wind turbine project group2

8/10/2019 Wind Turbine Project Group2

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MIPRJ: Multidisciplinary Project

Group 2

Battery ChargingWind Turbine


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Table of Contents

CHAPTER I - WIND DATA .................................................................................................................................. 2

1.1 GENERAL INFORMAION ABOUT THE WIND .................................................................................................. 2 1.2 METEOROLOGIC ........................................................................................................................................... 2

1.3 HISTORY ..................................................... ................................................................. .................................. 2 1.4 WEIBULL CURVE ............................................................... ................................................................. ............ 7

CHAPTER 2 - TYPES OF WIND TURBINES ......................................................................................................... 12

2.1 VERTICAL AXIS WIND TURBINES, VAWTS .................................................................................................... 12 2.1.1 TYPES OF VAWTs ................................................................................................................................. 13

2.2 HORIZONTAL AXIS WIND TURBINES, HAWTS .............................................................................................. 14 2.3 EVALUATION ......................................................... ................................................................. ..................... 16 2.4 FINAL DECISION .......................................................................................................................................... 17

CHAPTER 3 - DESIGN PRESENTATION ............................................................................................................. 19

3.1 TEHNICAL DATA .......................................................................................................................................... 19

CHAPTER 4 - THE ROTOR ................................................................................................................................ 22

4.1 BLADES........................................................................................................................................................ 22 4.2 NUMBER OF BLADES ........................................................ ................................................................. .......... 23


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6.3 THEORY ...................................................... ................................................................. ................................ 65 6.4 OUR FURLING SYSTEM DESIGN ................................................................................................................. .. 68

CHAPTER 7 - THE TOWER ............................................................................................................................... 70

7.1 AVAILABLE OPTIONS ........................................................ ................................................................. .......... 70 7.1.1 TRUSS TOWER ..................................................................................................................................... 70 7.1.2 TUBULAR STEEL TOWER ................................................................ ..................................................... 71 7.1.3 GUYED TOWER ............................................................................................................... ..................... 71

7.2 SPECIAL TOWER DESIGNS ........................................................................................................................... 72 7.3 CHOICE OF TOWER ..................................................................................................................................... 72 7.4 GUYED TOWER DESIGN ............................................................... ................................................................ 72

7.4.1 INSTALLATION ..................................................................................................................................... 72 7.4.2 ASSEMBLY METHOD ............................................................ .............................................................. .. 73 7.4.3 ANALYSIS &DESIGN ............................................................................................................................. 73 7.4.4 CONNECTIONS .......................................................... ................................................................. .......... 73

7.5 FOUNDATION ............................................................................................................................................. 74 7.5.1 AVAILABLE OPTIONS ........................................................................................................................... 74

7.5.2 MOST SUITABLE FOUNDATION ............................................................... ........................................... 75 7.5.3 DESIGN CONSIDERATIONS FOR SPREAD FOUNDATION ...................................................................... 75

ANNEX C ........................................................................................................................................................ 78

I.INITIAL CALCULATIONS ................................................................................................................................ 79

CHORD LENGHTS CALCULATIONS ................................................................................................................... 86

2. GEARBOX CALCULATIONS ............................................................. ................................................................ 89 GEAR PARTS 89


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FIRST SHAFT CALCULATIONS .......................................................................................................................... 121 SECOND SHAFT CALCULATIONS ........................................................ .............................................................. 123

THIRD SHAFT CALCULATIONS ........................................................................................................................ 124 FOURTH SHAFT .............................................................................................................................................. 125 CALCULATIONS OF THE FITTINGS ................................................................................................................... 127 FIRST SHAFT ..................................................... ................................................................. .............................. 128 SECOND SHAFT .............................................................................................................................................. 131 THIRD SHAFT .............................................................. ................................................................. ................... 134 FOURTH SHAFT .............................................................................................................................................. 137

8.BEARINGS SKF CALCULATIONS .................................................................................................................. 140

BEARING 1 ...................................................................................................................................................... 140 BEARING 2 ...................................................................................................................................................... 140 BEARING 3 ...................................................................................................................................................... 141 BEARING 4 ...................................................................................................................................................... 141 BEARING 5 ...................................................................................................................................................... 142 BEARING 6 ...................................................................................................................................................... 142

BEARING 7 ...................................................................................................................................................... 143 BEARING 8 ...................................................................................................................................................... 143


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INTRODUCTION

This report will contain our design of a battery charging wind turbine which will be able to provide electricity to people in off grid areas. The report will include theoretical analysis, technicaldrawings and computer models of the wind turbines rotor, nacelle, tower and foundations. The resultsof any practical tests of a prototype will be recorded in this project.

The Scope of the Project:

The Report Will Cover the Following Areas:

Calculation of wind forces on the turbine (rotor and tower) Theoretical analysis of wind turbine design and power production Design of a control system to prevent excess power in high wind speeds Design of a foundation base for the tower

The following specification list must be met at all times. The wind turbine must:

Be affordable


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PROJECT AGREEMENT

Project : BATTERY CHARGING WIND TURBINE

Institution : ENGINEERING COLLEGE OF AARHUS

Department : MECHANICAL ENGINEERING

Supervisor : Christina Munk

Members :

Vi Ti d Mi l (S i M h i l E i i )


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STATEMENT

We state that all the information in this report is original and if we used any externalreference we give the credits for the authors at the end of Report.

Date

7.12.2011

Victor Tienda Miguel David Gary Ogden


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CHAPTER I - WIND DATA


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CHAPTER I - WIND DATA

1.1 GENERAL INFORMAION ABOUT THE WIND

Everybody knows about the wind but nobody sees it. We are only able to see its effects on

different things. Wind is a part of our daily life like sunlight and rain. But wind was also veryimportant for the history of humanity and maybe it will also be a part of one of our most important problems, the search for renewable and environmental friendly energy sources.

This report is about designing a wind turbine. Without wind, no wind turbine! Because ofthis, the wind is also very important for us. So we have to take a look at what we have to know aboutthe wind conditions for the place where we want to build our turbine. First we want to take a look whywind in general exists and why it was important for the history of humanity.

1.2 METEOROLOGIC

This chapter doesnt intend to be a complete description of the met eorological mechanism. Itis only to mention some basic ideas. Meteorology in general and the mechanics of the wind are notfully and in every detail understood today but the general way of how wind develops is not toodifficult. To put it in a nutshell wind is the reaction of the air to different pressures in different places


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They used this potential mainly in two ways:

The first way was to use the wind to move a ship. This was a very obvious way to use it because like everybody knows the wind is very strong and most often blowing at the coast and thesea. The first ones who was able to build sail ships were the Egypts. They started ca. 1500 B.C. to

build ships with a sail to drive on the Nil.

Recreated Egyptian ship [fig.1.1]
http://egyptexperience.files.wordpress.com/2011/06/ancient-egyptian-ship.jpg


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The other way our ancestors used the force of the wind was the windmill. These machineswere developed further into the wind turbines we know today. The start of this technology was maybe1750 B.C. in Babylon but scientists are not one hundred percent sure about this. We definitely knowthat the people in Persia and China used windmills in the 9 th century. But they had a big differencecompared to the most used type of our modern wind turbines. They had a vertical rotation axes.

The first versions with a horizontal rotation axis were built in the 12 th century in Europe. Themodel which comes in most of us minds when we talking about windmills were first built in the 16 th century in the Netherlands.

Chinese windmill [fig. 1.4] Persian Windmill [fig. 1.3]


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Wind distribution and direction:

When you want to build a wind turbine on an elected place you mainly have to know twothings about the wind conditions on this particular place. The first one is the distribution. It not onlytells you the average of wind speed but also the frequency of occurrence of different wind speeds.This is very important to choose the right rotor diameter, profiles, generator etc. to get the aspired

power and the best possible relation between harvested wind and costs of the turbine.

A little example which is very good to show how important it is to know the right distributionof the wind and why the average wind speed alone is not enough. We imagine two different locations.At the first location the wind is blowing with 5m/s the whole year without any changing.

