Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this investigation is to determine the performance of an axial ow compressor operating in a closed loop helium cycle under high through- ow conditions. The GTHTR300 four-stage helium test compressor was chosen for this investigation. Limited information on the helium test compressor's blade pro les are available, therefore a mathematical model was developed to calculate the blade geometries based on the theory of Lieblein and Aungier. A locally available three-stage compressor was used to con rm whether the mathematical model calculated the blade pro le geometries correctly. The Stellenbosch University Compressor Code (SUCC), an axisymmetric inviscid through- ow code, was used to compare the performance of the calculated three-stage compressor blade geometries with available experimental data. Excellent correlation was obtained, thus it was concluded that the mathematical model as well as the SUCC could be used to predict the performance of an axial ow compressor. The blade geometries of the helium test compressor were calculated and the pressure ratio and e ciency predictions of the SUCC correlated well with the experimental data. The helium test compressor was simulated to verify the calculated blade geometries further using the Computational Fluid Dynamics (CFD) package NUMECA FINE /Turbo. The FINE /Turbo pressure ratio and e ciency predictions compared adequately with the SUCC and available experimental data, especially in the design region. At high mass ow rates the stator blade row experiences negative incidence stall which results in a large recirculation zone in the stator blade wake. / AFRIKAANSE OPSOMMING: Die doel van hierdie ondersoek is om vas te stel wat die werkverrigting is van 'n aksiale kompressor in 'n geslote lus helium siklus onderhewig aan hoë deurvloei kondisies. Die GTHTR300 vier-stadium helium toets kompressor is gekies vir die ondersoek. Daar is egter beperkte inligting oor die helium kompressor se lem geometrie, dus is 'n wiskundige model ontwikkel om dit te bereken gebaseer op die werk van Lieblein en Aungier. Om te bevestig dat die lem geometrie akkuraat was, was die lem geometrie van die 'n plaaslike beskikbare drie-stadium kompressor bereken. Die Stellenbosch University Compressor Code (SUCC), 'n aksisimmetriese nie-viskeuse deurvloei kode, is gebruik om die prestasie van die berekende lem geometrie met beskikbare eksperimentele data te vergelyk. Uitstekende korrelasie is verkry vir die drukverhouding en benuttingsgraad resultate, dus is die gevolgtrekking gemaak dat die wiskundige model sowel as die SUCC gebruik kon word om die lem geometrie en werkverrigting van aksiale kompressors te bereken en voorspel. Die helium toets kompressor is gesimuleer met behulp van die numeriese vloei-dinamika pakket NUMECA FINE /Turbo om die berkende lem geometrie verder te veri eer. Die FINE /Turbo drukverhouding en benuttingsgraad resultate het goed gekorreleer met beide die SUCC resultate en eksperimentele data, veral in die ontwerpsgebied. Teen hoë massa vloei tempo's vind daar groot wegbreking teen negatiewe invalshoek plaas in die stator lemry en dit veroorsaak 'n hersirkulasie sone in die naloop van die stator lem.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Cooling tower inlet losses and effective flow diameter under no crosswind conditions and the pressure distribution around a circular cylinder subjected to a crosswind are modelled using CFD. The CFD model used to evaluate the inlet losses is validated with data measured in an experimental cooling tower sector model and data obtained from literature. The effect of different inlet geometries on the inlet loss coefficient and the effective diameter are investigated in order to improve cooling tower inlet designs. CFD models are developed to investigate the pressure distribution around infinite and finite circular cylinders. The infinite cylinder is modelled with a smooth surface and a rough surface so that the results can be compared to experimental data from literature. Ultimately a finite cylinder model with a rough surface is developed and the results are compared to experimental data from literature. / AFRIKAANSE OPSOMMING: Koeltoring inlaatverlies en effektiewe vloei deursnit onder geen teenwind toestande en die drukverdeling rondom ‘n sirkelvormige silinder, onderworpe aan ‘n teenwind, word gemodelleer deur gebruik te maak van “CFD”. Die “CFD” model wat gebruik word om die inlaatverlies te evalueer is gevalideer met data verkry vanaf ‘n eksperimentele koeltoring sektor model. Verder word die “CFD” model gebruik in ‘n ondersoek om te bebaal wat die effek is van verskillende inlaat geometrieë op die inlaat verlies koeffisiënt en die effektiewe diameter sodat die inlaat geometrie van koeltorings verbeter kan word. ‘n “CFD” model word dan ontwikkel om die druk verdeling rondom ‘n sirkelvormige silinder te ondersoek. Die silinder word as oneindig gesimuleer met ‘n glade en ruwe wand sodat die resultate vergelyk kan word met eksperimentele data verkry vanaf literatuur. Die afdeling word afgesluit deur die silinder as eindig met ‘n ruwe wand te simuleer en dan word die resultate vergelyk met eksperimentele data verkry vanaf literatuur.

Thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Renewable and Sustainable Energy at the Stellenbosch University. / Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: This project investigated the feasibility of incorporating photovoltaic cells into plastic roof tiles using injection moulding. Such tiles have the potential to provide robust and distributed electricity contained within the building envelope. Current-voltage curves of amorphous silicon modules were measured under illumination using the PVPM 2540C power measuring instrument, both before and after moulding. The efficiency after moulding was reduced by 53% to 88%, with modules that were heated for longer being degraded more. Thus the duration of exposure to high temperatures affected the extent of performance reduction during moulding. This suggested that faster moulding at a lower temperature or faster cooling could solve the problem. Economic feasibility was examined by calculating the levellised cost of electricity provided by the tiles. A large-scale development in the Western Cape was simulated using a typical meteorological year of weather data and using the anisotropic diffuse irradiance model of Perez et al. (1988). Avoided costs due to replaced roofing, avoided costs due to electricity distribution infrastructure, and Clean Development Mechanism credits were accounted for. The cost of energy calculated was R11/kWh in 2010 rands, which did not compete with the price of conventional grid-based electricity at R1.8/kWh. The importance of the cost of balance-of-system components, such as the inverter, and not only of the photovoltaic modules, was highlighted for future cost reductions. Several clear guidelines for manufacturing photovoltaic roof tiles were discovered. The most important of these was that many bypass diodes make the system more robust. / AFRIKAANSE OPSOMMING: Hierdie projek het die haalbaarheid van die integrasie van fotovoltaïse selle in plastiek dakteëls deur spuitvorming ondersoek. Sulke dakteëls het die vermoë om robuuste en verspreide elektrisiteit te lewer, sonder om die gebou se vorm te verander. Stroom-spanning kurwes van struktuurlose silikon eenhede is onder verligting gemeet met die PVPM 2540C kragmeet instrument, voor en na spuitvorming. Die doeltreffendheid na spuitvorming is met 53% tot 88% verminder, met groter vermindering in die eenhede wat langer warm was. Dus het die duur van blootstelling aan hoë temperature die mate van vermindering van doeltreffendheid beïnvloed. Dit het suggereer dat óf vinniger spuitvorming by laer temperature óf vinniger verkoeling die probleem kan oplos. Ekonomiese haalbaarheid is ondersoek deur die koste van die elektrisiteit wat deur die dakteëls gelewer is te bereken. ’n Groot behuisingsontwikkeling in die Wes-Kaap is gesimuleer deur ’n tipiese weerkundige jaar van weerdata en die anisotroop model vir verspreide ligstraling van Perez et al. (1988) te gebruik. Vermyde kostes van vervangde dakteëls, vermyde kostes van elektrisiteit distribusie infrastruktuur en krediete van die Meganisme vir Skoonontwikkeling is in ag geneem. Die elektrisiteitskoste was R11/kWh in 2010 se randwaarde, wat nie mededingend met die R1.8/kWh koste van gewone netwerk elektrisiteit was nie. Die belang van die kostes van die res van die installasieonderdele, soos die wisselrigter, en nie net die fotovoltaïse eenhede nie, is beklemtoon vir kostevermindering in die toekoms. Verskeie duidelike riglyne vir die vervaardiging van fotovoltaïse dakteëls is voorgestel. Die belangrikste van hierdie was dat meer omloopdiodes die installasie meer robuust maak. / Centre for Renewable and Sustainable Energy Studies

Project report presented in partial fulfilment of the requirements for the degree of Master of Engineering at the University of Stellenbosch. / Thesis (MScEng (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2008. / Three SunSlates™ were investigated to predict the performance of a fully installed system. The three slates were mounted on a fixed tilt of 30°, but with different orientations. The tilt is close to latitude of the Stellenbosch site, which is 33.92°. The one faces due east, another due west and last due north. This is to determine the effect that orientation has on the energy from the SunSlates™. Another slate, also facing north, was mounted on an adjustable framework. The framework was used to adjust the tilt angle of the slate, the orientation of the slate was constantly north. This slate was used to determine the effect of tilt on the total daily energy produced by the slate. To determine the performance of the slates daily measurements of temperature, solar insolation and wind was taken. These were used to investigate the effects on the SunSlates™. During the test period, which scheduled from September to November, the results show a difference, smaller than commonly believed, in the daily and annual energy