Top Banner
Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU
25

Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Dec 18, 2015

Download

Documents

Gilbert Doyle
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Wind turbine blade design using FEMAFOLABI AKINGBE

WEI CHENG

WENYU ZHOU

Page 2: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

OutlineBasics of wind turbine bladeBlade element theoryMembrane & plate bending modelShell element in FEMANSYS model

Page 3: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

How wind turbine blades work

Page 4: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Essential blade conceptschord

Page 5: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Twist angle

Page 6: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Blade element theory

Page 7: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Membrane & plate bending3D structures under arbitrary loads

Split element into two types for different calculations

Membrane element for in-plane loads

Plate bending elements for transverse loads and bending

Page 8: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

FEM triangular blade model

Page 9: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Membrane element analysis

Assume linear displacements

◦ are 2x2 matrices

Page 10: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Membrane element analysis

Page 11: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Bending element analysis

Tranverse displacements and rotations are taken as degrees of freedom.◦

◦ are 4x4 matrices

Page 12: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Bending element analysis

Page 13: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

FEM for shell analysisA combination of a plate bending and membrane element

The DOF of a plate and plane stress finite element in a local element-aligned coordinate system are considered

Page 14: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Shell element

(a) Plane deformation (b) bending deformation

The finite element solution

Page 15: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Displacement model The displacement model for the flat shell is expressed as

Ni is the bilinear shape functions associated to node i,

and

Page 16: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Strain and curvature The membrane εm and curvature κ are defined as

Transverse shear strain is

Page 17: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Approximation of strain field

The membrane deformation, the approximation of the strain field is

Page 18: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Discrete curvature field The discrete curvature field is

Page 19: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Approximation of shear strain

The approximation of shear strain is written as

Page 20: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Linear system Combining simultaneously membrane and bending actions, a linear system for the vector of nodal unknowns q can be written

where ke is the stiffness matrix composed of membrane and plate stiffness element matrices

Page 21: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Load vector The load vector at each node i is of the form

fie = [Fxi Fyi Fzi Mxi Myi Mzi ]T

Page 22: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Element stiffness matrix The element stiffness matrix at each node i

Page 23: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

ANSYS Modeling

• Angular velocity

• Surface pressure

Page 24: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Deformation & stress contours

More stress at the blade root

Thicker material closer to root to endure high loads

(Displacement contour)

(Stress contour)

Page 25: Wind turbine blade design using FEM AFOLABI AKINGBE WEI CHENG WENYU ZHOU.

Composite Can use commercial code like ANSYS to quickly change material properties and mesh sizing.