Final Year Project - OWC Simulator

8/11/2019 Final Year Project - OWC Simulator

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SCHOOL OF INFORMATICS AND E NGINEERING

A BENCH-SCALE BLAST-BOX DEMONSTRATOR FOR DATA ACQUISITIONSYSTEM

by

Bruno Pereira Franco

Student of Automation Engineering at Universidade Federal do Rio Grande (FURG)Cincia sem Fronteiras / Science Without Borders

Bolsista da CAPES Proc. N CsF 88888.027597/2013-00 / Scholarship by CAPES Proc. N CsF 88888.027597/2013-00

CAPES Foundation, Ministry of Education of Brazil, Brasilia DF, Zip Code70.040-020, Brazil.

A report submitted in partial fulfillment of therequirements for the degree

BACHELOR OF E NGINEERING (HONOURS ) IN MECHATRONICS

SUPERVISOR : G ARRET BRADY SUBMISSION DATE : 01/05/2014


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BRUNO P EREIRA F RANCO BACHELOR OF E NGINEERING (HONOURS ) IN MECHATRONICS 01/05/2014

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ABSTRACT

The main objective of this project is to build a bench-scale blast box for a data

acquisition system. The blast-box basically consists in box that serves to generate

airflows in its interior. It will work with a turbine and a generator, to simulate the work ofan OWC renewable energy converter. The data acquisition will be held using the

National Instrument hardware, the NI-USB 6008, which will send the data for the NI

LabView. The project consists of 4 main parts, first is the building of the blast-box,

second is the design and 3d printing a turbine, third is the choice of a generator and forth

the implementation of the data acquisition system.


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DECLARATION

The work subm itted in this report is the results of the candidates own investigations and

has not been submitted for any other award. Where use has been made of the work ofother people it has been fully acknowledged and referenced.

Student Name

______________


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TABLE OF CONTENTS

ABSTRACT ...................................................................................................................................... i

TABLE OF CONTENTS ................................................................................................................ iii

LIST OF ABBREVIATIONS .......................................................................................................... v

LIST OF FIGURES ........................................................................................................................ vi

LIST OF TABLES ........................................................................................................................ viii

Chapter 1 Introduction ..................................................................................................................... 1

1.1 Problem ................................................................................................................................. 1

1.2 Background ........................................................................................................................... 2

1.3 Scope and Objectives ............................................................................................................ 3

1.4 Document Overview ............................................................................................................. 3

Chapter 2 Literature Review ............................................................................................................ 5

Chapter 3 Materials and Methods .................................................................................................... 8

3.1 Blast-Box .............................................................................................................................. 8

The blast box, as previously stated in this report, will be responsible for the OWC functions. Itwill generate an expansive and a compressive airflow that will drives a bi-directional turbine. 8

3.1.1 Piston ............................................................................................................................ 8

In an OWC device, the waves oscillatory movement has the task of pump the air in thechamber, however in the blast-box of the project this task will be done by a piston. In someexperiments with OWCs tests rigs (Nader & Sajadian, 2011) had been used a motor to drivethe piston, which is really useful to control the velocity of the airflow, however it loses theidea of a bench- scale project and wouldnt be so educational as well. In contrast, the project

piston will work in and out by hand. .......................................................................................... 8

3.1.2 Geometry of the blast-box ............................................................................................ 9

3.1.3 Building the Blast-Box ............................................................................................... 12

3.2 Turbine ................................................................................................................................ 13

3.2.1 Turbine Requirements ................................................................................................ 13

3.2.2 Turbine Draft .............................................................................................................. 14

3.2.3 3D Printing Process .................................................................................................... 18

3.3 Generator: ........................................................................................................................... 19

3.3.1 Mounting the turbo-generator system......................................................................... 25 3.3.2 Turbo-generator system into the turbine pipe ............................................................. 26

3.3.3 Rig Test ...................................................................................................................... 27

3.4 Data acquisition System ..................................................................................................... 29

3.4.1 Equipment Description ............................................................................................... 29

3.4.2 Data acquisition Experiments ..................................................................................... 29


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3.4.3 Execution of the experiments ..................................................................................... 40

Chapter 4 Results and Discussion .................................................................................................. 41

4.1 DA1 Results and Discussion .............................................................................................. 41

4.2 DA2 Results and Discussion .............................................................................................. 43

Chapter 5 Conclusions and Recommendations .............................................................................. 46 5.1 Conclusion .......................................................................................................................... 46

5.1.1 In relation to the project itself..................................................................................... 46

5.1.2 In relation to the area of study .................................................................................... 46

Chapter 6 Bibliography .................................................................................................................. 47

Appendix A Other material ............................................................................................................ 48


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LIST OF ABBREVIATIONS

WEC Wave energy converterNACA National Advisory Committee for AeronauticsOWC Oscillating water column

NI National Instruments

Mechanical Power Mechanical Rotational Power Pneumatic Power

Electrical PowerF Force

Piston velocityD Turbine Diameter

Hub Diameter Armature Resistance Back-Emf constant Angular Velocity Flow Rate Torque Pressure Drop

V Load VoltageIa Current in the generator

Pressure Coefficient Flow Rate CoefficientA Piston AreaL Piston side

Hub-tip-ratio Hub perimeter

Blade widtht Thickness ratio

Ea Emf voltage Resistor n

Vn Voltage n

%V Percentage of the load voltage Load total resistance Current n


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LIST OF FIGURES

Figure 1 Main idea of the OWC and the bench-scale blast box ....................................................... 2

Figure 2 Modified Nader Dizadji , Seyed Ehsan Sajadian. Modeling and optimization of thechamber of OWC system. Energy Volume 36, Issue 5 2011 2360 2366.

http://dx.doi.org/10.1016/j.energy.2011.01.010 .............................................................................. 5 Figure 3 Wells Turbine (Raghunathan, 1995) ................................................................................. 6

Figure 4 Airfoil Drafts (Thakker & Abdulhadi, 2007) .................................................................... 7

Figure 5 Blast Box Model ................................................................................................................ 9

Figure 6 Project Blast-box model .................................................................................................. 10

Figure 7 Part of the Turbine Design Spreadsheet (Brady, 2013) ................................................... 10

