Thesis (MScEng)--Stellenbosch University, 2009. / ENGLISH ABSTRACT: Minimal invasive surgery (MIS) enables surgeons to operate through a few small incisions made in the patient’s body. Through these incisions, long rigid instruments are inserted into the body and manipulated to perform the necessary surgical tasks. Conventional instruments, however, are constrained by having only five degrees of freedom (DOF), as well as having scaled and mirrored movements, thereby limiting the surgeon’s dexterity. Surgeons are also deprived of depth perception and hand-eye coordination due to only having two-dimensional visual feedback. Surgical robotics attempt to alleviate these drawbacks by increasing dexterity, eliminating the fulcrum effect and providing the surgeon with three-dimensional visualisation. This reduces the risks to the patient as well as to the surgeon. However, existing MIS systems are extremely expensive and bulky in operating rooms, preventing their more widespread adoption. In this thesis, a new, inexpensive seven-DOF primary slave manipulator (PSM) is presented. The four-DOF wrist is actuated through a tendon mechanism driven by five 12 VDC motors. A repeatability study on the wrist’s joint position was done and showed a standard deviation of 0.38 degrees. A strength test was also done and demonstrated that the manipulator is able to resist a 10 N opposing tip force and is capable of a theoretical gripping force of 15 N. / AFRIKAANSE OPSOMMING: Minimale indringende chirurgie (MIC) maak dit vir chirurge moontlik om operasies uit te voer deur ’n paar klein insnydings wat op die pasiënt se liggaam gemaak word. Deur hierdie insnydings word lang onbuigsame instrumente in die liggaam ingesit en gemanipuleer om die nodige chirurgiese take uit te voer. Konvensionele instrumente is egter beperk vanweë die feit dat hulle net vyf vryheidsgrade het, asook afgeskaalde bewegings en spieëlbewegings, en gevolglik die chirurg se handvaardigheid beperk. Chirurge word ook ontneem van dieptewaarneming en hand-oog-koördinasie, want hulle is beperk tot tweedimensionele visuele terugvoer. Chirurgiese robotika poog om hierdie nadele aan te spreek deur handvaardigheid te vermeerder, die hefboomeffek uit te skakel en die chirurg driedimensionele visualisering te bied. Dit verminder die risiko’s vir die pasiënt én vir die chirurg. Bestaande MIC-stelsels is egter uiters duur en neem baie plek op in teaters, wat verhoed dat hulle op ’n groter skaal gebruik word. In hierdie tesis word ’n nuwe, goedkoop sewevryheidsgrade- primêre slaafmanipuleerder (PSM) voorgelê. Die viervryheidsgrade-pols word beweeg deur ’n tendonmeganisme wat aangedryf word deur vyf 12 VDC-motors. ’n Herhaalbaarheidstudie is op die pols se gewrigsposisie gedoen, wat ’n standaardafwyking van 0.38 grade aangetoon het. ’n Sterktetoets is ook gedoen en het gewys dat die manipuleerder in staat is om ’n 10 N-teenkantelkrag te weerstaan en dat dit oor ’n teoretiese greepsterkte van 15 N beskik.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The cost of powering Antarctic research stations by conventional diesel electric generator systems is high (Steel, 1993). In order to reduce these costs and airborne pollution due to the combustion of fossil fuels, an investigation into renewable energy sources has been conducted, with the focus on wind turbine energy generation. The aim was to see whether a wind turbine is feasible, both technically and economically, for partial energy production at the SANAE IV base. The existing diesel electrical generators will still be used for the base demand, when there is not enough wind or when the energy demand is more than can be produced by the wind turbine. The work accomplished for this study explains and motivates a MSc. (Eng.) thesis on the feasibility of installing wind electricity generators at Antarctica. This evaluation was done for the South African research station SANAE IV in Antarctica. It provides information on the literature consulted to date, the theoretical and practical work covered, the theoretical investigations, the results obtained and future implementations. Also included in this work was a trip to Antarctica, so that all the relevant data, like wind speeds and wind direction could be measured. Another reason for having done the trip was to do an energy audit for SANAE IV, so that the energy demand for the base could be established. The energy demand of the base varies among other factors, for summer and winter conditions, for day and night conditions, and for population variations. With the information obtained during the trip, the theoretical evaluation of a possible wind turbine system was performed. With the aid of the data from the 6 m wind mast, wind profiles have been established, from which Wei bull distributions were obtained, and the energy output from 5 different wind turbines, in the range between 10 kW and 100 kW, were calculated. The annual energy production of the 100 kW wind turbine is 430 MWh with a capacity factor of 49 %. The annual energy demand of the base amounts to 1153 MWh, thus the wind turbine could contribute up to 30 % of the power needed at the