- Title
- Structural response and optimisation of a small wind turbine blade
- Creator
- Salles Pereira da Costa, Mariana
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- As worldwide demands for energy and concerns with the environment and sustainability continue to grow, the number of wind turbines installed across the globe continues to increase. Small wind turbines fulfil a unique niche of the energy market, mostly used on ‘off-grid’ applications in which they are connected to a battery and sited where the power is needed. These locations can have less than ideal wind resource, with low average wind velocities and high levels of turbulence, which impact the turbine’s performance. The work presented in this thesis is focused on improving the understanding of small wind turbine blade structural response and the structural optimisation tools available to small blade designers. The main aims of this research project are to propose a structural optimisation method for small-scale blades and a new formulation of the gyroscopic load on the blades of small turbines. Structural optimisation of small wind turbine blades is an under investigated topic in the current literature. In most cases, structural optimisation of small blades is undertaken simultaneously with aerodynamic optimisation, utilising low-fidelity structural models of the blade (1-dimensional models constructed with isotropic equivalent material properties). The proposed structural optimisation method is based on the well-known Bi-Directional Structural Optimisation (BESO) method. BESO is finite element based and the method was selected for this research project as it is implemented with a 3-dimensional high-fidelity structural model. The gyroscopic load on the blades of small wind turbines arises from the Coriolis acceleration of the rotating and yawing blades. The gyroscopic load on the blades is reported in the current literature as a net moment acting on the root of the blade. To apply the gyroscopic load to a blade finite element model it is necessary to understand the distribution of forces on the blade due to the gyroscopic load. Thus, the author derived a new formulation of the gyroscopic load, describing the load as forces acting on the blade, making it possible to apply the load to the blade finite element model and include the gyroscopic load case in the proposed optimisation routine. The new formulation of the gyroscopic load acting on the blades of small wind turbines brought about two secondary aims for the work reported in this thesis: the first – to establish a relationship between the magnitude of the gyroscopic load, blade size (mass and length) and turbine yaw rate. To investigate this relationship, a comparison exercise was developed in which small blades of 5 different sizes had their structural response to gyroscopic loading investigated. The most relevant finding from this comparison exercise was the large magnitude of the blade tip displacement in the lead-lag direction (in-plane of rotation), which increased as the blade length increased with a significant magnitude for the blade from a 50 kW wind turbine. The next secondary aim of this research project was experimental validation of the blade finite element model used to showcase the capabilities of the proposed structural optimisation, and validation of the proposed formulation of the gyroscopic load. For the experimental components of this project, the Aerogenesis 5 kW wind turbine was made available to the author. The Aerogenesis turbine is extensively instrumented, including the instrumentation of one of its blades with 10 strain gauge modules to capture blade response. Thus, data from this turbine were acquired during stationary blade tests, to validate the Aerogenesis blade finite element model and determine calibration parameters for the strain gauge signals, and data were acquired during operation of the turbine to validate the blade model response to applied loads. Once the Aerogenesis blade model and its response were deemed valid, the model was subjected to the proposed structural optimisation, while loaded with aerodynamic, centrifugal and gyroscopic loads. The structural optimisation objective was to minimise blade mass, and the optimisation was constrained by a maximum blade tip displacement and no buckling of the blade structure. The optimisation process was able to reduce the Aerogenesis blade model mass by 8.5%, resulting in an increase in blade tip displacement of 19.5% and no buckling of the structure.
- Subject
- finite element analysis; optimisation; small wind turbine blade; gyroscopic load
- Identifier
- http://hdl.handle.net/1959.13/1419710
- Identifier
- uon:37486
- Rights
- Copyright 2020 Mariana Salles Pereira da Costa
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 7 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 364 KB | Adobe Acrobat PDF | View Details Download |