Figure 8 Blast-box draft and measures .......................................................................................... 12

Figure 9 Piston draft and measures ................................................................................................ 12

Figure 10 Blast-Box Material ........................................................................................................ 13

Figure 11 Turbine with its respective measures ............................................................................. 15

Figure 12 NACA021 Thickness X Position graph ......................................................................... 16

Figure 13 Thickness X Position graph for the project blade width................................................ 17

Figure 14 Cylinder object: 3d view (left) and top view (right). ..................................................... 17

Figure 15 Airfoil NACA0021 Blade made in Blender .................................................................. 18

Figure 16 Printed turbines in the 3-D Printer ................................................................................. 18

Figure 17 Printed turbines in the 3D Printer Oven ........................................................................ 19

Figure 18 Basic generator circuit ................................................................................................... 20

Figure 19 Multimeter plugged in the motor that is fixed in the lathe machine .............................. 22

Figure 20 Getting the angular coefficient with the Excel .............................................................. 23

Figure 21 DC motor found in the mechatronics laboratory ........................................................... 24

Figure 22 Screw hub piece with measures ..................................................................................... 25

Figure 23 Turbo-Generator system. ............................................................................................... 26

Figure 24 Metal structure to hold the turbo-generator system. ...................................................... 26

Figure 25 Turbine inside the tube .................................................................................................. 27

Figure 26 Blast-box prepared for the first test ............................................................................... 27

Figure 27 Piston Movement in the blast-box - with the added paper in the structure ................... 28

Figure 28 Finished Rig................................................................................................................... 28

Figure 29 DA1 test circuit .............................................................................................................. 30

Figure 30 DA1 LabView block diagram........................................................................................ 31

Figure 31 Voltage Input Setup of DAQ Assistant (From NI LabView Software) ......................... 31

Figure 32 Input Voltage Electric Diagram (From the NI LabView software) ............................... 32


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Figure 33 Current Input Setup of DAQ Assistant (From NI LabView Software) ......................... 33

Figure 34 Figure 25 Input Current Electric Diagram (From the NI LabView software) ............... 34

Figure 35 VI Front Panel ............................................................................................................... 36

Figure 36 Physic Circuit for DA1 .................................................................................................. 37

Figure 37 DA2 Test Circuit ........................................................................................................... 38 Figure 38 DA2 LabView Block Diagram ...................................................................................... 39

Figure 39 Voltages Chart from DA1.............................................................................................. 41

Figure 40 Power Load graph in the left and Current Graph in the right from DA1 ...................... 42

Figure 41Voltages graph from DA2 .............................................................................................. 43

Figure 42 Power Load graph in the left and Current Graph in the right from DA2 ..................... 44


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LIST OF TABLES

Table 1Allowed flow rate values ................................................................................................... 11

Table 2 NACA021 Thickness Distribution .................................................................................... 16

Table 3 Thickness Distribution in the project blade width ............................................................ 16

Table 4 Results of the generators attributes experiment. ............................................................... 22

Table 5 Calculated information about the motors .......................................................................... 23

Table 6 Motor main properties ...................................................................................................... 24

Table 7 Estimated Values for DA1 ................................................................................................ 30

Table 8 Estimated Results For DA2 .............................................................................................. 39

Table 9 Results From DA1 ............................................................................................................ 41

Table 10 Results from DA2 ........................................................................................................... 43


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Chapter 1 Introduction

1.1 Problem

In this project, the main problem is to collect data from the blast-box, which will simulate

an oscillating water column (OWC) wave-generating plant. The oscillating water column

device is an offshore form of renewable energy, which uses the motion of ocean waves to

produce clean energy (Figure 1 Main idea of the OWC and the bench-scale blast box

) .

OWCs are usually installed on the coast and consist of an air chamber in which

the front wall has an aperture that lets the waves enter. Wave action causes the water

level in the air chamber to go up and down. Thus, the air in the chamber is propelled

through an air turbine. When the wave recedes, causing a fall in pressure, the air flows in

the opposite direction through the turbine.

This turbine have a unidirectional rotate movement, which is possible due to the

habitual use of Wells turbines, a specific type of turbine that is also analyzed in this work.

The angular velocity and the torque produced by the turbine makes it possible to drive a

generator that transforms the mechanical energy from the turbine into electrical energy.

A blast box is one popular way of demonstrating the OWCs. A pipe or box isopen at one end and is stopped by a piston, which can be worked in and out by hand,

pushing and pulling air through an orifice at the other end, in which a turbo-generator

system sits. The objective is to capture data to calculate the different power

transformations in the rig. And in the end compare this data and check the performance of

the rig.


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Figure 1 Main idea of the OWC and the bench-scale blast box

1.2 Background

At a time when the consumption of electricity has increased, and that a

progressive general awareness of the environmental impacts of fossil fuel use arises, it

becomes imperative a bet on clean energy sources, sustainably produced. Thus,

investment in renewable energy has been gaining momentum, driven by European

directives stipulate that an incorporation of renewable energy from the electrical system.

Currently, renewable energy sources with higher capacity are hydro, wind and

photovoltaic origin. Besides those mentioned there is another with great potential for

exploitation of wave energy. In recent years, wave energy has gone through a cyclical

process with good and a bad phase reflects the great difficulty is to obtain a feasible

solution.

OWC-type wave energy plants have been a subject of international research for a

number of years, and no single technology has yet emerged as a clear winner from the

hundreds of projects going on internationally. A notable example is the Pico Wave Plant

(http://www.pico-owc.net/), an experimental wave plant built in 1992 as the European

Wave Energy Pilot Plant, co-funded by the EC, in order to demonstrate the technical

viability of wave energy in a small Island grid


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1.3 Scope and Objectives

This project is about to build a functional rig, that simulate an OWC device, and

extract data from it. It is not a project about mechanical equations or thermodynamic

analyses, therefore, some approximations, with the respect in these areas, were made inthe project.

