Externally applied loads from high winds or impacts may cause structural damage to the
wind-turbine blade, and this may further affect the aerodynamic performance of the blade.
Wind-turbine blades experience high vibration levels or amplitudes under high winds.
Vibrations negatively affect the wind flow on the blade. This project considers the structural
dynamic analysis of a small-scale wind turbine with a particular focus on the blade; it involves
the finite element model development, model validation and structural analysis of the validated
model. The analysis involves a small-scale wind-turbine structural response when subjected to
different loading inputs. The analysis is specifically focused on on-shore systems. The use of
small-scale wind-turbine systems is common however, apart from initial structural analysis
during design stages, these systems have not been studied sufficiently to establish their
behaviour under a variation of real-life loading conditions. On-shore wind turbines are often
designed for low-wind speeds and their structural strength may be compromised. In addition,
these systems experience widely-varying wind speeds from one location to another to an extent
that it is extremely difficult to achieve a uniform structural performance. The main reason for
solving this problem is to evaluate the structural response of the blade, with special emphasis
on an 800 W Kestrel e230i. This involves the calculation of the distribution of blade deflections and stresses over the wind-turbine blade under different loading conditions. To solve the
problem, a three-dimensional model of a Kestrel e230i blade was firstly developed in Autodesk
Inventor Professional using geometrical measurements that were taken in the mechanical
engineering laboratory. A 3D finite element model was developed in ANSYS using
approximate material properties for fiberglass obtained from the literature. The model was then
validated by comparing its responses with those from a number of static tests, plus a simple
impact test for comparison of the first natural frequency. Finally, a number of numerical tests
were conducted on the validated finite element model to determine its structural responses. The
purpose of the numerical analysis was to obtain the equivalent von Mises stress and
deformation produced in the blade. It was determined that under the examined different loading
conditions, a higher stress contour was found to occur around the mid-span of the blade. The
calculated maximum flexural stress on the blade was observed to be less than the allowable
flexural stress for fiberglass which is 1,770 MPa. As expected, the highest deformation
occurred at blade tip. The first critical speed of the assembled three-bladed wind turbine was found to be at 4.3 rpm. The first mode shape was observed to be in the flap-wise bending
direction and for a range of rotor speeds between zero and 608 rpm, three out of a total of five mode shapes were in the flap-wise bending direction. Future studies should address issues
relating blade vibrations with generated power, validation of dynamic tests, fluid-structural
interaction and introduction of bio-inspired blade system. Although the performance of the bioinspired
blade has not been studied in great detail, preliminary studies indicate that this system
has a superior performance. / Mechanical and Industrial Engineering / M. Tech. (Electrical and Mining Engineering)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:unisa/oai:uir.unisa.ac.za:10500/27607 |
| Date | 06 1900 |
| Creators | Babawarun, Tolulope |
| Contributors | Ngwangwa, Harry, Hua, Ho Wei |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | 1 online resource (xv, 78 leaves) : Illustrations (chiefly color), graphs (chiefly color), color map, application/pdf |
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