At the second place the wind is blowing half of the year with 10m/s and the other half of theyear is no wind at all. So we have two locations where we could build a wind turbine. This twolocations have se same average wind speed. Without more information they are looking totally thesame. But they have a different distribution of different wind speed. Now we take a look at theinfluence of this difference. First we calculate the annual production.

For a more simple calculation we calculate with a wind turbine which hast a swept surface of10 2 and is able to generate the largest possible power according to Betz out of the wind. This is ofcourse not possible but so we dont have to think about efficiency factors and because this calculationis only to compare our two locations it is ok to do it like this. So our turbine generates the followingamount of power at different wind speeds.


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That shows us very good how big is the influence from the distribution of the wind on theannual production. So we are going to build out wind turbine at location 1. Well, it depends. If we areonly looking for the highest annual production, than we have of course to choose location 1. But thereis also a big disadvantage of this location. We have only electricity during the half of the year. So weneed another source of electricity for the other half of the year, or we have save the energy in someway like for example batteries.

Another point which is also a part of the distribution of the wind is the wind shear. The windhas not only a changing distribution according to the time axis but also according to the high axis.

Nearly everybody discovered that when he climbed on a look out or a church there is suddenly muchmore wind than on the ground. This is because the terrain, houses, trees and hills slow the wind downand make him more turbulent next to the surface. This effect can be stronger or weaker depending onthe terrain.

These differences are called roughness of the terrain. The normal range of roughness is

between 0,1m and 0,4m. The value of 0,1m we only reach at the open sea while the value of 0,4m isvalid in a city. So the values at the normal locations of a wind turbine are somewhere in between. Ifwe know the wind speed on a particular height and the roughness of the terrain, than we are also ableto calculate every other wind speed at different heights. Here a little example for the wind shear with ameasured wind speed of 10m/s at a height of 30m.


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The other important thing is the direction of the wind. This is essential because the terrain orother wind turbines have an influence on the wind. When you are planning to build a wind park withmore than one turbine than you have to think about shadowing. Behind a turbine the wind is slowerthan in front of a turbine because the turbine took energy out of a wind.

The air is also rotating behind a turbine. Both things are not good for the efficiency from aturbine placed behind the first one. Because of this you place the turbines in a wind park so that youhave the smallest possible shadowing effect when the wind comes out of his main direction. Also theterrain has a big effect on the wind.

The wind is slowed down, more turbulent, or diverted. Depending how often the wind comesfrom one direction you have to think more or less about the components you have to choose to be ableto harvest the wind in the best possible way under this conditions. Normally you design the windturbine so that it is optimal when the wind comes out of its main direction. There are special diagramsto show the distribution of the wind direction. So you are able to make fast and precise statements

about that.


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When do you want to know the probability of a wind speed v you have to know the values ofthe average wind speed (a) and the shape factor (k) on this location. The shape factor k is very similarto the roughness of the terrain but it describes the variability of the wind speed. It normally differsfrom 2 for very variable wind speed which you find especially in mountain regions to 4 for veryconstant wind speeds which you can find on the open sea. In the diagram you can see the differentshaped curves for an average wind speed of 8 m/s.

0.04

0.06

0.08

0.1

0.120.14

0.16

0.18

0.2

Weibull curve

probability (k=1)

probability (k=2)

probability (k=3)

probability (k=4)


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So we researched a couple of different locations and take the average of these to generate our designconditions.

[See Table 1.1]

Table 1.1 - Reference (http://www.windfinder.com/)

PLACE/STATION COUNTRY AVERAGE WIND SPEED

[knots]

AVERAGE WIND SPEED

[m/s]

Alger-Port Algeria 13 6,68772

Bahrain-Airport Bahrain 10 5,1444

Hurghada Egypt 16 8,23104

Cairo-Airport Egypt 14 7,20216

Aqaba Jordan 10 5,1444

Homs Libya 16 8,23104Al Hoceima Morocco 12 6,17328

Tanger-Airport Morocco 11 5,65884

Tetouan Morocco 10 5,1444

Walvis Bay-Airport Namibia 13 6,68772

Dakar Senegal 9 4,62996

Mtwara Tanzania 12 6,17328


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So we choose an average wind speed of 6m/s. But like it is described in the chapter before itis not enough to know only the average wind speed. It is at least as important to know the distributionof the different wind speeds. So how we get this data. If you know the kind of terrain where do youwant to place your turbine you can chose the k which you need to form the Weibullcurve out of table.

This is of course not as good and accurate as measuring the wind speed at a location indifferent heights for a year but totally ok for our circumstances.

Table 1.2

VALUES FOR K FOR DIFFERENT TERRAINS

Mountains 2

Hills 2.5

Coast 3

Plane 3.5

Islands, open sea: 4


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CHAPTER 2 - TYPES OF WINDTURBINE


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CHAPTER 2 - TYPES OF WIND TURBINESThis section will make a comparison of the different types of wind turbine that exist, in order

to find the best option for our project. There are two broad classes of turbines: vertical and horizontal.Each class has different varieties, and the following chapter gives a brief summary of the advantagesand disadvantages of the most common models.

2.1 VERTICAL AXIS WIND TURBINES, VAWTs

Vertical axis wind turbine are usually named as VAWTs, the main characteristic is that therotor shaft is arranged vertically.


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2.1.1 TYPES OF VAWTs

DARRIEUS WIND TURBINE

This turbine is robust, due to the structure of the blades. Is very efficient but there are large tension stresses in the tower that limit its reliability. Starting torque is very low; it needs an external power supply. The geometry of the blades is complex.

Figure 4.2 : Darrieus Wind Turbine


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GIROMILL WIND TURBINE

The Giromill is a Darrieus type wind turbine, and consists of two or three aerofoil's attachedto the central shaft by horizontal supports.

It is cheaper and easier to build than a standard Darrieus wind turbine, but it is less efficientand also requires stronger wind to start the movement of the rotor.

They work well in turbulent conditions and are an affordable option for small powerrequirements.

Figure 4.4: GiromillWind Turbine


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All the components are located at the top of the tower in a cabin called the nacelle. The mainshaft drives a rotor in which the blades are located. The rotor must be pointed into the wind direction.

Smaller wind turbines have a pallet system to go in the direction of the wind, while the largestwind turbines have sensors connected to a motor.

The blades are made rigid and strong enough to resist high wind speeds. They are located at aconsiderable distance from the tower to avoid possible collisions.

This type of wind turbine can be built to operate downwind or upwind. Most of the HAWTsare upwind machines, reducing the problem caused by turbulence around the nacelle.

Upwind Downwind


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2.3 EVALUATION

With the explanation of the types of wind turbine that it is possible to use for our project, we will proceed to make a comparative study to know which of the two types, VAWTs and HAWTs has more points in favor for meeting our criteria.

Our criteria are based on main ideas that are essential for the realization of the project.

Good efficiency and low cost. Flexibility on the design. Information. Environmental resistant. Easy to manufacture.

In this table are summarized the most important facts of the wind turbines.

Table 3.1

Wind Turbine Main characteristics

HAWT o High efficiencyo Most commonly used


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Table 3.2

POINTS GRADE

1 Unsatisfactory

2 Tolerable

3 Good

4 Very good

Figure 4.8 : Meaning of the evaluation points

With the data that are explained before and all the information that we found in our research , we

proceeded to evaluate each aspect and put a score :Table 3.3

HAWTs VAWTs

Efficiency 4 3


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CHAPTER III


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CHAPTER 3 - DESIGN PRESENTATION

This chapter is only for an overall idea of the Wind Turbine an the some Basic Technicalspecifications.

MAIN COMPONENTS: ROTOR - NACELLE - TOWER

ROTOR

NACELLE

TOWER


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OVERALL PICTURE


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CHAPTER IV - THE ROTOR 4.1 BLADES

4.2 NUMBER OF BLADES


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CHAPTER 4 - THE ROTOR

This chapter describes the rotor, which is considered to be a key component in the windturbine assembly. The purpose of the rotor is to harness the power of the wind and convert it intomechanical energy by turning the shaft of the electric motor.

