Thesis (MEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: In the present study, research was conducted to determine the feasibility of water energy storage through which the output of heated air by an upward facing solar air heater could be prolonged. Following a systematic approach, a number of experimental test swere initially performed on an upward facing solar air heater in order to obtain a benchmark that could be used to evaluate the influence of water storage during the day-time performance of a solar air heater. As expected, an increase in the air mass flow rate not only led to an increase in the collector efficiency but also to a decrease in the temperature gain across the collector. In addition, a number of day- and night-time experiments were executed on a plastic covered water tank in order to evaluate it's ability to store and discharge thermal energy. Results clearly indicated that the plastic covered water tank was both an ideal collector and storage medium of solar energy. Experimental results also revealed that the plastic covered water tank was an ideal source of thermal energy for a solar air heater during night-time operation. Subsequently, both day- and night-time experiments were performed on an upward facing solar air heater in which plastic covered water tanks were installed. Day-time experimental results revealed that the modified solar air heater still had the same collector efficiency tendency, as observed in the initial solar air heater experiments, but that the water energy storage led to a dramatic decrease in the absorber plate temperature and in the corresponding temperature gain experienced across the collector. In contrast, the night-time operation results clearly indicated that the water energy storage was not only able to prolong the output of heated air by the solar air heater, but was further able to increase the air temperature by between 7.5 and 1.5 °e, depending on the air mass flow rate. It was furthermore shown in the study that available theory is able to accurately predict the performance of an upward facing solar air heater, either with or without water energy storage, as long as the equations are employed within their range of validity / AFRIKAANSE OPSOMMING:In die hierdie studie is daar ondersoek ingestel na die lewensvatbaarhied van son-energiestoring in water ten einde die tydperk van lugverhitting deur 'n son-Iugverwarmer te verleng. 'n Sistematiese prasedure is gevolg waardeur daar aanvanklik 'n aantal eksperimente op 'n son-Iugverwarmer uitgevoer is am sodoende die eienskappe van so 'n lugverhiUingstelsel, sander energie storing, te vekry. Die resultate het getoon dat 'n toename in die massavloei tempo van die lug lei tot 'n toename in die kollektor effektiwiteit van die stelsel, maar terselfdetyd lei tot 'n afname in die temperatuur styging in die kollektor. Met die eienskappe van die lugverwarmingstelsel bekend, is daar voorts 'n aantal dag- en nag-eksperimente uitgevoer op 'n plastiek bedekte watertenk am die storing en vryselling van termiese energie deur die watertenk te kwantifiseer. Die resultate het daarap gedui dat die plastiek bedekte watertenk nie net beide 'n goeie kollektor en stoor medium vir son-energie is nie, maar oak dat dit 'n ideale bran van termiese energie vir 'n lugverwarmingstelsel tydens die nag is. Met inagname van die vorige resultate, is daar dan 'n aantal plastiek bedekte watertenks in die apparaat geinstalleer, en 'n aantal dag- en nag-eksperimente is uitgevoer. Die dageksperimente het getoon dat die die nuwe lugverwarmer met water energie storing dieselfde eienskappe toon ten opsigte van die kollektor effektiwiteit as die oorspronkilke son-Iugverwarmer. Tog, as gevolg van die laer absoberende plaat temperature was die temperatuur toename in die kollektor heelwat laer. In kontras hiermee dui die nagresultate aan dat die plastiek bedekte watertenks nie net die vermoe het am die tydperk van lugverwarming te verleng nie, maar oak dat die lug tempertuur, afhangende van die massavloei tempo van die lug, met tussen 1.5 en 7.5 °C verhoog kan word. Die studie het laastens oak getoon dat dit moontlik is am met behulp van beskikbare teorie die temperatuur toename in die kollektor van 'n son-Iugverwarmer met of sander water energie storing, akkuraat te voorspel, mits die vergelykings binne hul geldige gebiede gebruik word.

