Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Carsten Skamris (1) F P
(1) Blade Test Centre A/S (BLAEST), Aalborg, Denmark
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Blade test centre a/s – prepared for the future
BLAEST is a private company whose main activity is to perform structural tests on wind turbine blades. BLAEST was established in 2005 based on activities until then done by the Technical University of Denmark back in the eighties. The shareholders of BLAEST are, apart from the Technical University of Denmark, also DNV GL and FORCE Technology.
BLAEST offers a wide range of accredited services in connection with the wind turbine blade certification process. These include:
• Determination of natural frequencies
•Static load test
•Fatigue load test
BLAEST is accredited according to EN 61400-23, 2014. BLAEST also offers accredited tests in compliance with DNV-DS-J102 October 2010 and GL 2010 Edition.
Main body of abstract
Static load tests simulate as well as possible the different load cases. This involves often load application in many different directions. Static tests are carried out as a multipoint load application in vertical direction or in other angles as the customer may require. BLAEST uses a mechanical load system which introduces loads in multiple points simultaneously. The load introduction system works with very small deviations between the individual load points and can complete a static test within few minutes. Data are recorded with a sample rate of up to 250 Hz. The results from the static load test makes the design engineer and the certifying bode able to verify the structural model used for design the blade.
Fatigue blade testing is simulating the fatigue load on the Wind Turbine blade for the lifetime of the Wind Turbine. The large challenge is to reach the bending load distribution along the blade without overloading the blade too much in several points. BLAEST has tools to simulate the bending moment distribution and methods to achieve the bending moment distribution in the laboratory. These are newly developed oscillation amplifiers mounted on the floor to compensate for big masses on the blade. The reported data enables design engineers and certifying bodies to compare measured data to the calculated data of the design criteria.
Fatigue load testings are performed to determine inherent fatigue properties of a blade, predicting the long-term performance during the designed blade lifespan.
Thus full-scale blade fatigue tests are often an essential part of the approval process.
Fatigue tests may be performed in different ways. Edgewise fatigue load testing is normally performed in horizontal orientation and excitations are forced by rotating eccentric masses. For smaller blades, flap-wise fatigue testing can be executed by using rotating eccentric masses as well. Mainly for larger blades, BLAEST has two types of exciters mounted on the floor: An electric driven exciter with rotating masses, mounted on a seesaw. Furthermore, BLAEST has a newly developed lightweight electrically driven exciter with a pushrod connection to the blade.
BLAEST is located in Aalborg, which is in the northern part of Denmark right next to the waterfront. Access by sea and land is easy – even with very large blades. In May 2014 test hall was expanded to enable testing of +80 meter blades. In addition to this, a new test rig was constructed – mainly for fatigue testing of +80 m blades. With the last mentioned test rig BLAEST now has 4 test rigs for large WT blades.