The requirements of the project are:

1. Input Mechanical Power 40W

a. Input Force

b. Input velocity

2. Output Electrical Power 8W

a. Generator must be chosen following this eq:

3. Turbine rotational speed = 3000 rpm

4. Tube diameter D = 0,15m

5. Measure the power in each stage of the project

a. Mechanical Power Pmec = v x F

b. Pneumatic Power P pneu = Q x p

c. Rotational Power P rot = w x T

d. Electrical Power P l = V x I

1.4 Document Overview

Chapter 2 (Literature Review): This chapter presents some previous works that were

highlighted for their contribution in the project. Specifically, it bring some information

about the turbines and OWCs previous studies (which were the newest areas in the

project development)

Chapter 3 (Methods and Calculations): This chapter was divided in 4 parts, the blast-box

building, the turbine design and printing, the generator choice and the data acquisition


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system. Each one of these parts was fulfilled with a great amount of information and

details.

Chapter 4 (Results and Discussions): This chapter brings the results from the data

acquisition experiments that were made in the chapter 3. Also, discuss the validation ofthese results and their meaning for the entire project

Chapter 5 (Conclusion): This chapter shows what was learned in the project, and what the

main conclusion of doing this project is.


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Chapter 2 Literature Review

Lots of research has been done since the 70s on OWC type WECs. Studies had

already been done in relation of the geometry of the air chamber, (Kosow, 1991), and it

proved that choosing the right geometry it is possible to find a better conversion from

wave energy to pneumatic energy (with less energy loss). The studies had been made

changing the angle of the back and the front plates of the chamber, the length of the top

side of the chamber, the time that was measured (as when the compression as during the

expansion), the positing of the outflow air tube and the height and the length of the wave.

It was found a geometry that proves to have the best efficiency, Figure 2.

Figure 2 Modified Nader Dizadji , Seyed Ehsan Sajadian. Modeling and

optimization of the chamber of OWC system. Energy Volume 36, Issue 5 2011 2360

2366. http://dx.doi.org/10.1016/j.energy.2011.01.010

Central to the performance of an OWC WEC is the turbine. Since OWC was

created there are no total certainties about which turbine it must be used. Recent studies

(Setoguchi & Takao, 2012) compare the efficiency of some kinds of turbine in an OWC

plant. If the plant uses a conventional turbine, it must have a system of non-return valves

for rectifying the airflow. These valves will produce a unidirectional flow that allows the

work of the conventional turbines. Even if this system been functional it is not good at

all, because for a large scale plant the valves system turn to be too expensive, with

difficult implementation and with a complicated maintenance. For a system without non-


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return valves a self-rectifying air turbine can be used. This type of turbine will have a

unidirectional rotation independent of the airflow directions. Five types of those turbines

were compared: wells turbine, impulse turbines, radial turbines, cross-flow turbines and

Savonius turbines (Setoguchi & Takao, 2012). The studies show that the impulse turbine

has a superior performance under irregular flow conditions. However the Wells turbine is

more simple and cheapest for those applications, without loose too much performance.

According to Raghunathan (Raghunathan, 1995) the wells turbine has the

capability of rotate in the same direction regardless of the air flow direction. The blades

are symmetrical and they are arranged with a 0 angle in relation with the rotation plane.

The relative air velocity, W, creates forces in the blade thats depends of the incidence

angle, . One of these forces is the lift force, L, normal to W, and the other is the drag

force, D, that is parallel to W. These two forces can be expressed as coefficients of atangential force, F 0, and an axial force, F x. In a irregular bi-directional airflow the

directions and the magnitudes of L and D change a lot, however the direction of F 0

remains the same. This factor gives to the Wells Turbine the property of being self-

rectifying, i.e. regardless of the direction of the air flow, the direction of rotation of the

turbine remains unchanged. What makes the Wells turbine an ideal turbine for the OWCs

plants.

Figure 3 Wells Turbine (Raghunathan, 1995)


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Chapter 3 Materials and Methods

For a more efficient planning of the experiment rig the work was divided in four

parts, the design of the blast box, the design of the turbine, the choice of the generator

and the data acquisition system. In chapter it will be analyzed each one of these parts.

3.1 Blast-Box

The blast box, as previously stated in this report, will be responsible for the OWC

functions. It will generate an expansive and a compressive airflow that will drives a bi-

directional turbine.

3.1.1 Piston

In an OWC device, the waves oscillatory movement has the task of pump the airin the chamber, however in the blast-box of the project this task will be done by a piston.

In some experiments with OWC s tests rigs (Nader & Sajadian, 2011) had been used a

motor to drive the piston, which is really useful to control the velocity of the airflow,

however it loses the idea of a bench- scale project and wouldnt be so educational as well.

In contrast, the project piston will work in and out by hand.

The minimum input mechanical power of the system should be 40W (from the

projects requirements). The mechanical power generated by the piston will be:

(3.1.1) (3.1.2)

(3.1.3)

The value of 40W was chosen for the mechanical power to be a fair value for a

normal person to drive the piston. To test if this value was appropriate, a simple

experiment had been done in the mechatronics laboratory:

1. A person hold, with one arm, a weight of 40 N;

2. The person moved the arm up and down in a distance of approximated 50cm;

3. Another person used a chronometer to count how long it would take to perform

the entire movement (up and down).


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The experiment had shown that a normal person could move a weight of 40N with

a speed higher than 1m/s. With these results, it would be possible to change the minimum

input mechanical power of the system for a higher value. Nevertheless, the value of 40W

was the right choice. It is necessary to consider the fault of precision of a hand driven

piston, and, the fatigue of a person who will have to drive the piston. It will be assumed

that the force and the velocity, which result in the mechanical power, are respectively

40N and 1m/s.

3.1.2 Geometry of the blast-box

The geometry of the blast box is important for the take advantage of pneumatic

power generated by the piston. There are already studies (Nader & Sajadian, 2011) that

show the best geometry for a rig. By following this best geometry model, it was possible

to design a new blast-box model, adapted for the use of a piston (instead of ocean waves).

Figure 5 Blast Box Model

The Figure 5 shows the design draft of the blast box. The piston will cover a

length of 50cm on the Piston Motion Area; the airflow generated will follow the way up

until find the turbine in a tube (which will be opened to the atmosphere). In this project,

the main attention is focused in the rig data acquisition; therefore, any complicated aspect

in the blast-box building would be discarded. The 30 inclination in the top part of the

blast-box will not be applied in the project (it would take too much of the project time to

build it). But the turbine tube in the top part of the blast-box will be maintained.


