Smart Rotor Modeling: Aero-Servo-Elastic Modeling of a Smart Rotor with Adaptive Trailing Edge Flaps

161 Pages·2014·4.05 MB·English

by  Leonardo Bergami (auth.)

RESEARCH
TOPICS
IN WIND
ENERGY 3
Leonardo Bergami
Smart Rotor
Modeling
Aero-Servo-Elastic Modeling of a Smart Rotor
with Adaptive Trailing Edge Flaps
123
Research Topics in Wind Energy
Volume 3
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JoachimPeinke,UniversityofOldenburg,Oldenburg,Germany
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The series Research Topics in Wind Energy publishes new developments
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Leonardo Bergami
Smart Rotor Modeling
Aero-Servo-Elastic Modeling
of a Smart Rotor with Adaptive
Trailing Edge Flaps
ABC
LeonardoBergami
DTUWindEnergy
Roskilde
Denmark
ISSN2196-7806 ISSN2196-7814 (electronic)
ISBN978-3-319-07364-4 ISBN978-3-319-07365-1 (eBook)
DOI10.1007/978-3-319-07365-1
SpringerChamHeidelbergNewYorkDordrechtLondon
LibraryofCongressControlNumber:2014939948
(cid:2)c SpringerInternationalPublishingSwitzerland2014
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Preface
This book presents the formulationof anaero-servo-elasticmodel for a wind
turbine rotor equipped with Adaptive Trailing Edge Flaps (ATEF), a smart
rotor configuration. As the name suggests, an aero-servo-elastic model con-
sists of three main components: an aerodynamic model, a structural model,
and a control model. The book first presents an engineering type of aero-
dynamic model that accounts for the dynamic effects of flap deflection. The
aerodynamic model is implemented in a Blade Element Momentum frame-
work, and coupled with a multi-body structural model in the aero-servo-
elastic simulation code HAWC2.
The investigated smart rotor configuration mainly aims at alleviating the
fatigue loads the turbine rotor has to withstand during normal operation.
First, the characteristics of the prevailing loads are identified; then, two
model-basedcontrol algorithms areoutlined:thealgorithmscontrolthetrail-
ing edge flap deflection to actively reduce the fatigue loads on the structure.
The performance of the smart rotor configurationand its controlalgorithms
arefinallyquantifiedbyaero-servo-elasticsimulationsofthe smartrotortur-
bine operating in a standard turbulent wind field.
The book collects the work I carriedout during three years as Ph.D. can-
didate at DTU Wind Energy (formerly Risø),and organizesin a monograph
the material from the Ph.D. thesis ‘Adaptive Trailing Edge Flaps for Active
Load Alleviation in a Smart Rotor Configuration’. The book was made pos-
sible by the collaboration between the European Academy of Wind Energy
(EAWE),andtheseriesResearchTopicsinWindEnergy bySpringer.Igrate-
fully acknowledge the series editor and the EAWE board for this possibility.
I am also thankful to Mac Gaunaa, who is a Ph.D. supervisor with uncom-
mon enthusiasm, and provided me with continuous support and guidance
throughout the project. Mac, as well as my co-supervisor Niels K. Poulsen,
andotherpassionateresearchersLarsC.Henriksen,VasilisRiziotis,Joachim
Heinz,andPeterB.Andersenco-authoredthearticlesthatgivethebackbone
of this monograph.
VI Preface
Iwouldalsoliketoacknowledgeotherwonderfulpersons,whomaybewere
not directly involved in the thesis topic, but had nonetheless an important
roleinmakingamemorabletime ofthosePh.D. years,andmanymoreyears
to come. Some of them have been near for some years now, others for less
time,othersarenowgeographicallymoredistantbutstillveryclose:wherever
you are, or you are planning to be, thank you for many great moments and
smiles!Finally,Iwouldliketothanktwospecialladies:mymammaStefania,
and my sister Giulia. Thank you for all the things you have been teaching
me, and for the ones you are still trying to teach.
Roskilde, April 2014 Leonardo Bergami
Contents
Preface ....................................................... V
1 Introduction.............................................. 1
Chapters outline ............................................ 4
2 Simulation Environment .................................. 7
2.1 HAWC2 Aeroelastic Code ............................... 7
2.2 NREL 5 MW Reference Wind Turbine .................... 8
3 Load Analysis ............................................ 11
