nrel gearbox reliability collaborative: comparing in-field ... · • modified to mw state of the...

Brian McNiff - McNiff Light IndustryWilliam LaCava – NRELJeroen van Dam - NREL

NREL Gearbox Reliability Collaborative:

Comparing In-field Gearbox Response to Dynamometer Testing

1#

Gearbox Reliability Collaborative

• Gearboxes do not meet 20 year life, yet meet standards

• Something clearly missing in the design process

• Collaboration of manufacturers, owners, researchers

• Review Design Process : from rotor to gears/ bearings

• Failure Database: document bearing failures/modes

• Field Test: characterize bearing and structural response

• Dynamometer Test: reproduce in-field response, apply

simple to complex loading

• Analysis: compare simulation and design tools to data

2#

NREL Gearbox Reliability Collaborative Overview

• Understand internal and external gearbox response to specific loading

• Explore gaps in design process

• Develop dynamometer test to validate design assumptions

• Exercise current state of the art design tools from rotor to tribological surfaces

• Suggest improvements in design practices, validation testing and analytical tools

GRC Goals Field Testing Dynamometer Testing

Analysis

3#

Test Approach & Objectives

• Redesigned, rebuilt 2 identical 750 kW gearboxes • Modified to MW state of the art• Instrumented with over 125 signals to sense motions,

deflections, load distributions, strains and temp• Objective: Collect data to characterize gear and bearing

response in all operating situations• Field Test – capture normal operation and transients• Dyno Test – static torque, add rotor forces and

moments, add dynamics to reproduce field response• Develop data post processing and visualization tools• Validate data to provide to analysis partners• Presentation – can we match internal response in

Dyno#4

Main Shaft Bending and Torque

- two orthagonal directions of shaft bending moment gauges- Gauges mounted between main bearing and gearbox - calibrated with pull, known weight and shunt- Torque gauges same location

5#

NOTE: - static weight moment differ between field and Dyno- NTL forces applied at Fa- gear tooth couplings on LSS

Ring Gear Face Width Load Distribution

-24 gauges mounted on- tooth root centerline- 8 each at 0°-120°-240 °

6#

Ring gear gages

Gear Face load distribution, stepped loading to 100% Rated Torque

7#

The animated video associated with this slide is not available.

Planet bearing load distribution

8#

Planet bearing load distribution

Upwind

Downwind

Courtesy of Timken

9

Raw Signal

AxialDistribution

Load Zone Shift

Dyno

Non Torque Loading Mechanism

10#

Shaft Bending Effect at 240° CW

11

+My

+My

Field Data

- Captured 300+ hours of data at broad range of wind speeds

TORQUE WIND SPEED HISTOGRAM

12

Rotor Moments in Field Test

13

- Applied loads on NTL system in Dyno based on field data

Main Shaft Bending - Magnitude Statistics for Gearbox 1 Field Testing

Field vs Dyno - Torque

Comparison of 100% Torque in Field vs Dyno

Field data features a prominent 3p torque excitationDyno torque only excites at the shaft rotation frequency

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

1

2

3

4

5

6

7

8

9

10

11

X: 2.222Y: 1.361

Frequency (HZ)

Mag

nitu

de

X: 3.333Y: 2.982

X: 1.111Y: 11.46

X: 0.3784Y: 3.84

Field TorqueDyno Torque

0 10 20 30 40 50 60 70280

300

320

340

360

380

400

420

Time (sec)

Tor

que

(kN

m)

Field TorqueDyno Torque

14

Field vs Dyno – Shaft Bending Moment

Comparison of 100% Torque in Field vs Dyno & static NTL

- Variations in loading not accounted for in Dyno-Dyno dominant excitation at shaft rotation frequency- Field has beat frequencies of 1P plus

15

Pin Load Distribution – Field DataPLANET CARRIER

16

A

B C


Bearing Loading- Planet B

Varying Load Shareupwind/downwind Planet B - Field

Upwind

Downwind

Courtesy of Timken

Instrumentation

17


Dynamic Shaft Moments – Dyno vs Field

- Able to operate NREL dynamometer NTL to dynamically match shaft bending from actual field data

Dynamic Torque – Dyno vs Field

- Torque was more difficult- Limitations with VFD- Significant filtering

Conclusions

• Rotor forces/moments have an appreciable effect on ring gear and planet bearing load distributions

• Shaft moment and torque variations in the field are not reproduced in typical dynamometer testing.

• Dynamic non-torque load application can reproduce the in-field moment magnitudes and frequency content

• Torque dynamic variations in the field were difficult to reproduce on the NREL Dyno due to system limits

• But, we learned what we needed to do to make it work in upgraded NREL 5 MW Dyno facility

#20

#21

[email protected]

[email protected]

This paper availableat NREL Library:

Ruth Heffernan MarshMay 25, 2011

Advanced Wind Turbine Technology Assessment

Using Advanced Technology to Achieve Targets

© Det Norske Veritas AS. All rights reserved.