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(3.1.4)

(3.1.5)

This would be the relation of the pressure drop in the turbine and the flow rate, to get a pneumatic power of 40W. Using the turbine design spreadsheet a table was made to check what

value of the flow rate would suit the coefficient values to avoid the stalls conditions:

Flow Rate ) m/s Pressure Drop Pa Peak Pressure

Coefficient

Peak Flow Rate

Coefficient

0 0 - -

0.1 400 0.20 0.13

0.125 320 0.16 0.11

0.14 285.71 0.14 0.18

0.15 266.7 0.13 0.20

0.17 235.29 0.12 0.22

0.175 228.57 0.11 0.233

0.2 200 0.10 0.26

Table 1Allowed flow rate values

It is possible to determine that the flow rate value is between 0.14m/s and 0.17m/s. It is

possible to find the measures of the blast-box by considering the flow velocity equal to the piston

velocity (1m/s) and the flow area equals to the piston area:

(3.1.6) (3.1.7)

Choosing the value of 0.16m/s for the flow rate, and selecting a square shape for the

piston:


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The blast box will have the same square area in its width and depth. The blast box length

will be equal to the piston motion area (0.5m) plus the turbine tube diameter (0.16m).

Figure 8 Blast-box draft and measures

Figure 9 Piston draft and measures

3.1.3 Building the Blast-Box

The blast box was made by using:

1. 1.3m of Perspex;

2. 20 bended screw brackets;

3. PVC pipe, with diameter of 0.16m and a height of 0.2m;

4. A tool-handler was adapted for the piston;

5. Paper and cardboard;

Building Process:

1. The Perspex was cut in the laboratory cutting press machine;

2. Bended Screws brackets with 3mm screws were used to hold the structure;

3. In the top part, the Perspex was cut and lathed to be able to suit the turbine pipe;

4. The pipe was cut just after the turbo-generator system was complete;


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5. The piston was made by using less then 0,16m Perspex, and fulfilling the borders with

cardboard (by that way it would not causes interferences in the piston speed);

6. To hold the piston it was used a tool handler.

Figure 10 Blast-Box Material

3.2 Turbine

The turbine will be responsible to transform the pneumatic power generated by

the blast-box into rotational mechanical power.

3.2.1 Turbine Requirements

The requirements of the project affirm that the turbine should have an efficiency

at minimum 30%, different from a normal turbine which have a efficiency of 50%. In this

analyses there are some neglected factor, as viscosity, fluid flow behavior (analyses of

Reynolds number), turbulences, mechanical properties of the used material and also no

temperature analyses (which has some importance in a fluid analyze). That is why it is

not been considerate the value of 50% for the turbine efficiency.


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For a minimum pneumatic power of 40W:

(3.2.1) (3.2.2)

(3.2.3)

It was stated, in the requirements, that the minimum rotational speed of the

turbine must be 3000rpm or 314.16rads/s. With the values of the rotational power and the

angular velocity, it is possible to find out the value of the minimum torque generated by

the turbine by knowing that:

(3.2.4) (3.2.5)

(3.2.6)

(3.2.7)

3.2.2 Turbine Draft

The wells turbine was the chosen turbine type for this project, because of its

property of spin in the same direction in bidirectional airflow, and because of its buildsimplicity. Different than the impulse turbine, which works well in bidirectional airflow,

but is much more complicated and expensive to build (it would be necessary more project

time). The choice of the blade profile for the turbine was based in previous

works(Raghunathan, 1995)(Thakker & Abdulhadi, 2007). It was chosen the airfoil

NACA 0021, because it has already proved to be a good airfoil for small-scale

applications.

It is recommended the use of a hub-to-tip ratio of 0.6 (Raghunathan, 1995). Theturbine diameter would be 0.15m, that is a size capable to fit in a tube of 0,16m of

diameter (without touch the tube walls). The turbine would have eight blades. To find out

the blade width it is necessary to know the exactly hub perimeter and then divide it by the

number of blades:


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(3.2.8) (3.2.9)

(3.2.10)

(3.2.11) (3.2.12)

The blade width should be lower than 0.0353m, because it is good to have a

space, even with a very small size, between the blades. It was decided that the blade

width would be 0.034m. Therefore, the turbine has a distance of 0,001375m or 1.375mm

between each blade. Moreover, with the chosen hub-tip-ratio the blade length will be

0,03m. Now almost all the measurements of the turbine are described (Figure 11 Turbine

with its respective measures ).

Figure 11 Turbine with its respective measures

The only thing that is missing is the thickness distribution across the blade width,

and this is possible to know thanks to the NACA airfoil series number (in this case

NACA 0021). For the NACA four-digit series the first digit specifies the maximum

camber, the second indicates the position of the maximum camber and the last two digits

are the maximum thickness of the airfoil, all this number are in percentage to the blade


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width or the airfoil length. For the NACA0021 it is possible to see that there will be no

camber and that the thickness distribution in the blades width will be of 21%. It is

possible to calculate the thickness in each point of the blade width by using the following

formula, giver by the http://www.aerospaceweb.org/ (Scott, 2001):

(3.2.13)

This equation considers a blade width position from 0 to 1. For this interval of the

position and with the thickness ratio of 21% it was found the following draft for the

blade:

Position 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1Thickness 0 0,0819 0,1004 0,1050 0,1016 0,0926 0,0799 0,0641 0,0459 0,0253 0

Table 2 NACA021 Thickness Distribution

Figure 12 NACA021 Thickness X Position graph

It is necessary to multiply the entire table by 0.034 to find the thickness of the

blade with the current blade width (0.034m):

Position 0 0,0034 0,0068 0,0102 0,0136 0,017 0,0204 0,0238 0,0272 0,0306 0,034Thickness 0 0,0028 0,0034 0,0036 0,0035 0,0031 0,0027 0,0022 0,0016 0,0009 0

Table 3 Thickness Distribution in the project blade width

0

0,050,1

0,15

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 T

h i c k n e s s

Position

Blade Draft


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Figure 13 Thickness X Position graph for the project blade width

With the measurements and the airfoil draft, it is possible to draw the turbine in

3D software. The software used for this application was Blender, a free open source 3D

software that is useful for high number of applications, including modeling, rigging,

animation, simulation, rendering, compositing and motion tracking, even video editing

and game creation. In the software, a cylinder object was used to build the turbine blade.