The major components in the rotor of a Wind Turbine consist of:

Blades Mounting plate Hub

4.1 BLADES

This section focuses on general information about blades and airfoils, aerodynamic analysis,forces on the blade, selection of blade profile, material selection and virtual blade design.

An airfoil-shaped body moving through a fluid produces an aerodynamic force. Thecomponent of this force perpendicular to the direction of motion is called lift. The component parallelto the direction of motion is called drag and the angle between the chord line and the relative wind is
http://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Aerodynamic_forcehttp://en.wikipedia.org/wiki/Perpendicularhttp://en.wikipedia.org/wiki/Lift_%28force%29http://en.wikipedia.org/wiki/Drag_%28physics%29http://en.wikipedia.org/wiki/Drag_%28physics%29http://en.wikipedia.org/wiki/Lift_%28force%29http://en.wikipedia.org/wiki/Perpendicularhttp://en.wikipedia.org/wiki/Aerodynamic_forcehttp://en.wikipedia.org/wiki/Fluid


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The chord line is a straight line connecting the leading and trailing edges on the airfoil. The mean camber line is a line drawn halfway between the upper and the lower surfaces

The frontal surface of the airfoil is defined by the shape of a circle with the leading edgeradius. The centre of the circle is defined by the leading edge radius and a line with a givenslope relative to the chord line.

4.2 NUMBER OF BLADES

One of the most frequently asked questions prior to building a wind turbine is how many blades should be used. For the last 50 years, the majority of wind energy system manufacturers have


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The dependency of the power coefficient on the number of blades emphasizes why two orthree blades are generally the preferred solutions for wind turbines. The power coefficient of a windturbine with just one blade is relatively low and it furthermore suffers from anesthetic imbalance aswell as the need for a counterweight. Modern wind turbine engineers avoid building large machineswith an even number of rotor blades. The most important reason is the stability of the turbine. A rotorwith an odd number of rotor blades (and at least three blades) can be considered to be similar to a discwhen calculating the dynamic properties of the machine.

A rotor with an even number of blades will cause stability problems for a machine with a stiffstructure. The reason for this is because in high winds, the uppermost blade begins to bend backwards.As this happens, the lowermost blade begins to bend forwards, in front of the tower.

4.3 THE AERODYNAMICS OFTHE BLADE PROFILE

This chapter explains why blades have a special profile and what happens as the blades rotate.

The shape of the aerodynamic profile of the blade is crucial for the design, as it influences the performance of the blade. Therefore, the shape of the profile must be chosen from a widely usedcatalogue of airfoils developed in wind tunnel research by NREL (National Renewable Energylaboratory) or NACA (National Advisory Committee for Aeronautics) or another certified researchassociation. This wind turbines rotor will use the NREL-S822 (see fig. 4.4) profile. From the availableinformation about this profile (such as laboratory results, and virtual wind tunnel tests), it was decided


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As shown in figure 4.5, turbulence is relatively low, meaning that this profile is reasonablyefficient.

In the research laboratory, we can also conduct experiments to find out the performances ofthe profile, regarding the lift and drag coefficient.

Figure 4.6 shows the inviscid (potential-flow) pressure distributions for the S822 airfoil forvarious angles of attack.


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According to the graphic from figure 4.7 we was able to make this table for finding the optimumGlide Ratio.

Table 4.1

Alpha Coefficient of lift Coefficient of drag Glide Ratio

C_l C_d GR

-3 -0.834 0.01093 -76.3037511-2 0.0245 0.01125 2.177777778-1 0.1254 0.01141 10.990359330 0.2376 0.01144 20.769230771 0.3491 0.01192 29.286912752 0.4515 0.01162 38.85542169

3 0.5735 0.01134 50.573192244 0.668 0.01088 61.397058825 0.7657 0.01051 72.854424366 0.8475 0.01045 81.100478477 0.8726 0.01131 77.152961988 0.913 0.01496 61.029411769 0.9556 0.01877 50.91102824

10 1.0049 0.02257 44.5237040311 1.0532 0.02672 39.41616766


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-1

-0.5

0

0.5

1

1.5

-5 0 5 10 15 20 25 L i

f t a n

d D r a g c o e f f i c i e n t s

Angle of attack

NREL- S822

C

C

[fig 4.8] -Lift and Drag coefficients


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4.5 BLADE MATERIAL

We have carried out research into which material is most suitable for our needs so that the blade can be easily manufactured, cheap and have high resistance to atmospheric conditions.

The following materials and associated manufacturing methods have been taken intoconsideration :

Table 4.2

MATERIALMANUFACTURING METHOD

METAL Aluminum blades may be manufactured as solid shapes, machined using CNC, orfromrolled plates that are welded together on airfoil shaped support plates

COMPOSITE Blades of carbon or glass fiber reinforced polymer composites may bemanufactured in two-part moulds

WOODWooden blades may be machined from a wood work-piece, or by hand


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The material that best suits our needs is wood. Wood is cheap, has great flexibility, andcan be carved or machined from a block of wood into complex shapes such as blades withvarying chord length.

The next step is to use all the physical data that we acquired from our research and startcreating a virtual model of our blade using a specialized CAD software (SolidWorks 2012).Thiswill very helpful because we can conduct various fluid dynamics simulations and stress

calculations without making a real scale model and test it into a wind tunnel.

4.6 VIRTUAL POFILE DESIGN

For the virtual model of our profile, a parametric design that consists of coordinates onthe X axis and Y axis(as shown in the table 4.3) was used. The main benefit of this was that wehad the possibility to make a precise shape of the profile (fig4.9).


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Table 4.3

S822 AIRFOIL COORDINATES

No. Lower Surface Upper SurfaceX

[mm]Y

[mm]X

[mm]Y

[mm]1 0.00002 -0.00057 0.00012 0.001322 0.00042 -0.00244 0.00064 0.003363 0.00126 -0.0044 0.00176 0.006034 0.0053 -0.0101 0.00861 0.01515 0.01536 -0.01866 0.02029 0.024646 0.03018 -0.02713 0.03661 0.034257 0.04956 -0.03517 0.05742 0.04366

8 0.07336 -0.04253 0.08254 0.052719 0.1014 -0.04903 0.11172 0.0612210 0.13345 -0.05456 0.14466 0.0690411 0.16927 -0.05902 0.18104 0.0760712 0.20852 -0.06236 0.2205 0.0821813 0.25087 -0.06455 0.26262 0.0872914 0.2959 -0.0656 0.30696 0.0913315 0.34317 -0.06553 0.35305 0.09423


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The above tables and graphics of drag lift coefficient and angle of attack will be very usefulwhen we start the calculations. After creating the airfoil shape using X and Y coordinates wecan scale the airfoil so that the shape of the profile match our calculations (appendix C - chordlengths) . This is our result :

tip blade section

root blade section

mounting holes

blade tip


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4.7 MOUNTING PLATE

1. The mounting plate has the purpose of transmitting the force from the blades to themain shaft.

2. The blades are connected to this plate through M8 x 34 bolt connection3. Also on this plate are the mounting points for the hub 4. Material: Aluminum alloy 6061 or steel alloy 1023 carbon steel

The manufacturing process for this part is relatively simple, two plates are weldedtogether on a steel tube, and the three mounting point for the back cover of the hub are weldedon the back plate.

steel plates

steel tube

blade mounting holes


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4.8 THE HUB

For our wind turbine the hub doesn't have a very important roll. The main purpose ofthe hub is to protect the inner parts from the environment, and to add an aesthetic design to thewind turbine.

The material for this part can be plastic or metal, normally aluminum, as it`s lighter and

easier to manufacture than steel.

This part could be manufactured by a classic mill machine, or for faster manufacturing,a CNC machine could be used, using the virtual model created in SolidWorks(fig x).

For an advanced manufacturing process, this part could be made by injection molding.This would be advantageous if the wind turbine was to be mass produced.


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CHAPTER 5 - THE NACELLE

The nacelle is the housing that covers all of the components of a wind turbine. The nacelle issupported by the tower. Its main purpose is to protect all of the internal elements of the t urbineand prevent corrosion and damage which may occur from weathering and exposure to theelements.

The nacelle is made from metal and is lightweight.

