This study investigates unsteady aerodynamic effects for a vertical axial wind turbine through computational fluid dynamics simulations. A two-dimensional model of the turbine was created using a NACA0015 airfoil for the blades. Simulations were run at different tip speed ratios to analyze blade forces, torque, and dynamic stall. Results showed that maximum average torque occurred at a tip speed ratio of 1.3. Blade forces were highest when the rotor was at 50 degrees. Dynamic stall phenomena, such as vortex shedding and detachment, were observed and affected turbine performance.
Numerical Investigation Of Compression Performance Of Different Blade Configu...IJERA Editor
This project work is to investigate the compression efficiency of different configuration of Turbo-Prop Co-Rotor Blade System of Subsonic Axial Flow Compressor. By this method the highly compressed air can be passed over the intake of the engine to the compressor with high mass flow rate in change of low velocity and high pressure ratio. The length of the small rotor is varied in terms of large rotor length by 25,50 & 75% . Each will have three space configuration in terms of diameter of rotor and in the percentage of 5,10,15%. A total of 12 configurations will be simulated to arrive optimum blade configuration. The blades are made in the shape of an airfoil like wing of an aircraft. The engine rotates the propeller blades, which produce lift. This lift is called thrust and moves the aircraft forward. Blades are usually made of high lift airfoil which allows more rotation to generate high pressure for engine. ANSYS- Fluent is commercial software which is robust for most of the fluid dynamic problems and it is used in this project work to evaluate the different configurations of co-rotor propeller system to arrive the best.
Numerical Investigation Of Compression Performance Of Different Blade Configu...IJERA Editor
This project work is to investigate the compression efficiency of different configuration of Turbo-Prop Co-Rotor Blade System of Subsonic Axial Flow Compressor. By this method the highly compressed air can be passed over the intake of the engine to the compressor with high mass flow rate in change of low velocity and high pressure ratio. The length of the small rotor is varied in terms of large rotor length by 25,50 & 75% . Each will have three space configuration in terms of diameter of rotor and in the percentage of 5,10,15%. A total of 12 configurations will be simulated to arrive optimum blade configuration. The blades are made in the shape of an airfoil like wing of an aircraft. The engine rotates the propeller blades, which produce lift. This lift is called thrust and moves the aircraft forward. Blades are usually made of high lift airfoil which allows more rotation to generate high pressure for engine. ANSYS- Fluent is commercial software which is robust for most of the fluid dynamic problems and it is used in this project work to evaluate the different configurations of co-rotor propeller system to arrive the best.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Numerical simulation and optimization of high performance supersonic nozzle a...eSAT Journals
Abstract The Principle purpose of a nozzle is to accelerate the flow to higher exit velocities. The fluid acceleration is based on the design criteria and characteristics. To achieve good performance characteristics with minimum energy losses a nozzle must satisfy all the design requirements at all operating conditions. This is possible only when the nozzle theory is assumed to be isentropic irrespective of the changes in pressure, temperature and density which is generally caused due to formation of a Shock Wave. The thesis focuses on the design, development and optimization of a Supersonic Convergent-Divergent Nozzle where the analytical results are validated using theory calculations. The simulation work is carried out for CD Nozzles with different angles of divergence keeping the other inputs fixed. The objective of the proposed thesis is to show the best Expansion ratio, Nozzle Pressure ratio (NPR) and Nozzle Area Ratio(NAR) where the thrust obtained by the supersonic nozzle is maximum. The simulation is then repeated for expansion gas the results of which are later compared with standard air to show which possesses better performance characteristics. The Nozzle design chosen is based upon existing literature studies. Key Words: CD Nozzle, Expansion Ratio, Nozzle Pressure Ratio (NPR), Nozzle Area Ratio(NAR),Divergence Angle etc…
i. Introduction:
ii. Definition of Turbo machine,
iii. Parts of Turbo machines,
iv. Comparison with positive displacement machines,
v. Classification of Turbo machine,
vi. Dimensionless parameters and their significance,
vii. Unit and specific quantities,
viii. Model studies and its numerical.
