Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The trends in worldwide fuel consumption and availability were studied, these indicated a bigger growth in gaseous fuel use than that of crude oil over the last decade. The economics (cost of converting and running vehicles on LPG) were studied and compared with those of petrol and diesel fuels. The government's approach to LPG taxation and the structure of the fuel price was also considered in an attempt to foresee what the future holds for LPG use in the motor industry. Gas fuelling systems that are currently available were studied and briefly described. The information obtained from the background study was used to help in the conversion of a two litre petrol engine. The engine was equipped to run on petrol Injection, liquid phase LPG injection and LPG carburettion. In-cylinder pressures, exhaust emissions and fuel consumption were amongst the parameters that were recorded for each fuel. The in-cylinder pressure measurements were used to study the combustion characteristics of petrol and LPG. Computer modeling was also used to investigate the trends that were recorded and this gave valuable insight into the different combustion characteristics of each fuel and the effect of gaseous versus liquid supply. For the passenger bus market a 12 litre 6 cylinder diesel engine was converted to LPG operation only. This required several changes to the pistons, cylinder head, inlet manifold and the addition of an electronic ignition system. Some changes had to be made to the squish characteristics of the pistons to make it suitable for homogeneous fuel air mixtures. The reasons for this were studied and described. Dynamometer tests revealed inadequacies in the ignition system that still need to be addressed before the engine can be built into a bus. Recommendations are made as to best utilize LPG in the South African Automotive industry, so as to improve public transport and air quality in some of our cities. / AFRIKAANSE OPSOMMING: 'n Studie van tendense in wêreldwye energieverbruik en besikbaarheid is gedoen. Dit het aan die lig gebring dat die groei in die gebruik van gasagtige brandstowwe in die laaste dekade die van ru-olie oortref het. Die lewensvatbaarheid van Vloeibare Petroleum Gas (VPG) voertuie, ombouing sowel as lopende koste, is bestudeer en vergelyk met die van Petrol en Diesel voertuie. Die regering se benadering tot belasting op VPG en die struktuur van die brandstofprys is ook ondersoek om te bepaal of die gebruik van VPG in n groter skaal as tans lewenvatbaar is. Vir tegniese agergrond is gas aangedrewe voertuie wêreldwyd bestudeer om te sien watter brandstof-voorsiening stelsels en enjins gebruik word. Die verskillende stelsels word bondig beskryf. Hierdie inligting is onder meer gebruik in die ombouing van n twee liter petrolenjin na VPG. Die enjin is toegerus om op beide petrol en VPG te loop terwyl die VPG in gasfase met behulp van 'n vergasser of as vloestof deur brandstof inspuiting toegedien kon word. Ontbrandingskamerdruk, uitlaatgasse en brandstofverbruik is van die parameters wat tydens toetse gemeet is. Die ontbrandingskamerdukmetings is gebruik om die verbrandingskarakteristieke van elke brandstof te bepaal. Nagebootste verbrandingstempos is in n rekeraarprogram gebruik om verskillende verbrandings karakteristieke wat gemeet is te ondersoek en tendense te bevestig. Vir die swaarvoertuigmark is 'n 12 Liter diesel enjin ombebou na VPG gebruik. Die dieselpomp en inspuiters is vervang met elektroniese vonkontsteking en vonkproppe. Die verbrandingskamer moes verander word om spontane verbranding tydens samepersing te voorkom. Die redes hiervoor is ondersoek en beskryf. Dinamo toetse het tekortkominge uitgewys in die elektroniese vonkontstekingsstelsel wat nog nie ten volle aangespreek is nie. Aanbevelings is gemaak om die toenemende gebruik van VPG as motorvoertuigbrandstof in Suid Afrika aan te bevorder om sodoende beter gebruik te maak van die beskikbare energie uit ru olie en ander bronne. Aanbevelings is ook gemaak ten opsigte van die gebruik van VPG in openbare vervoer en verbetering van lug gehalte in sommige stede.

