Wind Turbine Stress Relievers - kweia.or.kr · Damper. Controller. Unwanted Turbulent Wind Power....

Wind Turbine Stress Relievers

Rolando Vega: Moderator

Mechanical Stress Reduction on the Gearbox of the Variable Speed Wind Turbines

Goran Mandi•, Ehsan Ghotbi, and Adel Nasiri Power Electronics and Electric Motor Drives Laboratory

University of Wisconsin-MilwaukeeEmail: [email protected]; URL: www.uwm.edu/~nasiri

Eduard MuljadiNational Renewable Energy Laboratory

Francisco OyagueBoulder Wind Power, Colorado

mailto:[email protected]�

http://www.uwm.edu/~nasiri�

Presentation Outline

Introduction

Mathematical models of a gearbox

Resonant vibration damping

Simulation results

Conclusion

Gearbox-Related Issues

Wind turbine gearboxes still cannot achieve 20 years of life expectancy.

Gearbox is one of the most expensive components in a wind turbine.

Types of gear failure: wear, abrasion, surface fatigue, micropitting, macropitting , spalling, crushing, plastic flow, and fracture.

Variable torque on the main shaft and the high speed shaft can cause vibrations at resonant frequencies of the internal components of the gearbox.

Wind Turbine Topologies

Inductionor PM

Generator

Trans.AC/DC

ConverterDC/AC

Converter

Grid

Li-IonUltracapacitor

StorageSystem

Gearbox

Proposed topology of double-conversion wind turbine system integrated with LIC energy storage.

Proposed topology of DFIG wind turbine system integrated with LIC energy storage.

• One planetary and two parallel stages.

• More degrees of freedom (DoFs) = Better accuracy of the model.

• 1 DOF, 2 DOF, 5 DOF and 11 DOF models were developed

Gearbox Modeling

IPC

Ring Gear

IS IG1

IP1 IG2

IP2

Low Speed Input Shaft

Planetary Stage I

Parallel Stage II

Parallel Stage III

HSS

N1

N3

N2IBlade

IGen

Braking Event Model Bounds

2 DOF Model Bounds

Brake

Sun

Planet Carrier

Generator

IB Keff

2eff GenI n I+

• Data recorded during transition from low to high rotational speed (left), and comparison of modeling and experimental cases (right).

Sequence 3

Sequence 2

Sequence 1

0 5 10 15 20 25 30-100

-50

0

50

100

150

time [s]T

orqu

e [N

-m]

Response for Data Set 1 Compared to Experimental Data: Zeta =0.024 Natural Freq=4.02 rad/s

Field Test Data

IB - lumped inertia of the turbine’s rotor and blades

Ieff - lumped inertia of the gearbox.

Igen -is inertia of the generator.

Two-Mass Model

IB Kef

2eff GenI n I+

Kf eff eff

feff eff

k kK

k k K

− =

− +

2

0

0B

eff Gen

II

I n I

= +

2 1( )eig I Kω −=

• Effective stiffness is calculated from the frequency of vibrations recorded from the recorded data and from the effective inertias of the subcomponents.• Generator torque reaction is represented as a spring with stiffness Kf.

Five-Mass Gearbox Model

1 1

1 1 2 2

2 2 3 3

3 3 4 4

4 4 5

0 0 0

0 0

0 0

0 0

0 0 0

e e

e e e e

e e e e

e e e

k k

k k k k

K k k k k

k k k k

k k k

− − + − = − + − − + − − +

1

2

3

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

h

S

S

S

Gen

I

I

II

I

I

=

• Rigid bodies representing moments of inertia of gear stages, generator, and the rotor are connected by flexible springs.• Stiffness coefficients and moment of inertias were extracted from the SolidWorks model of the gearbox.

Gearbox Stress Reduction Strategy

• Active damping control removes resonant frequencies from the torque acting on the gearbox.

• Feedforward control strategy.

