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Article Title

Yatay eksenli rüzgar türbinlerinin dinamik davranışı-teorik bir model

Abstract

Within renewable energy sources, wind energy is a natural, clean energy sources being observed that there is increasing use in recent years. Wind turbines are used to generate electricity energy from wind energy. Kinetic energy in wind turbine blades is converted into mechanical energy via power transmission systems, then, electrical energy is obtained from generator. They are classified as horizontal axis and vertical axis wind turbines according to the axis of rotation. In horizontal axis wind turbines, various power transmission mechanisms have been developed in order to obtain torque and power. These are direct drive, integrated, and conventional power transmission mechanisms. In a direct drive power transmission mechanism, torque and power are transmitted to the generator through a rotor. In an integrated power transmission mechanism, a gearbox and rotor are both used. In this study, conventional power transmission mechanism was used. Moreover, aerodynamic theories are used to determine the effect that wind has on the forces, torque, and power of blades of horizontal axis wind turbines. There are three main aerodynamic theories (one-dimensional lineer momentum theory, actuator disc momentum theory and blade element theory) related to wind turbine aerodynamics. Onedimensional momentum theory examines the force on the disc in the air flow tube. It is assumed that the disc consists of an infinite number of blades. The maximum power coefficient is limited to 0.593 based on Betz' Law. Actuator disc momentum theory assumes that the disc consists of an infinite number of blades. Additionally, friction caused by the blade is neglected but the vortex effect of the flow is considered. Blade element theory is used to determine the forces and torque that affect on aerofoil. In present study, two different aerodynamic theories (actuator disc momentum theory, blade element theory) investigated in order to define the amount of torque affecting on the blades In this study, a new theoretical model was designed based on energy conversion for basic dynamic behaviour of the three blades-horizontal axis wind turbines. By this model, dynamic behaviour of wind turbine was assessed by evaluating design parameters, geometrical and physical sizes of the blade in accordance with torque equations. In addition, dimensional parameters were converted to dimensionless parameters. Thus, effect of many parameters such as wind speed, blade radius, mass of the blades, power coefficient, tip-speed ratio, axial induction factor and angular induction factor were analyzed. By this model, various dimensional torques could be estimated by changing mR, R, V and αG in the same nondimensional torque. Consequently, it was found that NG1 is very close to the nominal power of the referenced wind turbine (2 MW). Different dimensionless parameters so called as the coefficient of effectiveness (Kt1, Kt2) were defined in order to estimate the wind power transmitted to the generator and they were used for analyzing the wind turbines. It was determined that the dimensional parameters (wind speed (V), blade radius (R), the mass of the blades (mR)) and the non-dimensional parameters (tip-speed ration (λ), blade angle, power coefficient (CP)) directly affected the coefficient of effectiveness (Kt). In conclusion, Kt1 and Kt2 could be 0.38 and 0.37 respectively if the wind turbine parameters being as mR=19500 kg, R= 39.5 m, i=100. In addition, it was approximately determined that 38% of wind power was transmitted to the generator. When Kt values were compared to CP values (when CP=0.40-0.45), the Kt values were less than the CP values. Finally, this theoretical model presents a more realistic approach in terms of estimating the main parameters of wind turbine. Consequently, it is suggested that this theoretical study is used as a model for designing horizontal axis wind turbines.

https://dergipark.org.tr/tr/download/article-file/302735

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