base taking losses, such as availability and maintenance losses, into account. From the automatic weather station of the South African Weather Services, positioned at SANAE IV, wind speed and direction data for the year 2001 was obtained and this data was analyzed. The results show that the winds at SANAE IV are highly directional, coming mostly from an eastern and southeastern direction. This highly directional wind pattern is well suited for wind turbine application. The average wind speed, being measured at 10m height, is 10.8 m/s and the hourly averaged maximum wind speed for the year 2001 is 38.9 mls. From the wind analysis, site survey, cold weather issues and connection to the electricity grid of the base, it becomes evident that the North Wind NWIOO/19 100 kW wind turbine is the best-suited wind turbine for installation at SANAE IV. One of the major advantages of the NW100/19 is that it features a tilt-up tower erecting system that enables the wind turbine to be installed without the use of a crane. The NW100/19 is the only turbine rated at 100 kW, with this feature. From the economic analysis it is evident that a wind turbine, with the complete installation, operation and maintenance costs, features a break even period of 10 years, when installed at SANAE IV. This relatively short breakeven period, considering that the life of the turbine is 30 years, originates from the fact that the average wind speed at the base is about 11 mis, which is relatively high and yields enormous power productions. This wind turbine operates for approximately 80 % during a year, which is very high, making this renewable energy source very attractive as a power-generating source for SANAE IV. The cost per kWh produced by the wind-diesel system is R1.63/kWh, while the cost per kWh produced by the current diesel generators, satisfying the power demand of the base, is R1.94/kWh. Thus the hybrid system can reduce the cost of power produced by almost 20 %, which again demonstrates the attractiveness of using wind power at SANAE IV. From an environmental point of view, the use of wind power at SANAE IV is favorable, since a wind turbine has minimal effects on the environment at Antarctica. The cost of emissions and fuel spills were calculated for SANAE IV. The fuel saving, resulting from the operation of a wind turbine at SANAE IV, converts to a saving in externalities of about R500 000.00 per year, using an evaluation method that was applied to remote Alaskan villages. It can therefore be concluded that the aims of the project have been fully accomplished and that the use of wind power at SANAE IV is indeed a very attractive option, regarding all the criteria mentioned above. When it is being decided that a budget will be provided for a wind turbine installation, the economic analysis has to be refined, due to the uncertainty of the market value of the South African currency. / AFRIKAANSE OPSOMMING: Die koste verbonde aan krag voorsiening vir Antarktiese navorsingstasies deur middel van konvensionele diesel elektriese kragopwekkers is baie hoog (Steel, 1993). Om hierdie kostes en lugbesoedeling weens die verbranding van fossielbrandstowwe te verminder, is 'n ondersoek na hemubare energiebronne gedoen, met die fokus op windturbiene energie opwekking. Die doelwit van die studie was om te sien of 'n windturbiene aanwending vir kragopwekking vir die SANAE IV stasie lewensvatbaar is, gebaseer op tegniese en ekonomiese uitgangspunte. Die bestaande diesel elektriese kragopwekkers sal nog altyd gebruik word vir kragopwekking, as daar nie genoeg wind is nie, of as die energievraag hoer is as wat kan verskafword deur die wind turbine. Die werk wat vir hierdie studie voltooi is belig en motiveer 'n MSc(Ing) tesis oor die lewensvatbaarheid vir installering van 'n windelektriese kragopwekker op Antarktika. Hierdie evaluasie is gedoen vir die Suid Afrikanse navorsingstasie, SANAE IV, op Antarktika. Dit behels informasie oor die literatuur verwerk tot dusver, die teoretiese en praktiese werk gedoen, die teoretiese ondersoeke, die resultate verkry en toekomstige verwesenlikings. Werk ook ingesluit was 'n expedisie na Antarktika toe, sodat al die relevante data, soos wind spoed en rigtings gemeet kon word. Nog 'n rede om die expedisie te doen was om energie data van SANAE IV te meet, sodat die energieverbruik van die basis bevestig kon word. Die energieverbruik van die basis varieer ten opsigte van somer en winter kondisies, van dag en nag variasies en inwonergetalle. Met die informasie verkry gedurende die expedisie kon 'n evaluasie gedoen word vir 'n moontlike windturbiene stelsel op Antarktika. Met die hulp van 'n 6tn wind toring kon wind profiele gekry word, waarvandaan Weibull verdelings bereken is en die kragopwekking van 5 verskillende windturbienes bereken is, wat wissel van 10 kW tot 100 kW. Die jaarlikse energieopwekking vir die 100 kW wind turbine is 430 MWh met 'n kapasiteitsfaktoor van 49 %. Die jaarlikse energieaanvraag van die stasie is 1153 MWh. Dus kan die wind turbine ongeveer 30 % van die jaarlikse energieaanvraag dek, as verliese soos beskikbaarheids- en instandhoudingsverliese III berekening