curveMeasurement vs. Calculation

Speed in rpm

Torq

ue in

%

Calculated curveMeasured points

Rated speeds in application

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Usage of high efficient bearing solutionsis not only a demand from energy

saving point of view, but even more from service life expectations

Functionality of the bearing becomes more important

than calculated L10

For Large Size Bearing applicationsIt is mandatory to do

advanced flexible calculations

Learning from experience

An overall approach is needed to optimise performance and reliability:Joint development, using DfSS tools

and advanced system modelling

2010-04-23 © SKF Group