In Figure 14 it is possible to see the 3d-view and the top-view of the cylinder. 32 vertices

can be seen from the top-view in the circular area of the cylinder. The position of each of

those 32 vertices were reorganized in a new position to fit the airfoil draft (Figure 15 ).

Figure 14 Cylinder object: 3d view (left) and top view (right).

0

0,002

0,004

0 0,005 0,01 0,015 0,02 0,025 0,03 T

h i c k n e s s

Position

Blade Draft for the project blade width


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Figure 15 Airfoil NACA0021 Blade made in Blender

3.2.3 3D Printing Process

After finish the design of one blade, the same design was copied 8 times. The 8

blades were adjusted in the turbine hub. The 3D turbine was exported to a .stl file format,

and then the turbine could be printed in the 3D-Printer.

Figure 16 Printed turbines in the 3-D Printer

In Figure 16 two turbines were printed in the InVision si 3-D PRINTER. It was

known that the printer could present some problems in the printing process, so 2 copies of


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the turbine would have a higher chance to got at least one good turbine. The two turbines

should then be put in the printer oven to remove the protective wax (Figure 17 ).

Figure 17 Printed turbines in the 3D Printer Oven

3.3 Generator:

The turbine will be connected in a generator shaft. With the spinning movement

of the turbine, the generator will produce an output electrical power. From the

eletromechanics conversion properties (Kosow, 1991) it is known that the relation

between the mechanical properties (torque and angular velocity) and the electrical

properties (voltage and current) is given by a known constant from the motor, or

generator. This constant can be called torque constant (when relates toque and current)

and back-Emf constant (when relates the Emf voltage with the angular velocity. The

following relations can be considerate:

(3.3.1) (3.3.2)

(3.3.3)

From section 3.2.1 is known the minimum angular velocity and the minimum

torque generated by the turbine. It is possible to state that:

(3.3.4)


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(3.3.5)

Figure 18 Basic generator circuit

In the circuit in Figure 18 Basic generator circuit is possible to find a relation

between the terminal voltage and the eletromotriz force, which is:

(3.3.6) (3.3.7)

From the project requirements is known that the minimum electrical power output

from the system must be 8 W. Considering that 12W of rotational power will arrive in a

generator with 70% of efficiency. By multiplying each side of equation 3.3.7 by the

current turns possible to see that the output power will be equal to:

(3.3.8) (3.3.9)

(3.3.10)

(3.3.11)

(3.3.12) (3.3.13)


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(3.3.14)

(3.3.15)

According these values it is possible to choose the generator that will fit in the

project, by just looking the values of its armature resistance and its back-emf constant.

No generator was bought for this project. In the begging of the tests there were

found just two motors available in the mechatronics laboratory and unfortunately there

was not any information about them there. The armature resistance of the motors was

found with a multimeter plugged in the motors terminals. The back-emf constant was

found by doing the following experiment with the motors:

1. The motor shaft was fixed in a lathe machine;

2. The motor was fixed to stop any movement;

3. The lathe machine was capable to produce velocities from 25rpm until

2500rpm;

4. The multimeter reader was plugged in the motor terminal (Figure 19 ):

a. With only the multimeter and none load resistor the measured

voltage in the motors terminal would be equal to its Emf voltage.


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Figure 19 Multimeter plugged in the motor that is fixed in the lathe machine

5. A table was created to save the information;

(rpm|rads/s) Ea(V) (rpm|rads/s) Ea(V)0 0 0 0 0 0

25 2,617994 0,04 40 4,18879 0,0445 4,712389 0,08 80 8,37758 0,0980 8,37758 0,14 125 13,08997 0,14

140 14,66077 0,25 260 27,22714 0,28470 49,21828 0,83 540 56,54867 0,58840 87,96459 1,50 1200 125,6637 1,26

1500 157,0796 2,69 1700 178,0236 1,852000 209,4395 3,55 2500 261,7994 2,57

Table 4 Results of the generators attributes experiment.

6. By knowing that the would be the angular coefficient

of the line from the graph

7. Used Microsoft Office Excel to create the graph and to find the angular

coefficient of the line:

a. Created a simple scatter graph;

b. Choose the line option Add Trendline;


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c. Select the linear and the display equation options;

d. The coefficient that is multiplying in the equation will be the

angular coefficient.

Figure 20 Getting the angular coefficient with the Excel

From these experiment was possible to extract the following information about

the motor:

Characteristics Motor 1 Motor 2Armature Resistance 12 15 Back-Emf Constant 0.017V/rads/s 0,0108V/rads/s

Table 5 Calculated information about the motors

Using the equation 3.3.15 to check if the motor would fit in the project:

Motor 1:

(3.3.16)

Motor 2:


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(3.3.17)

None of the motors would fit with project requirements. Therefore, in the last

building week a third motor was found in the mechatronics laboratory. The experiment to

find out the emf-back constant was not necessary in this motor because with the model

name (Figure 21 DC motor found in the mechatronics laboratoryFigure 21 ) it was possible to

find the datasheet in the fabricator seller website.

Figure 21 DC motor found in the mechatronics laboratory

Properties Units Motor CMax. Continuous Current A 0.22

Max. Recommended rpm 12000Max. Output Power W 3.8Back-EMF constant V/rads/s 2.6e-2Terminal Resistance ohm 61

Table 6 Motor main properties

The motor would not fit in the project as well, and this is possible to realize just by looking for the value of the maximum output power (3.8W), which it is not even a half

of the desired value (8W). By this stage of the project, it was noticed that the output

electrical power from the requirements would be reached.


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Motor C was the chosen one because it has the best performance and it has a

datasheet that can be helpful in the result analyses. A multimeter proved that the armature

resistance in motor C was 57.8 ohms instead of 61 ohms.

3.3.1 Mounting the turbo-generator systemA screw hub was created to fix the motor shaft in the turbine. It was made from a

small aluminum piece with a hollow in the centre.