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The automotive industry in South Africa is expanding as a result of pressure on the world economy that forces vehicle manufacturers to outsouree work to developing countries. In order to add value to automotive engine development, the capability to perform state-of-the-art engineering must be developed in this country. Threedimensional fluid flow simulation is one such area and is being developed in this study in order to enhance the ability to develop combustion systems. Another capability being developed at the University of Stellenbosch is the simulation of valve train dynamics. It was realised that there is a lack of research results of in-cylinder flow characteristics and how they influence combustion chamber processes. This project focuses on the investigation of two different combustion chamber geometries and how they influence the flow and combustion processes in two different combustion chambers. The aim is to gain a better understanding of combustion chamber flow as an indirect result from comparing the flow in two fundamentally different engines under similar operating conditions. The difference in the engines is that one was developed for reduced exhaust gas emissions while the other was developed to achieve high performance. The numerical simulation capability is developed in the process of achieving this goal. To achieve the above-mentioned aim, a literature study was performed on the different combustion chamber flow characteristics and how they are influenced by different configurations. An experimental method of measuring combustion characteristics is studied in order to establish the ability to perform the latter. Theory of numerical flow simulation is also studied with this same goal in mind. Experimental testing is performed and combustion analysis is done on the results. In conjunction to the experimental work, numerical flow simulations are performed on the two different combustion chambers. The results from experimental testing and numerical simulations have shown that obstructions in the flow into the combustion chamber, together with a port configuration that cause flow around the longitudinal axis of the cylinder, increases the rate at which fuel burns in the combustion chamber and thereby reduce the production of toxic emissions from the engine. The study also proved that reducing resistance to flow increases the amount of air that is breathed by the engine and thereby results in increased torque generation. Through this study, opportunities for further research are identified. The results of the study can be used when new combustion systems are developed, especially in the light of ongoing tightening of emission regulations. The contribution to numerical flow simulation capabilities developed in this study add value to the ability to develop new combustion systems in the future, especially when complimented by some of the further research topics identified. / AFRIKAANSE OPSOMMING: Die motorbedryf in Suid-Afrika is besig om vinnig te ontwikkel as direkte gevolg van druk op die wêreldekonomie wat internasionale motorvervaardigers forseer om werk na ontwikkelende lande uit te kontrakteer. Hoogs gesofistikeerde ingenieurstegnieke moet ontwikkel word in Suid-Afrika met die doelom waarde toe te voeg aan enjin ontwikkeling. Drie-dimensionele vloei simulasie is een van hierdie vermoëns en word tydens hierdie studie ontwikkelom die verbrandingstelsel ontwikkelings-vaardighede te bevorder. Nog 'n vaardigheid wat tans ontwikkel word aan die Universiteit van Stellenbosch is die vermoë om nok-en-klepstelsel dinamika te simuleer. Daar bestaan egter 'n leemte in navorsingsresultate van vloei eienskappe binne in die verbrandingsruim en hoe dit verbrandingsruim prosesse beïnvloed. Die projek fokus dus op 'n ondersoek van twee verskillende geometriese konfigurasies van die verbrandingsruim en hoe dit die vloei- en verbrandingsprosesse in die twee konfigurasies beïnvloed. Die doel is om 'n beter begrip te ontwikkel van verbrandingsruim prosesse as 'n indirekte gevolg van die vergelyking tussen twee fundamenteel verskillende enjins onder eenderse bedryfstoestande. Die verkil tussen die twee enjins is dat een ontwikkel is met die doelop verlaagde uitlaatgas emmissies en die ander ontwikkel is om verbeterde werkverrigting. Die numeriese simulasie vermoë is ontwikkel in die proses om die doel te bereik. Om bogenoemde doel te bereik is 'n literatuurstudie gedoen wat verskillende vloeieienskappe in die verbrandingsruim ondersoek, asook hoe dit deur verskillende konfigurasies beïnvloed word. 'n Eksperimentele metode III die bepaling van verbrandingseienskappe is ook bestudeer met die doelom laasgenoemde uit te voer. Teorie aangaande numeriese vloei simulasie is ook bestudeer met bogenoemde doel. Eksperimentele toetse is gedoen en verbrandingsanalise uitgevoer op die resultate. In kombinasie met die eksperimentale werk is numeriese simulasies van die prosesse in die twee verbrandingsruim konfigurasies uitgevoer. Die resultate van die eksperimentele toetse en numeriese simulasies toon dat obstruksies in die vloei na die verbrandingsruim, gesamentlik met die poort konfigurasie wat veroorsaak dat lug om die longitudinale as van die silinder vloei, die tempo waarteen die lug-brandstof mengsel verbrand verhoog en sodoende die vrystelling van skadelike uitlaatgasse na die atmosfeer verminder. Die studie het ook getoon dat die vermindering van weerstand teen vloei, die hoeveelheid lug wat in die verbrandingsruim invloei vermeerder en sodoende die wringkrag wat deur die enjin gelewer word verhoog. Deur die studie is verdere navorsingsgeleenthede uitgewys. Die resultate van die studie kan gebruik word in die ontwikkeling van nuwe verbrandingstelsels, veral in die lig van verstrengende regulasies rakende uitlaatgas emmissies. Die bydrae tot numeriese vloei simulasie vermoëns ontwikkel in hierdie studie voeg waarde toe tot die vermoë om nuwe verbrandingstelsels te ontwikkel, veral wanneer dit gekomplimenteer word met van die verdere navorsingsonderwerpe wat geïdentifiseer is.