DESIGN AND STRUCTURAL OPTIMIZATION OF SMALL SCALE HORIZONTAL AXIS WIND TURBINE (HAWT)

Project Title

DESIGN AND STRUCTURAL OPTIMIZATION OF SMALL SCALE HORIZONTAL AXIS WIND TURBINE (HAWT)

Project Area of Specialization Mechanical EngineeringProject Summary

The increasing size and flexibility of wind turbine blades introduces considerable aeroelastic effects, which are caused by FSI (fluid structure interaction). These effects might result in aeroelastic instability problems, such as edgewise instability and flutter, which can be devastating to the blades and the wind turbine. Therefore, accurate FSI modelling of wind turbine blades are crucial in the development of wind turbines. In this study, an FSI model for wind turbine blades at full scale is established. The aerodynamic loads are calculated using a CFD (computational fluid dynamics) model implemented in ANSYS FLUENT, and the blade structural responses are determined using a FEA (finite element analysis) model implemented in ANSYS Static Structural module. The interface of CFD and FEA is based on a one-way coupling, in which aerodynamic loads calculated from CFD modelling are mapped to FEA modelling as load boundary conditions. Validated by a series of benchmark computational tests, the one-way FSI model was applied to the modelling of HAWT with the maximum energy of 1kW and average energy of 400 W wind turbine blade, a representative horizontal-axis wind turbine blade. Maximum tensile/compressive stresses and tip deflections in each case are found to be within material and structural limits, according to relevant design standards.

Project Objectives

The communication channel considered in this thesis is assumed to be slow time-varying, Wind energy has been serving mankind from past decades by its quality to produce green energy environment friendly. Modelling of horizontal axis turbine and analyzing the computational fluid dynamics behavior on turbine by different wind velocities. A Fluid Structure Interaction , study of deformations in blades and overall turbine design by importing the fluid mechanics solutions at high and extreme weather conditions. Combined study of turbine including Fluent and structural module by implicit solution method. Improving the design by decreasing the weight and changing parameters of design to withhold in extreme weather conditions. Efficient and green technology method, Renewable energy Source as world is moving to renewable energy sources due to meet energy crisis of current conditions. Calculation of cost analysis for a domestic household or a commercial wind turbine and estimation of power production to meet needs of electricity.

Project Implementation Method

Methods

1. Wind Turbine Model

The wind turbine model used in this study is the 400W wind turbine. This wind turbine is a conventional three-bladed upwind horizontal-axis wind turbine, utilising variable-speed variable-pitch control.

Table 3.1 Main Parameters

Parameters	Values	Units
Rated Power	400	Watt
Number of Blades	3	-
Rotor Radius	1.1	m

Fig 3.1 3D model of HAWT

       2. CFD MODELLING

A CFD model of wind turbine blades is established using ANSYS FLUENT, which is a widely used CFD modelling software. The CFD model is then applied to the CFD modelling of Wind PACT 400 W wind turbine blades. The computational domain and boundary conditions, mesh, turbulence model, solution method and convergence criteria used in the CFD modelling are presented in this section.

        3.CFD MESH

Fig. 3.3 presents the mesh used in the CFD modelling. As can be seen from Fig. 3a, the computational domain is meshed with unstructured mesh. As illustrated in Fig. 3.4, prismatic inflation layers are applied to the blade surfaces to have a better resolution of boundary layer flow. two prismatic inflation layers are used, with an expansion rate of 1.35. The first layer height is 4.8e-6m, leading to a small y+ value (less than 1) around the whole blade surface. y+ is a non-dimensional wall distance, and it is given by: 

where u* is the friction velocity at the nearest wall, y is the distance to the nearest wall, v is the local kinematic viscosity of the fluid. In order to ensure accurate modelling of the boundary layer, y+ value of less than 1 is recommended.

