Savonius Turbine Modified Design

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Supervisor:� Dr Rola Afify� Dr AhmedSamir� Dr Walid Ghoneim

By:

• Aly Magdy
• Mahmoud Abobakr
• Maged Mohamed
• Mohamed samir
• Ahmed Tamer

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Chapter One�Introduction

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Vertical Axis Wind Turbine

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Types of Vertical Axis Wind Turbine

1) Darrieus wind turbine

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2) Savonius vertical axis wind turbine

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Advantages of Vertical Axis Wind Turbine

1) does not need to be pointed towards the wind

2) lower wind start up speed

3) doesn’t need any mechanisms in order to operate

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Disadvantages of Vertical Axis Wind Turbine

1) You are unable to take advantage of the wind speeds that occur at higher levels.

2) VAWT’s are very difficult to erect on towers, which means they are installed on base, such as ground or building.

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Design Of VAWT��

• It is formed by dividing a cylinder into half, along its central axis and relocating the two semi-cylindrical surfaces sideways. This shape is akin to “S” when viewed from top

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Components Of Savonius Turbine

• Guide wire: its function is to keep the rotor shaft in a fixed position and maximised possible mechanical vibration

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• Hub: it is the centre of the rotor to which the rotor blades are attached

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• Rotor: is the turbine component responsible for collecting the energy present in the wind and transforming this energy into mechanical motion 

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Components Of Savonius Turbine (cont.)

• Blades : Rotor blades take the energy out of the wind; they “capture” the wind and convert its kinetic energy into the rotation of the hub

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• Shaft: Turned by the turbine blades and is connected to the generator within the main housing

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Components Of Savonius Turbine (cont.)

• Mechanical breaking: use to stop turbine in emergency situation such as extreme gust events or over speed. This brake is also used to hold the turbine at rest for maintenance as a secondary mean, primarily mean being the rotor lock system

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• Gear box: The main function of the gear box is to take low rotational speed from shaft and increase it to increase the rotational speed of the generator
• Generator: it converts of rotational mechanical energy to electrical energy

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Parameters That Affect The Performance

• Effect of blades number
• Effect of Aspect Ratio
• Effect of end plates

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Effect Of Blades Number

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Effect Of Aspect Ratio

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Effect Of End Plates

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Applications

• Building
• Provide local electricity
• Power cellular communication towers

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Types of Savonius Turbine

• Swirling savonius rotor

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• Traditional savonius rotor

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Types of Savonius Turbine (cont)

• Swirl The swirling Savonius turbine is similar to the classic Savonius turbine, which consists of two identical semi-cylinder-like blades moving sideways and overlapping.

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• The swirling Savonius turbine differs from a traditional Savonius turbine in that it has been modified. The inner tips of the half cylinders were extended further to construct the swirling chamber

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Chapter Two �THEORETICAL MODELLING

Power Coefficient Analysis(Cp)�

H = rotor height

D=rotor diameter

T=actual torque developed by the rotor

W=angular velocity of the rotor

Cp= max power obtained from the wind / total available power

• Max power (pa) =1/2×ρ×H×D×V^3 (Watt)

Total available power(pt) = T×ω

• pt= kinetic energy * mass flow rate

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Torque coefficient (cm)

• Cm = actual torque of the rotor / theoretical torque of the rotor
• Theoretical torque =
• Note: The power coefficient and torque coefficient are related mathematically with all the parameters affecting the Savonius turbine performance.

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Tip Speed Ratio

The tip-speed ratio, λ, or TSR for wind turbines is the ratio between the tangential speed of the tip of a blade and the actual speed of the wind

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λ = velocity of the rotor/wind speed = (ω×r)÷V

• (W) is the rotational speed of the rotor
• (r) is the rotor radius
• (V) is the wind speed at the height of the blade hub.

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Performance of savonuis turbine

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Ratio of over lap on torque

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Ratio of over lap on torque

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Power Of Turbine

According to Bet’z law, the maximum power that is possible to extract from a rotor is (16÷27)×

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• ρ is the density of air
• A is the area of the blade
• v is the wind speed

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Relation Between Wind speed & RPM

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Relation Between Wind speed & Power

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Stresses on turbine rodes�Direct shear due to centrifugal�

• Ar= rod rea =
• Syr= yield for the rod material
• Fsr= factor of safety for the rod

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• Shear =

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direct shear due to weight

fg=blade weight = mass* gravitational force

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torsion due to weight (Fg)

T= actual torque

• Shear=

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Compression stress due to wind forces�

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So we can calculate the resistance force

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Material selection for the blades

• aluminum will be used as blades material as its density is smaller and yield strength is higher than that of steel.
• ρaluminum = 2700 kg/m3 .
• Syb :Yield stress of blades = 276 MPa.
• fsb: Factor of safety of blades = 3

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Tension stress due to centrifugal force

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Therefore , thickness of blade will be obtained

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Bending stress due to weight:

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• y: Distance from blade center to its edge = H/2
• H: Blade height