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Numerical design optimisation is a powerful tool that can be used by engi- neers during any stage of the design process. Structural design optimisation is a specialised usage of numerical design optimisation that has been adapted to cater speci cally for structural design problems. A speci c application of structural design optimisation that will be discussed in the following report is experimental data matching. Data obtained from tests on a physical structure will be matched with data from a numerical model of that same structure. The data of interest will be the dynamic characteristics of an antenna structure, focusing on the mode shapes and modal frequencies. The structure used was a scaled, simpli ed model of the Karoo Array Telescope-7 (KAT-7) antenna structure. Experimental data matching is traditionally a di cult and time-consuming task. This report illustrates how optimisation can assist an engineer in the process of correlating a nite element model with vibration test data. / AFRIKAANSE OPSOMMING: Numeriese ontwerp-optimisering is 'n kragtige ingenieurshulpmiddel wat ty- dens enige stadium in die ontwerpsproses ingespan kan word. Strukturele ontwerp-optimisering is 'n gespesialiseerde gebruik van numeriese ontwerp- optimisering wat aangepas is om spesi ek van diens te wees by die oplos van strukturele ontwerpsprobleme. 'n Spesi eke toepassing van strukturele ontwerp-optimisering wat in hierdie verslag bespreek sal word, is eksperi- mentele datakorrelasie. Data afkomstig van toetse op 'n siese struktuur sal gekorreleer word met data afkomstig van 'n numeriese model van die selfde struktuur. Die data van belang is die dinamiese eienskappe van 'n anten- nastruktuur, spesi ek die modusvorme en modale frekwensies. Die betrokke struktuur wat gebruik is, is 'n vereenvoudigde skaalmodel van die Karoo Array Telescope-7 (KAT-7) antennastruktuur. Eksperimentele datakorrelasie is, tradisioneel gesproke, 'n moeilike en tydro- wende taak. Hierdie verslag sal illustreer op watter wyse optimisering 'n inge- nieur van hulp kan wees in die proses om 'n eindige elementmodel met vibrasietoetsdata te korreleer.

Thesis (MEng)--University of Stellenbosch, 1995. / AFRIKAANSE OPSOMMING: Die moontlikheid om die warmteoordrag in die reensone van 'n natuurlike trek nat koeltoring te vcrbeter deur die gemiddelde druppel diameter van die sproei te verminder is ondersoek. Eksperimentele wcrk was daarop gerig om tipiese druppelgrootte verspreidings onder druppakking te bepaal, asook die verkryging van werklike verrigtings-data vir verskiJlende pakking en reensone kombinasies in 'n koeltoring toetsfasiliteit. 'n Fotografiese metode wat gebruik maak van beeldverwerkingstegniekc is ontwikkel om die druppelgrootte verspreidings wat in die )meltoring toetsfasiliteit gevind word te bepaal. 'n Rekenaar simulasieprogram wat ontwikkel is deur Dreyer [940Rl] is verder gebruik om reensone verrigtingsdata ( oordragskarakteristieke en druppelgrootte verspreidings) teoreties te vcorspel, vir vergelyking met en evalusie van die eksperimentele resultate. Dit is bewys dat die plasing van 'n laag spatroosters reg onder druppakking die gerniddelde druppeldiameter in die reensone verrninder het, wat gelei het tot 'n ooreenstemmende toename in oordragskarakteristiek. Met die gebruik van 'n rekenaar simulasie program is bereken dat hierdie opstelling die termiese kapasiteit van 'n koeltoring met tot 5 % kan verbeter. / ENGLISH ABSTRACT: The possibility of improving the heat transfer in the rain zone of large natural draft wet cooling towers, by decreasing the mean drop diameter in this region, has been investigated. Experimental studies were aimed at determining typical drop size distributions under trickle packs and obtaining actual performance data for packing and rain zone combinations in a cooling tower test facility. A photography-based method, which utilizes image processing techniques, was develo!Jed t() determine the drop size distributions found in the test facility. A computer simulation program developed by Dreyer [94DRI] was used to theoretically predict rain zone performance data (i.e., transfer coefficients and drop size distribution data) for comparison with and evaluation of the experimental data. I: was found that by placing a layer of splash grids beneath a trickle pack the mean drop diameter in the rain zone was decreased, resulting in corresponding increases in transfer characteristic. Using a computer simulation program it was calculated that this arrangement could increase the thermal capacity of a large natural draft cooling tower by up to 5 %.