GearBox

Power Converter

and Generator Useful

ElectricalPower

UsefulWindPower

StressDamper

Controller

Unwanted Turbulent Wind Power

Gearbox Stress Reduction Controller

• Each band-pass filter is tuned to one particular resonant frequency

• Only first three resonant vibrations are compensated. Other resonant frequencies exceed torque controller bandwidth.

• f1=2.95Hz, f2=292Hz, f3=371Hz

Simulink Model of the System

• A wind turbine systems is modeled from wind to grid, including mechanical and electrical components.

Wind Turbine Control Diagram With Energy Storage

• The existing wind turbine controls have been modified to allow for energy storage and drivetrain stress reduction.

Torque and Power Characteristics

0 5 10 15 20 25 30 350

100

200

300

400

500

600

Tor

que

[kN

m]

Rotational speed [rpm]0 5 10 15 20 25 30 35

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Pow

er [k

W]

Rotational speed [rpm]

6m/s

8m/s

10m/s

12m/s

8m/s

14m/s

4m/s

6m/s

8m/s

10m/s

12m/s

14m/s

RPMrated

Trated

Red Line = Electrical Torque

Blue Line = AerodynamicTorque

Cut-offWind speed

Cut-inWind speed

P vs wind-speed

• The value of torque is calculated to adjust the RPM of the turbine for any wind speed.

0

50

100

150

Mag

nitu

de (d

B)

10-2

10-1

100

101

102

103

104

-90

0

90

180

Pha

se (d

eg)

Bode Diagram

Frequency (Hz)

Frequency Characteristics of the Proposed Controller

• This is one of the transfer functions from generator torque to torsional angle of one of the drivetrain stages. There are totally 8 transfer functions. Three poles are evident in the transfer functions.

0 10 20 30 40 50 608

9

10

11

12W

ind

sp

eed

[m

/s]

0 10 20 30 40 50 6021

22

23

24

Time [s]

Ro

tati

on

al s

pee

d[

rpm

]

Modeling Results – Case I

• When wind speed is constant plus an oscillating component at 2.95Hz.

• Rotational speed is identical with and without stress reduction due to large inertia (no effect on MPPT).

0 10 20 30 40 50 602

4

6x 10

-3

0 10 20 30 40 50 602

3

4x 10

-4

0 10 20 30 40 50 601

1.52

x 10-6

0 10 20 30 40 50 601

2

3x 10

-5

Time [s]

Torsional Angles at Each Stage of the 5-Mass Model

• Torsional angle difference at four stages of the drivetrain with and without the stress reduction filter.

10-2

10-1

100

101

102

103

0

0.005

0.01

0.015

0.02

0.025

Fequency [Hz]

Torsi

on an

gle (to

tal) (d

eg)

10-2

10-1

100

101

102

103

0

2

4

6

8

10

12

Frequency [Hz]

Torqu

e diffe

rence

[kNm]

Frequency Spectrum of Torsional Angles and Torque Difference

• Frequency spectrum of torque difference and torsional angle difference.

Modeling Results - Case II

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

Win

d sp

eed

[m/s

]

0 10 20 30 40 50 60 70 80 90 10010

15

20

25

30

Rot

atio

nal s

peed

[rpm

]

Time [s]

• Actual wind speed profile and rotor speed.

10-2

10-1

100

101

102

103

0

0.5

1

1.5

2

2.5

3To

rque

diff

eren

ce [k

Nm

]

Frequency [Hz]

Frequency Spectrum of the Torque Difference Between LSS and HSS

• Frequency spectrum of torque acting on drivetrain with reductions at three resonant frequencies.

102

103

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

To

rqu

e d

iffe

ren

ce [

kNm

]

Frequency [Hz]

292Hz

371Hz

Frequency Spectrum of the Torque Difference Between LSS and HSS (cont’d)

• This figure shows the reduction of torque difference at two resonance frequencies.