Figure 22 Screw hub piece with measures

As it is possible to see in Figure 22 the length of the screw hub is 8cm, which was

perfect to fit in the turbine hub (9cm). Two 6mm screws were used to fix the screw hub

in the turbine, and two 1mm grub screws were used to fix the motor shaft in the middle of

the screw hub hollow (without touching the turbine).


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Figure 23 Turbo-Generator system.

3.3.2 Turbo-generator system into the turbine pipe

It was necessary to guarantee that the turbine would stay right in the center of the

pipe, in that wa y, the turbine would no hit the pipes walls while it spins. It was build a

structure that would go above the pipe and it would hold the turbine by squeezing the

generator (without damage its interior). It was used two bended metal plates and two

8mm screws with two nuts to create the structure. In Figure 25 it is possible to see that

there are no turbine blades touching the pipe.

Figure 24 Metal structure to hold the turbo-generator system.


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Figure 25 Turbine inside the tube

3.3.3 Rig Test

The first rig test was made by just plugging a multimeter in the motors terminal

wires and by pumping the blast-box with the hand-piston.

Figure 26 Blast-box prepared for the first test


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The maximum voltage output from this test was 10V, which it is not a bad result.

But it was possible to realize that a large amount of airflow was being lost by the small

spaces left in the construction of the blast-box, and that the piston was not so efficient (it

was dropping the airflow by its sides).

The efficiency of the blast-box was increased more than 150% by fulfilling all the

spaces with adhesive tape and by putting a normal flexible paper around the piston

(which would guarantee no airflow looses, and at the same time, it would not impose any

difficult in the piston movement). With these new changes in the blast-box, the maximum

voltage measured in the multimeter was around 25V.

Figure 27 Piston Movement in the blast-box - with the added paper in the structure

After these tests, the rig was finished. Now it would be necessary to take the data

from the rig.

Figure 28 Finished Rig


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3.4 Data acquisition System

3.4.1 Equipment Description

The NI USB 6008 was used to collect the data. This USB device can read

measurements from a variety of sensor, reading from analog or digital inputs, and can

generate signals outputs. The 6008 is a device from the National Instruments, and it

works with the NI LabView software. The LabView is a graphic programming language

created by National Instruments, and specially used for automation and measurements.

The VIs, the programs in Labview, are composed by the front panel (int erface) and the

block diagram (the graphic code of the program). For the NI-USB 6008 and the NI

LabView work together, the software driver NI-DAQmx must be installed in the

computer. The DAQmx turn available the communication between hardware andsoftware and add to the LabView new block diagrams corresponding to the NI-USB

measures devices.

The NI-USB 6008 can only measure voltages between -10V and 10V; It can only measure current between -10mA and 10mA;

3.4.2 Data acquisition Experiments

In the first moment the only available resistor for the project were ones with a

great resistance value (R1 = 10K ohms and R2 = 82K). Knowing that, the armature

resistance in Motor C is 57.8 ohms it is possible to realize that just a small percentage of

the total emf voltage would be dropped in the armature resistance. And that would be

necessary to put the resistors in series to measure the voltage from the lower one (R1) and

then multiplying the value of the relation between the resistances. This first data

acquisition would be called Data Experiment 1 (DA1).

Two lower resistance resistors (R1 = R2 = 120 ohms) were acquired for the

project, with the help of the other mechatronics students. The Data Experiment 2 (DA2)

was made using these two new resistors.

3.4.2.1 Data Experiment 1

3.4.2.2.3 Estimated Values


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Considering the follow circuit from Figure 29 , for the experiment 1:

Figure 29 DA1 test circuit

It is correct to state that:

(3.4.1)

However, considering the maximum Emf voltage as 25 V, the load voltage V

would probably be more than 10V, and the USB 6008 would not be capable to measure

it. In that case, the load voltage V will be measured in relation of its lower component

R2.

(3.4.2)

It is correct to affirm that:

(3.4.3)

(3.4.4)

By following the previous equations from section 3.3 and the equation 3.4.4, it is

possible to create a table predicting the results of this data collection:

Ea (V) Ia (A) V2(V) V(V) Pl(W)0 0 0 0 05 5,43E-05 0,543137 4,996661 0,000271

10 0,000109 1,086274 9,993322 0,00108615 0,000163 1,629411 14,98998 0,00244220 0,000217 2,172548 19,98664 0,00434225 0,000272 2,715685 24,9833 0,006785

Table 7 Estimated Values for DA1


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3.4.2.2.3 Data Coll ection

Figure 30 shows the block diagram that was built to make acquire and manipulate

the data from the NI-USB 6008.

Figure 30 DA1 LabView block diagram

The DAQ Assistant box guarantee the communication with the NI-USB

6008 to measure the current (Ia) and the voltage in the 10k ohms resistor

(V2). Configuring the DAQ Assistant:

o Setting the voltage measure properties:

Figure 31 Voltage Input Setup of DAQ Assistant (From NI LabView Software)


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Figure 31 shows the DAQ assistant window. There it is

possible to configure what would be measured ( the voltage

in the first case) and where it would make the

communication with the NI-USB 6008 (Physical channel

ai0);

In the time settings, in Figure 31 , the acquisition mode

defines how the measure will be capture in relation to the

time. The continuous samples mode was selected with the

intention of capture data until the user decide to stop. In

this same setting it is possible to choose the number of

samples to read and the rate of samples per second;

The terminal configuration defines how the measuringwires will be set (FIGURA Y):

Figure 32 Input Voltage Electric Diagram (From the NI LabView software)

In this case, the maximum predict voltage for V2 is

2.715V, so it is not necessary to make any changes in the

signal input range.


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o Setting the Current measures properties:

Figure 33 Current Input Setup of DAQ Assistant (From NI LabView Software)

There are only two small differences from the current

measures properties and the voltage measures properties.

In the current properties is necessary to give the value of

the resistance. The current will be measured in the load

resistor (Rl=92k ohms).

The current will be measured using the physical channel

ai2 (Figure 34 )


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Figure 34 Figure 25 Input Current Electric Diagram (From the NI LabView software)

In each 0.05 (rate of 20Hz) seconds the DAQ assistant will collect the two

data signals and send them in one wire to be used in the VI.