May 25, 2011

23

Project Information

Project Sponsor:

Electric Power Research Institute

EPRI Program Manager:

Charles R. McGowin, Ph. D.

DNV Research Team:

Ruth Heffernan Marsh

Morten Andersen

Matthew Malkin

Timothy McCoy

Hugh Turnbaugh



May 25, 2011

24

The Modern Wind Turbine

Mature commercial technology?

Or work in progress?



May 25, 2011

25

Improvements Under Development for Many Components or Subsystems

Constant stream of “solutions”

FoundationsOnshore and offshoreSource: Danish Wind Energy Association



May 25, 2011

2626

26 Technologies Reviewed

Blades/Rotor (12)

Passive aerodynamic devices

Active aero control

Sweep-twist blades

Material innovations: PVC resin

Material innovations: WebCore

Segmented structures

"Stealth" rotor blade

"Smart" blades

Flatback airfoils

Non-destructive inspection

Blade de-icing: super-hydrophobic

Automated blade manufacturing

Drive Train and Power Electronics (6)

Medium-voltage power electronics

Silicon-carbide IGBTs

Low-speed PM generators

Superconducting low-speed generator

Single-stage gearbox with medium speed generator

Hydrodynamic couplings



May 25, 2011

2727

26 Technologies Reviewed

Sensors and Controls (3)

Short-term forecasting - lidar

Independent blade pitch

Advanced control algorithms (adaptive control)

Towers (3)

Concrete/hybrid towers

Integrated foundation/tower

Tall towers > 120 m

Offshore (2)

Towable gravity foundation

Floating platforms

Which have the greatest potential?



May 25, 2011

2828

Evaluation Criteria

CAPEX

O&M Costs

Performance

Reliability

Environment

Cost ofEnergy ?



May 25, 2011

2929

Example: Sweep-Twist Coupled Rotor Blades

CAPEX

O&M Costs

Performance

Reliability

Environment

50%

EstimatedChange

WeightingFactor

15%

25%

5%

5%

Example:Total potential impact score = 6.5/10



May 25, 2011

3030

Levelized Cost of Energy (LCOE)

Cc_annualized = Annualized CAPEX

CO&M = O&M costs

AEP = Annual energy production

Example: sweep-twist coupled blades • LCOE = -10% to -15%

+=

AEP

CCLCOE MOannualizedc &_



May 25, 2011

3131

Which Component/Subsystem?

Rotor6% Gearbox and

Generator19%

Converter5%

Tower5%

Foundation/ Construc.

29%

Other36%

Rotor9%

Gearbox and Generator

29%

Converter8%Tower

8%

Foundation/ Construc.

20%

Other26%

Offshore (~$4,000/kW)Onshore (~$1,600/kW)

Installed Cost (CAPEX)



May 25, 2011

3232

Technology Potential Score: 8.9/10Impact on LCOE: -0 to -5%

Source: “Offshore Wind Technology” presented by Walt Musial, National Renewable Energy Laboratory, at AWEA Offshore Wind Workshop, September 9, 2008



May 25, 2011

3333

Rotor Blade Sweep-Twist Coupling

----- Conventional Blade Shape____ Sweep-Twist Blade Shape




May 25, 2011

3434


Medium-speed drive train

Source: Global Energy Concepts, National Renewable Energy Laboratory WindPACT Advanced Wind Turbine Drive Train Design Study



May 25, 2011

3535

Tall Towers > 120 m

Hybrid tower concepts

Pre-stressed concrete

H1 H2 H3

Steel tower

Pre-str. concrete section



H1 H2 H3

Steel tower




H1 H2 H3

Steel tower





May 25, 2011

3636

Conclusions and Recommendations

• Innovation needed to achieve industry goals

• Not all technology improvements will have a significant impact

• Good evaluation criteria help focus priorities

• Combining promising technologies can lead to greater improvements



May 25, 2011

37

Safeguarding Life, Property And The Environment

www.dnv.com

Contact Information:

Ruth Heffernan Marsh

[email protected]

(206) 387-4200, ext 328

mailto:[email protected]�

Testing of Wind Turbine Blade Pitch Bearings In A

Scaled Test Rig

Robert A. PalliniSerge Bochnovich

John H CowlesRobert Lugosi

Presented May 25, 2011

ConfidentialContains Material Non—public Information© 2011 RBC Bearings Incorporated