The main components inside the nacelle are:


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Figure 5.3: picture of a belt transmission

ADVANTAGES

Simple.


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Figure 5.4: picture of a gear transmission

ADVANTAGES


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5.1.2 DIFFERENT TYPES OF GEARING

SPUR GEARING

Spur gears are the most common type of gear, they are the simplest to design andmanufacture, also are the most efficient and cheapest. Spur gears have straight teeth that aresituated parallel to the gear axis.


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HELICAL GEARING GEAR

In the helical gears the teeth are cut at an angle to the face of the gear. When two teeth areengage, the contact start at one of the end of the tooth and gradually spreads as the gears rotate,until the two teeth are in full engagement.

This engagement allows operate more smoothly than spur gears. Also, these types of gearscan be mounted on perpendicular shafts.


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BEVEL GEARING

The bevel gears are common used when the direction of a shafts rotation needs to be changed. In general they are always mounted on shafts that are 90 degrees apart, but also can be mounted in other angles.

The teeth of bevel gearing can be straight, spiral or hypoid. This type of gear is used in many industrial applications, especially moderns ones.


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PLANETARY (EPICYCLIC GEARING)

The epicyclic gearing or planetary gearbox is highly efficient, and consists of one or moregears revolving around a central gear. The central gear is called sun and the other gears planets.

Figure 5.8: planetary gearing picture

ADVANTAGES

High reduction ratios.


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High load capacity. Possibility of using different materials.

Easier maintenance.

5.1.4 THE GEARBOX

Our gearbox is composed by two pair of spur gears inside of a compact box. All thecomponents of the gearbox have been designed by us, and the calculations can been seen in the

Annex.

In the following picture shows the design of our gearbox. The transmission ratio isi =6 , tochoose this ratio we made the next steps:

Knowing the tip speed ratio and the radius as explained in the First Calculations chapter wewere able to find the rotation speed in the shaft which connect the gearbox with the rotor.

=

[See annex C gear calculation]

Then, with this rotation speed and looking in the table of the generator, it is possible tocalculate the required transmission ratio to have the necessary rotation speed in the second shaft.


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shaft and hold the weight of the rotor. Therefore, to achieve appropriate gears we decided todesign a gearbox with two pairs of gears. The first one have a transmission ratio of 1:3 and the

second one have a transmission ratio of 1:2 , getting a gear transmission ratio of 1:6 in thegearbox.

MOST IMPORTANT FACTORS ON A GEAR


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THE GEARBOX HOUSNG

The gearbox housing has the main purpose to fix the shafts with the bearings and secondly to protect the inner parts .Also keeping the oil inside of the gearbox for a correct lubrication.

The gearbox is made out of cast iron and in the project we are not allow to used cast material but our idea is to use a supplier.


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Also, the lubricant is used for lubricating others components of the gearbox, like the bearings. Thanks to these aspects of improvement provides by the lubricant, the gear systemefficiency increased significantly since

the coefficient of friction will decrease if the lubricant has been correctly chosen. Normally, theefficiency using a lubricant is between 80% -98%.

Another very important aspect about the lubricant is that it avoids gear wear and increasesthe life of the components. Otherwise the lubricant is not used it could be considerable wear andthe fatigue failures could occur.

If the lubricant film on the gear wheel teeth is insufficient to protect the surfaces of the gearsfor stress, resulting in pitting in the contact region and scuffing. This would cause and increasein the temperature causing distress and wear.

GEARBOX LUBRICAITION PROPERTIES

To meet the current needs of the gears, lubricating oils must have the following properties:


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The classifications can be seen in the official table:

Table 5.1

API Classification Typical Application

GL-1 Manual transmission.

GL-2 Manual transmission and spiral bevel gearing.

GL-3 Manual transmission, spiral bevel gearing andfinal drives.

GL-4 Gears in moderate load service.

GL-5 Gears in moderate and several service.

GL-6 Several service, high load and high speeds.

Figure 6.1.11: Table of API Classification. Reference : Mechanical Engineers- Roger Timings


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5.1.6 MAINTENANCE

An employee with an appropriate amount of mechanical engineering knowledge must carryout the maintenance of the gearbox. The gearbox is one of the most important components ofthe wind turbine and also the most expensive to replace, so the maintenance must be gradual.

The gears, shafts and other components have to be properly lubricated with any of themethods mentioned above.

Thanks to the design of the box, the maintenance worker only needs to take away four boltedunions to remove the top cover of the box. Without cover, the access is very easy as shown inthe figure below;


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Once the cover has been removed, disassembly of the shafts is easier as both are connected by couplings. The worker can see all of the components and in case of failure, he can do adiagnostic and replace, or repair, the damaged part.

5.2 BEARINGS, SHAFTS, COUPLINGS

5.2.1 BEARINGS

GENERAL OUR DESIGN CALCULATIONS

5.2.1.1 GENERAL

Bearings are used to keep turning components on their place, give them the possibilityto rotate with a very low friction and absorb the forces from the component and transfer them tothe housing. The most common type of bearing is the deep groove ball bearing.

They have a simple design, are not expensive, support radial and axial loads, need onlylittle maintenance, can perform one nearly every rotational speed and are robust. These are alsothe main reasons why we choose to use them in our wind turbine.


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A roller bearing has three main parts; the outer ring, the balls and the inner ring. The balls move in a groove in the rings. The balls are kept in place by a cage (not shown in the picture).

5.2.1.2 OUR DESIGN:

Our wind turbine needs eight roller bearings for our four shafts. To remain staticallydeterminate, one of the two bearings on each shaft is mounted fixed and one is floating. We areusing two different bearings with different diameters. That is a big advantage. Of course wecould maybe also use four or more different types of bearings to have the optimal one for each

position.

But to have only two types of bearings is a big advantage when we are starting to talkabout the costs of supplying and maintain. To have less different types of parts make it easierand cheaper in the major of cases. We have two bearings 6010 from SKF on the first two

shafts and two bearings 6002 on the other two. The bearing 6010 has an inner diameter of50mm. The type 6002 has an inner diameter of 15mm.


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5.2.1.3 CALCULATIONS:

We will be using bearings provided by SKF. We will also be using the bearingcalculator provided on SKFs website. This can be used to calculate the lifetime of our bearings.

Table 5.2

Bearing Revolutions (*10^6): Hours of rotation at 6 m/s

1 (6010) 13500 8446002 (6010) 141000 >10000003 (6010) 141000 >10000004 (6010) 22600 >10000005 (6002) 40700 8479006 (6002) 926900 >10000007 (6002) 21600 2249008 (6002) 3130 32500

Lifetime of our bearings [Table 5.1] - See annex C - bearing calculation for details

5.2.2 SHAFTS

GENERAL


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5.2.2.3 CALCULATIONS:

We have two extreme load cases. The first one is when the wind turbine is running atthe maximum wind speed, before the furling system starts to work. This wind speed is 12m/s.The second case is if the furling system fails or the wind becomes so strong that the manualemergency break is used. In the first cases all shafts are running and transmitting the torque andrevolutions. In the second case only the first shaft has to resist torque because the disc brake

which is on this shaft stops the revolution after a short time. So we have to calculate with thefollowing forces at shaft 1.

Table 5.3

Load case 1 (12m/s; running) T = 37,74 Nm F axial = 250N F radial = 300N

Load case 2 (55m/s; stopping; only shaft one) T = 800 Nm F axial = 1000N F radial = 300N

Loads taken from ANNEX C FIRST CHAPTER- WIND DATA TABLE

With these forces acting on shaft 1 and our gear design, we can also calculate the torqueand the bending force which are caused from the gears at the other shafts. We only have to dothis for load case 1 because the other shafts like mentioned before dont have to resist forces at


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So we get the minimum diameter of each shaft;

Table 5.5

Shaft 1 19,2mm (load case 1) < 41,65mm (load case 2) 41,65mmShaft 2 15,04mmShaft 3 10,14mmShaft 4 9,71mm

See Annex C -Shaft calculations

After the designing of the shafts it is very important to check the dynamic safety tomake sure that the safety for resisting the changing loads is big enough. A very important factorin this is the surface notches on the shaft, caused by fittings, varying diameters, and the generalsurface quality. These calculations give us the safety for the different cross sections of a shaft;

Table 5.6

Shaft: Minimum safetyShaft 1 1,58Shaft 2 22,46Shaft 3 2,86Shaft 4 2,87


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5.2.3 COUPLINGS

THE COUPLING

The coupling is a mechanical connection used to connect two shafts together for the purposeof transmitting power.

