Post on 19-Mar-2018
transcript
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
Development and Analysis of a Swept Blade Aeroelastic Model for a Small Wind Turbine
Robert Preus, Rick Damiani, and Sang Lee National Renewable Energy Laboratory
Scott Larwood University of the Pacific Small Wind Conference
June 17, 2014 Stevens Point, Wisconsin
PR-5000-62197
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Acknowledgments
• U.S. Department of Energy (DOE) – For Competitiveness Improvement Project (CIP) funds and computer-aided engineering (CAE) tools funds
• Scott Larwood – For implementing the original version of FAST2ADAMS in FAST6
• Reference turbine loosely based on Bergey Wind Power Excel S10.
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Outline
• Quest towards optimized/advanced rotors
• CAE tools: FAST and ADAMS
• Case study
• Summary of results.
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• Reduce loads at current rotor diameter OR
• Increase rotor diameter at same loading level
• Reduce material • Optimize utilization
• Reduce the levelized cost of energy (LCOE).
Why Advanced Rotors?
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• The lift at the tip induces pitch-feather
Blade SweepBend-Twist Coupling
Courtesy of Wetzel Engineering, Inc.
• Load mitigation: reduce ultimate and fatigue loads
Viryd CS-8 wind turbine under test at the National Wind Technology Center, Photo by Mark Murphy, NREL 22258
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• FAST– Aero-Hydro-Servo-Elastic CAE Tool in Development Since 1996: o Open source = FREE!
o Capable of simulating tail and furling dynamics for small wind o Twenty-four degrees of freedom (DOFs)
horizontal-axis wind turbine only— vertical-axis wind turbine aerodynamics
captured in upcoming V8 o Use for design to International Electrotechnical Commission load cases – certification o V8 will be capable of blade torsional (twist) degree of freedom o Can be used to prepare ADAMS input files and models.
CAE Tools: FAST and ADAMS
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• MSC ADAMS – Multibody Dynamics: o Commercial product o Can be coupled to Aerodyn (FAST module) – FAST2ADAMS available for FREE o Can be highly customizable with user’s controller library (requires a bit of
programming) o Highly flexible – virtually any geometry you can think of o High fidelity – as many DOFs as the user requires.
CAE Tools: FAST and ADAMS (continued)
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• Original preprocessor would use the sheared approach: o Leads to inaccurate representation of aerodynamic and inertial loads
• New preprocessor follows curved properties of blade elements: o Higher fidelity and physically consistent results o Improved accuracy.
FAST2ADAMS
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• Started the case study from a much simpler FAST input model and created an ADAMS model of a small wind turbine
• Small wind research turbine (SWRT) baseline rendering • Design load cases (DLCs): 1.1 from 61400-2,NTM, WS 8–16 m/s • Five configurations: baseline and 0, 5, 10, 15, 20 deg sweep
angles • Input and output channels.
Case Study
70% radius
ɸ Pitch axis
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Case Studies baseline 10 deg 5 deg
15 deg 20 deg
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• Time series 0 deg and 20 deg at 14 m/s wind
Case Study
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Case Study
14 m/s 0 deg sweep
14 m/s 20 deg sweep
- 5.6 times slowed down
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• The mean power has not shown more than 5% variation across the various configurations
Note: This finding needs to be revised as the aero marker may need to be adjusted for simple blade element momentum and crossflow effects
o Furling limits power anyways - more investigation needed o Stall-regulated turbine: possible power increase
• Furling standard deviation slightly reduces with sweep.
Case Study Results
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• Blade tip twist
• 20 deg sweep doubles the twist at the blade tip
Case Study- ULS from DLC 1.1
0
1
2
3
4
5
6
7
8
Load Cases
Bla
de T
ip T
wis
t Mag
nitu
des
[deg
]
DLC2
0deg
DLC1
5deg
DLC1
0deg
DLC0
5deg
DLC0
0deg
TipRDzc1TipRDzc2TipRDzc3
15
0
0.05
0.1
0.15
0.2
0.25
Load Cases
Min
imum
Tow
er C
lear
ance
[m]
DLC2
0deg
DLC1
5deg
DLC1
0deg
DLC0
5deg
DLC0
0deg
TipClrnc1TipClrnc2TipClrnc3
• Blade root bending moment • 20 deg sweep mitigates UL load by
some 15% • 10 deg sweep increases UL load by
some 15%.
Case Study- ULS from DLC 1.1
0
1
2
3
4
5
6
7
Load Cases
Bla
de M
omen
t Mag
nitu
des
[kN
m]
DL
C20d
eg
DLC1
5deg
DLC1
0deg
DLC0
5deg
DLC0
0deg
RootM1RootM2RootM3
Tower clearance almost unaffected
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• Tower base bending moments • Twenty degree sweep mitigates UL load by some 15% • Five degree sweep increases UL load by some 10%.
Case Study - ULS from DLC 1.1
0
50
100
150
200
250
300
350
400
450
500
Load Cases
Tow
er M
omen
t Mag
nitu
des
[kN
m]
DLC2
0deg
DLC1
5deg
DLC1
0deg
DLC0
5deg
DLC0
0deg
TwrBsMTwrBsMzt
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• Blade root bending moments • Twenty degree sweep mitigates damage equivalent loads
(DELs) by some 15% (flap) to 20% (edge) • Ten degreee sweep increases DELs by some 5% (edge).
Case Study - FLS from DLC 1.1
0
0.2
0.4
0.6
0.8
1
1.2
05 deg 10 deg 15 deg 20 deg
DEL
/DEL
@0d
eg
Root bending DEL ratios with respect to the baseline (m=10)
RootMxb1
RootMxb2
RootMxb3
RootMyb1
RootMyb2
RootMyb3
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• Yaw-bearing bending moments DELs reduced (shaft life) • Tower-base moments DELs reduced by some 20% • Twenty degree sweep mitigates DELs by some 20%.
Case Study - FLS from DLC 1.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
05 deg 10 deg 15 deg 20 deg
DEL
/DEL
@0d
eg
Yaw-bearing DEL ratios with respect to the baseline
YawBrMxp m=3
YawBrMxp m=4
YawBrMxp m=5
YawBrMyp m=3
YawBrMyp m=4
YawBrMyp m=5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
05 deg 10 deg 15 deg 20 deg
DEL
/DEL
@0d
eg
Tower-base DEL ratios with respect to the baseline
TwrBsMxt m=3
TwrBsMxt m=4
TwrBsMxt m=5
TwrBsMyt m=3
TwrBsMyt m=4
TwrBsMyt m=5
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Conclusions • A new ADAMS preprocessor is now available for FAST 7.02 which
allows for higher fidelity representation of pre-sweep and bend of blades.
• A case study on a small wind turbine revealed the capabilities of
simulating the effect of blade sweep using FAST2ADAMS • Results show promising effects in terms of load mitigation:
• ULS decrease by 15% at 20 deg sweep (likely 10%–15%) • DELs decrease by 20% at 20 deg sweep (likely 15%–20%) • Little effect on power production (same rotor area) to be
revised with new aeromarkers, possibly eliminating furling.
• Use sweep to grow the rotors or thin the blades and reduce costs, but use caution in selecting amount of sweep, as some angles may create nonlinear effects on the dynamics of the machine and increase loads.
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
For More Information
Rick.Damiani@nrel.gov