Therefore thickness of blade will be obtained

And we will choose the bigger one to bear the stresses

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Direct shear due to weight (Fg)

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Therefore, (a) will be the only unknown and it will be obtained

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� Direct shear due to centrifugal force (Fc)

therefore, (a) will be obtained ,, and we will take the bigger value to satisfy all the shear stresses

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bearing or crushing stress on rod�Checking

• Bearing or crushing due to centrifugal (fc)

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• If left side≤ right side
• Dimenstions of dr and t are suitable for design

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bearing due to weight (fg)

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• If left side≤ right side

Dimenstions of dr and t are suitable for design

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Design of Shaft�

• Design based on Distortion energy theory

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d : The solid shaft diameter ( mm )

f.s : Factor of safety of the shaft

M : Maximum bending moment in the shaft

T : Maximum Torque in the shaft

Therefore, diameter of shaft will be obtained

Design of shaft (cont)

• Design based on Rigidity

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• T : Torque applied on shaft
• L : Length of shaft affected by the torque
• G : Modulus of rigidity
• Theta all: Allowable shaft twist angle

Therefore, diameter of shaft will be obtained

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Design of shaft (cont)

• Design based on Fatigue loading

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• q : Notch sensitivity
• kt : Stress concentration factor
• Se : Corrected endurance stress (MPa)

Therefore, third diameter for the shaft will be obtained

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Design of shaft (cont)

• Design based on ASME formula for ductile material (bukling)

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• di : Inner shaft diameter
• do : Outer shaft diameter
• tall : Allowable shear stress of [ 0.3 Sy or 0.18 Su ] for no keyway (and obtain the minimum value)

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Selection of bearing

reaction Calculations on bearing

Fa= Axial load

Fr = radial load

• Static load bearing:

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• Dynamic load bearing:

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Chapter Three

Experimental Method

Experimental Study

The experimental study will be carried out in three main parameters

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•  Experiment 1: Measure the static torque , rotational speed & power for different angular position at various wind speeds coming from wind tunnel.

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Experimental Setup

Equipment Used

• 1-Load Cell (Beam Type)

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• The load cell may be used to measure the force F1 in tight side of the nylon string in kg
• The load cell was selected as a beam type of 20 kg constructed in a cantilever beam serves as the elastic member to measure the force F1

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Equipment Used

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• 2-Arduino (Micro processor)

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• Write codes of programming using C or C+ program in order to measure torque & rotational speed of rotor effectively.

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Equipment Used

• 3-Thermo Anemometer

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• A device used to measure air velocity coming from the wind tunnel & entering into the rotor.

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Blade Design & Manufacturing

• The blades were twisted into a C shape, the diameter was set at 200 mm, and the aspect ratio was set at 1 (aspect ratio: the ratio between height and width).
• Height= 200 mm
• Width= 200 mm
• Radius= 100 mm

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Shaft

• It’s a hollow shaft made of aluminium
• Shaft: Length=280 mm

Thickness=2 mm

Do=19 mm

Di=17 mm.

• Artilon Piece: Do=25 mm

Di=17 mm

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Electric Panel of Setup

1. Display set of torque sensor
2. Circuit breaker
3. 24V power supply
4. Amplifier
5. 12V power supply
6. Arduino board

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Apparatus

1- Blades

2- Artylon Coupling

3- Dynamic torque sensor

4- Load cell

5-RPM Speed Sensor

6- Worm gear configuration

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Traditional Design VS Modified Design

Traditional Design VS Modified Design

4 Pieces of Part 1

1 Piece of Part 2

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Data Reduction

�Experiment Procedure � Measuring Torque ,RPM , Power��

1- Adjust the rotor blades to be perpdicular

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2- Rotate the worm to increase the forces F1 and F2and then loading the rotor of the turbine.

3- Start the wind tunnel and adjust the speed of the fan to obtain the required value of the air velocity at downstream from the wind tunnel exit section.

�Experiment Procedure � Measuring Torque ,RPM , Power��

4- Use the thermo anemometer to measure the velocity of the free air stream up stream of the rotor position.

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5- Make a fine turning for the fan speed to get the desired value of the free air velocity.

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6- Release the loading of the brake down system by ready the worm gradually in the c.c.w direction till the rotor start to move.

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Experiment Procedure � Measuring Torque ,RPM , Power�

7- Record the value of F1 (load cell) and F2 (weight balance).

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8- Determine the value of static torque using the relation

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9- Determine the value of rpm of rotor

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10-Calculate the power by multiplying torque by RPM

Chapter 4

Results & Discussion

Rpm Readings

Traditional Design

Modified Design

Torque Readings

Traditional Design

Modified Design

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Power Readings

Traditional Design

Modified Design

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Conclusion

We followed the same experimental procedure in both cases and it can be concluded that :

• traditional Savonius turbine produces higher torque
• it rotates with a higher RPM than the Modified Savonuis
• so this derives that the traditional design produces more power.
• However,start up of modified savonius is faster than traditional design

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• due to instability of the modified turbine

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