3.1 Reduced Set of Design Load Cases........................ 12
3.1.1 Fatigue Damage Equivalent Loads.................. 12
3.1.2 Ultimate Loads .................................. 15
3.2 Contributions to the Fatigue Damage ..................... 18
3.2.1 Periodic and Stochastic Components................ 18
3.2.2 Spectral Load Characterization:Power Spectral
Density ......................................... 23
3.2.3 Frequency Contributions to Fatigue Damage ......... 24
3.3 Aerodynamic Model Approximations, Effects on Load
Simulation............................................. 27
3.4 Conclusion on Load Analysis............................. 29
4 ATEFlap Aerodynamic Model ............................ 33
4.1 The ATEFlap Model.................................... 33
4.1.1 Lift: Attached Flow Dynamics ..................... 35
4.1.2 Lift: Dynamics of Flow Separation.................. 41
4.1.3 Drag............................................ 43
4.1.4 Moment......................................... 45
4.2 Preprocessing Algorithm for Dynamic Stall Steady Input .... 48
4.2.1 Numerical Method................................ 50
4.3 Indicial Lift Response for Finite Thickness Airfoils.......... 52
VIII Contents
4.3.1 Indicial Response Coefficients as Function
of the Airfoil Geometry ........................... 53
4.3.2 Improved Agreement with CFD Simulations ......... 59
4.4 Model Validation....................................... 61
4.4.1 Test Case Airfoil and Flap Configuration ............ 62
4.4.2 Numerical Methods Considered in the Comparison ... 64
4.4.3 Steady Aerodynamic Response Comparison.......... 65
4.4.4 Unsteady Aerodynamic Response Comparison........ 69
4.4.5 Validation Conclusion............................. 79
5 Adaptive Trailing Edge Flap Placement................... 81
5.1 Flap Steady Aerodynamic Properties...................... 81
5.2 Flap Placement along the Blade Span..................... 82
5.3 Flap Spanwise Extension ................................ 86
5.4 ATEF Rotor Configuration .............................. 86
6 Preliminary Evaluation with Feed-Forward Cyclic
Control................................................... 89
6.1 Method ............................................... 90
6.1.1 Cyclic Control Trajectories Optimization ............ 90
6.1.2 Estimation of Actuation Energy.................... 93
6.2 Cyclic Control for Blade Load Alleviation ................. 95
6.2.1 Load Assessment in Ideal Conditions................ 96
6.2.2 Load Assessment in Realistic Simulation
Conditions ...................................... 98
6.3 Cyclic Control for Enhanced Power Capture ............... 98
6.3.1 Preliminary BEM Analysis ........................ 99
6.3.2 Cyclic Optimization .............................. 100
7 Model Based Control Algorithms for a Rotor
with ATEF ............................................... 107
7.1 Overview on Control Algorithms ......................... 108
7.1.1 Definition of the Control Models ................... 108
7.1.2 Optimal Controller Algorithms..................... 109
7.2 SISO Linear Quadratic Control for Active Load
Alleviation ............................................ 111
7.2.1 Simulation Environment........................... 112
7.2.2 Control Design................................... 113
7.2.3 Aeroelastic Simulation Results ..................... 121
7.3 MIMO Model Predictive Control ......................... 129
7.3.1 Simulation Environment........................... 130
7.3.2 Control Design................................... 130
7.3.3 Aeroelastic Simulation Results ..................... 133
Contents IX
8 Summary of Findings and Future Work................... 139
8.1 Aerodynamic Model .................................... 139
8.2 Load Analysis.......................................... 140
8.3 Smart Rotor Configuration and Preliminary Evaluation ..... 141
8.4 Active Load Alleviation with Adaptive Trailing Edge
Flaps ................................................. 142
8.5 Cost of Energy Estimation............................... 144
8.6 Indications on Flap Actuator Requirements ................ 145
9 Conclusion ............................................... 147
References.................................................... 151