gebring word. Wind spoed en rigting data vir die jaar 2001 is verkry van die outomatiese weerstasie van die Suid Afrikaanse Weer Diens, wat geposisioneer is by die SANAE IV stasie, en hierdie data is geanaliseer. Die resultate verkry bewys die direksionele stabiliteit van die winde by SANAE IV, waarvandaan die meeste winde uit die oostlike en suidoostlike rigting kom. Hierdie hoogs gekosentreede winde is baie goed geskik vir windturbiene aanwending. Die gemiddelde wind spoed, wat gemeet is op 'n hoogte van 10 m is 10.8 m/s en die uurlike gemiddelde maksimum wind spoed vir die jaar 2001 is 38.9 m/s. Van die wind analise, terrein analise, koue weer informasie en koppeling van die wind turbine by die bestaande elektrisiteits netwerk word bevestig dat die North Wind NW100119 100 kW windturbiene die geskikste windturbiene vir installasie en werking by SANAE IV is. Een van die grootste voordele van die NW100/19 windturbiene is dat dit 'n selfoprigdende meganisme het, wat sonder die hulp van 'n kraan werk. Die NW100/19 is die enigste windturbiene in sy klas, wat so 'n funksie het. Van die ekonomiese analise kan afgelei-word, dat 'n wind turbine met volledige installasie, werking en diens kostes, 'n kapitale terugbetalings periode van 10 jaar het, as dit by SANAE IV geinstalleer word. Hierdie tydperk is relatief kort, as gekyk word na die ontwerp leeftyd van 30 jaar van die NW100/19 wind turbine. Die rede vir die kort terugbetalings periode is afkomstig van die hoe gemiddelde wind spoed by SANAE IV, wat enorme kragopwekking tot gevolgtrekking het. Dit kan ook gesien word aan die hoe werkingsure van die turbine wat 6942 uur per jaar is. Dus wek die turbine vir omtrent 80 % van die jaar krag op, wat beinvloed dat 'n wind turbine opsie vir SANAE IV baie aantreklik is. Die koste per kWh krag opgewek vir die wind-diesel sisteem is R1.63/kWh, terwyl die koste per kWh krag opgewek vir die huidige diesel generator opstelling R1.941kWh is. Dus kan 'n kostebesparing van tot 20% van die energie onkostes verkry word, wat weer eens beklemtoon, dat die wind-diesel sisteem baie aantreklik vir kragopwekking by SANAE IV is. Vanaf 'n omgewingsoogpunt gesien het die gebruik van 'n wind turbine stelsel by die SANAE IV stasie net weglaatbaar klein invloede op die omgewing in vergelyking met die lugbesoedeling van die diesel kragopwekkers. As die koste verbonde aan lugbesoedeling en brandstof lekkasie besoedeling bereken word kan die wind turbine stelsel omtrent R500000.00 per jaar aan besoedeling onkostes spaar. Die getalle vir besoedelings onkostes is gebaseer op die evaluasie van besoedeling vir afgelee Amerikanse dorpies (Isherwood et al., 1999). Dit kan dus afgelei word vanaf die bogenoemde bevindings, dat die doelwitte van die tesis bereik is en dat wind krag opwekking by SANAE IV inderdaad 'n baie aantreklike moontlikheid is. Wanneer 'n begroting beskikbaar gestel word vir 'n windturbiene stelsel vir SANAE IV, moet die ekonomiese analise geoptimeer word weens die onsekerheid van die markwaaarde van die Suid Afrikaanse Rand.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Minimally Invasive Surgery (MIS) in human beings is performed by making small incisions in the abdominal region of the patient and inflating the abdominal cavity with CO2. This procedure enables the surgeon to manipulate long rigid surgical instruments inside the patient in order to perform the surgery. Unfortunately the current methods of insertion and assembly of MIS instruments limit the surgeon to only five (of a possible seven) Degrees of Freedom (DOF). Along with this, the surgeon’s movements are mirrored (called the Fulcrum effect) and scaled around the point of incision. Minimally invasive surgical robots attempt to alleviate these drawbacks by eliminating the Fulcrum effect, as well as improving dexterity and accuracy. These robots’ abilities to improve the surgeon’s hand-eye coordination, enables the surgeon to perform surgeries using their natural movements with reduced fatigue. As a result of this, the risk to both patient and surgeon is reduced. Existing MIS robotic systems are extremely expensive and large, and as a result they are not widely used. In this thesis a new, lower cost, seven DOF robotic manipulator is further developed. The thesis focuses on the external three DOF Secondary Slave Manipulator (SSM) and combines it with the Primary Slave Manipulator (PSM) that was developed by a previous Masters student. Tests done on the SSM showed that the manipulator has a minimum resolution of 0.7 ± 0.2 mm (mean ± standard deviation) on the shoulder joint’s yaw rotation and 0.5 ± 0.2 mm in pitch rotation. The linear actuator used for insertion has a minimum resolution of 0.2 ± 0.2 mm. A strength test was also conducted and showed that the manipulator is easily capable of producing a 10 N actuation force as required during Minimally Invasive Robotic Surgery (MIRS) procedures. In conclusion the complete system has potential as a viable alternative to the existing systems due to its accuracy and lower cost. Future work will include the development of a user interface and control system for the complete robot. / AFRIKAANSE