| Nowadays, the wind power engineering following the nuclear energy has possessed the most developed technology and the most prospective commercial application among other ways of clean power generation due to its characters of cleanness, renewable and widely deployment all over the world. Over the past decades the utilization of wind energy has experienced great development in response to the climate change, environmental pollution and energy crisis. As the keys parts of the wind energy capture and transformation, the statistic characteristics of wind resources and wind turbine aerodynamics have been playing significant roles in the research of the wind power utilization. In the thesis, the local statistic characteristics of the wind resources around University of Wyoming, where the author attended the U.S and China jointly trained exchange program during the graduate study, is analyzed through field measurement. Furthermore, the aerodynamic performance, numerical models and flow field features of straight-bladed vertical axis wind turbine (VAWT) operated under different inflow conditions are predicted, established and validated, separately. The detailed objective of the thesis is described as the followings:Firstly, the wind resources statistic characteristics and utilization are studied in depth. Having a deep understanding of the wind features, wind measurement and wind regime assessment in order to select the location of the wind farm are the bases of the strategic planning of the wind power projects and wind turbine aerodynamic and structure design. After macroscopic analysis of the wind resources in each states in America, especially in the southeast area of Wyoming where the University of Wyoming is located, the local wind energy resources in terms of average wind speed probability density functions, which is accumulated and computed through field measurement is described by using mathematical statistical methods. Then the estimation methods of wind turbine single-machine capacity and wind farm capacity are established, which can be used to predict the wind energy utilization and also provide the reliable references to the site selection of wind farm. Meanwhile, the statistic features of average wind speed offers practical inflow parameters to the wind turbine aerodynamic simulation and experimental test, which gives considerable value in the wind power engineering.Secondly, the aerodynamic streamtube models are established to analyze the straight-bladed H-type vertical axis wind turbine in two-dimensional scale based on its own advantage of structure during operation. The classical aerodynamic streamtube models based on the blade element moment (BEM) theory are introduced and the improved double-multiple streamtube (DMST) model is newly established by introducing angular induction factors into the original model to form a pair of iterative equation sets for rotor upwind and downwind areas, which makes the distribution of the inductive velocity at the rotor’s blade more similar to the real velocity field. As a result, the improved double-multiple streamtube model enhances the accuracy of the turbine’s aerodynamic performance computational results and has low computational cost at the same time.Next, the higher fidelity approach, named three-dimensional vortex panel method is established by applying the3-D panel method with the free-wake method to the rotor’s whole blade analysis to compensate for the disadvantage of the2-D improved DMST model. This approach is basically a vortex method based on the low speed incompressible potential flow theory by calculating the velocity field through the influence of the near wake system. This model extends the computation from2-D plane to3-D space around the whole rotor so that the aerodynamic loads acting along the blade can be computed and the velocity distribution in the whole flow field around the turbine can be predicted. Furthermore, the structure and position of wake system behind the rotor is validated clearly. The3-D vortex panel method provides a more accurate solution since the blade span, blade chord and rotors wake effects are all taken into considerations, which makes the aerodynamic analysis become a more practical and general way in predicting the turbine’s performance.The two aerodynamic models for H-Type VAWT established above are simulated by computer program to predict the performance of the wind turbine. The effect which the tip speed ratio and number of blade have on the rotor’s aerodynamic load and the flow field around the whole turbine is discussed. The prediction results computed by the improved DMST model and3-D vortex panel method are compared to the experimental data in order to testify the feasibility and correctness of two models. Also, the advantage and disadvantage of these two models are analyzed to conclude each model’s scope of application in engineering so that a multi-fidelity approach for H-Type VAWT aerodynamic performance under different operating conditions and rotor’s structure features is provided. In addition, the spatial arrangement and deployment of the wind turbines in the wind farm together with the numerical simulation for the whole wind farm can be deduced by improving the method established in this thesis in the further work. |
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