delivered from the differently orientated slates. The slates facing east and west, however, have similar energy outputs, even though the power profiles differ. The north facing slate has the highest annual energy output, as expected. It was found that during the months of summer, November to January, the optimal tilted slate (Slate tilted to have a incidence angle of 0° from solar rays at noon) had a slightly lower energy output, but higher maximum power output per day than the 30 degree tilted slate. This is in contrast to the energy output predictions for the winter months where in the winter the energy can be as much as double that of the 30 degree tilted slate. The thorough testing and expert installation of the SunSlates™ are essential. From the case study it can be seen that some problems during installation, possibly a single faulty slate or shadowing, can cause a complete system to lose 30% of its efficiency. / Centre for Renewable and Sustainable Energy Studies

ENGLISH ABSTRACT: This document details the design process of a 97 kW microhydro system for Roman Bay Sea Farm in Gansbaai in the Western Cape Province of South Africa. It contains a literature study of microhydro power, with a focus on the use of Pump-as-Turbine technology and direct-drive systems. The literature study leads to several possible concepts for the project, which are then evaluated and the most suitable design is found to be a reverse running pump that powers a different pump through a direct drive system. Experimental data from KSB is used to test the accuracy of various correlations that can be used to generate turbine-mode operation curves from pump curves. The final design parameters for the complete system are then determined, and presented along with a cost benefit analysis. / AFRIKAANSE OPSOMMING: Hierdie verslag dokumenteer die ontwerpsproses van ‘n 97 kW mikro hidro stelsel vir Roman Bay Sea Farm in Gansbaai in die Wes-Kaap van Suid Afrika. Dit bevat ‘n literatuurstudie van mikro hidrokrag, met ‘n fokus op Pomp-as-Turbine en direk-gekoppelde stelsels. Die literatuurstudie lei tot ‘n aantal moontlike konsepte vir die projek wat dan evalueer word sodat die mees gepaste ontwerp gekies kan word. Dit word gevind dat ‘n pomp wat verkeerd om hardloop en ‘n ander pomp direk van krag voorsien die mees gepaste ontwerp is. Eksperimentele data van KSB word gebruik om die akkuraatheid van verskeie korrelasies te toets wat gebruik kan word om turbine-mode gedrag van pomp kurwes te bepaal. Die finale parameters van die hele stelsel word dan bepaal en word dan saam met ‘n koste-analise aangebied. / Centre for Renewable and Sustainable Energy Studies

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The focus of this thesis is on the investigation of the functioning of a liquefied-gas thruster. Such a thruster could be used to provide secondary propulsion to a microsatellite in orbit. A general overview of the need for thrusters in micro-satellites is put forward in the introduction. Motivation for deciding to investigate a liquefied-gas system is presented. Recent developments in the field of micro-satellites are discussed as well as their relevance to the project undertaken. Fundamental background theory relevant to the engineering problems associated with the development and analysis of such a system is also presented. Computer programs were written to simulate such a liquefied-gas thruster system. The experimental work carried out to analyse the system from a practical view-point is documented. Attention is also given to the measurement and calibration techniques used to obtain experimental data. One-dimensional fully explicit transient mathematical models of the thruster system were developed to model the system using both compressed air and butane as propellants. These models were incorporated into computer programs used to simulate the transient behaviour of the system. Although it is intended to use butane as the propellant onboard a satellite, the reason for modelling and simulating a system using compressed air is because air is a convenient fluid to work with from both a theoretical and practical point of view. An experimental model of a thruster system was designed, built and tested using air and butane as propellants. Most of the model was built using perspex to allow for the observation of the two-phase behaviour of the propellant inside the system. Locally purchased components were used for the solenoid and fill valves. Readily available butane lighter fluid was used for butane testing. Self-made heating elements were used to provide heat input to the propellant. Testing was done at different back pressures ranging from 100 kPa down to 20 kPa in a vacuum chamber. Good comparison between theoretical and experimental results was obtained for air. Theoretical results for peak thrusts tended to over predict experimental results by approximately 15 % for a system exhausting to a pressure of 100 kPa. Peak thrusts as high as 0.2 N were obtained for vacuum tests conducted at an absolute pressure of 20 kPa. Peak thrusts of approximately 50 mN were achieved for experimental testing III atmospheric conditions using butane with a starting pressure of between 270 and 290 kPa. Typical average thrusts of between 20 mN and 30 mN were noted for butane testing with initial pressure of between 200 to 300 kPa. Peak thrusts of over 0.1 N were observed for vacuum testing at an absolute pressure of 20 kPa. An equation to correlate the experimentally determined average thrust as a function of pulse duration and starting pressure was developed. This correlated most of the experimental data to within ±25 %. Theoretical results for butane testing are able to predict peak thrusts within approximately 20 % for starting pressures in the range of 200 to 300 kPa. Since the project was an exploratory investigation into a liquefied-gas thruster, some additional aspects relating to such systems were also given attention. The effect of liquid propellant motion or sloshing was considered and recommendations regarding the design and placement of the propellant tanks were made. The use of heat pipes as an alternative to electrical heating elements was investigated and some elementary design aspects are presented graphically. The management of the liquid propellant using surface tension devices was examined qualitatively. Recommendations relating to future projects in the field of simple, low-cost propulsion systems for micro-satellites are put forward. More specifically these recommendations are with regard to: thermo-fluid modelling of the propellant, future experimental work to be done, techniques to measure small thrusts and vacuum chamber testing. / AFRIKAANSE OPSOMMING: Die tesis ondersoek die funksionering van 'n vervloeidegas stuwer. So 'n stuwer kan gebruik word om sekondêre aandrywing aan 'n mikro-satelliet in 'n wentelbaan te verskaf. 'n Algemene oorsig oor die behoeftes van stuwers vir mikro-satelliete word voortgesit in die inleiding. Redes vir die gebruik van 'n vervloeidegas stuwer word bespreek. Onlangse ontwikkelinge in die veld van mikro-satelliet aandrywing word bespreek asook die toepaslikheid daarvan. Fundamentele teoretiese agtergrond verbonde aan die ontwikkeling en analise van so 'n stuwer stelsel word ook gegee. Rekenaarprogramme is geskryf om die gedrag van so 'n stuwer stelsel te simuleer. Eksperimentele werk is gedoen om die stelsel vanuit 'n praktiese oogpunt te analiseer. Aandag word ook gegee aan die metings- en kalibrasietegnieke soos toegepas vir die eksperimentele werk. Eendimensionele volle eksplisiete wiskundige modelle is ontwikkelom die oorgangsgedrag van die stuwer-stelsel te simuleer met beide lug en butaan as dryfmiddel. Hierdie modelle is geïnkorporeer in die rekenaar programme om die stuwer stelsel te simuleer. Alhoewel dit beoog word om butaan as die dryfmiddel aan boord die satelliet te gebruik, is lug ook gebruik vir simulasie weens sy gerieflikheid as 'n vloeier uit beide 'n teoretiese en 'n praktiese oogpunt. 'n Eksperimentele model van die stuwer stelsel is ontwerp, gebou en getoets met beide lug en butaan as dryfmiddels. Die model is hoofsaaklik uit perspex gebou sodat die twee-fase gedrag van die butaan uitgebeeld kon word. Vrylik beskikbare butaan aansteker vloeistof IS gebruik VIr butaan toetsing. Selfvervaardigde verhittingselemente is gebruik om hitte aan die dryfmiddel te verskaf. Toetse is gedoen deur verskeie omgewingsdrukke varieërend van 100 kPa af tot 20 kPa in 'n vakuumtenk te gebruik. Goeie ooreenstemming tussen die teoretiese en eksperimentele resultate vir die toetsing van lug is verkry. Die teoretiese resultate neig om die piek stukrag 15 % hoër te voorspel as die eksperimentele resultate vir 'n stelsel wat tot 'n omgewingsdruk van 100 kPa by die uitlaat. Piek stukragte van meer as 0.2 N is gekry vir vakuum toetse wat gedoen is by 'n omgewingsdruk van 20 kPa. Tydens eksperimentele toetsing met butaan teen 'n aanvanklike druk tussen 270 en 290 kPa, in atmosferiese toestande, is piek stukragte van ongeveer 50 mN behaal. Tipiese gemiddelde stukragte van tussen 20 en 30 mN is waargeneem vir butaan toetsing teen 'n aanvanklike druk tussen 200 en 300 kPa. Piek stukragte van meer as 0.1 N is behaal vir vakuum toetse met 'n absolute druk van 20 kPa. 