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    The aerodynamic effects of blade pitch angle on small horizontal axis wind turbines
    (Emerald Group Publishing Ltd, 2023) Kaya, Mehmet Numan; Uzol, Oguz; Ingham, Derek; Kose, Faruk; Buyukzeren, Riza
    Purpose The purpose of this paper is to thoroughly investigate the aerodynamic effects of blade pitch angle on small scaled horizontal axis wind turbines (HAWTs) using computational fluid dynamics (CFD) method to find out the sophisticated effects on the flow phenomena and power performance. Design/methodology/approach A small HAWT is used as a reference to validate the model and examine the aerodynamic effects. The blade pitch angle was varied between +2 and -6 degrees, angles which are critical for the reference wind turbine in terms of performance, and the CFD simulations were performed at different tip speed ratio values, lambda = 2, 3, 4, 5, 6, 7, 9 and 10.5 to cover the effects in various conditions. Results are examined in two different aspects, namely, general performance and the flow physics. Findings The power performance varies significantly according to the tip speed ratio; the power coefficient increases up to a certain pitch angle at the design tip speed ratio (lambda = 6); however, between lambda = 2 and 4, the more the blade is pitched downwards, the larger is the power coefficient, the smaller is the thrust coefficient. Similarly, for tip speed ratios higher than lambda = 8, the positive effect of the low pitch angles on the power coefficient at lambda = 6 reverses. The flow separation location moves close to the leading edge at low tip speed ratios when the blade is pitched upwards and the also tip vortices become more intense. In conclusion, the pitch control can significantly contribute to the performance of small HAWTs depending on different conditions. Originality/value In the literature, only very little attention has been paid to the aerodynamic effects of pitch angle on HAWTs, and no such study is available about the effects on small HAWTs. The change of blade pitch angle was maintained at only one degree each time to capture even the smallest aerodynamic effects, and the results are presented in terms of the power performance and flow physics.
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    Aerodynamic Optimization of a Swept Horizontal Axis Wind Turbine Blade
    (Asme, 2021) Kaya, Mehmet Numan; Kose, Faruk; Uzol, Oguz; Ingham, Derek; Ma, Lin; Pourkashanian, Mohamed
    The aerodynamic shapes of the blades are still of high importance and various aerodynamic designs have been developed in order to increase the amount of energy production. In this study, a swept horizontal axis wind turbine blade has been optimized to increase the aerodynamic efficiency using the computational fluid dynamics method. To illustrate the technique, a wind turbine with a rotor diameter of 0.94 m has been used as the baseline turbine, and the most appropriate swept blade design parameters, namely the sweep start-up section, tip displacement, and mode of the sweep have been investigated to obtain the maximum power coefficient at the design tip speed ratio. At this stage, a new equation that allows all three swept blade design parameters to be changed independently has been used to design swept blades, and the response surface method has been used to find out the optimum swept blade parameters. According to the results obtained, a significant increase of 4.28% in the power coefficient was achieved at the design tip speed ratio with the newly designed optimum swept wind turbine blade. Finally, baseline and optimum swept blades have been compared in terms of power coefficients at different tip speed ratios, force distributions, pressure distributions, and tip vortices.
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    Aerodynamic performance of a horizontal axis wind turbine with forward and backward swept blades
    (Elsevier Science Bv, 2018) Kaya, Mehmet Numan; Kose, Faruk; Ingham, Derek; Ma, Lin; Pourkashanian, Mohamed
    Blades are the most important components of wind turbines in order to convert wind energy to mechanical energy. This study investigates the aerodynamic performance of Horizontal Axis Wind Turbines (HAWTs) with forward and backward swept blades. The effect of the blade sweep direction, the location of the sweep start up and the tip offset on the aerodynamic performance are investigated using a model HAWT with a 0.9 m rotor as the baseline configuration. Changes in power and thrust coefficients with swept blades are investigated for the design tip speed ratio of the baseline wind turbine at a wind speed of 10 m/s. The wind turbine with the forward swept blade that has sweep start up at r(ss)/R = 0.15 and tip offset of d/D = 0.2 has been found to give a remarkable boost to the power output with an increase of about 2.9% over the baseline turbine. The backward swept blade with r(ss)/R = 0.75 and d/D = 0.2 has shown the highest reduction in thrust coefficient, namely 5.4%, at the design tip speed ratio. In conclusion, it is found that the forward swept blades have the ability of increasing the performance while the backward swept blades tend to decrease the thrust coefficient.