This thesis investigates the use of the Stagnation-Point Reverse-Flow (SPRF) combustor geometry for burning low-grade solid fuels that are attractive for specific industrial applications because of their low cost and on-site availability. These fuels are in general, hard to burn, either because of high moisture and impurity-content, e.g. biomass, or their low-volatiles content, e.g., petroleum-coke. This results in various challenges to the combustor designer, for example reduced flame stability and poor combustion efficiency. Conventional solutions include preheating the incoming flow as well as co-firing with high-grade fuels. The SPRF combustor geometry has been chosen because it was demonstrated to operate stably on standard gaseous and liquid-fuels corresponding to ultra fuel-lean conditions and power densities at atmospheric-pressure around 20-25 MW/m3. Previous studies on the SPRF combustor have proven that the unique, reverse flow-geometry allows entrainment of near-adiabatic products into the incoming reactants, thereby enhancing the reactivity of the mixture. Further, the presence of the stagnation-end created a region of low mean velocities and high levels of unsteadiness and mixing-rates that supported the reaction-zones. In this study, we examine the performance of the SPRF geometry on a specific low grade solid fuel, petroleum coke. There are three main goals of this thesis. The first goal is the design of a SPRF combustor to operate on solid-fuels based on a design-scaling methodology, as well as demonstration of successful operation corresponding to a baseline condition. The second goal involves understanding the mode of operation of the SPRF combustor on solid-fuels based on visualization studies. The third goal of this thesis is developing and using reduced-order models to better understand and predict the ignition and quasi-steady burning behavior of dispersed-phase particles in the SPRF combustor. The SPRF combustor has been demonstrated to operate stably on pure-oxygen and a slurry made from water and petroleum-coke, both at the baseline conditions (125 kW, 18 g/s, ~25 µm particles) and higher power-densities and powder sizes. For an overall combustor length less than a meter, combustion is not complete (global combustion efficiency less than 70%). Luminance imaging results indicate the incoming reactant jet ignites and exhibits intense burning at the mid-combustor region, around 15 jet diameters downstream of the inlet, most likely due to enhanced mixing as a result of the highly unsteady velocity field. This roughly corresponds to the location of the reaction zones in the previous SPRF combustors operating on gas and liquid fuels. Planar laser visualization of the reacting flow-field using particle-scattering reveals that ignition of a significant amount of the reactants occurs only after the incoming jet has broken into reactant packets. Post-ignition, these burning packets burn out slowly as they reverse direction and exit the combustor on either side of the central injector. This is unlike the behavior in liquid and gas-fueled operation where the incoming reactants burned across a highly corrugated, thin-flame front. Based on these findings, as well as the results of previous SPRF studies, an idealized model of combustor operation based on a plug flow reactor has been developed. The predictions suggest that fuel-conversion efficiency is enhanced by the combustor operating pressure and lowered by the heat-losses. Overall, this effort has shown the SPRF geometry is a promising compact-combustor concept for self-sustained operation on low-grade solid-fuels for typical high-pressure applications such as direct steam-generation. Based on these findings, it is recommended that future designs for the specific application previously mentioned have a shorter base-combustor with lower heat-losses and a longer steam-generation section for injection of water.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis comprises of the development of a facility were spark ignition engine fuels can be tested. Development of the facility included the installation of a standard spark ignition engine, an engine dynamometer, control and monitoring equipment, control and monitoring software, and an in-cylinder pressure measurement setup. The system was tested using petrol as well as a petrol-ethanol blend. The results indicated good accuracy and repeatability of the system. Analysis of the performance and combustion of the petrol-ethanol blend showed no significant difference in comparison to the petrol fuel. The petrol-ethanol blend showed a slight increase in oxygen content and fuel consumption as well as an increase in CO2 emissions and a decrease in CO emissions. During the project, a comparison was also made between the performance of fibre optic transducers and a piezoelectric transducer. It was found that the fibre optic transducers performed similarly to the piezoelectric transducer during low engine load conditions. At high load conditions however, the fibre optic transducers were not able to produce the same accuracy as the piezoelectric transducer. / AFRIKAANSE OPSOMMING: Hierdie tesis bestaan uit die ontwikkeling van 'n fasiliteit waar brandstowwe vir 'n vonkontsteking binnebrandenjin getoets kan word. Ontwikkeling van die fasiliteit sluit in die installering van 'n standaard vonkontsteking binnebrandenjin, 'n enjin rem, beheer en monitering toerusting, beheer en monitering sagteware, en 'n insilinder drukmeting opstelling. Die fasiliteit is getoets met suiwer petrol sowel as 'n petrol-etanol mengsel. Die resultate het hoë vlakke van akkuraatheid en herhaalbaarheid getoon. Ontleding van die werksverrigting en verbranding van die petrol-etanol mengsel het geen beduidende verskil getoon in vergelyking met die suiwer petrol brandstof nie. Die petrol-etanol mengsel het 'n effense toename in suurstofinhoud, brandstofverbruik, sowel as CO2 vrylating en 'n afname in CO vrylating getoon. Tydens die projek is 'n vergelyking getref tussen die akkuraatheid van optiese vesel drukmeters en 'n piësoëlektriese drukmeter. Daar is bevind dat die akkuraatheid van die optiese vesel drukmeters soortgelyk is aan die piësoëlektriese drukmeter gedurende lae enjin lastoestande. By hoë las omstandighede was die optiese vesel drukmeters egter nie in staat om dieselfde akkuraatheid as die piësoëlektriese drukmeter te handhaaf nie.