'n Vergelyking om die gemiddelde stukrag, wat eksperimenteel bepaal is, as 'n funksie van puls tydsduur en aanvanklike druk te korreleer, is ontwikkel. Die meeste eksperimentele data se afwyking van die korrelasie-vergelyking was minder as 25 %. Teoretiese resultate vir butaantoetse het piek stukragte binne 20 % van die eksperimenteel metings korrek voorspel vir aanvanklike drukke tussen 200 tot 300 kPa. Weens die feit dat die projek 'n oorhoofse ondersoek in In vervloeidegas stuwer behels, is aandag ook gegee aan addisionele aspekte wat verband hou met sulke stelsels. Die effek van die vloeistof-dryfmiddel se onstabiele beweging in sy tenke is in ag geneem en voorstelle vir die ontwerp en plasing van die dryfmiddel tenke is gemaak. Die gebruik van hitte pype as 'n alternatief vir elektriese verhittingselemente is ondersoek. Verskeie ontwerp aspekte word grafies voorgestel. Die bestuur van die vloeistof-dryfmiddel deur van oppervlak spannings apparaat gebruik te maak, is kwalitatief ondersoek. Voorstelle vir verdere navorsing in die veld van eenvoudige, lae-koste stuwer stelsels vir mikro-satelliete is gemaak. Meer spesifiek is hierdie voorstelle gerig op die termo-vloeidinamiese modellering van die dryfmiddel, verdere eksperimentele navorsing, tegnieke om klein stukragte te meet en vakuumtenk toetse.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The aim of the thesis is to compare results obtained from a finite element analysis method (FEM) to experimental results of a 12.2m long semi-trailer driven off-road. Semi-trailers are of great importance in the transport industry. Furthermore, the need to obtain optimum and reliable semitrailers in this crucial stream of industry is indispensable. The work focuses on comparing the two results so that the finite element method may be used as design analysis and redesigning tool as a substitute to testing. The semi-trailer was driven on a relatively rough off-road at different speeds, at 70kmlh, 50kmlh and 40kmlh loaded with about 12 tonnes of brick pallets. The forces at the suspension of the semitrailer and strains at different parts were measured with the help of strain gauges and other data acquisition equipment. A finite element model of the semi-trailer was modelled in Nastran for Windows. The trailer parameters in the finite element were tuned to curve fit the test results. A comparison of the two /' results was made based on the average of absolute values and standard deviation, to verify the validity of the finite element model. / AFRIKAANSE OPSOMMING: Die doel van die tesis is om die resultate wat verkry is deur eindige element metodes (EEM) met eksperimentele resultate van 'n 12.2 m lang leunwa wat bestuur is op 'n grondpad te vergelyk. Leunwaens is baie belangrik vir die vervoer industrie. Verder is die behoefte om optimum en betroubare leunwaens in die industrie te vervaardig baie nodig. Die werk fokus daarop om die 2 resultate te vergelyk sodat die EEM gebruik kan word as ontwerp analiese en herontwerp gereedskapstuk en as 'n vervanging vir toetsing. Die leunwa was op 'n redelike rowwe pad teen verskillende snelhede nl. 70km/h, 50km/h en 40km/h met 'n 12 ton baksteen vrag gery. Die kragte by die suspensie van die leunwa en die vervorming by verskillende onderdele is gemeet met behulp van rekstrokies en ander data versamelings toerusting 'n Eindige element model van die leunwa is gemodelleer in "Nastran for Windows". Die sleepwa parameters in die eindige element model is verstel d.m.v krommepassing van die toets resultate. 'n Vergelyking van die 2 resultate is gebasseer op die gemiddelde van die absolute waardes en standaard afwykings, om die geldigheid van die eindige element model te kontroleer.

Thesis (MScEng)--Stellenbosch Universit, 2004. / ENGLISH ABSTRACT: The requirements regarding the quality of engines and vehicles have increased constantly, requiring more and more sophisticated engine testing. At the same time, there is a strong demand to reduce lead time and cost of development. For many years steady state engine testing was the norm using standard principles of power absorption. Since the mid 1980's increasing importance has been attached to the optimisation of transient engine characteristics and the simulation of dynamic real world driving situations on engine test stands. This has led to the use of bi-directional DC or AC regenerative dynamometers a practice now known as dynamic engine testing. Interfacing a computer with vehicle simulation software to an engine on a dynamic test stand and using "hardware in the loop" techniques, enables the simulation of real world driving situations in a test facility. In dynamic engine testing a distinction can be made between simulation testing and transient testing. In simulation testing the set point values are predetermined whereas in transient testing a model generates set point values in real time. Speeds and loads are calculated in real time on the basis of real time measurements. The model can be in the form of a human or driver simulation. This project involved the application of dynamic engine testing to simulating a racing application. It is termed Real Time Full Circuit Driving Simulation System due to the simulation of a race car circling a race track, controlled by a driver model and running the engine on a dynamic test bench in real time using "hardware in the loop" techniques. By measuring the simulated lap times