The clutch has the following purposes:

To provide connection between shafts and units that are separated, like a gearbox andan alternator.

To provide disconnection for repairs or in extreme cases. To reduce the shocks loads. To provide misalignment of the shafts or mechanical flexibility. To protect against overloads.

To protect against vibrations.

There are two main types of coupling depending on if is a rigid union or flexible union.

Normally, the rigid union is the most effective and help to improve the efficiency but theshafts must to be perfectly aligned. The flexible union can be used when the shafts are slightlymisaligned. Making sure two shafts are perfectly aligned in an assembly can be quite complex,therefore the most recommended option is use a flexible couple to prevent future mishaps.


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ELASTOMERIC TYPES

This type is the best to applications that require or permit :

Torsional softness.

Absorption of shock and vibration, better tolerance of engine drive and high loads.

Greater radial softness, allows more angular misaligned between shafts.

Lighter weight and lower cost.


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MODEL SERIES EKL- CHARACTERISTICS VIEW

Figure 6.4.3: 3D model of the EKL coupling made in SolidWorks. Reference: R+W Coupling Technologies

For this wind turbine, there shall be two couplings; one on the main shaft, which connectsthe rotor to the gearbox, and other in the generator shaft, which connects the gearbox to thegenerator.In case of failure, excessive wind speed or torques, the coupling will protect thegearbox and the generator, as they are the most expensive parts to repair.


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The coupling has to resist the maximum operating wind speed of 20 m/s.

Then for the main shaft the coupling is :

= 104.83

= 50

Coupling S450 will resist a maximum torque of 660 Nm

Then for the generator shaft the coupling is :

= 17.47

= 25

Coupling S20 will resist maximum torque of60 Nm


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5.3 BRAKE SYSTEM

To prevent failure and damage in the components of the wind turbine during high windspeeds, for example in a storm, a braking system is needed that blocks the main shaft, thus

preventing the rotation transmission to the other components, gearbox and generator.

Also when maintenance of the wind turbine is required, this system is very useful to block and

prevent the operator from being injured.The system consists of a disc brake, as commonly used in the automotive industry. The

calipers block the main shaft due to it having a disk-shaped portion. The caliper drive isconnected to a cable that is placed in tension by a hand crank. In extreme cases of very highwind speeds, the crank needs to be turned, activating the disc brake to lock the turbine. Thesame procedure can be followed in order to carry out maintenance.

The braking system is rudimentary, as the furling system will control the turbine in highwind speeds.The braking system acts a fail-safe, although it is still very useful for performingmaintenance work.


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5.4 GENERATOR

The generator is the component of the wind turbine that transforms mechanical energyinto electrical energy. The rotational energy in the transmission system goes into the generator,making electrical energy, which provides energy to the electrical grid.

The distinction between alternator and generator; the former is a machine producing

alternating current (AC) and the latter is a machine producing direct current(DC). The generatorin this project has been provided, and all the data and specifications are available in the projectspecification. The generator model is Bosch K1-14V 35A 20.


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Our electrical system is an off-grind, wind electrical system based on a rechargeable battery.This system is very common in small electric installations because the energy is not exported tothe grid and the connection is cheaper.

Off grid systems are limited in capacity by the size of the generating sources and theresources available; in this case the wind and the battery size.

The main components of the system are:

Power Line

Electric current conductor.

Battery

The battery is an electric device that converts chemical energy into electrical energy.

ConverterConverters transform the electricity produced by the generator into the AC electricity

commonly used in most homes for powering lights and appliances.

The following illustration includes the main parts of the system :


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A slip ring is an electromagnetic device allowing the transmission of electricity from astationary to a rotating structure. Its operation consist in two coupling parts. One side is keptstationary, in the case of this turbine connected to the cables that connect the generator with the

battery. The other part can rotate freely which the wires from the wind turbine are connected.This achieves that while the turbine rotates, the rotation is not transmitted to the cables belowthe rings.


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CHAPTER VI - FURLING SYSTEM


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CHAPTER 6 - FURLING SYSTEM

6.1 DESIGN OBJECTIVES

The objectives of this project are to meet the design brief. The proposed wind turbinemust be appealing to potential buyers with a unique selling point, to standout from the

competition or least be looked upon favorable.

The allocation of particular sections of the design process to each member of group was carriedout at random but with measure to ensure fairness and balance. A governing constitution in thegroup decisions, during the preliminary stage of the project was that each member was requiredto make rational decisions with the consensus of other group members to achieve best outputresults for the wind turbine under consideration.

6.2 INTRODUCTION

Our wind turbine is designed to provide power in remote land-based applications. Thedesign must be simple and reliability for our wind turbine to be favored for providing power tothese remote places, and considering the unpredictable nature of the weather system in sub-Sahara Africa, especially during seasonal shifts and, and also taking to account the ever shifting


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Figure 1. NCEP/NCAR reanalysis of Northern Africa during the period June15-July15 2008 showing the surface pressure (left) and 500 mb (milibars) height (right) gradientswhich drives the south westerlys and African easterly jet. The turning of the low level winds(left) is barotropic instability while the difference between south westerlys and jet easterlys is

baroclinic instability. (1.0) http://www.wunderground.com/blog/Weather456/archive.html?year=2010&month=06

Genesis of African Waves
http://www.wunderground.com/blog/Weather456/archive.html?year=2010&month=06http://www.wunderground.com/blog/Weather456/archive.html?year=2010&month=06http://www.wunderground.com/blog/Weather456/archive.html?year=2010&month=06


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peak power while furled. When wind speed drops, the tail or head drops back into a normalconfiguration via gravity and tracks the wind straight on once again.

There are a host of proprietary systems, like 'Autofurl', Furlmatic or hinged vanesafety system'. In all cases the systems work on very similar principles, activated by wind

pressure on the rotor itself. As the wind speed increases, the thrust on the rotor increases too, sodoes the yawing moment, until it reaches a point where it activates the furling mechanism, andso the lift on the tail also increases and so the equilibrium of forces keeps the blades facing thewind. The ingenious notion of the furling design is in the way the tail is mounted. When the liftforce reaches a certain magnitude, it moves the tail into a new position. In this position the windturbine either yaws away from the wind sideways, or tilts back so that it faces upwards.

The thrust force is thereby reduced and a new equilibrium is established. In either casethe rotor becomes skew to the wind. This effectively reduces the component of wind speedthrough the rotor, limiting the speed and the power output. This said however the complete haltof the wind turbine is not, thus a constant restoring moment (pulling the rotor back into thewind), throughout the range of movement, will ensure a constant thrust on the rotor, giving aconstant output independent of wind speed. In many cases the restoring moment becomesweaker as the wind turbine furls. This kind of wind turbine furling system do come at a cost of

instability in high winds, but the exchange for safety of over speeding makes it worth having.

On a turbulent high wind scenario, there may be cases of the turbine yawing abruptly, putting high gyroscopic bending stresses on the blade roots. This particular problem our groupis planning to solve by employing a manually activate disk breaking systems as a secondary anda last resort means of ensuring the survival of the turbine.