10-2

10-1

100

101

102

103

104

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

Frequency Spectrum of the Total Torsional Angle Between LSS and HSS (Radians)

• Frequency spectrum of the torsional twist angle on drivetrain with main reduction at smallest resonant frequency.

UWM Wind Turbine Emulator

50kW Wind turbine Emulator

InductionMotor

Rockwell Powerflex500

Protection

Torque

Transducer

AC/DC/ACConverter

Protection

AC/DC

480V, 60Hz

Protection

DC/AC

Protection

Charger/Discharger

50kWhStorage

Slip RingInduction

Gen

PMGenerator

Existing Wind Turbine Emulator

Energy StorageSystem

LIC Storage

LIC Storage

480V, 60Hz

Conclusion and Future Work

Resonant vibrations of the gearbox are damped by reducing torque spectral components from the torque difference that cause resonant vibrations.

Stress reduction controller can be implemented by modifying the controller of the generator currents.

Next step is implement and test the proposed system on a full-scale wind turbine.

Acknowledgement

• We would like to acknowledge the support received from the U.S. Department of Energy under Award Number: 09EE0001386 to conduct this project.

Rolando Vega: Moderator

Challenges with Wind Blade Road-transportation & in-situ Dynamics

May 25, 2011

Presented by

PARI TATHAVADEKARSr. Test Engineer, ValidationClipper Windpower, Inc.

© 2010 Clipper Windpower, Inc. and subsidiaries All rights Reserved

AWEA Windpower 2011Conference & Exhibition

Co-authors

Patrick Desnoyers, Clipper Windpower, Inc.Mark Elliot, Clipper Windpower, Inc.Marc Regelbrugge, Rhombus Consulting GroupMike Neiheisel, LMS North America

© 2011 Clipper Windpower, Inc. and Subsidiaries All Rights Reserved

• Background• Objective• Problem statement• Technical approach

• Break-down of in-situ Dynamics• Reaction-loads Analysis – Testing• Design Validation – Finite Element (FE) analysis

• Results • Conclusions• Comments• Acknowledgements

OVERVIEW

28


• Wind turbines are erected at remote sites, therefore, the wind turbine blades are transported on a variety of roads leading up to the sites (paved roads, sharp bends, dirt roads, etc.)

• Modern wind turbine blades weigh several tons and far exceed common trailer lengths available for road-transportation

• A wind turbine blade is a “pay-load” (should not act as an extension of the shipping fixture/structure) that needs to be isolated, thus protected from any damage during road-transportation

• The structural-dynamic behavior of “trailer + blade” is complicated and needs attention to ensure blade safety

BACKGROUND

29


• To ensure that wind turbine blades are transported safely during road-transportation and protected against a combination of static, dynamic, and stochastic loads

• To develop a methodology to calculate loads on the wind blade during road transportation• Testing – Dynamic motion of the blade and the trailer is measured

• To analyze competing designs using finite element models• Analysis – cannot account for all loading phenomena

• To identify isolation needs of the blade and subsequent design requirements

OBJECTIVE

30


• A wind turbine blade is commonly supported at discrete locations during road-transportation – (1) near the root, and (2) approximately 60-75% outboard along the blade span

• A wind turbine blade is subjected to a variety of static and dynamic loads (reaction- forces and moments),• Blade mass distribution– as borne by discrete support locations• Wind loads – cross winds on the aerofoil during transportation• In-situ harmonic behavior of blade + trailer – a combination of resulting

flap-, edge-, and twist motion• Impact or transient loading caused by road bumps, pot-holes #

• Quasi-static loading (torsion and bending) at low speeds

• Reaction loads escalate when a harsh combination of loads is experienced causing highly concentrated strains in support vicinity

PROBLEM STATEMENT

# Potentially non-linear loading behavior

31


• Various loading mechanisms described in the problem statement cause strain in the wind turbine blade and contribute towards the resultant, Sres

TECHNICAL APPROACH

randomimpactharmonicswindmassres XSSSSS ++++=• Smass can be calculated (FE model) or measured• Swind is stochastic and can be approximated by averaging

blade strains during periods of quiescence (of road induced excitation) during the test