OPSOMMING: Minimaal Indringende Chirurgie (MIC) op mense word uitgevoer deur klein insnydings in die pasiënt se buik te maak en dan die abdominale holte met CO2 te vul. Dit stel die chirurg in staat om lang, onbuigbare instrumente binne die pasiënt te manipuleer om sodoende die operasie uit te voer. Die manier waarop die MIC instrument ontwerp is en die pasiënt binnegaan, laat egter slegs vyf vryheidsgrade toe, terwyl die chirurg self sewe vryheidsgrade in sy handbewegings het. Verder veroorsaak hierdie instrumente ook dat die chirurg se aksies in spieëlbeeld vertolk word (Fulcrum effek) en geskaleer is. Chirurgiese robotika poog om hierdie nadele teen te werk deur die Fulcrum effek te verwyder, en ook om handvaardigheid en akkuraatheid te bevorder. Die robot se potensiaal om die chirurg se hand-oog koӧrdinasie te verbeter, maak dit moontlik vir die chirurg om op ’n meer natuurlike en gemaklike manier te werk te gaan en bring minder vermoeienis mee. Dit verminder die risiko’s vir beide die pasiënt en die chirurg. Bestaande robotiese stelsels is egter baie duur en groot, en word dus nie meer algemeen gebruik nie. In hierdie tesis word ‘n nuwe sewe-vryheidsgraad robotiese manipuleerder ontwikkel. Die tesis fokus op die eksterne drie-vryheidsgraad Sekondêre Slaaf Manipuleerder (SSM) en kombineer dit met die Primêre Slaaf Manipuleerder (PSM) wat deur ʼn vorige Meestersstudent ontwikkel is. Toetse wat uitgevoer is op die SSM het getoon dat dit ’n minimum resolusie van 0.7 ± 0.2 mm (gemiddeld ± standaard afwyking) op die skouer se afwyking en 0.5 ± 0.2 mm om die onderskeie skouer aslyne toon. Die linieêre aktueerder wat vir inlassing gebruik word het ’n minimum resolusie van 0.2 ± 0.2 mm. ’n Sterktetoets is uitgevoer en het getoon dat die manipuleerder maklik die nodige 10 N krag soos benodig in Minimaal Indringende Robotiese Chirurgie (MIRC) prosedures kan lewer. Ter afsluiting, die volledige stelsel het die potensiaal as lewensvatbare alternatief tot die bestaande stelsels vanweë die akkuraatheid en laer koste verbonde. Toekomstige navorsing kan moontlik die ontwikkeling van ʼn gebruikerkoppelvlak en beheerstelsel vir die volledige robot insluit.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In percutaneous procedures, where the surgeon inserts a needle into a target in the patient, it is challenging to access the target at the rst attempt. Repeated needle insertion attempts are highly undesirable, as they lead to increased theatre time, patient haemorrhage and radiation exposure. The proposal of this thesis was to develop a low-cost system to aid surgeons with the process of positioning and orientating the needle prior to insertion. The proposed system uses a stereo pair of images produced by a standard C-arm uoroscope. By applying computer vision techniques, such as triangulation, the desired needle position and orientation are determined from the set of images. An articulated manipulator is used to position and orientate the needle. The surgeon makes selections on the images, via a graphical user interface (GUI), to indicate the desired position and orientation of the needle. Following these selections, an algorithm determines the necessary angles for the manipulator. The surgeon then positions the manipulator accordingly. Results from tests on a phantom showed the system to be repeatable and accurate to 2 mm. This is less accurate than similar, existing systems which, reported accuracies of 0:25 and 1:21 mm. However, 2 mm accuracy is considered adequate as it allows a range of percutaneous procedures to be performed such as needle biopsy, regional anaesthesia, brachytherapy and percutaneous nephrolithotomy (PCNL). Tests on both a phantom kidney and a porcine kidney indicated that the system can function in a real percutaneous procedure and with an anatomical target. The total cost to develop the prototype system was R15 000. The accuracy of the proposed system and the time to gain access to the target indicate that the system can be a bene cial aid to surgeons when performing percutaneous procedures. As minimal X-ray imaging is required, patients will also be spared excessive radiation exposure and theatre time. / AFRIKAANSE OPSOMMING: In perkutane prosedures, waar die chirurg 'n naald in 'n teiken op die pasiënt invoeg, is dit moeilik om met die eerste probeerslag toegang tot die teiken te bekom. Herhaalde pogings om die naald in te voeg is hoogs ongewens, aangesien dit tot verlengde teatertyd, bloeding by pasinte sowel as stralingsblootstelling lei. 'n Laekostestelsel is ontwikkel om chirurge by te staan met die proses om die naald voor invoeging te plaas en te oriënteer. Die stelsel gebruik 'n paar stereobeelde wat deur 'n standaard-C-arm- uoroskoop voortgebring word. Met behulp van rekenaarsigtegnieke, soos triangulasie, word die gewenste naaldposisie en -oriëntasie uit die stel beelde bepaal. 