(Note: Since dimensional analysis is covered in Fluid Mechanics subject, questions on dimensional analysis may not be given. However, dimensional parameters and model studies may be given more weightage.)
Simple Numerical; on Model Analysis.
previous year question papers solved
Determination of Buckling Loads of Wave Spring Using ANSYSIJRES Journal
Special performance characteristics are individually built into each spring to satisfy a variety of precise operating conditions. Typically, a wave spring will occupy an externally small area for the amount of work it performs. The present work deals with the structural analysis of wave and coil spring by modeling the structural behavior of these springs using three dimensional finite elements (FE) software. The design of spring in suspension system is very important. In this work a wave type of spring is designed and a 3D model is created using CREO software. The model is also varied by changing the length of the spring. Structural analysis has been conducted on the wave spring by varying thickness and number of turns. For the analysis, loads are bike weight with single and two persons. The buckling load is then estimated for both Wave spring and coil spring with the same parameters.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Modal 05: Question Number 9 a & 9 b
Centrifugal Pumps:
i. Classification and parts of centrifugal pump,
ii. Different heads of centrifugal pump
iii. Different efficiencies of centrifugal pump,
iv. Theoretical head – capacity relationship,
v. Minimum speed for starting the flow,
vi. Maximum suction lift,
vii. Net positive suction head,
viii. Cavitation,
ix. Need for priming,
x. Pumps in series and parallel. Problems.
Previous Year Question papers
Modal 04: Hydraulic Turbines (Question Number 7 a - 7 b & 8a - 8b)
i. Definition
ii. Classification of Hydraulic Turbines
iii. Various efficiencies of Hydraulic Turbines and Various types of Head
iv. Pelton Wheel – Principle of working,
Velocity triangles,
Maximum efficiency
Design parameters,
Numerical problems.
v. Francis turbine – Principle of working
Velocity triangles
Design parameters
Numerical problems
vi. Kaplan and Propeller turbines - Principle of working
Velocity triangles
Design parameters
Numerical Problems.
vii. Theory and types of Draft tubes.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Enhancement of energy absorption of thin walled hexagonal tube by using trigg...eSAT Journals
Abstract This paper presents the using of non-linear finite element simulations on the crash behavior and to enhance the energy absorption of the thin walled hexagonal tube subjected to dynamic loading and to decrease the peak load to ensure the occupants safety during front collisions. Triggers have been applied to the thin walled hexagonal tube. Three trigger geometries have been applied circular, rectangular and elliptical geometry. Three type of trigger distribution already have been studied. The positions and the size of triggers are also investigated. It was found that the 10% per cent reductions with elliptical trigger revealed the best choice, it shows enhancing in energy absorption about 8 percent and CFE about 13 percent and decreasing in peak force by 2.5 percent. Index Terms: energy absorption; Finite element modeling; trigger
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Numerical simulation and optimization of high performance supersonic nozzle a...eSAT Journals
Abstract The Principle purpose of a nozzle is to accelerate the flow to higher exit velocities. The fluid acceleration is based on the design criteria and characteristics. To achieve good performance characteristics with minimum energy losses a nozzle must satisfy all the design requirements at all operating conditions. This is possible only when the nozzle theory is assumed to be isentropic irrespective of the changes in pressure, temperature and density which is generally caused due to formation of a Shock Wave. The thesis focuses on the design, development and optimization of a Supersonic Convergent-Divergent Nozzle where the analytical results are validated using theory calculations. The simulation work is carried out for CD Nozzles with different angles of divergence keeping the other inputs fixed. The objective of the proposed thesis is to show the best Expansion ratio, Nozzle Pressure ratio (NPR) and Nozzle Area Ratio(NAR) where the thrust obtained by the supersonic nozzle is maximum. The simulation is then repeated for expansion gas the results of which are later compared with standard air to show which possesses better performance characteristics. The Nozzle design chosen is based upon existing literature studies. Key Words: CD Nozzle, Expansion Ratio, Nozzle Pressure Ratio (NPR), Nozzle Area Ratio(NAR),Divergence Angle etc…
i. Introduction:
ii. Definition of Turbo machine,
iii. Parts of Turbo machines,
iv. Comparison with positive displacement machines,
v. Classification of Turbo machine,
vi. Dimensionless parameters and their significance,
vii. Unit and specific quantities,
viii. Model studies and its numerical.