• “Sharmonics + Simpact” is the most concerning and also the hardest to quantify since the former is caused by several contributing structural modes of “blade + trailer” and the latter occurs due to random road input

• Xrandom is small, caused by factors such as temperature32


TECHNICAL APPROACH

Blade + Support Measurements

Accelerations

Strains

Blade + SupportFE Model

Modal Behavior

Stiffness and BC capture

Correlate the model

Loads analysis

Design Iterations

StrainsCorrelate one design


TEST SET-UP

3

4

56

1

2

3’

4’

6’

Root Section • Multiple blade lengths• Design alternatives to

support all blades

Numbers in Red indicate accelerometer locations

Accelerometer Lay-out

Strain Gauge Lay-out

Salient Features• x-, y-, and z- acceleration

data was collected at various blade sections (locations 1-6) on the trailer, the support-frame, and the blade

• Strain gauges were installed at multiple span-wise sections as shown

34


• Time history of motion of support-frame and blade were recorded during the test using accelerometers

• Using periods quiescence as the initial condition, support-frame and blade motion (therefore the relative motion) were calculated £ (by integrating time data)

• Spring rates of isolation pads were known, so the resulting discrete forces and moments at the support location were calculated

REACTIVE LOADS ANALYSIS

nn

n

w

v

u

w

v

u

xy

xz

yz

xy

xz

yz

w

v

u

−−

−−

−−

=

=

−

2

2

2

1

1

1

1

22

22

22

11

11

11

0

0

0

0100

0010

0001

0100

0010

0001

ψθϕ

q

• x1-2, y1-2, and z1-2 are global co-ordinates of frame and blade on two sides of the interface

£ u1-2, v1-2, and w1-2 are computed motions from time series

35

Ref: Rhombus Consultants Group


RESULTS – Reaction Loads

10 cm

Translation Frame Twist

50

36

Force (kN) Moment (kN-m)

10 kN

5 kN-m


• Strains were zeroed before taking data in transit,

Smass = 0 µS• As predicted, a review of

strain history of 30 min showed that strain (at any location) is caused by;

1. Harmonics2. Impact loading

• A particularly harsh loading period of ‘30 s’ was considered for FE analysis

RESULTS – Test Strain Data

F 64:LE00:428:+ZF 65:LE45:428:+ZF 66:LE90:428:+ZF 67:SLE:328:+ZF 69:PLE:528:+ZF 70:PLB:628:+ZF 72:PTB:728:+ZF 73:LE00:429F 74:LE45:429F 75:LE90:429F 76:SLE:329F 78:PLE:529F 81:PTB:729F 82:LE00:430F 83:LE45:430F 84:LE90:430F 85:SLE:330F 86:SLB:230F 88:PLB:630F 90:PTB:730

Time (0-1800 s)

Str

ain

at v

ario

us g

auge

s

1 2

Strain history (30 min) at various strain gauges along the aerofoil

37


Salient Features• Linear finite elements• Composite aerofoil c/s with UNI

and BIAX layers modeled in detail

• Spring rates of all rubber elements were known

• Termination at the support-frame interface considered “rigid”; a logical assumption since the support-frame is nearly inflexible below 20 Hz

FE MODEL

Aerofoil

Saddle including rubber mat

Rubber Isolator

A design alternative

38


RESULTS – Aerofoil Strains

LP Side HP Side

Max acute strainsDesign Alternative 1

Design Alternative 2

Stresses/Strains are better diffused and lowered in peak values

39


• Presented methodology enabled an engineering review of various design alternatives for shipping fixtures

• Results ensured that a design alternative was available (for all blade lengths) such that aerofoil strains during road-transportation did not exceed the target (i.e. maximum allowable strain)