© 2011 RBC Bearings Incorporated

Pitch Bearing Function and Requirements

• Pitch Bearing and Purpose– Located between the rotor blade

and the rotor hub– Rotates the blades to adjust to

varying wind and operating conditions

– Transmits turning torque to the blade

• Drive motor and integral gear• Hydraulic actuator arm

39



• Typical Pitch Bearing Requirements– 20 year service life– -40oC to +60oC ambient temperatures– Slow rotational speed (< 2 rpm)– Small amplitudes of oscillation– Non-leak seals– Friction torque restrictions

40



41

Typical Pitch Bearing Cross Section

© 2011 RBC Bearings Incorporated42

Pitch Bearing Test Rig

• Purpose– Bench test a scale model bearing to verify design

assumptions for static load, case depth, torque, and fatigue adequacy

• Concept– Test rig to simulate rolling element load / stress levels

occurring in wind turbine pitch blade bearings– Scale model bearing with exact ball / ball groove geometry

and design as pitch blade bearing– Must be able to rotate (oscillate) under load


Test Bearing - Pitch Bearing

43


Pitch Bearing Test Rig – Final Concept

Facts and Figures• Test Bearing

• Two Single Row 4-point BB• 35” OD• 1.75” Ball• M36 Bolts Each Ring

• Rig Dimensions / Weight• Height 96.6” (Table 20”)• Width 54”• Length 109”• Total Weight 17,000 lb

• Applied Loading• Axial Thrust 6,000 lb• Moment 1,700,000 in-lb• 365,000 psi Contact Stress• Breakaway Torque 18,000 in-lb

• Drive System• Roller Screw Actuator• Speed 6.6 in/sec (3 rpm)• Oscillate +/- 30o

44

Axial Load Super Bolt

Moment Load Arms

Moment load Bolts and Load Cells

Linear Actuator

TestBearings


Pitch Bearing Test Rig – Final Concept


Pitch Bearing Test Rig FEA

46

Simplified, Quarter Symmetry Model of Test Rig

Linear Displacement Across Bearing with Applied Moment Load

Cosine Load Distribution Across Bearing with Moment Load Applied


Pitch Bearing Test Rig FEA

47

Initial Rig Design had shorter cylinder height and no gussets

Maximum Stress in vertical direction applied to top of bearing is not on plane

of symmetry for initial design

-20000

-15000

-10000

-5000

0

5000

10000

15000

0 30 60 90 120 150 180

Theta (degrees)

Ver

tica

l Str

ess

(psi

)

Case 1

Case 2

Case 3

Case 4

Case 5

Case 6

Theta

Ver

tica

l Str

ess

Analyzed Several Test Rig Design Configurations to get Proper Cosine Distribution of Load

0 30 60 90 120 150 180

Final Stress Distribution


Pitch Bearing Test Rig


Test Plan

• Load Ramp-Up Tests– Intervals of centric axial load and moment Load

• Rig shake-down• Start-up torque levels• Bearing stack height to datum

• Endurance Test– Full axial and moment load

• 347 days / 60o cycles / 3 rpm (20 year service)• Monitor running torque / height / grease contamination• Re-grease every 20 days

49


Torque Data

Running Torque Calculation (Harris, Rumbarger, & Butterfield NREL Design Guideline DG03)

Mr = (µ) (dm/2) [ 4.4Fm/dm + 2.2Fr + Fa] + Mconst

µ = coefficient of friction (0.003 for pitch bearings)

dm = bearing raceway diameterFm = applied overturning moment loadFr = applied radial loadFa = Applied axial loadMconst = Constant torque (seals, grease, bolt torque, etc.)

Mconst = 624 Nm (as measured – fully assembled, greased, sealed, and mounted test bearings)

50


Torque Data – Test Results

51

1 in/sec 3 in/sec 7 in/sec

Axial Load Only Fa = 233.5 kN

872 339 - 791 395 - 678 339 - 678

Moment Load Only Fm = 192 kNm

1892 1695 - 2034 1582 - 1808 1356 - 1582

Endurance Test Loads Fr = 8.9 kN

Fa = 26.7 kN Fm = 192 kNm

1941 - - - - - - - - - -

1977 - 2034 1356 - 1921 1130 - 1977 Avg. 1638

Running Torques (Nm)Measured

Load CaseCalculated

•Computer Analysis = 1800 Nm

-20000

-15000

-10000

-5000

0

5000

10000

15000

20000

0 10 20 30 40 50

Mea

usr

ed B

eari

ng

To

rqu

e (i

n-l

b)

Actuator Travel (in)

Torque Vs. Travel

Typical Torque Trace


Test Results – Grease Sample Results

• Grease Sample Analyses (results in ppm)