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    Comparison of aerodynamic performances of various airfoils from different airfoil families using CFD
    (Techno-Press, 2021) Kaya, Mehmet Numan; Kok, Ali Riza; Kurt, Huseyin
    In this study, three airfoil families, NACA, FX and S, in each case three from each series with different shapes were investigated at different angles of attack using Computational Fluid Dynamics (CFD) method. To verify the CFD model, simulation results of the NACA 0012 airfoil was compared against the available experimental data and k-omega SST was used as the turbulence model. Lift coefficients, lift to drag ratios and pressure distributions around airfoils were obtained from the CFD simulations and compared each other. The simulations were performed at three Reynolds numbers, Re=2x10(5), 1x10(6) and 2x10(6), and angle of attack was varied between -6 and 12 degrees. According to the results, similar lift coefficient values were obtained for symmetric airfoils reaching their maximum values at similar angles of attack. Maximum lift coefficients were obtained for FX 60-157 and S 4110 airfoils having lift coefficient values around 1.5 at Re=1x10(6) and 12 degrees of angle of attack. Flow separation occurred close to the leading edge of some airfoils at higher angles of attack, while some other airfoils were more successful in keeping the flow attached on the surface.
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    Comparison of aerodynamic performances of various airfoils from different airfoil families using CFD
    (Techno-Press, 2021) Kaya, Mehmet Numan; Kok, Ali Riza; Kurt, Huseyin
    In this study, three airfoil families, NACA, FX and S, in each case three from each series with different shapes were investigated at different angles of attack using Computational Fluid Dynamics (CFD) method. To verify the CFD model, simulation results of the NACA 0012 airfoil was compared against the available experimental data and k-omega SST was used as the turbulence model. Lift coefficients, lift to drag ratios and pressure distributions around airfoils were obtained from the CFD simulations and compared each other. The simulations were performed at three Reynolds numbers, Re=2x10(5), 1x10(6) and 2x10(6), and angle of attack was varied between -6 and 12 degrees. According to the results, similar lift coefficient values were obtained for symmetric airfoils reaching their maximum values at similar angles of attack. Maximum lift coefficients were obtained for FX 60-157 and S 4110 airfoils having lift coefficient values around 1.5 at Re=1x10(6) and 12 degrees of angle of attack. Flow separation occurred close to the leading edge of some airfoils at higher angles of attack, while some other airfoils were more successful in keeping the flow attached on the surface.
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    Wind-Hydro Pumped Storage Power Stations to Meet the Energy Demands of Irrigation: Feasibility, Optimal Design and Simulation of a System
    (Chinese Soc Mechanical Engineers, 2018) Kose, Faruk; Kaya, Mehmet Numan
    The present study focuses on design and use of a grid connected optimal hybrid wind-hydro power station to supply energy for irrigation. To select the optimal system components, an optimization program that selects the cost-optimal wind-hydro pumped storage system components is developed and the energy flow in the system is simulated for the optimal system. Economic analysis was performed for the optimal option by calculating the key financial figures such as basic payback period (BPP), net present value (NPV) and internal rate of return (IRR). The optimal system is found to be feasible having a basic payback period of approximately eight years. Although the hybrid system has an energy storage component, still grid connection was necessary to ensure cheaper energy flow in some time periods. According the simulation results, all the components of the hybrid system are actively used and a great part of the electricity is supplied from the wind pumped hydro hybrid system. One more observation of this work is that the pumped hydro storage systems are very suitable to be used together with wind energy.