'n Geartikuleerde manipuleerder word gebruik om die naald te plaas en te oriënteer. Die chirurg voer die vereiste invoerdata deur middel van 'n gra ese gebruikerskoppelvlak (GGK) in, waarna 'n algoritme die vereiste hoeke vir die manipuleerder bepaal. Die chirurg plaas dan die manipuleerder dienooreenkomstig. Die resultate van toetse op 'n fantoom toon dat die stelsel herhaalbaar en tot op 2 mm akkuraat is. Dit is minder akkuraat as soortgelyke, bestaande stelsels, wat 'n akkuraatheid van 0:25 mm en 1:21 mm onderskeidelik aangemeld het. Tog kan akkuraatheid van 2 mm as voldoende beskou word, aangesien dit 'n verskeidenheid perkutane prosedures moontlik maak, soos naaldbiopsies, regionale anestesie, bragiterapie en perkutane nefrolitotomie (PCNL). Toetse op 'n fantoomnier dui daarop dat die stelsel wél in 'n werklike perkutane prosedure kan funksioneer. Toetse op 'n varknier toon dat die stelsel wél ook met 'n anatomiese teiken kan werk. Die totale koste om die prototipe te ontwikkel was R15 000. Die akkuraatheid van die voorgestelde stelsel en die tydsduur om toegang tot die teiken te bekom, dui daarop dat die stelsel 'n nuttige hulpmiddel kan wees vir chirurge wat perkutane prosedures uitvoer. Aangesien minimale Xstraalbeelding vereis word, sal dit pasiënte ook oormatige stralingsblootstelling en verlengde teatertyd spaar.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The thesis evaluates control strategies for reconfigurable manufacturing systems by using a welding assembly cell as a case study. The cell consists of a pallet magazine, conveyor, feeder subsystem (comprising an articulated robot and singulation unit), welder subsystem (which uses a modular Cartesian robot), and inspection and removal subsystems. The research focuses on control strategies that enhance reconfigurability in terms of structure, hardware and software using agent-based control and the IEC 61499 standard, based on PC control. Reconfiguration may occur when a new product is introduced, as well as when a new subsystem is introduced or removed from the production cell. The overall control architecture is that the subsystems retain no knowledge of the product, but product information resides in the cell controller, while services offered by the subsystems are registered with the directory facilitator of the Java agent platform. The control strategies are implemented on the modular Cartesian weld robot and the cell controller for assembly cell. A layered architecture with low-level control and high-level control is used to allow separation of concerns and rapid changes in both hardware and software components. The low-level control responds in hard real-time to internal and external events, while the high-level control handles soft real-time actions involving coordination of control related issues. The results showed IEC 61499 function blocks to be better suited to low-level control application in distributed systems, while agents are more suited for high-level control. Modularity in software components enhances hardware and software scalability. Additionally, agents can support online reconfiguration of reconfigurable machines. / AFRIKAANSE OPSOMMING: Die tesis evalueer beheerstrategieë vir herkonfigureerbare vervaardigingstelsels deur gebruik te maak van ’n sweismonteersel as ’n gevallestudie. Die sel bestaan uit ’n palletmagasyn, vervoerbande, voersubstelsel (bestaande uit ’n geartikuleerde robot en singulasie-eenheid), sweissubstelsel (wat gebruik maak van ’n modulêre Cartesiese robot), en inspeksie- en verwyderingsubstelsels. Die navorsing fokus op beheerstrategieë wat herkonfigureerbaarheid verhoog in terme van struktuur, hardeware en sagteware met behulp van agent-gebaseerde beheer en die IEC 61499 standaard, wat gebaseer is op PC-beheer. Herkonfigurasie mag voorkom wanneer ’n nuwe produk in-gestel word, sowel as wanneeer ’n nuwe substelsel bygevoeg of verwyder word van die produksiesel. Die oorhoofse beheerargitektuur is dat die substelsels geen kennis van die produk hou nie, maar die produkinligting in die selbeheerder geberg, terwyl dienste wat aangebied word deur die substelsels wat geregistreer is by die gidsfasiliteerder van die Java agent platform. Die beheerstrategië is geïmplementeer op die modulere Cartesiese sweisrobot en die selbeheerder vir die monteersel. ’n Gelaagde argitektuur met ’n lae-vlak beheer en hoë-vlak beheer word gebruik om skeiding van oorwegings en vinnige veranderinge in beide hardeware en sagteware komponente toe te laat. Die lae-vlak beheer reageer hard intyds op interne en eksterne gebeure, terwyl die hoë-vlak beheer sag intyds die koördinering van beheerverwante kwessies hanteer. Die resultate het getoon dat IEC 61499 funksie-blokke beter geskik is vir lae-vlak beheer toepassing in verspreide stelsels, terwyl agente meer geskik is vir hoë-vlak beheer. Modulariteit in sagteware komponente verhoog hardeware en sagteware skaleerbaarheid. Boonop kan agente ook aanlyn herkonfigurasie van herkonfigureerbare masjiene ondersteun.