Thesis (MEng.) -- Stellenbosch University, 1988. / ENGLISH ABSTRACT: In this report various mathematical models for the thermal evaluation of evaporative coolers and condensers are presented. These models range from the exact model based on the work by Poppe [84P01] to the simplified logarithmic models based on the work of McAdams [54Mcl] and Mizushina et al. [67MI1], [68MI1]. Various computer programs were written to perform rating and selection calculations on cross-flow and counterflow evaporative coolers and condensers. Experimental tests were conducted on a cross-flow evaporative cooler to determine the governing heat and mass transfer coefficients. The experimentally determined coefficients were cqrrelated and these correlations are compared to the existing correlations. The two-phase pressure drop across the tube bundle was also measured and a correlation for two-phase pressure drop across a tube bundle is presented.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The vibrations and noise “pollution” that rail vehicles produce have become of particular concern in recent years. More pressure is being placed on operators of trains and trams (especially those operating in urban environments) to reduce their impact on neighbouring infrastructure. This project investigated the infrastructure available for vibration and noise mitigation and generated material models for some of the materials used in these types of rail infrastructure. The most common type of rail infrastructure used in South Africa is ballasted sleepers. Rail pads are sometimes used to reduce the transmitted vibration of these sleepers; this study focused on the materials used in the manufacture of these pads. Since most of these materials can be described as resilient/viscoelastic, the study of literature regarding these materials is essential within the scope of this project. Models found in literature were adapted by the addition of a non-linear stiffness element to account for the material behaviour at higher preloads. Three commercially available materials were tested and optimisation algorithms applied to determine their material coefficients (damping and stiffness), focusing on the preload and frequency dependency of these coefficients. / AFRIKAANSE OPSOMMING: Die vibrasie en geraas “besoedeling” wat spoor voertuie genereer het in die in die afgelope paar jare van kritieke belang geword. Meer druk word op operateurs van treine en trems geplaas (veral die operateurs met operasies in stedelike gebiede) om hulle impak op aangrensende infrastruktuur te verminder. Hierdie projek is dus daarop gemik om te bepaal watter infrastuktuur beskikbaar is vir die vermindering van vibrasie en geraas asook die ontwikkeling van materiaal modellle vir sommige van die materiale wat gebruik word in hierdie tipes van spoor infrastruktuur. Die mees algemene spoor infrastruktuur wat gebruik word in Suid-Afrika is dwarslêers met ballas. Spoor blokke word soms gebruik om die oordrag van vibrasies te verminder vir hierdie dwarslêers en daarom het hierdie studie fokus geplaas op die materiale wat gebruik word in die vervaardiging van hierdie blokke. Aangesien die meeste van hierdie materiale beskryf kan word as veerkragtig/visco, is 'n literatuurstudie oor hierdie materiale noodsaaklik binne die bestek van hierdie projek. Modelle wat gevind is in die literatuur is aangepas deur 'n nie-lineêre styfheids element by te voeg wat voorsiening maak vir die materiale se gedrag by hoër voorspannings. Drie algemene kommersieël beskikbare materiale is getoets en optimeringsprossesse is toegepas om hulle materiaal koëffisiënte (demping en styfheid) te bepaal met die klem geplaas op die voorspanning en frekwensie afhanklikheid van hierdie koëffisiënte.