(Note: Since dimensional analysis is covered in Fluid Mechanics subject, questions on dimensional analysis may not be given. However, dimensional parameters and model studies may be given more weightage.)
Simple Numerical; on Model Analysis.
previous year question papers solved
Determination of Buckling Loads of Wave Spring Using ANSYSIJRES Journal
Special performance characteristics are individually built into each spring to satisfy a variety of precise operating conditions. Typically, a wave spring will occupy an externally small area for the amount of work it performs. The present work deals with the structural analysis of wave and coil spring by modeling the structural behavior of these springs using three dimensional finite elements (FE) software. The design of spring in suspension system is very important. In this work a wave type of spring is designed and a 3D model is created using CREO software. The model is also varied by changing the length of the spring. Structural analysis has been conducted on the wave spring by varying thickness and number of turns. For the analysis, loads are bike weight with single and two persons. The buckling load is then estimated for both Wave spring and coil spring with the same parameters.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Modal 05: Question Number 9 a & 9 b
Centrifugal Pumps:
i. Classification and parts of centrifugal pump,
ii. Different heads of centrifugal pump
iii. Different efficiencies of centrifugal pump,
iv. Theoretical head – capacity relationship,
v. Minimum speed for starting the flow,
vi. Maximum suction lift,
vii. Net positive suction head,
viii. Cavitation,
ix. Need for priming,
x. Pumps in series and parallel. Problems.
Previous Year Question papers
Modal 04: Hydraulic Turbines (Question Number 7 a - 7 b & 8a - 8b)
i. Definition
ii. Classification of Hydraulic Turbines
iii. Various efficiencies of Hydraulic Turbines and Various types of Head
iv. Pelton Wheel – Principle of working,
Velocity triangles,
Maximum efficiency
Design parameters,
Numerical problems.
v. Francis turbine – Principle of working
Velocity triangles
Design parameters
Numerical problems
vi. Kaplan and Propeller turbines - Principle of working
Velocity triangles
Design parameters
Numerical Problems.
vii. Theory and types of Draft tubes.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Enhancement of energy absorption of thin walled hexagonal tube by using trigg...eSAT Journals
Abstract This paper presents the using of non-linear finite element simulations on the crash behavior and to enhance the energy absorption of the thin walled hexagonal tube subjected to dynamic loading and to decrease the peak load to ensure the occupants safety during front collisions. Triggers have been applied to the thin walled hexagonal tube. Three trigger geometries have been applied circular, rectangular and elliptical geometry. Three type of trigger distribution already have been studied. The positions and the size of triggers are also investigated. It was found that the 10% per cent reductions with elliptical trigger revealed the best choice, it shows enhancing in energy absorption about 8 percent and CFE about 13 percent and decreasing in peak force by 2.5 percent. Index Terms: energy absorption; Finite element modeling; trigger
Transient flow analysis for horizontal axial upper-wind turbineinventy
This study is to carry out a transient flow field analysis on the condition that the wind turbine is working to generate turbine, the wind turbine operating conditions change over time, Purpose of this study is try to find out the rule from the wind turbine changing over time . In transient analysis, the wind velocity on inlet boundary and rotation speed in the rotor field will change over time, and an analytical process is provided that can be used for future reference. At present, the wind turbine model is designed on the concept of upwind horizontal axis type. The computer engineering software GH Bladed is used to obtain the relationship between the rotor velocity and the wind turbine. Then the ANSYS engineering software is used to calculate the stress and strain distribution in the blades over time. From the analytical result, the relationship between the stress distribution in the blades and the rotor velocity is got to be used as a reference for future wind turbine structural optimization.