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: The Council for Scientific and Industrial Research has developed a vibration excitation system. The system is designed to excite the rotor blades of an axial compressor in the specified vibration mode and at the specified frequency. The vibration excitation system was tested on Stellenbosch University’s Rofanco compressor test bench. A two-way staggered fluid-structure interaction (FSI) model was created that was capable of simulating the vibration of the rotor blades excited by the system. The results of the FSI model were verified using available experimental data. It was concluded that the FSI model is able to recreate the vibration excited by the system to within the desired level of accuracy. In addition, the results of the FSI model showed that the vibration excitation system should be able to excite the blades in the selected vibration mode and at the selected frequency provided that the excitation frequency is close the natural frequency of the first bending mode. The results also suggested that a transient computational fluid dynamics model should be sufficient for the prediction of the aerodynamic forces acting on the rotor blades. Furthermore, a one-way staggered FSI model should be adequate for calculating the motions of the blades. / AFRIKAANSE OPSOMMING: Die Wetenskaplike en Nywerheidnavorsingsraad het ’n vibrasie-opwekkingstelsel ontwerp om die rotorlemme van ’n aksiaalvloei kompressor in die gespesifiseerde vibrasiemodus en teen die gespesifiseerde frekwensie op te wek. Die vibrasieopwekkingstelsel is met behulp van die Universiteit Stellenbosch se Rofanco kompressortoetsbank getoets. Daarna is ’n tweerigting vloeistof-struktuur-interaksie model geskep om die vibrasie van die rotorlemme, wat deur die stelsel opgewek is, te simuleer. Beskikbare eksperimentele data is gebruik om die resultate van die vloeistof-struktuur-interaksie model te bevestig. Die gevolgtrekking is gemaak dat die model wél die vibrasie van die lemme met die nodige akkuraatheid kan simuleer. Die resultate van die vloeistof-struktuur-interaksie model toon ook dat die stelsel die lemme in die gekose vibrasiemodus en teen die gekose frekwensie behoort te kan opwek, solank die opwekkingsfrekwensie na aan die natuurlike frekwensie van die eerste buigmodus is. Voorts dui die resultate daarop dat ’n berekeningsvloeimeganika model die aërodinamiese laste van die lemme sal kan voorspel. ’n Eenrigting vloeistof-struktuur-interaksie model behoort voldoende te wees om die beweging van die rotorlemme te bereken.

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: The coating thermal conductivity, the effective coated-tube thermal conductivity and the coating factor of three artificial protective coatings (APCs) applied to condenser tubes are experimentally evaluated. This testing broadens the limited available knowledge of these coatings, which is necessary for effective condenser refurbishment and operation. The coatings are applied to 25.4 mm brass tubes at thicknesses of 44, 46, 50, and 130 μm. Steady state heat transfer tests are performed on these tubes fitted in a double-pipe counter-flow heat exchanger, with heated water in the annulus and coolingwater inside the tube. The experimentally determined thermal conductivities of the coatings range from 0.5 to 2.3 W/m·K. The effective coated-tube conductivity and the coating factor depend on the tube material and size, as well as the coating thickness. A one-dimensional condenser model is used to parametrically investigate the relative overall effect on condenser performance. From these results, coating guidelines for Admiralty brass tubes are proposed in terms of the minimum and maximum coating conductivity and thickness. The effect of the coating on the thermal performance is equivalent to a Heat Exchange Institute (HEI) cleanliness factor of at least 0.85, when adhering to these guidelines. APCs provide a layer of protection against corrosion, erosion and fouling and can preferentially fill tube-wall pits. They can therefore be used to extend the condenser life-span effectively, but, to ensure minimal impact on the overall condenser performance, the coating thickness and conductivity must be carefully controlled and verified experimentally. / AFRIKAANSE OPSOMMING: Die termiese geleidingsvermoë, die effektiewe termiese geleidingsvermoë van bedekte buise en die bedekkingsfaktor van drie kunsmatige beskermingsbedekkingslae wat op kondensorbuise aangewend word, word eksperimenteel geëvalueer. Hierdie evaluering verbreed die beperkte beskikbare kennis oor sodanige bedekkingslae, wat nodig is vir effektiewe kondensor herinrigting en bedryf. Die lae word teen diktes van 44, 46, 50 en 130 μm in 25.4 mm geelkoperbuise aangewend. Warmteoordragstoetse by gestadigde toestande word gedoen op hierdie buise in ’n dubbelpyp-teenvloeiwarmteoordraer, met verhitte water in die annulus en verkoelingswater binne-in die buis. Die eksperimenteel bepaalde termiese geleidingkoëffisiënte wissel tussen 0.5 tot 2.3 W/m·K. Die effektiewe geleidingsvermoë en bedekkingsfaktor hang af van sowel die buis se materiaal en grootte sowel as die dikte van die bedekkings. ’n Eendimensionele kondensormodel word gebruik om die algehele effek van hierdie beskermingsbedekkingslae op kondensorwerkverrigting parametries te ondersoek. Riglyne ten opsigte van aanwending van beskermingslae vir buise van “Admiralty” geelkoper word verskaf in terme van die minimum en maksimum geleidingsvermoë en dikte van bedekkingslae. Met behulp van hierdie riglyne word ’n “Heat Exchange Institue” (HEI) ekwivalente skoonheidsfaktor van minstens 0.85 op ’n nuwe buis behaal. Hierdie kunsmatige bedekkingslaeslae bied beskerming teen korrosie, erosie en bevuiling en kan klein kuile in die buiswand vul. Hulle kan dus gebruik word om die lewensduur van die kondensator te verleng, maar hul dikte en geleidingsvermoë moet noukeurig beheer word en moet eksperimenteel geverifieer word.