There is a variety of furling system designs:


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Figure 3 (3.0) http://greenterrafirma.com/wind-turbine-furling.html

o Folding Vane; Similar to the furling tail, but the tail boom is fixed, witha hinged vane underneath. The main disadvantage is that tail and vane are more

highly stressed from wind force during furling, as they still are sticking outthere in the gale.

o Flexible Blades; the theory is that the blades flex both back toward thetower and around their main axis, and therefore protect themselves from overspeeding. It does work if the materials and details are correct (for example, theblades must not flex back far enough to hit the mast and they must withstand
http://greenterrafirma.com/wind-turbine-furling.htmlhttp://greenterrafirma.com/wind-turbine-furling.htmlhttp://greenterrafirma.com/wind-turbine-furling.htmlhttp://greenterrafirma.com/wind-turbine-furling.html


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6.4 OUR FURLING SYSTEM DESIGN

Our group after much consideration has decided to employ the most common, reliableand what to our group objective is most suitable choice of wind turbine furling systems the sidefurling tail. This was the consensus after much though and inclination towards the most obviousdesign, the spring-loaded tail, which folds up when the force on the spring is exceeded. But aspring is vulnerable to weathering and fatigue. Nor does it lend itself to producing a constantrestoring moment. The tension in the spring increases as the spring stretches. The radius ofaction of the spring (its distance from the hinge) will also change. The best way to make areliable, self-furling tail is to use gravity instead of a spring to pull the tail into its normalworking position. This is achieved by mounting the tail on an inclined hinge. The tail falls downagainst a stop under its own weight, in the normal (lowSomewhat, reaching a peak at the midpoint of the tail's swing, but in practice this variation isusually tolerable. Hence, also we are able to control the wind speed at which furling takes place

by making the tail heavier or lighter. A simpler approach is to use a fixed tail boom, with a vanesuspended under it on hinges. This tail however is less precise in operation, and becomes highlystressed in storms because it projects across the wind, and is subjected to its full fury, with avane flapping off it.

The tail furl model operates much on the same principle as described earlier, where thethrust of the wind on the rotor drives the furling movement. The thrust on the rotor is centeredon its axis. If this axis is offset from the yaw axis, then the thrust creates a yawing moment,turning the wind turbine away from the wind. In normal wind speeds we do not want the rotor toyaw sideways, we want it to face the wind directly and catch all the power. So we build a taillarge enough to withstand the yawing, moment caused by the offset, using a vane area at a value


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CHAPTER VII - THE TOWER


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CHAPTER 7 - THE TOWER

7.1 AVAILABLE OPTIONS This section outlines the different options available for wind turbine towers. There are 3

main types of tower systems, and their advantages, disadvantages and other useful informationis detailed in section 7.1.

7.1.1 TRUSS TOWERThe truss tower, is a simple design that provides the ability of creating both a stiff and tall

tower. For this reason the lattice tower was the preferred tower design of the first experimentaland small commercial wind turbines. [9]

The lattice tower is manufactured using welded steel profiles. In countries where thelabour costs are low the lattice construction is an economical solution, as it only requires half asmuch material to achieve the same stiffness as free standing tubular tower.

In countries with high labour costs the economical advantage is limited or non-existent.[10]


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7.2 SPECIAL TOWER DESIGNS

Besides the prevailing tower types mentioned, there are some special tower designs thatare either hybrids of the mentioned types or novel towers. The hybrids may be slender latticetowers or concrete towers that are additionally fitted with guy wires [36, p. 423]. The noveltowers include rooftops, silos, wooden poles and trees. None of them are very suited as towersfor wind turbines due to turbulence and vibrations in the structure on which they are mounted

[39, p. 156-159]. Furthermore they all require availability of the particular structure at thedesired site.

7.3 CHOICE OF TOWER

GUYED TOWER

For this project, the guyed tower best matches the specification, and shows the best

compromise between strength, ease of installation, cost and appearance. Th e guyed towersmain disadvantage is that the foot-print area is large compared to that of a freestanding tower.However, as the wind turbine is only required to be 5m above the ground, this is not a majorissue. A tilt up system will be the best way to install this tower.

7.4 GUYED TOWER DESIGN


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7.4.2 ASSEMBLY METHOD1. Assemble the wind turbine on the ground.2. Attach a gin pole perpendicular to the base of the tower.3. Mount the towers base plate onto the foundation and attach the tower to the base plate

with a hinge.4. Erect the tower by attaching a towing wire to the gin pole.5. When the tower is vertical, attach the guy wires to the foundation.6. Fix all foundation connections.

7.4.3 ANALYSIS &DESIGN

In order to design the tower for the turbine, it is very important to calculate the forces thatwill be acting on the tower as accurately as possible. The following information is in accordancewith

(EN 1991) Eur ocode 1 Actions. (See Annex 2.1)

The tower must resist the following actions:

= 4,10

= 2,780 2 = 1,5


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uplift. The strength of the base plate and the welds is checked in see annex C, chapter 4 - towercalculation);

220 mm sqr. x 10mm thick base plate with full profile 6mm fillet weld to column. 4 No M24grade 4.6 x 200 mm long cast-in holding down bolts.

The tower will also have a flange welded to the top of it, so that the yaw and furling

system has a surface to be bolted to tower. The strength of this connection needs to be strongenough to resist the drag forces on the tail of the furling system, and the tension this causes inthe bolts.

7.5 FOUNDATIONThe design of foundations often causes confusion. Ground bearing pressures are usually given as

safe bearing pressures that is, serviceability pressures. [12]


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made so deep that there is no need for reinforcement. This is called a mass concrete base, and is normallythe most inexpensive foundation option available.

7.5.1.2 RAFT FOUNDATIONS

Raft foundations are ideal for foundations carrying more than one column. An appropriate methodfor analysing the interaction between the ground and the raft needs to be selected, and thinner, moreflexible rafts often require finite element analysis.

7.5.1.3 PILED FOUNDATIONS

The pile design fore piled foundation needs to be carried out by a qualified piling contractor.However, the structural engineer needs to design the pile cap. A pile cap can be modelled as a beam in

bending or as a truss. Using these analogies, the amount of reinforcement required in the pile cap can becalculated.

7.5.2 MOST SUITABLE FOUNDATION

Spread foundations are the cheapest and easiest type of foundation to construct, and mass concretefoundations require the least amount of labour too. For these reasons, a spread foundation would be bestsuited for the wind turbine.

7.5.3 DESIGN CONSIDERATIONS FOR SPREAD FOUNDATIONThe maximum ( unfactored ) pressure below the base must not exceed the bearing resistance of the

soil. The effects of any moments or eccentricity of axial load on the base must be accounted for.

If th t i it i t th L/6 th lt t f th b li t id th iddl thi d f


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For a mass concrete base, the foundation must be made deep enough so that there is no needfor reinforcement;

If the 45 line passes through the side of the base, no reinforcement is required. If this linepasses through the bottom of the base, the concrete must be reinforced according to EN 1992-1.1.

GUY WIRES

For the design of the guy wires foundations, special considerations need to made to account forthe fact that soil has no resistance to tensile stresses.

45


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MAJOR REFERENCE BOOKS:

[1] - Pitch-Controlled Variable Speed Wind Turbine Generation February 2000 . NREL/CP-500-27143

[2]- Basics_2010_Fluid Mechanics Course

[3]-Wind Turbines - Fluid Mechanics Compendium

[4]- Guidelines For Design Of Wind Turbines A Publication From Dnv/Ris

[4]-Bonus Wind Turbines Publication 1999

[5]- Evaluation of Airfoils for Small Wind Turbines

[6]- Theoretical Aerodynamic Analyses Of Six Airfoils For Use On Small Wind Turbines

[7]- Wind Turbine Post-Stall Airfoil Performance Characteristics Guidelines for Blade-Element Momentum Methods

[8] -Gear Design Handbook Second Edition

[9]- Wind Turbines: Fundamentals, Technologies, Application, Economics. Berlin: Springer,2006


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I.INITIAL CALCULATIONS

The following chapter explains the methodology for calculating the fundamental aspects ofour wind turbine.

First of all, it was necessary choose a reference parameter to start the calculations.

The following chart shows the optimal tip speed ratio of the different types of wind turbine.As our wind turbine is a HAWT, the optimal tip speed ratio is X =7.


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Secondly, it was necessary calculate the diameter of the rotor in order to calculate geometric

aspects of the wind. Using the optimal power with Betz formula, at the wind speed of 6m/s, theswept area of the rotor was calculated, and with this value the radius of the rotor could beobtained.