This project work is to investigate the compression efficiency of different configuration of Turbo-Prop Co-Rotor Blade System of Subsonic Axial Flow Compressor. By this method the highly compressed air can be passed over the intake of the engine to the compressor with high mass flow rate in change of low velocity and high pressure ratio. The length of the small rotor is varied in terms of large rotor length by 25,50 & 75% . Each will have three space configuration in terms of diameter of rotor and in the percentage of 5,10,15%. A total of 12 configurations will be simulated to arrive optimum blade configuration. The blades are made in the shape of an airfoil like wing of an aircraft. The engine rotates the propeller blades, which produce lift. This lift is called thrust and moves the aircraft forward. Blades are usually made of high lift airfoil which allows more rotation to generate high pressure for engine. ANSYS- Fluent is commercial software which is robust for most of the fluid dynamic problems and it is used in this project work to evaluate the different configurations of co-rotor propeller system to arrive the best.
Power Generation through the Wind Energy Using Convergent Nozzletheijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Brimmed diffuser is collection�acceleration device which shrouds a wind turbine.For a given turbine di ameter,the power augmentation can be achieved by brimmed diffuser,p opularly known as wind lens. The present numerical investigation deals with the effect of low pressure region created by wind l ens and hence to analyze the strong vortices formed by a brim attached to the shroud diffuser at exit. Also in this analysis,a c omparative numerical prediction of mass flow rates through the wind turbine has been carried out with various types of wind lens wh ich in turn helps to optimize the torque augmentati on. It has been numerically proved that there is significant increase in the wa ke formation & vortex strength when brimming effect is added to a diffuser
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Performance and Fault diagnosis of Horizontal Axis Wind Turbine Componentsijsrd.com
With recent surge in fossil fuel prices and demand for cleaner renewable energy sources, Wind Turbine has become an alternative approach for power generation technology. Therefore operation, maintenance and repair techniques will be developed for efficient wind power generation. Failure analysis can support operation, management of spare components and accessories in wind plants, maintenance and repair of wind turbine. In this paper author aiming at eye of wind plants i.e. structure, function and analysis of common faults to find out fault laws, fault causes and effect on their corresponding performance measures.
Numerical Simulation of the Aerodynamic Performance of a H-type Wind Turbine ...Capvidia NV
Wind Turbine Self Starting CFD Simulation with FlowVision This is a nice example for moving bodies. Moment of inertia of turbine is defined and rotation is induced by aerodynamics forces. Simulation results of rotation speed variation during self-starting are in well agreement with the experimental results.
The air streams from the outlet of an air compressor can be used to generate electricity. For instance, if a micro-sized Vertical-Axis Wind-Turbine (VAWT) is installed towards the airflow, some amount of electricity can be generated before being stored in a battery bank. The research’s objectives are to design, fabricate and analyze the performance of Helical Savonius VAWT blade rotors, which is tested with and without using a wind concentrator. The Helical Savonius VAWT is tested at 0 cm without the concentrator, whereas the blade rotor is tested at concave-blade position when using the concentrator. The blade and the wind concentrator designs were based on the dimensions and the constant airflow of the air compressor. The findings suggested that the blade produced its best performance when tested using wind concentrator at concave-blade position in terms of angular speed (ω), tip speed ratio (TSR) and the generated electrical power (PE). The findings concluded that the addition of wind concentrator increases the airflow which then provided better performances on the blades.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
The flow velocity over airfoils increases over the convex surface resulting in lower average pressure on the 'suction' side of the airfoil compared with the concave or 'pressure' side of the airfoil.