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The majority of power stations in South Africa are located in coal rich, but arid regions where wet-cooled condenser systems are not feasible from an environmental and economic perspective. Consequently the focus on power generation cooling has shifted towards dry-cooling systems using air-cooled steam condensers (ACSC). The steam passing through the ACSC units is cooled by an air-draught, mechanically induced by large diameter axial flow fans. Consequently the effectiveness of the cooling is impacted by the performance of these fans, which ultimately affects the overall efficiency of the power plant. However, due to the large diameters (> 10 m) of these fans, their performance is predicted based on small scale test results using the fan scaling laws. The objective of this project was to develop a methodology which accurately predicts the fan performance of more than one fan configuration using computational fluid dynamics (CFD) software and validating the results with experimental tests. Four fans were considered in this study of which three were scaled fan models of large air-cooled axial fans. The performance of the scaled fan models (L1-, L2- and N-fan) were measured in a type A, BS 848 standard fan test facility. The geometries of the fans were scanned three-dimensionally to obtain the models for simulation purposes. The other fan considered was an 8- bladed axial fan designed by Bruneau (1994) and referred to as the B-fan. Simulations were carried out for the L2-, N- and B-fan for different computational domains while implementing the multiple reference frames (MRF) and steady RANS approach. Three variations of the k-ε turbulence model were also investigated. Noticeable differences were found between the experimental and numerical results of the B-fan. Good correlations between the numerical and experimental fan static pressure, fan power and fan static efficiency were found for the two scaled model fans over a large operating range. The performance of the full scale fans, however, did not correlate well with the performance of the scaled models. It is concluded that accurate simulations of axial fans are possible although these domains require a large number of mesh elements. It is recommended that further research is carried out to investigate the relationship between full scale and small scale fan models. / AFRIKAANSE OPSOMMING: Die meerderheid steenkool kragstasies in Suid-Afrika is geleë in droë, maar steenkool ryke streke waar natverkoelde kondensor stelsels uit ʼn omgewings en ekonomiese perspektief nie geskik is nie. Die fokus in kragopwekking verkoeling het dus verskuif na droë-verkoelings stelsels en spesifiek die gebruik van lugverkoelde stoomkondensors (LVSKs). Die stoom in LVSK eenhede word verkoel deur atmosferiese lug wat meganies geïnduseer word deur groot aksiaalvloeiwaaiers. Die effektiwiteit van die verkoelingsproses word gevolglik beïnvloed deur die werksverrigting van hierdie waaiers wat uiteindelik die algehele effektiwiteit van die kragstasie beïnvloed. As gevolg van hierdie waaiers se grootte word hulle werksverrigting egter bepaal op grond van kleinskaal toetsresultate en deur gebruik te maak van die waaierskaleringswette. Die hoofdoelwit van hierdie projek was om ‘n metodiek te ontwikkel wat die werksverrigting van ʼn aksiaalwaaier akkuraat kan voorspel vir ʼn verskeidenheid opstellings, deur gebruik te maak van berekenings vloei meganika (BVM) sagteware en die resultate eksperimenteel te verifieer. Die projek het vier waaiers ondersoek waarvan drie van hierdie waaiers geskaleerde modelle van groot lugverkoelde aksiaalwaaiers was. Die werksverrigting van die geskaleerde waaiers (L1-, L2- en N-waaier) was met ‘n tipe A, BS 848 standaard waaier toetsfasiliteit gemeet. Die geometrie van dié waaiers was ook drie-dimensioneel opgemeet vir simulasie doeleindes. Die B-waaier, ‘n 8 lem aksiaalwaaier, wat ontwerp is deur Bruneau (1994) was slegs numeries ondersoek. Die L2-, N- en Bwaaier was gesimuleer in verskillende berekeningsdomeine deur gebruik te maak van die multi verwysingsraamwerk en gestadigde vloeiberekenings benaderings. Drie k-ε turbulensie modelle was ook ondersoek. Merkbare verskille tussen die eksperimentele en numeriese resultate van die Bwaaier was waargeneem. Goeie korrelasie tussen die eksperimentele en numeriese resultate van die geskaleerde waaiers vir ‘n wye bedryfsbestek was gevind. ‘n Vergelyking tussen die volskaal en kleinskaal waaiers se werksverrigting het egter beduidende afwykings aangetoon. Deur gebruik te maak van ‘n groot aantal selle in die berekeningsdomein was dit moontlik om ʼn verskeidenheid aksiaalvloeiwaaiers akkuraat te simuleer. Verdere navorsing wat die verhouding tussen volskaal en kleinskaal waaiers ondersoek woord aanbeveel.