The Split Signal block diagram divides the signals that are coming from

the Daq Assistant wire (voltage V2 and current Ia). Therefore, its turn

possible to manipulate this two signals separately.

Voltage Signal:

o The signal that goes to the upper part is the voltage signal. It is

possible to see that the first thing that happens with this signal is

the division by 0.1087 (%V), which will transform the voltage V2

in the load voltage V.

o The first ramification (the one that goes down) is to make the

multiplication with the current (Ia), and find the output power.

o The output power signal: This signal is a new one that comes from a multiplication

of two signals. If this signal was send directly to the Writeto measurement file box it would take a name as Voltage 2

or Current 2, thats happens because this new signal doesnt

have any nam e yet. The Set dynamic data Attributes box

allows it to give a name for the signal (LOAD POWER)


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o The second ramification (the one that goes up) is to make the

division by the motor back-emf constant to obtain the angular

velocity.

o The angular velocity ramification: From the result of the angular velocity, there are two wires;

one displays the value of the angular velocity in the front

panel. The other makes the multiplication with 60/2 to

obtain the frequency of rotation (N), which is also

displayed in the front panel;

o The third ramification (second one that goes down) is sum with the

voltage drop in the armature resistance to obtain the EMF voltage.

The EMF voltage will pass throw the Set Dynamic DataAttributes (to define its signal name).

o The lasts ramifications from the voltage signal are to display in the

front panel a waveform graph (Voltage x Time) and a numeric

indicator given the exact measured voltage.

o Current Signal:o The signal that goes down, from the split signal box, is the current

signal.

o The first ramification (the one that goes up) is to make the

multiplication with the load voltage (V), to find the output power.

o The second ramification (the one that down up) is to make the

multiplication with the motor back-emf constant to obtain the

torque.

o The toque ramification will display the torque in the front panel in

a tank numeric indicator.

o The third ramification (second one that goes up) is to multiply the

current (Ia) with the armature resistance (Ra) to obtain the voltage

drop in the armature resistance. After calculated this value will

sum with the load voltage (V) to calculate the EMF voltage.


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o The lasts ramifications from the current signal are to display in the

front panel a waveform graph (Current x Time) and a numeric

indicator given the exact measured current.

The merge signal box will be responsible to take the voltage, the emf

voltage, the load power and the current signal signals and put them in just

one wire.

The output wire from the merge signal box will go to the Write to

meas urement file box. This box write the data received in a TDMS

binary file format. The TDMS is a NI low size file format, which can be

opened using the Microsoft Office Excel Ad-In TDM Importer.

VI Front panel:

Figure 35 shows the front panel created for the block diagram. It is possible to see

that the measured electric properties are in the right side of the panel. In this side, there

are two graph panels for the load voltage and the current. In the left side, it was put some

information about the turbine and the generator. It was also put the estimation for the

torque, the rotational velocity and the angular velocity generated by the turbine.

Figure 35 VI Front Panel


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resistance and the load. In addition, the current would be high. There is no resistor of this

value in the project equipment, but putting the two 120 ohms resistor in parallel in the

circuit would be equivalent than use a 60 ohms resistor, which is close from the desired

value.

3.4.2.2.3 Estimated Values

Considering the follow circuit from Figure 37 , for the experiment 1:

Figure 37 DA2 Test Circuit

It is correct to state that:

(3.4.5) (3.4.6)

(3.4.7)

Considering the maximum current supported by motor C is 22mA, by equation

BADERE:

(3.4.8)

(3.4.9)

The current would be probably more than 10m, and the USB 6008 would not becapable to measure it. In that case, the current Ia will be measured in relation of one of

the 120 ohms resistors.

(3.4.10)


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It is possible to create a table predicting the results of this data collection:

Ea (V) Ia (A) i(V2) V(V) Pl(W) 0 0 0 0 0

0,5 0,00424 0,00212 0,25467 0,00108

1 0,00849 0,00424 0,50934 0,00432 1,5 0,01273 0,00637 0,76401 0,00973 2 0,01698 0,00849 1,01868 0,0173

2,5 0,02122 0,01061 1,27334 0,02702 Table 8 Estimated Results For DA2

3.4.2.2.3 Data Coll ection

Figure 38 DA2 LabView Block Diagram

From Figure 38 it is possible to see that the DA2 block diagram will be the almost

equal from the block diagram of DA1. The only differences:

The value of %V that will divide the voltage V2 to find the load voltage V

would not be necessary;

A multiplication with 2 is needed in the current signal to obtain the Ia

current;

The value of the resistance, to measure current, will be 120 ohms; The front panel will be just the same as in the DA1.


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3.4.3 Execution of the experiments

Both experiments were executed by running the VI to start the data acquisition.

And by pressing the STOP button to finish the data acquisition. DA1 was executed in 80seconds, in each second 20 samples were acquired. DA2 was executed in 50 seconds,

also with 20 samples per second. The data from both experiments were saved in a TDMS

file type and after they were converted to a spreadsheet file.


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Chapter 4 Results and Discussion

4.1 DA1 Results and Discussion

From the DA1 experiment, it was obtained the following results:

Right Time Time (s) Load Voltage (V) Power Load(W) EMF Voltage (V) Current (A)

03:18:17,255 0 0 0 0 0

03:18:23,305 6.05 5,06443435 0,000260839 5,06741128 5,1504E-05

03:18:28,705 11.45 10,17351316 0,001059178 10,17953079 0,000104111

03:18:38,155 20.9 15,04823055 0,00231334 15,05711605 0,000153728

03:18:48,105 30.85 20,01669251 0,004079169 20,02847147 0,000203788

03:19:13,505 56.25 25,07889903 0,005688518 25,09200951 0,000226825

03:19:32,155 74.9 0 0 0 0

Table 9 Results From DA1

Figure 39 Voltages Chart from DA1

By comparing these results with the estimated values in the Table 7 Estimated Values for

DA1, it is correct to affirm that the experiment work as it was predicted.

0

5

10

15

20

25

30

0 20 40 60 80

V o l t a g e

( V )

Time (s)

Voltages Graph

Load Voltage (V)

EMF Voltage (V)


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Around of 99.94% of the EMF voltage was directly transferred for the load resistance. In

Figure 39 it is possible two see that the two lines have been represented in the graph. The load

voltage line was behind the EMF voltage line.