Meanwhile, viscous friction between the air and the airfoil surface slows the airflow to some extent next to the surface.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
The flow velocity over airfoils increases over the convex surface resulting in lower average pressure on the 'suction' side of the airfoil compared with the concave or 'pressure' side of the airfoil.
Meanwhile, viscous friction between the air and the airfoil surface slows the airflow to some extent next to the surface.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
The flow velocity over airfoils increases over the convex surface resulting in lower average pressure on the 'suction' side of the airfoil compared with the concave or 'pressure' side of the airfoil.
Meanwhile, viscous friction between the air and the airfoil surface slows the airflow to some extent next to the surface.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
The flow velocity over airfoils increases over the convex surface resulting in lower average pressure on the 'suction' side of the airfoil compared with the concave or 'pressure' side of the airfoil.
Meanwhile, viscous friction between the air and the airfoil surface slows the airflow to some extent next to the surface.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
The flow velocity over airfoils increases over the convex surface resulting in lower average pressure on the 'suction' side of the airfoil compared with the concave or 'pressure' side of the airfoil.
Meanwhile, viscous friction between the air and the airfoil surface slows the airflow to some extent next to the surface.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
The flow velocity over airfoils increases over the convex surface resulting in lower average pressure on the 'suction' side of the airfoil compared with the concave or 'pressure' side of the airfoil.
Meanwhile, viscous friction between the air and the airfoil surface slows the airflow to some extent next to the surface.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
The flow velocity over airfoils increases over the convex surface resulting in lower average pressure on the 'suction' side of the airfoil compared with the concave or 'pressure' side of the airfoil.
Meanwhile, viscous friction between the air and the airfoil surface slows the airflow to some extent next to the surface.
Airflow over an airfoil produces a distribution of forces over the airfoil surface.
DEVELOPMENT AND TESTING OF ADVANCE HYBRID SAVONIUS AND ARM GEAR BASED STRUCTU...IAEME Publication
Wind energy is becoming the most important renewable source in terms of globally installed capacity, after solar and hydro power. China is experiencing a rapid expansion in the wind power industry. This paper provides a good overview of the current status and future development of wind generation. As per the technical evolution and technical trends consideration so we have created a “Advanced Hybrid Savonius and arm gear based effective Mechanical Structure for Multi-Station Optimized Power Generation. This system uses an advanced savonius hybrid turbine which will rotate over multiple natural resources water force, wind power and related parameters having efficiency greater than aerodynamic turbine.
1. Study of Unsteady Aerodynamic Effects for a Vertical Axial Wind Turbine
Tzong-Hann Shieh1,2,3,a,#
, Charng-Chin Hsiao2
, Yung-Ting Chen1,2,b
, Ya-Tzu Hsu3,c
and
Yang-Hsu Liao1,d
1
Department of Aerospace and Systems Engineering, Feng Chia University,
No.100 Wenhwa Rd., Seatwen, Taichung, Taiwan 40724, R.O.C.
2
Ph.D. Program of Mechanical and Aeronautical Engineering, Feng Chia University,
No.100 Wenhwa Rd., Seatwen, Taichung Taiwan40724,R.O.C.
3
Master Program in Creative Design, Feng Chia University,
No.100 Wenhwa Rd., Seatwen, Taichung, Taiwan 40724, R.O.C.
a
thshieh@fcu.edu.tw, b
m0211619@fcu.edu.tw, c
tarisa284@gmail.com, d
yanghsuliao@hotmail.com
#
corresponding author / TEL: +886-4-24517250 EXT.3960-, FAX: +886-4-24510862
Keywords: VAWT, Dynamic Mesh, Tip Speed Ratio, Blade Force, Dynamic Stall
Abstract. This study is investigated through a two dimensional model of vertical-axis wind turbine
generator. The aerodynamic disturbances during operation of three types of blades design are
discussed. The simulation model is built by lateral section profile of the vertical-axis wind turbine.