=

=

0.37 0.95= 554

= 0.37 = 0.95

=1627

12

3

= 6 , = 1,225 2


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( )

= = 6 = 6

Once the diameter of the rotor and the gear transmission was obtained, a spreadsheet

containing the following calculations was completed;

= 2 2 4 ( )2 , = 6 /


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= 12 3

=

2

4 ( 2 )

=1627

= 1,225 2 ( / )

= : Mechanical efficiency, mainly determined by losses in the gearbox. Can be taken as 0,85.


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From this data, we can establish a mathematical relationship between the generators RPMand its efficiency.

Figure : Efficiency of the Generator According to RPM

To simplify this process, we can model the curve as 2 straight lines:

1500 0 075 71 917

0

5

10

15

20

25

30

35

40

45

0 1000 2000 3000 4000 5000 6000 7000 8000

e t a

( % )

n(rpm)


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Figure : Power Curve

.00

100.00

200.00

300.00

400.00

500.00

600.00

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

P ( v )

[ W ]

Wind Speed at hub height, V [m/s]

Power Curve


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Figure : Annual Production/Energy Production Curve

0

200

400

600

800

1000

1200

1400

1600

18002000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

E n e r g y

, E ( k W

h )

Wind Speed at hub height, V [m/s]

Annual Production


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12 M/S


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55 m/s


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2. GEARBOX CALCULATIONS

GEAR PARTSTERMS SYMBOL

Module M Pitch P

Pitch Circle Dp Outside Circle De Base Circle Db Root Circle Di Circular thickness e Teeth distance c Addendum a Dedendum b Number of teeth Z Face width W Fillet R

FF Figure : table with terms and symbols of the gear parts


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FIRST PAIR OF GEARS, TRANSMISSION RATIO 1:3

GEAR

= 2 = 75 = = 2 = 6.283

= = 75 6.283 = 150

= + 2 = 150 + 2 2 = 154


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PINION

= 2 = 25 = = 2 = 6.283

= = 25 6.283 = 50


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SECOND PAIR OF GEARS, TRANSMISSION RATIO 1:2

GEAR

= 2 = 50 = = 2 = 6.283

= = 50 6.283 = 100

= + 2 = 100 + 2 2 = 104


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FORCES

The spur gear transmission force which is normal to the tooth surface can be resolved into atangential component and a radial component .

= =

There will be no axial force,

.

Figure : diagram of forces in the gear tooth.Reference : Mechanical Engineers- Roger Timings


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In the next pages, there are the calculations of the forces at two wind speeds, reference and

maximum operating wind speed. The forces have been calculated in the driven gear because them aretransmitting to the other gear in the pair.

GEARS FORCES, FIRST PAIR OF GEAR TRANSMISSION RATIO 1:3

= 12 = 37.74 = 150 = 20

2 =2000

=2000 37.74

150= 503.2

2 =

1 = 503.2 tan 20 = 183.14

2 = 2 2 + 2 2 = 503.2 2 + 183.14 2 = 535.49


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Figure : forces ratio in a gear systemReference : Mechanical Engineers- Roger Timings

GEARS FORCES, TRANSMISSION RATIO 1:2

= 12 = 37.74 50 20


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For calculate the forces in the second gear, the tangential component of the drive gear 1 , is equal

to the driven gear's tangential component 2 but the directions are opposite. Is the same idea that inthe first pair 1:3.

STRENGTH CALCULATIONS

This section contains the calculations of stresses required to determine the thickness of the gears.The gears have to resist the torque in the maximum operating wind speed but we decided also tocalculate the gears in the reference wind speed.

The reason is that in our region, the wind speed average is 6m/s, and wind speeds of 20 m/s onlywould occur during very rare, extraordinary weather conditions. Although the average wind speed is6m/s, we choose 12 m/s at reference wind speed to have a safety margin. Then we have two types ofgears, there are ones designed with the maximum operating speed of 20m/s where the torque is high

and the width of the gears is too large, and others designed with the reference wind speed of 12m/swhere the ratio width-size is better and are the gears that we are using in the project.

For the strength calculations is used the Lewis Formula:

=


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=

( )

= = To calculate the Velocity Factor:

=

2

Where:

= ( ) = ( )

=6.1 +

6.1

= ( ) In the following pages there are calculations for the two pairs of gears. The gear that is called

critical is the gear with more tangential force and small size that the reason why this gear is going to


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= 0.43

= 20

=

=

2.45 503.220 2 0 .43

= 71.67

255 = 1.25

, . 71.67

204

,

GEARS FORCES, TRANSMISSION RATIO 1:2

.

= 12 =

2000 =

2000 37.7450

= 1509.6

3 1: 3


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.

= 20 =

2000 =

2000 104.8350

= 4193.2

3 1: 3

= 2 60 = 2 1605

60 = 168

=2

=0.05 168

2= 4.2

=6.1 +

6.1=

6.1 + 4.2

6.1= 1.68

. = 25 = = 20 = 0.33

= 20 255 = 1 25


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3. SHAFT CALCULATIONSAttention : In this chapter you will find only the way of calculation. For detailed calculations andresults you should check SHAFT EXCEL CALCULTION starting at page 125.

3.1 PREDIMENSION OF THE SHAFTS

Make FBD Determinate the distribution of the forces and moments in the shaft Calculate a reference bending moment out of the bending moment and torsion

= ( 2 + 34 ( 0 2 ) =

=

0 = ,= 1 = 0 = 0,7 =


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Determine the flexibility of the parts

=1 + 1 + 2 (1 2 )

=1 + + 1 2 (1 2 )

= +

= = 0,3 = = 0,3 = = 210.000 2 = = 210.000 2 Calculate the smoothing of the surfaces when they get pressed together

= 0,8 +


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3.2 DYNAMIC CALCULATION

Bending:

You have to calculate the shaft for bending and then for Torsion. As a last step you put both results together to get the final dynamic safety.

Calculate the equivalent bending moment with the original moment and the servicefactor.

=

= =

To calculate the stresses you first need the section modulus of the shaft.=

32

3

= Now you can find the actual bending stress in the cross section

=


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Stepped shaft:

,

2,0

=

=

= 1 +

( 2,0 1) Fitting:

Now we have to find the

= 1 0,2log 157,5

20 1 =

7 5


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Now we can calculate the construction factor for bending by using all the calculatedks.

=

+

1

0

1

= ; = 1 Now we have to calculate the influence of to our shafts.

=

= = 0,00035

=

0,1

=1 +

As a last step we can calculate the dynamic safety for bending. That is of course notnecessary because we will calculate later the combined dynamic safety against

bending and torsion. This safety should be always bigger than 1,5.


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Now you can find the amplitude torsional stress in the cross section

=12

We also have to define the mean stress

=

Now you need to define the technological size factor for ultimate strength and yieldstrength. This is the factor reduce the allowable stress per area for big cross sections

because they have not a perfect homogeny mixture of material inside.

1 = 1 0,23log 100 1 With this k value you can now determine the value for this cross section out of thenormed values.

= 1 = 1

, = To find the right table for the notch factor you first have to decide if you have astepped shaft or a fitting on the place you want to calculate. That are two possibilitieswe can have. Then you can just look in the right table.


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=

= 1

0,2

log

7,5

20 1

With this we can now determinate the for our cross section.

= Now we calculate the geometrical size factor

= 1 0,2 log 7,520 1 The next k factor to calculate is the 0 which describe the influence of the surface

roughness.0 = 0,575

0 + 0,425

Now we can calculate the construction factor for bending by using all the calculatedks.

= + 10 1 1


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FINAL SAFETY FOR BENDING AND TORSION

As a very last step we will now combine results from the previous calculations to thecalculation of the final dynamic safety for bending and torsion.

As a first step we have to calculate a reference sigma stress out of the bending andtorsion stresses.

= 2 + 3 2 Now we have to determine a reference allowable sigma stress.=

1 +

The last step of the shaft calculation is the calculation of the final safety out of thisreference stress.