To generate this EMF voltage the motor should receive a high value of angular speed.

(4.1.1)

(4.1.2)

Figure 40 Power Load graph in the left and Current Graph in the right from DA1

The load power in this case was low either, even that the voltage in the load was

considerable high. That happens because of the low current in the circuit.

The high load resistance value was responsible for a low value of the generated current

and consequently a low torque.

(4.1.3) (4.1.4)

Considering the 70% of efficiency of the motor c, the mechanical rotational power would

have a low value in this case:

(4.1.5)

00,0010,0020,0030,0040,0050,006

0 20 40 60 80

P O W E R

( W )

Time (s)

Power Load Graph

Power Load(W)

00,00005

0,00010,00015

0,00020,00025

0,0003

0 20 40 60 80

C u r r e n t ( A

)

Times (s)

Current

Current (A)


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4.2 DA2 Results and Discussion

From the DA2 experiment, it was obtained the following results:

Right Time Time (s) Load Voltage (V) Power Load(W) EMF Voltage (V) Current (A)

03:35:15,4 0 0 0 0 0

03:35:17,7 2,3 0,329699 0,001812 0,647309 0,005495

03:35:19,3 3,9 0,489038 0,003986 0,960145 0,008151

03:35:32,0 16,6 0,746798 0,009295 1,466213 0,012447

03:35:47,6 31,6 1,060374 0,01874 2,081868 0,017673

03:35:56,4 41 1,117466 0,020812 2,193959 0,018624

03:35:58,7 43,3 0 0 0 0

Table 10 Results from DA2

Figure 41Voltages graph from DA2

By comparing these results with the estimated values in the Table 8 Estimated Results

For DA2 it is correct to affirm that the experiment doesnt work perfectly as it was predicted.

0

0,5

1

1,5

2

2,5

0 10 20 30 40 50

V o l t a g e

( V )

Time (s)

Voltages Graph

load voltage

Emf voltage


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Even that the piston were pumped with a lot of strength (much more from the DA1) the turbine

has not spun faster. In addition, the desired Emf voltage of 2.59 V was not acquired. The most

reasonable cause for this particular problem can be related to the maximum current that the motor

used could support. In the datasheet of the motor is stated that it can holds 22mA, but maybe the

way that this motor has been stored could change some of its electrical properties.

Around of 50.09% of the EMF voltage was transferred for the load resistance. In Figure

41, it is possible to see that the two lines have been represented in the graph.

To generate this EMF voltage the motor should receive a low value of angular speed.

(4.2.1)

(4.2.2)

Figure 42 Power Load graph in the left and Current Graph in the right from DA2

The load power in this case was low, compared with project requirements, but it was

really high compared with load power from DA1. That happens because of the choice of an load

resistor with almost the same value of the armature resistance in the circuit.

The load resistance value was responsible for current value close from the maximumcurrent allowed in the motor and consequently a higher torque.

(4.1.3) (4.1.4)

0

0,005

0,01

0,015

0,02

0,025

0 20 40 60

P O W E R

( W )

TIME (s)load power

0

0,005

0,01

0,015

0,02

0,025

0 20 40 60

C u r r e n t ( A

)

TIME (s)

Current


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Considering that the motor/ generator has an efficiency of 70%, it is possible to deduce

the mechanical rotational power:

(4.2.5)


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Chapter 5 Conclusions and Recommendations

5.1 Conclusion

5.1.1 In relation to the project itself

To conclude the project has not met with most of its requirements. Apart of the

power output, there was no precise way to measure the others types of power in the rig.

Ending up with a poor data acquisition system (just two measures were read). To

complete, the only requirement that was fulfilled (the measure of the output electrical

power) it was not capable to get not even 1% of the required value. Therefore, in further

researches it would be necessary to get all the necessary sensors before.

Despite of the requirements, the rig was capable to simulate very well the working

principles of an OWC device. It turns to be a very educational rig, with the possibility of

reuse to other studies in the area. For example, it is possible to use the rig as a test

ambient for turbines or generator for OWCs applications; the rig can be adapted to work

in a real wave generator.

5.1.2 In relation to the area of study

The wave energy converter is an emerging area in the renewable energy field. And for

engineering studies is an area that can be highly explored. In this small data acquisition projectalmost all the fields in engineering studies can be found (pneumatics, mechanical, electronic,

computational and even more), which means that the WEC technologies can accept researchers of

a variety of areas.

The data acquisition part of the project had given a new view of the National Instruments

hardware and software. The NI-USB 6008, one of si mplest hardwares from NI, prove to have a

good capacity to deal with analog and digital inputs. In addition, the NI LabView proves to be

one of the most powerful softwares in the data acquisition and manipulation area. With many

functions a simple interface, it turns to be one of the most enjoyable parts of the project.


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Chapter 6 Bibliography

Brady, G. (2013). Turbine Design.

Falco, A., & Gato, L. (2012). Air Turbines. In S. A., Comprehensive Renewable Energy, Vol 8.

(p. 111). Oxford: Elsevier.

Halliday, & Resnick. (2011). Fundamentals of Phisics 9th Edition.

Kosow, I. L. (1991). Eletric Machinery and Transformers. Prentice Hall.

Nader, D., & Sajadian, S. (2011). Modeling and optimization of the chamber of OWC system.

Energy .

Raghunathan, S. (1995). THE WELLS AIR TURBINE FOR WAVE ENERGY CONVERSION.

Scott, J. A. (2001, August 26). Aerospaceweb.org . Retrieved march 3, 2014, fromhttp://www.aerospaceweb.org/question/airfoils/q0041.shtml

Setoguchi, T., & Takao, M. (2012). Air Turbines for Wave Energy Conversion. Internacional

Journal of Rotating Machinery .

Thakker, A., & Abdulhadi, R. (2007). Effect of Blade Profile on the Performance of Wells

Turbine under Unidirectional Sinusoidal and Real Sea Flow Conditions. Rotating Machinery .


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Appendix A Other material

MOTOR C DATASHEET:

Documents

Final Year Project - OWC Simulator