 Figure 3.3. CFD mesh: mesh of the computational domain, prism layers on blade surfaces

  

Fig 3.4 Inflation layers used on the blades of the turbine

     4. FEA MODELLING

SOLVE AND POST PROCESS RESULTS

A FEA model of wind turbine composite blades is established using ANSYS Static Structural module, which is a widely used FEA modelling software. The FEA model is then applied to the FEA modelling of HAWT 400W wind turbine blades. The geometry, material properties, composite layups, mesh and boundary conditions used in the FEA modelling are presented in this section.

   GEOMETRY

The geometry of the HAWT 400W wind turbine blade is created based on the aerodynamic shape information (i.e. chord, twist angle and sectional airfoil shape) given in Refs. [24, 27-29]. The created blade geometry is depicted in Fig. 3.1 of Section 3.1.

   FEA MESH

The blade structure is meshed using structured mesh with shell elements. In order to determine appropriate mesh size, a mesh sensitivity exercise is carried out, considering four mesh sizes, i.e., 4mm, 2mm, 1mm and 0.5mm. In this exercise, the blade is non-rotating, and a fixed boundary condition is applied to the blade root.

Fig 3.8 FEA MESH of Rotor Blades

Parameters

Rated Power

Number of Blades

Rotor Radius

Benefits of the Project

As wind turbine is a free energy source and with modern technology it can be captured efficiently. It would help to overcome the energy crisis that world is facing especially the Pakistan. Once the wind turbine is built the energy it produces doesn't cause green house effect or other pollutants. It would help to produce pollutant free energy free of cost. Although wind turbines can be very tall each takes up only a small plot of land. This means that the land below can still be used and multiple wind turbines can be installed at a small area of land which could fill up the big portion of energy needs. Many people find wind farm an interesting feature of the landscape so it could help to better the country's image as well. Remote areas that are not connected to the power grid can use wind turbines to produce their own electricity. 
Wind turbines have the role in both the developed and third World. Wind turbines sizes can be varied which means a vast range of people and businessman can use them. From single households to small towns and villages can make good use of a range of wind turbines available today. 
The purpose of our project is to introduce the mini scales household wind turbines that can fulfil energy needs of residential areas as it is not very common concept in Pakistan but if in the future it gets implemented it'll help to give a cheap energy to the people.

Technical Details of Final Deliverable

Main Parameters

Parameters	Values	Units
Rated Power	400	Watt
Number of Blades	3	-
Rotor Radius	1.1	m

An FSI (fluid structure interaction) model for horizontal-axis wind turbine blades has been established by coupling CFD (computational fluid dynamics) and FEA (finite element analysis). The coupling strategy is based on one-way coupling, in which the aerodynamic loads calculated by CFD modelling are mapped to FEA modelling as load boundary conditions. 

The FSI model was applied to the FSI modelling of HAWT 400W wind turbine blade, a representative of large-scale horizontal-axis wind turbine blades. The following conclusions can be drawn from the present study: 

1) Reasonable agreement (with maximum percentage difference of 18.6%) is achieved in 

comparison with FAST code, which confirms the validity of the aerodynamic component (based on CFD) of the FSI model. 

2) Good agreement (with maximum percentage difference of 2.6%) is achieved in comparison with the modal frequencies provided in the Sandia NuMAD Blade Mode Report, which confirms the validity of the structural component (based on FEA) of the FSI model.

4) The blade pressure coefficients from the present model show reasonable agreement with the results from inviscid model, both in terms of distribution shape and magnitude. 

5) The maximum tensile stress and maximum compressive stress at the third layer of composite blade are respectively found to be 5.32MPa and 5.5MPa, which are well below the material strength limits, indicating the blade is unlikely to experience material failure under the given five operational conditions. Additionally, the established one-way FSI model can be also applied to other similar applications, such as vertical axis wind turbines and tidal devices, due to its high flexibility.

Parameters

Rated Power

Number of Blades

Rotor Radius

Final Deliverable of the Project HW/SW integrated systemCore Industry Energy Other IndustriesCore Technology Clean TechOther TechnologiesSustainable Development Goals Affordable and Clean Energy, Responsible Consumption and Production, Climate ActionRequired Resources

Parameters	Values	Units
Rated Power	400	Watt
Number of Blades	3	-
Rotor Radius	1.1	m