Abstract
It is about a wind turbine blade of five meters of length in composite material, Glass Fiber Reinforced Plastics (GRP), calculated using the finite elements method (FEM) to determine the influence of the gyroscopic coupling on its dynamic behavior. First, using the blade element momentum method (BEM)
we wrote the aerodynamic forces applied on the blade, depending on the wind speed.
Then we incorporated these expressions into the laws of structures behavior to reach a matrix formulation of the equations of motion of the blade taking into account the nonlinear deformation. The obtaining of the mechanical stiffness, geometric stiffness, mass and gyroscopic coupling matrices of the blade allows to simulate its dynamic response in transient and permanent phases under the action of its weight, and under a sudden variation of the wind speed.
Introduction
The wind turbine blades in normal operation are subject to aerodynamic, centrifugal and gravity forces. These external forces are classified into three categories: temporary, constant or cyclical. Indeed, the variation of wind speed, the change of orientation of the turbine axis due to a change in the wind direction, or the action of gravity under gyroscopic effect. These efforts, often cyclical, are the cause of the vibration of the blade and therefore disrupt the air flow around its profile, which justifies the loss of a part of the aerodynamic useful energy to decrease its performance. A wind turbine blade must resist during an emergency stop, in case of a gust of wind, in violent hurricanes, and have the power coefficient close to the theoretically maximum, the limit of Betz: 59.26% [1].
This coefficient is function of the rotor angular speed, and also depends on the airfoil, the shape and the layout of the blades. In this work we are interested in determining the action of the gyroscopic forces on a blade of five meters of length, built of composite material, glass fiber reinforce plastics (GRP), taking into account nonlinear deformation.
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