Varied tip speed ratios are involved in the simulating conditions. Computational domain contains
both dynamic and stationary mesh. Numerical method is used to solve unsteady Reynold’s average
Navier-Stokes (RANS) equations and k-ω SST turbulence model with near wall correlation function
such that can simulate the motion of blades. The interactions of blades are indicated by distribution of
action forces, average torque and dynamic stall in different rotational position of blades. The results
are preliminary discussions of structural and aerodynamic effects of vertical-axis wind turbine
generator, and will be validated through experiment in the future.
Introduction
In recent years, the global renewable energy and new energy developing area, wind power is the
one of the most potential renewable energy, no matter based on requirement of world economic or
business development. The principles of wind power is that blades of wind turbine can be rotated
through breeze flow by and then to drive the converting mechanism. The generator is connected with
the mechanism such that can convert rotational power into electricity. To obtain the optimized
converting efficiency of the turbine, however, the aerodynamic performance of blades and overall
flow design of the wind turbine has to be achieved first. There are two types of wind turbine,
vertical-axis and lateral-axis, which are defined by the axial direction of the generator of wind turbine.
The vertical-axis wind turbine has specific advantages on aerodynamic properties if compared with
lateral wind turbine. But on commercial market development, the advantages will be taken over by
lateral-axis type. The specific aerodynamic property of vertical-axis wind turbine is it can accept
wind from any direction without yawing. The blades of vertical-axis wind turbine have uniform wing
sections in the direction of span and untwist, which is the biggest difference comparing with lateral
one. Therefore, vertical type is more easily manufactured than lateral type. For vertical-axis wind
turbine, the maintainance of its components can be finished on the ground, and this also cost saved for
logisitic. However, torque differences between each rotation are significant and it cannot be
self-activated [1].
Moreover, the design of blade is the most important factor of wind turbine’s performance.
Vertical-axis wind turbines can be classfied into three major groups by silhouette of blade [1]. There
are Savonius type of wind turbine invented by Sigurd Johannes Savonius from Finland [2], Darrieus
wind turbine which is invented by French engineer Georges Jean Marie Darrieus [3], and Darrieus
type with straight blads, also called H-rotor type. The important parameters of design are mainly on
modifying the shape of blade and how to control the feedback of blades when approaches to
2. maximum loading. In addition, generator’s property, and strength and stiffness of blades both are
considered. Consquently, the optimized design of a vertical-axis wind turbine can be obtain. How to
optimize the converting efficiency, from wind energy to electricity, the blade‘s aerodynamic property
has a significant effect influence. Ferreira et al. [4] mentioned that the angle of attack of blades can be
larger than the static stall angle if the tip speed ratio dynamic stall was less than 4. That can also
induce the dynamic stall since the blades are in unsteady flow field. To reduce the cost of experiments,
applying CFD in simulating the fluid deattached phenomenon during dynamic stall situation of
vertical-axis wind turbine in preliminary study is much valuable.
Computational Method
This study uses numerical method to solve two dimensional problem of unsteady flow, and the
coupling effects between turbine and fluid under 7m/s free stream condition. Pressure based and finite
volume method both are utilized in discrete numerical model and the Navier-Stokes equations are is
solved through Reynold averaged method. For discrete space model, pressure and velocity are
coupled via SIMPLE method. For discrete momentum equations, the power law is considered in
solving fluid flow with low Reynold number so that the results are more accurate than using first
order formulation. Otherwise, to solve large pressure gradient in highly rotional flow, the PRESTO
method is considerd. In time discrete, implicit and second order method are considerd hence the
periodic unsteady phenomenon of relative motion, rotational velocity, and numbers of blade can be
investigated. Time step is also setup for distrete computation. Moreover, two equation ω−k
SST(Shear-Stress Transpor) turbulence model is used to resolve inverse pressure gradient and
detached phenomenon on blades. Considering the detached problem in boundary layer, the near wall
correction formula is also involved into analysis to improve accuracy computational results of inverse
pressure gradient.