for a certain engine configuration on the test bench in real time, it is possible to select the optimal engine set-up for every circuit. The real time nature of the simulation subjects the engine on the test bench to similar load and speed conditions as experienced by its racing counterpart in the race car yielding relevant results. The racing simulation was achieved by finding a suitable dynamic vehicle model and a three dimensional race track model, developing a control strategy, programming the software and testing the complete system on a dynamic test stand. In order to verify the simulation results it was necessary to conduct actual track testing on a representative vehicle. A professional racing driver completed three flying laps of the Killarney racing circuit in a vehicle fitted with various sensors including three axis orientation and acceleration sensors, a GPS and an engine control unit emulator for capturing engine data. This included lap time, vehicle accelerations, engine speed and manifold pressure, an indicator of driver input. The results obtained from the real time circuit simulation were compared to actual track data and the results showed good correlation. By changing the physical engine configuration in the hardware and gear ratios in the software, comparative capabilities of the system were evaluated. Again satisfactory results were obtained with the system clearly showing which configuration was best suited for a certain race track. This satisfies the modem trend of minimizing costs and development time and proved the value of the system as a suitable engineering tool for racing engine and drive train optimisation. The Real Time Full Circuit Driving Simulation System opened the door to further development in other areas of simulation. One such area is the driveability of a vehicle. By expanding the model it would be possible to evaluate previously subjective characteristics of a vehicle in a more objective manner. / AFRIKAANSE OPSOMMING: Die vereistes om die kwaliteit van enjins en voertuie te verhoog, word daagliks hoër. Meer gesofistikeerde enjintoetse word daarom vereis. Terselfdertyd is dit 'n groot uitdaging om die tydsduur en koste van ontwikkeling so laag as moontlik te hou. Gestadigde toestand enjintoetse, wat op die prinsiep van krag absorpsie werk, was vir baie jare die norm. Vanaf die middel tagtigerjare het die optimering van dinamiese enjinkarakteristieke en die simulasie van werklike bestuursituasies op enjintoetsbanke van al hoe groter belang geword. Die gevolg was die gebruik van twee rigting wisselof gelykstroomdinamometers en staan vandag bekend as dinamiese enjintoetsing. Deur 'n rekenaar met simulasiesagteware aan 'n enjin op 'n dinamiese toetsbank te koppel, word die moontlikheid geskep om enige werklike bestuursituasies van 'n voertuig te simuleer in die enjintoetsfasiliteit. Dinamiese enjintoetse kan opgedeel word in simulasietoetse en oorgangstoestandtoetse. By laasgenoemde genereer 'n "bestuurdersmodel" die beheerwaardes intyds deur te kyk na intydse metings terwyl by simulasietoetse die beheerwaardes vooraf bepaal word. Die "bestuurder" kan in die vorm van 'n persoon of rekenaarsimulasie wees. Die projek behels die toepassing van dinamiese enjintoetse vir renbaansimulasie en staan bekend as'n Intydse, Volledige Renbaansisteem weens die simulasie van 'n renmotor om 'n renbaan, onder die beheer van 'n bestuurdersmodel. Dit geskied terwyl die enjin intyds op 'n dinamiese enjintoetsbank loop en gekoppel is aan die simulasie. Deur die intydse, gesimuleerde rondtetye te analiseer, word die moontlikheid geskep om die enjinkonfigurasie te optimeer vir 'n sekere renbaan. Dit is bereik deur die keuse van 'n gepaste dinamiese voertuigmodel, 'n driedimensionele renbaanmodel, ontwikkeling van 'n beheermodel, programmering van die sagteware en integrasie van die dinamiese enjintoetsstelsel. Die simulasieresultate verkry is gestaaf deur werklike renbaantoetse. 'n Professionele renjaer het drie rondtes van die Killarney renbaan voltooi in 'n verteenwoordigende voertuig wat toegerus was met verskeie sensors o.a. drie as versnellings- en orientasiesensors, GPS en 'n enjinbeheereenheidemmuleerder vir die verkryging en stoor van enjindata. Die sensors het data versamel wat insluit rondtetyd, voertuigversnellings, enjinspoed en inlaatspruitstukdruk. Die korrelasie tussen die simulasie waardes en werklik gemete data was van hoë gehalte. Deur die fisiese enjinkonfigurasie te verander in die hardeware en ratverhoudings in die sagteware, is die vergelykbare kapasiteite van die renbaansimulasie geevalueer. Die resultate was weer bevredigend en die simulasie was in staat om die beste enjinkonfigurasie vir die renbaan uit te wys. Dit bevredig die moderne neiging om koste en ontwikkelingstyd so laag as moontlik te hou. Sodoende is bewys dat die stelsel waarde in die ingenieurswêreld het. 