Geometric and dynamic characterization of 12 blades-Chalmers
These tests were performed during the spring and summer of 2012, presented at IMAC XXXI, Orange Grove, CA, February 2013: Spread in Modal Data Obtained From Wind Turbine Blade Testing
This page discusses the testing only. For the calculations performed, see the calculations page Analysis of blade spread from 12 blades-Chalmers.
Dynamic testing
The dynamic testing was performed by students in the Chalmers Master course "Structural dynamics - validation" during late spring. The tests were conducted with shaker excitation using a stepped sine input. Each student was assigned one of the twelve blades; as there were more students than blades, some blades were tested twice. Further testing was performed during the summer by Mladen Gibanica, Anders Johansson, Majid Khorsand Vakilzadeh and Sadegh Rahrovani to yield a group of blades tested thrice by different people.
21 accelerometers were used in the dynamic tests of which 20 were placed in approximate accordance with the study presented by Julie Harvie et al at University of Massachusetts at Lowell during IMACXXX. The 21st accelerometer was used to verify that a direct accelerance measurement was indeed achieved at the input. See further picture below. The frequency range tested was 30-500Hz with a uniform step size of 0.25Hz.
Geometric characterization
The geometry of the blades was characterized by using the geometrical tracking system of a milling machine together with a fixture, both seen below. The principal method for comparison of blade-to-blade geometrical spread was comparison of the twist angles of the blades at three different positions; P1-P3, P10-P11 and P18-P19, shown in the figure above. It was found that the discrepancy towards the tip could be as large as 10 degrees.
Data
All data sets are in the matlab data file format .mat. Use WinRAR or similar to decompress the Dataset Files. If this data is not readable, contact anders.t.johansson@chalmers.se.