Physical Model and Meshes
The model in this research is refered to the real model of cyclic subsonic wind tunnel experiments
we built. The model of wind tunnel test section and wind turbine are indicated in Fig. 1. The initial
wind speed is also refered to real operating condition, 7m/s. To reduce the difficulty of manufacturing
blades, low Reynold number airfoil – NACA0015 is chosed as the turbine’s blade (shown as Fig. 2).
Two tips of blade are cut vertically with repect to span direction. The whole wind turbine model are
built with three blades as a rotor. The rotor’s related dimentions are shown in Table 1.
Fig. 1 Computational model and dimension Fig. 2 Dimensionless of NACA0015
airfoil
3. Table 1 Geometric properties of blades and rotor
Name Number Dimension Unit Note
Airfoil NACA0015 -/- -/-
Chord Length -/- 0.05 m
Ridus of Rotor -/- 0.165 m
Ridus of Pole -/- 0.023 m
Blade Span (Z Dir.) -/- 1 m 2D
To simulate the flow of inside rotor’s domain of a vertical-axis wind turbine, dimensionless near
wall distance
( ) μρ τuyy =+
should be as low as possible. The phenomena of dynamic stall,
interaction between blades and air, and vortex detachment on blade during the turbine rotating can be
resolved. Hence, the meshes near blades are refined to approach the analytical requirements.
Dynamic mesh is used to simulate the rotational motion of turbine. The fluid model is divided into
three calculation domains, stationary, rotational, and near wall meshes. The combination of
non-sturctured and structured meshes is used in this study (shown as Fig. 3). Fig. 4 indicates refined
structured meshes around the blade. The meshes assist to solve reaction force, dynamic stall, and
vortex detachment of blades. Besides the near wall domain, fluid meshes are built in non-sturctured
type. Total meshes are nearly 230,000.
Fig. 3 Whole meshes Fig. 4 Structured meshed near wall
Results and Discussions
To obtain the average torque, the tip speed ratio (TSR) is defined as Eq. 1.
V
R
TSR
ω
= (1)
R, ω , and V are radius of rotor, rotaitional speed, and free stream speed respectively. By the
defination of TSP, the optimized value of the simulation model is shown in Fig. 5. The optimized
average torque can be obtained when TSP equals to 1.3. The TSP over 2, however, the greater TSP
the smaller average torque is obtained. According to the result, this paper uses 1.3 as the optimized
TSP condition, means that rotional speed equals 55 RPM and free stream speed equals 7 m/s. The
reaction force of blade and dynamic stall phenomenon is investaged under the condition.
Reaction forces of vertical-axis wind turbine, the action force indeuced by inverse tangent force
affects the torque of turbine directly. That also means the torque of turbine will increase if the tangent
force of blade increases. The tangent force coefficient of blade is defined as Eq. 2.
cVFC tt
22
2
1
∞= ρλ (2)
Which Ft is tangent force, λ is TSP, and ∞V is speed of free stream. The variance of tangent force
coefficient with azimuth is shown in Fig. 6. The maximum tangent force of blade is achieved when
rotor at 50 degree of rotational position. Additionally, the moment of rotor which induced by the axial
4. force of bla
turbine. Th
Fig
Fig
Fig. 7 a
position re
phenomeno
There are n
appeared a
potition eq
isosurface
unsteady f
performanc
Summary
The two
between bl
center pole
increase th
TSP. The a
The dyn
turbulence
dynamic, s
ade is not ev
he effect of
g. 5 Varianc
re
g. 7 Isosurfa
rota
and Fig. 8 d
epectively.
on of fluid
no vortices w
at 90 degre
quals to 135
of vortices
flow. It will
ce becomes
o dimension
lades, and i
e is mainly
he distance. O
average torq
namic mesh
model and
such that dy
vident. The
axial force
ces of avera
espect to TS
ace of vertic
ational posi
display isos
The result
detach in n
which induc
ee rotationa
degree, sin
. Vortices d
l decrease t
s low.