• A hybrid approach involving test and analysis succeeded such that1. Dynamic motion of the blade and the support-frame and resulting

strains in the blade were measured for correlation with the model2. Once loads (forces and moments) acting on the blade were

calculated, multiple design alternatives were analyzed

• Additional valuable information regarding trailer quality needs, and blade isolation requirements were obtained

CONCLUSIONS

40


• Dynamic behavior of the blade during road-transportation was well replicated by the model but strain correlation was not perfect for all load cases• Interface between blade and support-frame is modeled one way,

but a greater variation exists in reality• Strains introduced by blade mass and cross-winds were filtered out

of the FE analysis (however considered in decision making)

• Proposed methodology worked very well for comparing design-alternatives, but the correlation with absolute measured strains can be improved• A non-linear FE model• Trailer shake/harshness measurements in a controlled environment

• An alternative method in structural analysis called Transfer Path Analysis is available to compute reactive loads

COMMENTS

41


• American Wind Energy Association• Clipper Technical Team

• Pari Tathavadekar, Patrick Desnoyers, Mark Elliott

• Rhombus Consultants Group• Marc Regelbrugge

• LMS North America• Mike Neiheisel

• TECSIS (blade manufacturer)

ACKNOWLEDGEMENTS

42

This document, or an embodiment of it in any media, discloses information which is proprietary, is the property of Clipper Windpower, inc. & It’s subsidiaries, is anunpublished work protected under applicable copyright laws, and is delivered on the express condition that it is not to be used, disclosed (including reproduction as aderivative work), or used for manufacture for anyone other than Clipper Windpower inc. & It’s subsidiaries without its written consent, and that no right is granted todisclose or so use any information contained therein. All rights reserved. Any act in violation of prior agreement or applicable law may result in civil and criminalpenalties.

Thank You!

Advanced drive train analysis and validation at NREL of a 3MW wind

turbine

Anaheim,CA May 25th 2011

Albert Fisas

© ALSTOM 2011. All rights reserved. Information contained in this document is indicative only. No representation or warranty is given or should be relied on that it is complete or correct or will apply to any particular project. This will depend on the technical and commercial circumstances. It is provided without liability and is subject to change without notice. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited.

P 45

Alstom Wind - North America

Amarillo Assembly, TX

NIRE – TTU, TX

Adams WF, MN

NREL, CO

Danielson WF, MN

MIT, MA

Richmond HQ, VA


P 46

• ECO 100 3 MW Wind Turbine installed atNREL’s National Wind TechnologyCenter in Boulder,CO under a CRADA

• Unit in operation since March 2011, running at full power and on track for power quality certification

• R&D collaboration with NREL underway with initial focus on ALSTOM PURE TORQUETM Technology

• Starting research in Advanced Controlsand Offshore Wind

R&D collaboration with NREL


P 47

Drive Train layouts

Three point suspension Double main bearing ALSTOM PURE TORQUETM

• High non-torsional loads

• Gearbox is part of the structure!

• Overconstrained

• Vertical loads on support up to 3000 kN*

* Data courtesy of Energie und Schwingungstechnik Mitsch GmbH

• Load separation

• Floating gearbox & low speed shaft (LSS)

• Only torque transmitted to the gearbox…


P 48

Gearbox Reliability Collaborative (GRC)

• Goal - evaluate the design process for critical gaps. Led by NREL with a large group of partners > 70 attended last annual meeting

• Two 700kW public domain gearboxes: Designed specifically for the GRC (three-point support system) and heavily instrumented (130 channels). Tested in the field and in dynamometer

• Analysis: Modeling of both the field and dynamometer tests

• Condition Monitoring- Round Robin using NREL Dyno test data

• Failure database- Gathering failure root cause data


P 49

GRC – Sympack Analysis Approach

• FAST in combination with Sympack

- FAST: Aeroelastic model of all loads passing from rotor through main shaft

- Sympack: Detailed simulation of all rotor loads and Internal gearbox gears and bearings loads.

