Development of a Dual-Axis Phase-Locked Excitation (PhLEX) Resonant Fatigue Test Method for Wind Turbine Blades

2013 ◽  
Author(s):  
Jenna A. Beckwith ◽  
Darris White ◽  
Domenic L. Barsotti
Keyword(s):  
Wind Turbine ◽  
Fatigue Test ◽  
Structural Integrity ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Test Method ◽  
Wind Loading ◽  
Testing Time ◽  
Wind Turbine Blades ◽  
Operation Conditions

Collaborative efforts between Embry-Riddle Aeronautical University (ERAU) and the National Renewable Energy Laboratory (NREL) have resulted in an innovative dual-axis Phase-Locked EXcitation (PhLEX) resonant test method for structural fatigue testing of wind turbine blades. Laboratory fatigue test results give blade manufacturers important information regarding the structural integrity of their designs and can offer insight on how to further increase the strength and efficiency of these blades. The PhLEX test method applies loads in a manner that is more representative of wind loading experienced through field operation conditions as compared to current dual-axis quantum resonant methods. The method developed involves exciting the blade at resonance in the edge direction, while simultaneously applying a direct actuation force in the flap direction at the first edge frequency. As a proof of concept, this method was employed on a 9-meter (m) blade test article at NREL’s National Wind Technology Center (NWTC) located near Boulder, Colorado. Preliminary results show that the PhLEX method is able to control the phase angle between application of flap and edge loads while decreasing testing time due to faster test frequencies and the ability to maintain constant amplitude loading.

Development of a Dual-Axis Phase-Locked Resonant Excitation Test Method for Fatigue Testing of Wind Turbine Blades

2011 ◽  
Author(s):  
Darris White ◽  
Michael Desmond ◽  
Waleed Gowharji ◽  
Jenna A. Beckwith ◽  
Kenneth J. Meierjurgen
Keyword(s):  
Wind Turbine ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Test Method ◽  
Resonant Excitation ◽  
Wind Loading ◽  
Cycle Phase ◽  
Testing Time ◽  
Wind Turbine Blades ◽  
Operation Conditions

Collaborative efforts between Embry-Riddle Aeronautical University (ERAU) and the National Renewable Energy Laboratories (NREL) have resulted in an innovative dual-axis phase-locked resonant excitation (PhLEX) test method for fatigue testing of wind turbine blades. The Dual-axis phase-locked test method has shown to provide more realistic load application as compared to wind loading experienced through field operation conditions. The current concepts involved exciting the blade at its fundamental edgewise natural frequency while applying a force in the flap direction at that same frequency. This advanced test method incorporates existing commercially available test hardware, known as the Universal Resonant Excitation (UREX), combined with an additional hydraulically actuated member to dynamically force the blade using adaptive algorithms and advanced control strategies in order to provide cycle-to-cycle phase control and decreased testing time. In short, this paper will outline the development of a finite element model for predicting performance and evaluation of the results.

Finite Element Modeling of a Dual Axis Resonant Test System for Wind Turbine Blades

2009 ◽  
Author(s):  
Michael Desmond ◽  
Darris White ◽  
William Barott
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Test System ◽  
Full Scale ◽  
Wind Turbine Blade ◽  
Test Method ◽  
Wind Turbine Blades ◽  
Design Assessment

Structural testing of wind turbine blades is required for designing reliable, structurally efficient blades. Full-scale blade fatigue testing conducted at the National Renewable Energy Laboratory’s (NREL) National Wind Technology Center (NWTC) provides blade manufacturers quantitative information on design details including design assessment, manufacturing quality, and design durability. Blade tests can be conducted as a single axis test (flapwise or lead-lag) or a dual-axis test (flapwise and lead-lag simultaneously). Dual-axis testing is generally the preferred full-scale test method as it simulates to a greater extent the characteristic loading the blade is subjected to in the field. Historically, wind turbine blade fatigue testing has been performed through forced displacement methods using hydraulic systems which directly apply load to the blade. More efficient methods of fatigue testing are being developed at the NWTC that employ resonant excitation systems to reduce hydraulic supply requirements, increase the test speed, and improve distributed load matching. In the case of a dual-axis resonant test, the blade is excited through multiple actuators at two distinct frequencies corresponding to the flapwise and lead-lag frequencies. A primary objective of a dual-axis test is to test the blade to equivalent damage moments in multiple axes. A code was developed to simulate the performance of the dual-axis resonant test system, comparing the predictions to actual test results. Modeling of this test system was performed using a MATLAB script that integrates the NREL FAST code with a commercial dynamic simulator package ADAMS. This code has the advantage over existing methods to more accurately simulate the coupled response between the flapwise and lead-lag directions. In summary, this paper will provide information on the modeling of wind turbine blade dual-axis resonant test systems.

scholarly journals Review of Icing Effects on Wind Turbine in Cold Regions

2018 ◽  
Vol 72 ◽  
pp. 01007 ◽  
Author(s):  
Faizan Afzal ◽  
Muhammad S. Virk
Keyword(s):  
Wind Turbine ◽  
Structural Integrity ◽  
Turbine Blades ◽  
Leading Edge ◽  
Added Mass ◽  
Cold Climate ◽  
Ice Accretion ◽  
Wind Turbine Blades ◽  
Turbine Performance ◽  
Ice Shedding

This paper describes a brief overview of main issues related to atmospheric ice accretion on wind turbines installed in cold climate region. Icing has significant effects on wind turbine performance particularly from aerodynamic and structural integrity perspective, as ice accumulates mainly on the leading edge of the blades that change its aerodynamic profile shape and effects its structural dynamics due to added mass effects of ice. This research aims to provide an overview and develop further understanding of the effects of atmospheric ice accretion on wind turbine blades. One of the operational challenges of the wind turbine blade operation in icing condition is also to overcome the process of ice shedding, which may happen due to vibrations or bending of the blades. Ice shedding is dangerous phenomenon, hazardous for equipment and personnel in the immediate area.