n model use
interaction b
caused by t
Otherwise,
que decreas
method can
d near wall
ynamic stall
amplitude o
cannot be ig
age torque w
SR
ces at 90 de
ition.
surface of v
ts indicate
near wall bo
ced by fluid
al position a
nce vortices
detaching m
the tangent
ed in this st
between bla
the distance
for rotors w
es as TSP in
n simulate t
correlation
phenomena
of axial forc
gnored norm
with
c
egree Fig.
vortex grad
that ω−K
oundary laye
d detaching a
and show t
detaching t
may affect th
force of bl
tudy can re
ade and cen
e between b
with three bl
ncreases aft
he rotation
n function c
a between b
ce is the maj
mally but in
Fig. 6 Vari
coefficient o
8 Isosurfac
rota
dent in 90 d
ω SST turb
er and dyna
at lower rota
the trend of
the dynamic
he followin
ade and ave
solve the d
nter pole. O
blade and po
ades, the av
ter achievin
of blades w
can also be
blades and th
jor cause of
n this study.
ances of tan
of blade wit
azimuth
ce of vertice
ational posit
degree and
bulence mo
amic stall w
ational posi
f detaching
c stall can b
ng blades so
erage torqu
dynamic stal
Overall, the
ole. The eff
verage torqu
ng of optimi
well. The com
e applied in
he rotor can
f structure di
ngent force
th respect to
es at 135 deg
tion.
135 degree
odel can pr
when turbine
tion. The vo
g. When the
be discovere
o that the bl
ue so that th
ll of blade,
aerodynam
fect can be
ue is mainly
ized average
mbination o
n simulating
n be predict
isruption of
o
gree
e rotational
redict flow
e’s rorating.
ortices have
e rotational
ed from the
lades are in
he turbine‘s
interaction
mic effect of
reduced by
affected by
e torque.
of k-ω SST
g rotational
ted. Though
f
l
w
.
e
l
e
n
s
n
f
y
y
T
l
h
5. pressure coefficient and vortices distribution are used to demonstrate the dynamic effect of blade’s
vortice detaching, the mechanism of reduceing detaching at tail of blade and postpone votices
detaching can be investaged from the results. Three dimensional effects of fluid flow cannot be
simulated by two dimension model. To improve the model‘s accuracy, the three dimensional effects
need to be considered for further study.
Acknowledgement
This research project is supported by the Ministry of Science and Technology of Taiwan, ROC under
grant MOST103-2221-E-35-064 & NSC102-2221-E-035-029-.
References
[1] A. Goude, Fluid Mechanics of Vertical Axis Turbines:Simulation and Model Development, Acta
Universitatis. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of
Science and Technology 998(2012).
[2] M. Islam, D. S.-K. Ting, and A. Fartaj, “Aerodynamic Models for Darrieus-Type Straight-Bladed
Vertical Axis Wind Turbines,” Renewable & Sustainable Energy Reviews, Vol. 12, pp.
1087-1109(2008).
[3] J. O. Ajedegba, Effects of Blade Configuration on Flow Distribution and Power Output of a
Zephyr Vertical Axis Wind Turbine, MS Thesis, University of Ontario Institute of
Technology(2008).
[4] B. K. Kirke, and L. Lazauskas, “Limitations of Fixed Pitch Darrieus Hydrokinetic Turbine and the
Challenge of Variable Pitch,” Renewable Energy, Vol. 36, Issue 3, pp. 893-897(2011).
[5] C. J. S. Ferreira, A. van Zuijlen, H. Biji, G. van Bussel, and G. van Kuik, “Simulating Dynamic
Stall in a Two-Dimensional Vertical-Axis Wind Turbine: Verification and Validation with
Particle Image Velocimetry Data,” Wind Energy, Vol. 13, pp. 1-17(2010).