1,720,983 research outputs found
Aero-Structural Optimization of Vertical Axis Wind Turbines
Full text linkThis Thesis focuses on the aero-structural simulation and optimization of Darrieus Vertical Axis Wind Turbines.
Aerodynamic simulation tools based on different techniques are developed, improved with respect to state-of-art tools, and validated against experimental data. The main considered approaches are based on the Blade Element Momentum, Vortex, two- and three-dimensional Unsteady Reynolds-Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) models. The models are developed keeping in mind the final coupling with an optimization algorithm, therefore with particular emphasis on the computational effort and simulation robustness. A structural simulation tool based on the Euler-Bernoulli beam theory is also developed and validated against experimental data to perform an efficient aero-structural simulation.
The validated models are coupled with an optimization algorithm under certain constraints to create an iterative loop able to produce improved designs. Different applications are considered based on the most relevant research topics and real case scenarios. The particular case of a floating Troposkien Vertical Axis Wind Turbine is analysed by improving the baseline aerodynamic design for the 5 MW rotor developed in the FP7 DeepWind project and evaluating the aerodynamic performance under rotor tilted conditions for the 1 kW demonstrator. The airfoil shape for the blade of a 500 kW H-rotor is also subjected to an optimization analysis with the aim to increase the aerodynamic production, obtaining a new geometry different from literature design. Finally, the aerodynamic and structural simulation tools are coupled to perform a complete aero-structural optimization of blade shape and chord distribution for a 500 kW Troposkien rotor. Both aerodynamic production and rotor stress are targeted in the routine and new blade shapes are found and discussed.
The Thesis results, beside the increased performance with respect to the baseline case, prove that iterative loops, obtained by coupling a fast simulation tool and an optimization algorithm, can be adopted in the design and test phase of Darrieus Vertical Axis Wind Turbines, by providing the designer an advanced insight on the aerodynamic and structural phenomena experienced by these complex machines
Numerical Validation of a Blade Element-Momentum Algorithm based on Hybrid Airfoil Polars for a 2-m Darrieus Wind Turbine
No full textA dynamic stall-corrected Blade Element-Momentum algorithm using a hybrid database is validated through the numerical comparison with Sandra experimental measurements on a 2-m diameter wind turbine of Troposkien shape. The numerical predictions are compared to experimental data and also to numerical computations based on an existing literature database, allowing to explore the potential of the proposed hybrid database for vertical-axis wind turbine power prediction
Performance-optimized airfoil for Darrieus wind turbines
No full textAn optimization method, featuring a loop algorithm which includes a genetic optimizer, a twodimensional
URANS CFD model, a fitness calculator and an airfoil generator, is created and deployed
to develop a new airfoil shape which can possibly increase the aerodynamic performance of a Darrieus
wind turbine. The two-dimensional URANS CFD model is validated against a baseline Darrieus rotor,
whose experimental data are available in literature. The optimization included as initial solutions the
most common airfoils described in literature and is targeted to increase the aerodynamic performance of
the two-dimensional model of the baseline rotor at fixed wind and rotational speeds. The optimization
resulted in a new airfoil shape showing a particular configuration of mean line and thickness distribution.
The airfoil aerodynamics is analyzed by estimating the aerodynamic coefficients and pressure
distributions at different operative conditions
A computational assessment of the aerodynamic performance of a tilted Darrieus wind turbine
Full text linkThe aerodynamic performance of a Darrieus wind turbine operating with the rotation axis tilted with respect to the free-stream wind
speed is investigated in this paper. An Unsteady Reynolds Averaged Navier Stokes (URANS) Computational Fluid Dynamics
(CFD) model is proposed in order to provide wind turbine manufacturers with a reliable simulation tool to forecast the power
conversion characteristics of vertical axis wind turbine prototypes that operate in tilted conditions. The outputs of the model are
compared against experimental performance of a non-tilted rotor corrected to the standard sea level conditions. Two different
tilted configurations are studied (i.e., a tilt angle of 10 and 20), and the aerodynamic performance are presented in terms of the
mechanical power production and the power coecient. A sensible decrease in the power production is observed for increasing
tilt angles. Comprehensive physical interpretations of the results are provided, considering also the predictions of a methodology
based on semi-empirical methods
Optimization of a Darrieus Vertical-Axis Wind Turbine Using Blade Element Momentum theory and Evolutionary Algorithms
Full text linkWind turbine design procedures usually involve the adoption of the blade element e momentum theory.
Nevertheless, its use is limited by the lack of extended database regarding the aerodynamic coefficients
for most used airfoils. In the present work, an extended database generation procedure for symmetric
profiles is discussed and validated with the aim of adopting numerical optimization methods for verticalaxis
wind turbine design.
Evolutionary algorithms are thereby utilized to provide optimal configurations for different design
objectives. The pure performance and the annual energy production are here considered in order to
show the capabilities of the numerical code. A relevant increase in performance is achieved for all the
obtained results, showing that the numerical optimization can be successfully adopted in vertical-axis
wind turbine design procedures
Aero-structural design optimization of vertical axis wind turbines
Full text linkIn the last decade, vertical axis wind turbines acquired notable interest in the renewable energy field. Different techniques are available to perform aerodynamic and structural simulation of these complex machines, but, to the authors' best knowledge, a comprehensive approach, which includes an automatic optimization algorithm, has never been developed. In this work, a methodology to conduct an efficient aero-structural design of Darrieus vertical axis wind turbine is presented. This relies on a code-to-measurement validated simulation tool based on Blade Element-Momentum algorithm adopting a particular set of aerodynamic coefficients, and a code-to-code validated structural model based on the Euler–Bernoulli beam theory. The algorithms are coupled with a Genetic Algorithm to perform the optimization. The adopted decisional parameters allow to completely vary the blade shape and the airfoil geometry to reduce the structural stress and improve the aerodynamic performance. Different individuals are explored to perform a wide aerodynamic and structural analysis of improved configurations
Proposal for an innovative chord distribution in the Troposkien vertical axis wind turbine concept
No full textAn innovative design for the Troposkien concept is introduced by means of an advanced chord distribution, computed using the WOMBAT (Weatherly Optimization Method for Blades of Air Turbines) algorithm for the performance optimization of vertical axis wind turbines. Five rotor blade architectures, characterized by a constant value of the thickness-to-chord ratio and a varying chord length along the blade span, are evaluated. The optimization process is conducted with respect to the power coefficient for a target wind speed of 9 m/s, obtaining a consistent improvement of rotor performance with respect to the baseline blade configuration
Optimal Spanwise Chord and Thickness Distribution for a Troposkien Darrieus Wind Turbine
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