'n Intydse, Volledige Renbaansisteem die skep die geleentheid vir verdere ontwikkeling op verskeie terreine van simulasie. Een so 'n veld is die bestuurbaarheid van 'n voertuig. Deur die model verder te ontwikkel word die moontlikheid geskep om voorheen subjektiewe karakteristieke van 'n voertuig meer wetenskaplik te analiseer.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: A need exists for the development of an unmanned rotorcraft capable of autonomous flight, as would be required for the survey of high voltage electricity supply lines. A program was initiated at the University of Stellenbosch in December 2002 in order to develop such an aircraft. The first goal of this thesis was the development of software that could calculate the stability and control derivatives of a model helicopter. These derivatives could then be used in the formulation of an appropriate helicopter control strategy. The second goal of the thesis was an investigation of the stability and control characteristics of model helicopters. The trim settings of the helicopter were required in the calculation of the stability and control derivatives. A computer program was developed to determine the trim settings of a helicopter in forward flight. Another program was developed to calculate the stability and control derivatives, using the results of the trim analysis. The trim analysis was based on the assumption of negligible coupling between the longitudinal and lateral modes of motion. The method proposed by Bramwell (1976) was used to perform the trim analysis. The stability and control derivatives were calculated by obtaining the trim settings from the trim analysis. These derivatives were then used to solve the roots of the characteristic equations of the longitudinal and lateral modes of motion. The stability of the helicopters were investigated firstly by examining the stability derivatives and secondly through root-loci analyses. The most important results were the following: • The root-loci analyses indicated that a helicopter without a horizontal stabiliser suffered from instability of the phugoid mode. It was also found that the short-period motion of these helicopters was heavily damped. Fitting a horizontal stabiliser to these helicopters caused the phugoid motion to become stable even at low speeds. This was achieved at the cost of a reduction in short-period motion damping. • The periods of the lateral and longitudinal motions were smaller than those found on full-scale helicopters. This was attributed to the small mass and inertia properties of the model helicopters. An increase in speed is generally accompanied by an increase in the stability of the helicopters. This could be attributed to the effective operation of the tail surfaces at higher speeds. • The axial climbing speed of a helicopter is influenced by the rotor speed. A low rotor speed allows higher climbing velocities at a given power setting. This was due to lower induced power losses at low rotor speed, assuming that no blade stall occurs. • The rotor speed does not influence the incremental amount of power (M:,) required to achieve a certain climbing velocity, due to the fact that the profile power losses are constant for a certain rotor speed. • The simplified horseshoe-vortex theory can be used to analyse the downwash angle at the horizontal stabiliser if the helicopter is in high-speed forward flight. / AFRIKAANSE OPSOMMING: Daar is tans 'n vraag na die ontwikkeling van onbemande rotor-vlerk vliegtuie wat die vermoë beskik om hulself te beheer. Hierdie tipe vliegtuie sal gebruik word om byvoorbeeld hoë-spannings elektrisiteitverskaffingsdrade na te gaan. 'n Program is in Desember 2002 by die Universiteit van Stellenbosch begin om sulke vliegtuie te ontwikkel. Die eerste doel van hierdie tesis was om sagteware te ontwikkel wat die stabiliteit- en beheerafgeleides van 'n model helikopter kon bereken. Hierdie afgeleides kan dan gebruik word om 'n gepaste helikopter beheerstrategie saam te stel. Die tweede doel van die tesis was om die stabiliteit- en beheerseienskappe van model helikopters te ondersoek. Die berekening van die stabiliteit- en beheerafgeleides van die helikopter berus op die beheerinsette benodig om die helikopter in ewewig te hou (trim). 'n Rekenaarprogram is ontwikkelom hierdie beheerinsette vir 'n helikopter in voorwaartse vlug te bereken. 