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This study describes the design and construction of a low-cost linear Fresnel solar concentrator. Ray-trace simulation models that analyse optical performance were developed and then used to perform sensitivity analyses of various characteristics of linear Fresnel concentrators. The design of a small-scale concentrator was optimised using the simulation models, after which the concentrator was constructed in the solar laboratory. The concentrator consists of a single-motor tracking system, flat primary mirrors and a low-cost secondary concentrator that approximates a compound parabolic concentrator. Testing revealed satisfactory performance that was comparable to the simulation models’ prediction. The construction of a low-cost solar concentrator that can replace existing thermal sources for the generation of power and process heat is thus achievable. / AFRIKAANSE OPSOMMING: Die ontwerp en konstruksie van 'n laekoste- lineêre Fresnel-sonkonsentreerder word in hierdie studie beskryf. Stralingsimulasiemodelle wat optiese werksverrigting analiseer is ontwikkel en gebruik om sensitiwiteitsanalises van die verskillende eienskappe van lineêre Fresnel-konsentreerders te doen. Die modelle is verder gebruik om die ontwerp van 'n kleinskaalse konsentreerder te optimeer, waarna die konsentreerder in die sonlaboratorium gebou is. Die konsentreerder bestaan uit 'n enkelmotorvolgingstelsel, plat primêre spieëls en 'n laekoste- sekondêre konsentreerder soortgelyk aan 'n saamgestelde, paraboliese konsentreerder. Toetsing dui bevredigende werksverrigting aan, vergelykbaar met wat die simulasiemodelle voorspel het. Dit is dus moontlik om 'n laekoste-sonkonsentreerder wat bestaande termiese bronne vir kragopwekking en proseshittegenerasie kan vervang, daar te stel.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Turbomachinery plays an important role in the efficiency of power generation and combustion processes used in the automotive and aerospace industries. The potential for fulfilling future energy needs has been identified in both civilian and military applications, for example micro gas turbines (MGTs) used in unmanned aireial vehicles (UAVs). The goal of this thesis was to build a performance testing facility for small-scale centrifugal compressors, for use in MGTs. The objectives of this study were mainly achieved through experimental work. In addition to the experimental work, numerical simulations using computational fluid dynamics (CFD) software were performed to substantiate the experimental results. The project methodology followed the process whereby a compressor performance map is constructed from experimental data and compared to map obtained from theoretical data. The test facility consists of a turbocharger fitted with an experimental compressor section. The turbocharger turbine is driven by unheated compressed air. Sensors, data acquisition and ancillary equipment required to perform performance test measurements, were obtained and installed on the test facility. Performance curves at three different rotational speeds were successfully obtained for the experimental compressor. When compared to the CFD results there was good qualitative agreement, although deviations in the results increased with rotational speed. In addition a second impeller design was tested which correlated well with the theoretical data. / AFRIKAANSE OPSOMMING: Turbomasjinerie speel 'n belangrike rol in die doeltre endheid van kragop- wekking en verbrandingsprosesse wat in die motor- en lugvaartbedryf gebruik word. Die potensiaal om in toekomstige energiebehoeftes te voorsien is in beide burgerlike en militêre toepassings uitgewys, byvoorbeeld mikrogastur- bines (MGT's) wat in onbemande vliegtuie (OLV's) gebruik word. Die doel met hierdie tesis was om 'n prestasietoetsfasiliteit vir kleinskaalse sentrifu- gale kompressors te bou wat in MGT's gebruik kan word. Die doelstellings van hierdie studie is hoofsaaklik deur eksperimentele werk behaal. Daarbe- newens is numeriese simulasies met gebruikmaking van sagteware vir bereke- ningsvloeidinamika (BVD) gedoen om die eksperimentele resultate te staaf. Die projekmetodologie volg die proses om 'n kompressorprestasiekaart uit eks- perimentele data op te stel en dit te vergelyk met 'n kaart wat uit teoretiese data bekom is. Die toetsfasiliteit bestaan uit 'n turboaanjaer wat met 'n eksperimentele kompressordeel toegerus is. Die turboaanjaer se turbine word deur onverhitte druklug aangedryf. Sensors, dataverwerwing en bykomstige toerusting, wat benodig is om prestasietoetsmetings mee te doen, is bekom en op die toetsfasiliteit geïnstalleer. Prestasiekrommes is vervolgens by drie verskillende omwentelingsnelhede suksesvol met die eksperimentele kompres- sor bekom. In vergelyking met die BVD-resultate was daar goeie kwalitatiewe ooreenstemming, ofskoon afwykings in die resultate vergroot het namate die omwentelingspoed toegeneem het. Daarby is 'n tweede stuwerontwerp getoets wat goed met die teoretiese resultate korreleer.