52

Sample Fe Cr Ni Al Mn Mo Si K Li Ca P Zn

Baseline 3 0 0 0 0 0 0 0 170 0 3 1

20 day 66 0 0 3 0 2 0 0 2483 10 21 16

40 day 35 0 0 4 0 0 0 8 948 0 16 3

80 day 83 0 0 1 0 0 0 1 5315 27 90 80

100 day 41 0 1 3 0 1 27 1 1688 25 85 22

140 day 25 0 0 0 0 4 3 0 1862 0 46 4

Wear Metals Contaminants Additives

Major Thickener Agent

Typical AdditivesNormal Wear and Run-inRaceway and Cage


Test Results – Bearing Characteristics

• Maximum Contact Stress (Max Loaded Ball)– Calculated = 2456 MPa to 2508 MPa– Goal = 2482 MPa

• Contact Patch Length– Calculated Inner Race 5.7 mm to 15.4 mm

Outer Race 4.7 mm to 15.5 mm – Observed Inner Race 7.1 mm to 16.5 mm

Outer Race 4.6 mm to 16.0 mm

53


Test Results – Bearing Photos (152.5 days)

54

Typical Appearance of Test Bearing Raceways

Contact Patch


SUMMARY

• The ability to test operating characteristics of a scaled pitch blade bearing has been demonstrated

• Measured torque values are in reasonable agreement with calculated values

• Results suggest assumed friction coefficient is conservatively high

• Observed contact lengths and contact angles are in agreement with calculated values

• Endurance test will be resumed

55


THANK YOU!

Component Certification

Hallmark and entrance for US-suppliers to worldwide wind market

2011-05-25AWEA 2011 - Component Certification 58

• Introducing GL Renewables Certification

• What is „Certification“?• Component Certification

Content of presentation


GL Renewables Certification is• Apart of the GL Group, • The leading certification body,

primarily focussed on the certification of wind farms, wind turbines and their components.• At the forefront of understanding in renewables technology • Abreast of all the necessary standards and requirements and takes a harmonised approach in ensuring that these are

met.

Manufacturers, banks and insurers around the world rely on the state-of-the-art service provided by GL Renewables Certification.

GL Renewables segments 750 Employees in 22 Countries

Offshore Wind

Onshore Wind

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Wave Power

Tidal Power

Solar

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New ZealandBrazil

CanadaUSAMexico

Ireland

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NetherlandsPoland

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• Introducing GL Renewables Certification

• What is „Certification“?

• Component Certification



Definition of Certification (ISO / IEC 17000)

• Certification• third-party attestation related to products,

processes, systems or persons

• Attestation• issue of a statement, based on a decision

following the review, that fulfilment of specified requirements has been demonstrated

• Review• verification of the suitability, adequacy and

effectiveness…

• in short: Confirmation of Compliance for a

product or a service withdefined requirements


• Introducing GL Renewables Certification• What is „Certification“?

• Component Certification



The object of Component Certification

is the confirmation that a component for a wind turbine is

• designed, • documented and • manufactured

in conformity with

• design assumptions, • specific standards and • technical requirements.


Moduls of Component Certification

The specific scope for the assessment within a module depends on the actual component.

The procedures and requirements that must be applied are described in technical standards and guidelines, like

[1] “Guideline for the Certification of Wind Turbines”, Edition 2010[2] “Guideline for the Certification of Offshore Wind Turbines”, Edition 2005[3] ”Conformity testing and certification”, IEC 61400-22 Edition 1.0, 2010-05


Component Certificates are often required

• Rotor blades• Gearboxes• Generators • Tower

but more and more also for • Rotor hubs• Main shafts • Main and generator frames • Main bearings• Locking devices • Main brakes• Couplings• Pitch and yaw drives and their

bearings• Transformers • Converters• Lifting devices


Moduls of Component Certification

The specific scope for the assessment within a module depends on the actual component.

The procedures and requirements that must be applied are described in technical standards and guidelines, like

[1] “Guideline for the Certification of Wind Turbines”, Edition 2010[2] “Guideline for the Certification of Offshore Wind Turbines”, Edition 2005[3] ”Conformity testing and certification”, IEC 61400-22 Edition 1.0, 2010-05


Germanischer Lloyd Renewable Certification can provide tailored solutions for wind turbine manufacturers and component-suppliers.

You will receive a hallmark showing that your component meets both

• International standards and your • Customer’s needs.

Axel DombrowskiDepartment Machinery Components and Electrical Engineering Germanischer Lloyd Industrial Services GmbH Renewables CertificationBrooktorkai 18, 20457 Hamburg GERMANY Phone: +49 (0) 40 - 3 61 49 - 74 08 Fax: +49 (0) 40 - 3 61 49 - 17 20 Email: [email protected] WWW: www.gl-group.com/GLRenewables

Thank you very much for your attention

Questions and AnswersPart 1

Questions and AnswersPart 2

nrel gearbox reliability collaborative: comparing in-field ... · • modified to mw state of the...

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