AllLoads


P 50

GRC – Sympack Analysis Approach

• FAST in combination with Sympack

- FAST: Aeroelastic model of all loads passing from rotor through main shaft

- Sympack: Detailed simulation of all rotor loads and Internal gearbox gears and bearings loads.

AllLoads

Internal Gearbox Loads

Conventional Three Point Suspension Drive Trai


P 51

GRC - Modeling Validation

• Measurements - Shaft loads (LSS and HSS)

• Bending and Torsion- Shaft speed and azimuth- Gearbox position (translation and

rotation)- Housing accelerations- Gear tooth and bearing loads

• Compare with Analysis- Gear and Bearing Load distributions- Dynamic response and modal analysis- Tolerance and alignment sensitivity


P 52

• Non-torque loading has a effect on internal gearbox load distributions for the GRC 3-point loading system

• Torque transients can exceed design loads – depending on controls

• Planet carrier and other gearbox compliance contributes to planet ring edge loading – must be accurately modeled for design analysis

• The NREL 2.5 MW dynamometer drive system can reproduce field response data accurately at low frequency

52

GRC - Early Field/Dyno Test Results

Dyno actual vs. target bending loads


P 53

ECO 100 - Drive Train layout

ALSTOM PURE TORQUETM

• Two functions handled separately

-Structural support of hub-Torque transmission from hub to drive train


P 54

ECO 100 - Test setup

Powered by Winergy

ECO 100 Prototype, 2008


P 55

ECO 100 - Test setup

ECO 100 Prototype, 2008


P 56

ECO 100 - Measurement Results


P 57



P 58



P 59


Load Mean St. Dev.

Mx 2000 kNm 100 kNm

My (LSS) 45 kNm 10 kNm

My (Frame) 700 kNm 800 kNm

Mz (LSS) 0 kNm 10 kNm

Mz (Frame) 0 kNm 800 kNm

Rough data @ 20 m/s


P 60


Load Mean St. Dev.

Mx 2000 kNm 100 kNm





Rough data @ 20 m/s


P 61


Load Mean St. Dev.

Mx 2000 kNm 100 kNm





Rough data @ 20 m/s


P 62

ECO 100 – Measurement Correlation

• Drive Train weight loading calculation


P 63

ECO 100 – Measurement Correlation

• Drive Train weight loading calculation


P 64

ECO 100 - Spectral analysis

• 2 My ( Frame ) measuring planes• Same methodology than LSBx • Frame and LSS My data @10 m/s

analyzed and compared in frequency domain


P 65

ECO 100 - Spectral analysis

• 2 My ( Frame ) measuring planes• Same methodology than LSBx • Frame and LSS My data @10 m/s

analyzed and compared in frequency domain

EDC

A B

F

EDCA B F


P 66

• NREL and Alstom have installed in 2010 an ECO 1003MW wind turbine to evaluate the performance of adifferent drive train configuration

• ECO 100 Drive Train layout transfers pure torque loadingto the gearbox hence relieving gears and bearings ofadditional induced stress or uneven loads

• First step of R&D project consists in analyzing the ECO100 with GRC – Sympack Approach and performingadvanced Field Measurement based on GRC andECO100 previous experiences

• This collaborative R&D project is expected to providepaths of optimization of drive train reliability for the USindustry. 66

CONCLUSIONS

www.alstom.com/power

Thank you for your attention!

Questions?

May 2011 AWEA WINDPOWER 2011 68

WIND TURBINE TOWERS:

Practical Advice for Stress Verification and Structural Risk Avoidance

byNestor Agbayani

A S E

STRUCTURALENGINEERING

A G B A Y A N I

May 2011 69

BACKGROUND

• NESTOR AGBAYANI, SE

• Bakersfield, California, USA

• 20 years experience in wind tower design

• Tower Engineer of Record for over 2000 MW of wind projects

• Licensed in 20(+) states and Canadian provinces

AWEA WINDPOWER 2011

A S E


A G B A Y A N I

• PART 1: OVERVIEWTower Design / Stress Analysis

• PART 2: TOWER STRESS RELIEF“A Tower Designer’s Wish List for

Design Stress Reduction.”