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The removal of grape berries from the stems is an important step in the wine making process. Various problems are experienced using the destemming machines currently available, where the berries are mechanically removed and separated from the stems by a rotating beater shaft and drum. Not all berries are removed from the stems and broken stems can end up with the removed berries which can result in unwanted characters and flavours in the wine. The development of these machines is currently limited to experimental tests. In this study, the destemming process was investigated experimentally. The ability of the Discrete Element Method (DEM) to simulate this process was also investigated. A range of experiments was designed to obtain the material properties of the grapes. These experiments included the measurement of the stem stiffness and break strength, the berry stiffness, and the force needed to remove a berry from the stem. Experiments were conducted to gain further insight into the destemming process. Firstly, a simplified destemming machine with only a beater shaft and a single grape bunch was built. The influence of the bunch size and the speed of the beater shaft on the number of berries removed from the stems were investigated. Secondly, field tests on a commercial destemming machine were conducted and the performance of the machine was measured. A DEM model of both the simplified and the commercial destemming machine were built. Commercial DEM software was used with linear contact and bond models. The stems were built from spherical particles bonded together and a single spherical particle was used to represent each berry. The measured stiffnesses and break strengths were used to set the particle and bond properties. Modelling the simplified destemming machine, it was found that the DEM model could accurately predict the effect of the bunch size and the speed of the beater shaft on the number of berries removed from the stems. The model of the commercial destemming machine could accurately predict the machine’s performance in terms of the number of berries removed as well as the number of broken stems. / AFRIKAANSE OPSOMMING: Die verwydering van druiwekorrels vanaf die stingels is ʼn belangrike stap tydens die wynmaak proses. Verskeie probleme word ondervind met huidige beskikbare ontstingelaars, waar die korrels meganies verwyder en skei word vanaf die stingels deur middel van ʼn roterende klop-as en drom. Nie alle korrels word vanaf die stingels verwyder nie en gebreekte stingels kan saam met die verwyderde korrels beland, wat ongewensde karakters en geure in die wyn kan veroorsaak. Die ontwikkeling van ontstingelaars is tans beperk tot eksperimentele toetse. In hierdie studie is die ontstingel proses eksperimenteel ondersoek Die vermoë van die Diskrete Element Metode (DEM) om hierdie proses te simuleer is ook ondersoek. ʼn Reeks eksperimente is ontwikkel om die materiaal eienskappe van die druiwe te bepaal. Hierdie eksperimente sluit in die meet van die styfheid en breeksterkte van die stingel, die korrel styfheid, en die krag benodig om ʼn korrel vanaf die stingel te verwyder. Eksperimente is gedoen om verdere insig oor die ontstingel proses te bekom. Eerstens is ʼn vereenvoudigde ontstingelaar gebou, met slegs ʼn klop-as en een tros. Die invloed van die trosgrootte en die klop-as spoed op die aantal korrels wat verwyder is, is ondersoek. Tweedens is ʼn toets in die veld gedoen met ʼn kommersiële ontstingelaar om die werkverrigting van die masjien te bepaal. ʼn DEM model van beide die vereenvoudigde en kommersiële ontstingelaar is gebou. Kommersiële DEM sagteware is gebruik met lineêre kontak- en bindingsmodelle. Die stingels is gebou deur sferiese partikels aan mekaar te bind en ʼn enkele sferiese partikel is gebruik om ʼn druiwe korrel voor te stel. Die gemete styfhede en breeksterktes is gebruik om die partikel- en bindingseienskappe te spesifiseer. Die modellering van die vereenvoudigde ontstingelaar het getoon dat die DEM model akkuraat kan voorspel wat die invloed is van die trosgrootte en die klop-as spoed op die aantal korrels wat verwyder is. Die model van die kommersiële ontstingelaar kon die werkverrigting van die masjien akkuraat voorspel in terme van die aantal korrels wat verwyder is asook die aantal gebreekte stingels.