Acoustic Emission for Structural Integrity Assessment of Wind Turbine Blades

2014 ◽  
pp. 369-382 ◽  
Author(s):  
Nikolaos K. Tsopelas ◽  
Dimitrios G. Papasalouros ◽  
Athanasios A. Anastasopoulos ◽  
Dimitrios A. Kourousis ◽  
Jason W. Dong
Keyword(s):  
Acoustic Emission ◽  
Wind Turbine ◽  
Structural Integrity ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Integrity Assessment

Predictions of Structural Testing Characteristics for Wind Turbine Blades

2009 ◽  
Author(s):  
Michael Desmond ◽  
Darris White
Keyword(s):  
Wind Turbine ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Structural Testing ◽  
Wind Turbine Blades ◽  
Static Testing ◽  
Extreme Load ◽  
Design Loads ◽  
Certification Requirements ◽  
Blade Loads

Static and fatigue structural testing of wind turbine blades provides manufacturers with quantitative details in order to improve designs and meet certification requirements. Static testing entails applying extreme load cases through a combination of winches and weights to determine the ultimate strength of the blade while fatigue testing entails applying the operating design loads through forced hydraulics or resonant excitation systems over the life cycle of the blade to determine durability. Recently, considerable efforts have been put forth to characterize the reactions of wind turbine blades during structural testing in order to develop load and deflection predictions for the next generation of blade test facilities. Incorporating years of testing experience with historical test data from several wind turbine blades, curve fits were developed to extrapolate properties for blades up to one hundred meters in length. Furthermore, conservative assumptions were employed to account for blade variations due to inconsistent manufacturing processes. In short, this paper will outline the predictions of wind turbine blade loads and deflections during static and fatigue structural testing.

Evaluation of dual-axis fatigue testing of large wind turbine blades

2011 ◽  
Vol 226 (7) ◽  
pp. 1693-1704 ◽  
Author(s):  
Peter R Greaves ◽  
Robert G Dominy ◽  
Grant L Ingram ◽  
Hui Long ◽  
Richard Court
Keyword(s):  
Service Life ◽  
Wind Turbine ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Bending Moment ◽  
Fatigue Tests ◽  
Simulation Software ◽  
Wind Turbine Blades ◽  
Moment Distribution ◽  
Large Wind

Full-scale fatigue testing is part of the certification process for large wind turbine blades. That testing is usually performed about the flapwise and edgewise axes independently but a new method for resonant fatigue testing has been developed in which the flapwise and edgewise directions are tested simultaneously, thus also allowing the interactions between the two mutually perpendicular loads to be investigated. The method has been evaluated by comparing the Palmgren–Miner damage sum around the cross-section at selected points along the blade length that results from a simulated service life, as specified in the design standards, and testing. Bending moments at each point were generated using wind turbine simulation software and the test loads were designed to cause the same amount of damage as the true service life. The mode shape of the blade was tuned by optimising the position of the excitation equipment, so that the bending moment distribution was as close as possible to the target loads. The loads were converted to strain–time histories using strength of materials approach, and fatigue analysis was performed. The results show that if the bending moment distribution is correct along the length of the blade, then dual-axis resonant testing tests the blade much more thoroughly than sequential tests in the flapwise and edgewise directions. This approach is shown to be more representative of the loading seen in service and can thus contribute to a potential reduction in the weight of wind turbine blades and the duration of fatigue tests leading to reduced cost.

An experimental investigation into passive acoustic damage detection for structural health monitoring of wind turbine blades

2020 ◽  
Vol 19 (6) ◽  
pp. 1711-1725 ◽  
Author(s):  
Jaclyn Solimine ◽  
Christopher Niezrecki ◽  
Murat Inalpolat
Keyword(s):  
Signal Processing ◽  
Structural Health Monitoring ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Health Monitoring ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Wind Turbine Blade ◽  
Wind Turbine Blades ◽  
Structural Health

This article details the implementation of a novel passive structural health monitoring approach for damage detection in wind turbine blades using airborne sound. The approach utilizes blade-internal microphones to detect trends, shifts, or spikes in the sound pressure level of the blade cavity using a limited network of internally distributed airborne acoustic sensors, naturally occurring passive system excitation, and periodic measurement windows. A test campaign was performed on a utility-scale wind turbine blade undergoing fatigue testing to demonstrate the ability of the method for structural health monitoring applications. The preliminary audio signal processing steps used in the study, which were heavily influenced by those methods commonly utilized in speech-processing applications, are discussed in detail. Principal component analysis and K-means clustering are applied to the feature-space representation of the data set to identify any outliers (synonymous with deviations from the normal operation of the wind turbine blade) in the measurements. The performance of the system is evaluated based on its ability to detect those structural events in the blade that are identified by making manual observations of the measurements. The signal processing methods proposed within the article are shown to be successful in detecting structural and acoustic aberrations experienced by a full-scale wind turbine blade undergoing fatigue testing. Following the assessment of the data, recommendations are given to address the future development of the approach in terms of physical limitations, signal processing techniques, and machine learning options.

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