May 2011 70

OUTLINE

AWEA WINDPOWER 2011


COMPARE & CONTRAST

MACHINE

MACHINE SUPPORT

Complex Machine

Expensive: $Millions

Mechanical, Electrical, Aerospace Systems

“Simple” Structure & Foundation

$Hundred Thousands

Civil, Structural Systems

BUCKLING STRENGTH

May 2011 72

A SIMPLE STRUCTURE?

AWEA WINDPOWER 2011

From Troitsky, M.S., Tubular Steel Structures

From EN 1993-1-6

Manual Methods Complex Nonlinear Analysis


A SIMPLE STRUCTURE?

FATIGUE: MINER’S RULE

10

100

1000

1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08 1.0E+09

Str

ess

Ran

ge (

N/m

m^2

)

Number of S tress Cycles, N (cycles)

∆σ1

N1

∆σ2

∆σi

N2 Ni

DEMAND:( ∆σi , ni )

CAPACITY:∆σi • Ni

DAMAGE:D=Σ (ni / Ni )

FINITE ELEMENT ANALYSIS (FEA)

May 2011 74

A SIMPLE STRUCTURE?

AWEA WINDPOWER 2011

GRAPHICS COURTESY OF MDEC

TUNED MASS DAMPERS (TMD)

May 2011 75

A SIMPLE STRUCTURE?

AWEA WINDPOWER 2011

From Agyriadis, K., and Hille, N., Determination of Fatigue Loading on a Wind Turbine With Oil Damping Device, on www.gl-wind.com.


A SIMPLE STRUCTURE?

COMPUTATIONAL FLUID DYNAMICS (CFD)

COURTESY OF J. Richmond of MDEC


HEIGHT COMPARISON

80M

100M

65M50M

30M24M


SENSITIVITY TO LOCAL BUCKLING


LOCAL BUCKLING

DENT

• Control Strategies to Reduce Governing Extreme Design Loads–Due to EWM Extreme Wind:

• Consider site-specific loads versus standard IEC site class rating

–Due to Fault Conditions–Due to Emergency Stop:

• Consider that these are added to seismic

May 2011 80

STRESS (LOAD) REDUCTION

AWEA WINDPOWER 2011


OVERSPEED: LOCAL BUCKLING


OVERSPEED: CAUGHT ON TAPE!


OVERSPEED = OVERLOAD

• Avoidance of Overspeed–Due to Lightning Strike–Due to Non-failsafe Electrical Failure–Due to Non-failsafe Mechanical Failure

May 2011 84


AWEA WINDPOWER 2011


BLADE STRIKE

BLADE STRIKE

• Avoidance of Blade Strike–Due to Blade Failure–Due to Inadequate Clearance:

• Blade weight & flexibility versus widest allowable tower diameter at blade pass

May 2011 86


AWEA WINDPOWER 2011


SENSITIVITY TO FATIGUE

10

100

1000

1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08 1.0E+09

Str

ess

Ran

ge (

N/m

m^2

)

Number of S tress Cycles, N (cycles)

DAMAGE: D • (∆σ / ∆σALLOW )m

4020


VIBRATION & FATIGUE

• Avoidance of Fatigue–Control strategies to reduce fatigue–Consideration of site-specific winds–Rotor and blade balance–Long term maintenance

May 2011 89


AWEA WINDPOWER 2011


SENSITIVITY TO RESONANCE

• Mode Shapes

• Avoidance of Resonance–Adequate frequency separation:

• System Natural Freq. versus Turbine Operational Freq.

• Consider effect of tower head mass and large loads on freq.

• Validity of Loads Analysis Model–Fatigue & Extreme load magnitudes

May 2011 91


AWEA WINDPOWER 2011


THE END

THANK YOUA S E


A G B A Y A N I

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