Thesis (MEng) -- Stellenbosch University, 1991. / ENGLISH ABSTRACT: In the present study various mathematical models have been developed for the analysis of spray cooled finnned-tube heat exchangers. These models range from simplified models based on the work by Kreid et al. [78KR1], Nakayama et al. [88NA1] and Erens et al. [90ER1] to a more comprehensive model based on the work by Poppe [84P01]. Computer programs were written to evaluate the performance prediction of these models on spray cooled heat exchangers in the vertical air flow mode. Experimental tests were conducted on a four-row finned-tube heat exchanger in a vertical air /water mist flow to verify the mathematical models and it was found that the performance of this heat exchanger could be predicted within 20 per cent using the accurate model. Significant performance enhancement (up to 3.5 times the dry performance) was found by spraying relatively small amounts of water onto the heat exchanger. The spray water massflow rate was found to have a significant effect on the two phase pressure drop across the heat exchanger. The present study indicated certain important factors which have to be taken into consideration when designing spray cooled heat exchanger units. These include the geometry of the finned-tubes, the temperature difference between the process water and the optimum air and the air /spray water ratio. / AFRIKAANSE OPSOMMING: In die tesis is 'n aantal wiskundige modelle ontwikkel wat gebruik kan word vir die analise van sproei verkoelde vinbuis warmte uitruilers. Die wiskundige modelle wissel van eenvoudige modelle wat gebaseer is op die werk van Kreid et al. [78KR1 ], Nakayama et al. [88NA1] en Erens et al. [90ER1] tot 'n omvattende model wat gebaseer is op die werk van Poppe [84 PO 1]. Rekenaar programme is geskryf om die die modelle se voorspellingsvermoe van die kapasiteit van sproei verkoelde warmte uitruilers te evalueer. 'n Eksperimentele ondersoek is gedoen op 'n warmte uitruiler met vier vinbuis rye in 'n toetsseksie met vertikale lugvloei. Die toets resultate is gebruik vir die evaluasie van die wiskundige modelle en het getoon dat die akkurate model se voorspellings binne 20 per sent van die gemete kapasitiet van die uitruiler val. Die eksperirnentele werk het verder aangetoon dat deur klein hoeveelhede water op die uitruiler te sproei, 'n toename in kapasiteit tot 3.5 keer die droe werkverrigting moontlik is. Die twee-fase drukval oor die uitruiler is sterk bei:nvloed deur die sproei water massavloei. Die analitiese navorsmg wat gedoen is met behulp van die rekenaar programme het aangedui dat daar 'n paar belangrike faktore is wat in ag geneem moet word met die ontwerp van sproei verkoelde warmte uitruilers. Die faktore sluit die vinbuis geometrie, die temperatuur verskil tussen die proses water en lug en optimum lug/sproeiwater massavloei verhouding in.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The use of micro gas turbines (MGTs) for the propulsion of unmanned aerial vehicles (UAVs) has become an industry standard. MGTs offer better performance vs. weight than similar sized, internal combustion engines. The front component of an MGT serves the purpose of compressing air, which is subsequently mixed with a fuel and ignited to both power the turbine which drives the compressor, and to produce thrust. Centrifugal compressors are typically used because of the high pressure ratios they deliver per stage. The purpose of this project was to design a centrifugal compressor impeller, and to devise a methodology and the tools with which to perform the aforementioned. A compressor impeller adhering to specific performance and dimensional requirements was designed. The new compressor was designed using a mean-line performance calculation code. The use of the code was vindicated through comparison with the results from a benchmark study. This comparison included mean-line, Computational Fluid Dynamic (CFD), and experimental results: the new design mean-line results were compared to the results of CFD simulations performed on the same design. The new design was optimised using an Artificial Neural Network (ANN) and Genetic Algorithm. Prior to and during optimisation, the ANN was trained using a database of sample CFD calculations. A Finite Element Analysis (FEA) was done on the optimised impeller geometry to ensure that failure would not occur during operation. According to CFD results, the final design delivered good performance at the design speed with regards to pressure ratio, efficiency, and stall margin. The mechanical stresses experienced during operation were also within limits. Experimental results showed good agreement with CFD results of the optimised impeller. Keywords: micro gas turbine, centrifugal compressor, impeller, CFD, experimental, optimisation, FEA. / AFRIKAANSE OPSOMMING: Die gebruik van mikrogasturbines vir die aandrywing van onbemande vliegtuie het ‟n standaard geword in die industrie. Mikrogasturbines bied beter werkverrigting teen gewig as binnebrandenjins van soortgelyke grote. Hierdie eienskap verseker dat mikrogasturbines as aandryfmotors vir onbemande vliegtuie uiters voordelig is. Die voorste komponent van ‟n mikrogasturbine dien om lug saam te pers, wat dan met brandstof gemeng en daarna aan die brand gesteek word om krag aan die kompressor en stukrag te voorsien. Sentrifugaalkompressors word tipies gebruik as gevolg van die hoë drukverhoudings wat hierdie komponente per stadium kan lewer. Die doel van hierdie projek was om ‟n sentrifugaalkompressor te ontwerp, en ‟n metode en die hulpmiddels te ontwikkel om laasgenoemde uit te voer. ‟n Kompressor rotor wat voldoen het aan sekere werkverrigtings en dimensionele vereistes is ontwerp. Die nuwe kompressor rotor is met behulp van 1-dimensionele werkverrigting-berekeningskode ontwerp. Die berekeningsakkuraatheid van die kode en díé van ‟n kommersiële Berekenings Vloeidinamika pakket is bevestig deur die berekende resultate te vergelyk met die van eksperimente. Die nuwe rotor is gevolglik deur middel van ‟n Kunsmatige Neurale Netwerk en Genetiese Algoritme geoptimeer. Die Kunsmatige Neurale Netwerk is voor en gedurende optimering deur Berekenings Vloeidinamika simulasies opgelei. Die meganiese sterkte van die geoptimeerde rotor is nagegaan met behulp van ‟n Eindige Element Analise. Dit is gedoen om te verseker dat die rotor nie sal faal by die bedryfspunt nie. Berekenings Vloeidinamika resultate het getoon dat die finale rotor ontwerp ‟n goeie werkverrigting lewer by die ontwerpspoed, met betrekking tot drukverhouding, bennutingsgraad, en stakingsmarge. Eksperimentele resultate het goeie ooreenstemming met die Berekenings Vloeidinamika resultate van die geoptimeerde rotor getoon. Sleutelwoorde: mikrogasturbine, sentrifigaalkompressor, rotor, Berekenings Vloeidinamika, eksperimenteel, optimering, Eindige Element Analise.