=1


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: Eurocode partial safety factor for permanent loads , = 1,35

= 4,10

Variable Actions

Calculation of simplified wind pressure for insignificant orthography according to EN1991;

= ,0 : The basic 10 minute mean wind velocity,

,0 : The characteristic 10 minute mean wind velocity, (design for 55ms -1)

& : Correlation factors; can be conservatively taken as 1,0,

: Altitude factor. This may conservatively be taken as = 1 + 0,001 , where A isthe site altitude. As the turbine is intended to be located mainly in coastal regions, is negligible.

= 55 1

=2 2

: Basic wind velocity pressure,

: Density of air = 1 225 kgm -3


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For the design of this tower, this pressure distribution can be conservatively estimated as beinguniformly distributed along the length of the tower.

h > 2b

b

h

b

b

( )hq p

( )e p z q

( )bq p z e


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FREE BODY DIAGRAM

4.2 DESIGN OF COLUMN (FULL INTERACTION CHECK)

For class 1 2 and 3 hollo sections the follo ing interaction check m st be satisfied:


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As both transverse forces are from the wind, we can assume their direction to be the same.

Therefore, , = 0.

The interaction check is now,

,

, ,+

,

, , 1.0

Check the resistance of the column for the attached load.

As the tower will be subject to a changing load direction, it makes sense to use a circular crosssection, which is equally strong and aerodynamic in all directions

Section Properties for 168 3x10 Circular Hollow Section :


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Slenderness:

For circular section, = 1, ( < 1 ,2)

=10000

56,193,91 = 1,898

= 10 , (< 100 )

= 235

;


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4,10253,056

+4,6729,471 1.0

0,016 + 0,493

1.0

, . Check of Stresses:

< + , , < 2351,1 41004970

+4672000186000

root^3((32*Mref)/(pi*sigmaballow)) 15,04410862mmsigmaballow= 82 N/mm^2

THIRD SHAFT CALCULATIONS


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summM(A)=0Fa*x1-Fr*(x1+x2)-Bz*(x1+x2+x3)=0Bz=(Fa*x1-Fr*(x1+x2))/(x1+x2+x3)=-54,6006 NsummFz=0Az-Fa+Fr+Bz=0Az=Fa-Fr-Bz= 166,602N


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d(gear)= 50,00mmratio2= 2,00

summFx=0Ax=0 and Bx=0summFy=0Ay=0 and By=0

summM(A)=0Bz*x2+Fr*(x2+x3)=0


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CALCULATIONS OF THE FITTINGS


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FIRST SHAFT


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THIRD SHAFT


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FOURTH SHAFT


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8.BEARINGS SKF CALCULATIONS

BEARING 1


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BEARING 3


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BEARING 7


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BEARING 7


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7

9

10

81 BEARING 19

1 TOWER SHAFT 18

1 BREAK DISK 17

1 BEARING HOUSE 16

1 COUPLNG ASSEMBLY 15

1 GEARBOX ASSEMBLY 14


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A

1

2

3

4

5

611

12

13

A

SCALE (1 : 10)

141516

18 19 20

1 CRANK 13

1 NACELLE BASE 12

1 HUB 11

1 BLADES 10

3 NACELLE 9

1 TAIL PIVOT 8

1 TAIL BOOM 7

1 TAIL VANE 6

1 MOUNTING FLANGE 5

1 MOUNTING BRAKETS 4

1 STEEL TUBE TOWER 3

3 GUY WIRE 2

1 FOUNDATION 1

QTY. Description Item no.

1:100Ingenirhjskolen i rhusDepartment of Mechanical EngineeringEngineering College of Aarhus

Qty. Item Item no. Drawing no. Material / Model no.Scale: Group ID: Date:

Student ID: Initial:

Drawing no.:Description:

WIND TURBINE MAJOR COMPONENTS 1ASM-2011B

IY11219 DMV

8.12.2011GROUP 2

SolidWorks Student Edition. For Academic Use Only.

16 ELASTOMER

15 COUPLING FITING

14 MAIN BEARINGS

13 MAIN SHAFT

12 BRAKING DISK

11 BACK HUB COVER SCREWS


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1

2

3

4

5

6 7 8

9

11

1413 16

12

10

15 15

10 BRAKE MOUNTING SCREWS

9 BREAKING SYSTEM

8 BACK HUB COVER

7 WASHER

6 HEX NUT

5 BLADE S822 x 3

4 BASE PLATE FOR THE BLADES

3 BLADE MOUNTING SCREW

2 HUB COVE R

1 HUB COVER MONTING SCREW

Itemno. Description

1:5Ingenirhjskolen i rhusDepartment of Mechanical EngineeringEngineering College of Aarhus




ROTOR ASSEMBLY 1ASEM-2011

IY11219 DMV

24.11.2011GROUP 2



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TABLE OF CONTENT

13 HEX NUTS

12 MOUNTING SCREW

11 OUTPUT SHAFT

10 BEARINGS

9 SECONDARY PINION


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2

12

34

13

106

7

1

8

11

9

10

5

2ASSEM-2011GEARBOX ASSEMBLY

8 SECONDARY GEAR

7 INTERMEDIATE SHAFT

6 MAIN PINION

5 MAIN GEAR

4 MAIN INPUT SHAFT

3 MAIN BEARING PAIR

2 GEARBOX COVER

1 GEARBOX HOUSING

Item no. Description

DMVIY11219

GROUP 2 22.11.20111:2

Ingenirhjskolen i rhusDepartment of Mechanical EngineeringEngineering College of Aarhus



Drawing no.:Description:SolidWorks Student Edition. For Academic Use Only.

3 12

1 3 ELASTOMER PART

1 2 COUPLING PART 1

1 1 COUPLING PART 2

QTY. Item no. Description


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3 12

COUPLING 1 ASSEM3-2011

IY121191:2




Drawing no.:Description:DMV

22.11.2011GROUP 2



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3X 9

121 77

221

B B

30

R162

A

8

22.40R40

A-A


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R168.79 121.77

452 4 1

R 1 7 2

R90.17

R100

A

2 1

. 4

10

R5

A A

R 1 0

10221

B-B

DMVIY11219

GROUP 2 22-11-111:5

BACK COVER 2D-2011


Qty. Item

1

Item no. Drawing no. Material / Model no.

1 2D-2011 PLASTIC

Scale: Group ID: Date:



1


12 X 11 266.86

266.86

3 X M10x1.0 20 D


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3 2 0

A A

4 6

. 5 0

4 X 45 90

4530

3

4 X 45

A-A

3 6

30 D

3 X 45

106.50

D-D

MDVIY11219

Group 2 22-11-111:5

Mounting plate for the Blades 3D-2011


Qty. Item

1Item no. Drawing no. Material / Model no.

1 3D-2011 Steel




1


2 X 45

Note:

1) Deburr sharp edges aprox 0.5 x 45

2)All nudges should have a min radi of 0.5

3) All surfaces finished atRz 25

Unless otherwise specified

GENERAL TOLERANCES (FREE SIZE TOLERANCE)

PER DIN - 7148-mL INEAR DEVIAT ION ANGUL AR DEVIAT ION

0.5UP TO

6

6UP TO

30

30UP TO

120

120UP TO

400UP TO

10

10UP TO

50

50UP TO

120

120UP TO

400

0.1 0.2 0.3 0.5 1 30 20 10

ABOVE 400 mm SEE DIN 7148-m


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2 0 0

6 0

5 0

k 6

+ + 0

. 0 2

0

4 5

s 6

+ + 0

. 0 6

0 . 0

4

R22 X 45

165

185

230

10

45

65

105

2 X 45

4 5

5 0

6 0

1 4

5 0

k 6

+ + 0 . 0 2

0

R10

R 1 0

gridingRz 2.5

gridingRz 6.3

gridingRz 6.3

0.01

0.01 B

0.3 A

A

B

DMVIY11219

GROUP2 24-11-111:2

MAIN ROTOR SHAFT 1SH-2011


Qty. Item

1

Item no. Drawing no. Material / Model no.

1 1SH-2011 STEEL




1


gridingRz 6.3

Note:

1) Deburr sharp edges aprox 0.5 x 45

2)All nudges should have a min radi of 0.5

3) All surfaces finished atRz 25

Unless otherwise specified

GENERAL TOLERANCES (FREE SIZE TOLERANCE)

wind turbine project group2

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