'n Ander program is ontwikkelom die stabiliteit- en beheerafgeleides te bereken met behulp van die ewewig beheerinsette. Die analise van die helikopter in ewewig berus op die aanname dat die grootte van die koppeling tussen die longitudinale en laterale beweginsmodusse weglaatbaar klein is. Die beheerinsette van die helikopter in ewewig tydens voorwaartse vlug is bereken deur van Bramwell (1976) se metode te gebruik. Die stabiliteit- en beheerafgeleides is bereken deur van hierdie beheerinsette gebruik te maak. Die afgeleides is gebruik om die wortels van die karakteristieke vergelykings van die longitudinale en laterale bewegingsmodusse te bereken. Die stabiliteit van die helikopters is eerstens beoordeel deur die stabiliteitsafgeleides te ondersoek en tweedens deur middel van 'n wortel-lokus analise. Die belangrikste resultate is as volg: • Die wortel-lokus analise toon dat 'n helikopter sonder 'n horisontale stabiliseerder phugoid-onstabiliteit (Iangperiode onstabiliteit) het. Die kort-periode beweging van hierdie helikopters het verder groot hoveelhede demping aangetoon. Die phugoid-beweging kon selfs teen lae snelhede gestabiliseer word deur 'n horisontale stabiliseerder aan te heg. Hierdie stabiliteit is egter bereik ten koste van die demping van die kort-periode beweging wat verminder is. • Die periodes van die longitudinale en laterale bewegings is kleiner gewees as vir volskaal helikopters. Dit kan toegeskryf word aan die klein massa en inersie van die model helikopters. • Die stabiliteit van die helikopter is in die algemeen verbeter soos die snelheid verhoog. Dit kan toegeskryf word aan die beter werking van die stert teen die verhoogde snelhede. • Die klimtempo van die helikopter word beïnvloed deur die hoofrotor snelheid. 'n Lae hoofrotor snelheid laat 'n hoër klimptempo toe teen 'n spesifieke drywinginset. Dit is as gevolg van die laer geïndusseerde drywingsverliese teen die laer hoofrotor snelheid. Daar word aanvaar dat die lugvloei oor die lem nie staak nie. • Die hoofrotor snelheid beïnvloed nie die inkrimentele drywing (M,,) wat benodig word om 'n sekere klimtempo te bereik nie. Dit is as gevolg van die konstante drywings verliese teen 'n sekere hoofrotor snelheid. • Die vereenvoudigde perdeskoenwerwel teorie kan gebruik word om die afspoel hoek by die horisontale stabiliseerder te bereken indien die helikopter in hoë-spoed voorwaartse vlug is.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The purpose of this study was to investigate the specification and use of appropriate seating systems to reduce whole-body vibration exposure in typical vehicles used in South African industry. As part of this study six suspension seats, which the manufacturers claim satisfy the requirements in ISO 7096 (2000), were tested. Six test subjects, three light and three heavy as specified in ISO 7096, were used to estimate the seat transmissibility functions in the vertical direction of the six different suspension seats. Transmissibility functions were measured in the laboratory using two excitation levels, 1m/s2 and 2 m/s2 r.m.s., of broadband frequency vibration and a spectrum approximating the EM5 spectral class in ISO 7096. SEA T values were calculated for operational vibration data measured in an articulated dump truck and a three-wheeled logger. It was shown that SEAT values for the EM1 spectral class could not be reliably estimated from seat transmissibility functions and need to be measured directly in the time-domain. The measurement procedures and seat selection criteria developed in this research project were used to compile a set of "Design Guidelines for Seat Selection for Whole-Body Vibration Control in Industrial Vehicles". These guidelines will provide manufacturers with an easy-to-implement methodology to control whole-body vibration transmitted to the operators of industrial vehicles and to comply with international regulations for whole-body vibration transmission. / AFRIKAANSE OPSOMMING: Die doel van die studie was om die spesifikasies en gebruike van geskikte sitplek stelsels van uit Suid Afrikaanse industriële voertuie, wat heel-liggaam vibrasies verminder, te ondersoek. Ses suspensiesitplekke, wat deur die vervaardigers voorgeskryf word, is getoets om te sien of hulle aan die ISO 7096 (2000) vereistes voldoen. Ses persone, waarvan drie lig en drie swaar is, soos in ISO 7096 voorgeskryf, is gebruik om die sitplek oordragsfunksies in die vertikale rigting vir die ses verskillende suspensiesitplekke te skat. Die oordragsfunksies is in die laboratorium gemeet deur twee opwekkingsvlakke, 1m/s2 en 2m/s2 w.g.k., van wyeband frekwensie vibrasie en n spektrum beraam tot die EMS spektrum soos in ISO 7096. 'SEA T' waardes was vanaf operationele vibrasie data wat in ge-artikuleerde vragmotors en driewiel- 'loggers' gemeet is bereken. Daar is gewys dat betroubare 'SEAT waardes vir die EM1 spektrum nie van sitplek oordragsfunksies geskat kan word nie, maar dat dit eerder direk van die tyd-gebied afgelees moet word. Die metings prosedures en die sitplek keuse vereistes wat in die navorsingsprojek ontwikkel is, is gebruik om "Ontwerp Riglyne vir Sitplek Keuse Vereistes vir Heel- Liggaam Vibrasie in Industriële Voertuie" saam te stel. Hierdie riglyne sal vervaardigers met maklik toepasbare metodes toerus om heel-liggaam vibrasie, wat oorgedra word na industriële voertuig operateurs, te beheer en om aan internasionale regulasies t.o.v. heel-liggaam vibrasie oordrag te kan voldoen.