Thesis (MEng.)-- University of Stellenbosch, 1992. 140 leaves on single pages, preliminary pages i-xi and numbered pages 1-113. Includes bibliography. Digitized at 600 dpi grayscale to pdf format (OCR),using an Bizhub 250 Konica Minolta Scanner and at 300 dpi grayscale to pdf format (OCR), using a Hp Scanjet 8250 Scanner. / Thesis (MEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 1992 / ENGLISH ABSTRACT: The large variety of turbo-machinery blade root geometries in use in industry prompted the question if a optimum geometry could be found. An optimum blade root was defined as a root with a practical geometry which, when loaded, returns the minimum fillet stress concentration factor. A literature survey on the subject provided guidelines but very little real data to work from. An initial optimization was carried out using a formula developed by Heywood to determine loaded projection fillet stresses. The method was found to produce unsatisfactory results, prompting a photoelastic investigation. This experimental optimization was conducted in two stages. A single tang defined load stage and a single tang in-rotor stage which modeled the practical situation. The defined load stage was undertaken in three phases. The first phase was a preliminary investigation, the second phase was a parameter optimization and the third phase was a geometric optimization based on a material utilization optimization. This material optimization approach produced good results. From these experiments a practical optimum geometry was defined. A mathematical model which predicts the fillet stress concentration factor for a given root geometry is presented. The effect of expanding the single tang optimum to a three tang root was examined. / AFRIKAANSE OPSOMMING: Die groot verskeidenheid lemwortelgeometrieë wat in turbomasjiene gebruik word het die vraag na 'n optimum geometrie laat ontstaan. Vir hierdie ondersoek is 'n optimum geometrie gedefineer as 'n praktiese geometrie wat, as dit belas word, die mimimum vloeistukspanningskonsentrasiefaktor laat ontstaan. 'n Literatuur studie het riglyne aan die navorsing gegee maar het wynig spesifieke en bruikbare data opgelewer. Die eerste optimering is met die Heywood formule, wat vloeistukspannings in belaste projeksies bepaal, aangepak. Die metode het nie bevredigende resultate opgelewer nie. 'n Fotoelastiese ondersoek het die basis vir verdere optimeering gevorm. Hierdie eksperimentele optimering is in twee stappe onderneem. 'n Enkelhaak gedefineerde lasgedeelte en 'n enkelhaak in-rotor gedeelte het die praktiese situasie gemodeleer. Die gedefineerde lasgedeelte is in drie fases opgedeel. Die eerste fase was n voorlopige ondersoek. Die tweede fase was 'n parameter optimering. 'n Geometrie optimering gebasseer op 'n materiaal benuttings minimering het die derde fase uitgemaak. Die materiaal optimerings benadering het goeie resultate opgelewer. Vanuit hierdie eksperimente is 'n optimum praktiese geometrie bepaal. 'n Wiskundige model is ontwikkel, wat die vloeistukspanningskonsentrasiefaktor vir 'n gegewe wortelgeometrie voorspel. Die resultaat van 'n geometriese uitbreiding van die enkelhaaklemwortel na 'n driehaaklemwortel op die spanningsverdeling is ondersoek.