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Development of analytical methods to characterise biodiesel has become central to the overall success of the marketing of biodiesel fuel. In this regard, different bodies including the American Society for Testing and Materials (ASTM) and the European normalization (EN) have come up with various methods to determine important biodiesel parameters such as total glycerol, methanol and the fatty acid methyl esters (FAMEs), etc. Various studies have been conducted on the parameters mentioned above using a variety of instrumentation and sample preparations. The best methods reported are those that have been adopted by both the ASTM and EN standards. The purpose of this study was to develop alternative analytical methods to both the recommended ASTM and EN methods and, in some cases, to make modifications to both standards (ASTM D 6571 and EN 14214) and methods to determine total and bound glycerol, the ester content and also methanol content in biodiesel. Moreover, water washing after transesterification and the effect this practice has on biodiesel cold flow properties such as kinematic viscosity, cloud and pour point and density were evaluated. The possibility of using the iodine value to predict the feedstock source of an unknown biodiesel was also investigated. Six different vegetable oil samples were transesterified with methanol and used for this study. The six samples used were palm, crown, sunflower, waste vegetable oil (wvo), peanut and rapeseed biodiesel. Quantitative results indicated that the use of programmable temperature volatilisation (PTV) for total glycerol did not produce the required repeatability of between 1-4% relative standard deviation(RSD) for total glycerol analyses in biodiesel with precision of 25%, 86%, 25% and 56% for free glycerol (FG), monoglycerides (MG), diglycerides (DG), and triglycerides (TG) respectively. The standard requires a relative standard of between 1-4% As an alternative to the method using gas chromatography, normal phase high performance chromatography (HPLC) with binary gradient elution was used to determine the bound glycerol content. This method proved accurate and repeatable with RSD % of 0.33, 1.12, and 1.2 for TG, DG and MG respectively. Following the EN14103 protocol (European standard ester determination), the Zebron ZBWAX column which is comparable to the specification recommended by EN14103 but afforded the determination of ester content from the esters of myristic acid (C14:0) to behenic acid (C22:0) with reproducibility with RSD % of 6.81, 1.91, 7.27, 0.64, 1.18, 1.55, 6.03, 1.96, and 5.21 for methyl esters of myristic, palmitic, stearic, oleic, linoleic, linolenic, arachidoic, gadoleic and behenic acid respectively. Solid phase micro extraction (SPME) using GC-MS was developed as an alternative to both the EN14110 and ASTM D93 protocols for determining the methanol content in biodiesel. For this method, polyethylene glycol fibre (PEG) was used together with a deuterated methanol internal standard and a DB-FFAP (60m×0.25um×0.25um) column. Less volume of sample was required as compared to the EN14214 method. This method was found to be sensitive, accurate and repeatable with a RSD % of 4.82. The Iodine number of biodiesel decrease compared to their corresponding feed stock and therefore predicting the feed stock of an unknown biodiesel was going to be difficult .Results from this study indicated that it is not possible to predict the feed stock source of an unknown biodiesel from its iodine value. The effect of water washing after phase separation on biodiesel cold flow properties such as kinematic viscosity, density, cloud and pour point depended on the type of biodiesel produced. We observed that water washing after transesterification caused an increase in all the cold flow properties of sunflower biodiesel, whereas only the densities and kinematic viscosities increased in the case of palm and waste vegetable oil biodiesel. The cloud and pour point of the latter two diesel samples remained unchanged after water washing. Thus, the effect of water washing on biodiesel cold flow depended on the type of biodiesel. Blending a highly saturated biodiesel (fewer numbers of double bonds) with a less saturated biodiesel (higher number of double bonds) resulted in an improvement of both the pour and cloud points of the resultant biodiesel blend. / AFRIKAANSE OPSOMMING: Die ontwikkeling van analitiese metodes om biodiesel te karakteriseer word tans as ‘n kernmaatstaf gesien om biodiesel suksesvol te bemark. Hiervoor het verskeie liggame wat die Amerikaanse Vereniging vir Toetsing van Materiale (AVTM) en die Europese Normalisering (EN) insluit met verskeie standaard analitiese metodes vorendag gekom om belangrike biodiesel parameters soos bv. totale gliserol, metanol en vetsuur metielesters te meet. Om hierdie parameters te bepaal is van ‘n wye verskeidenheid toetse met verskillende instrumente en monsterbereidings gebruik gemaak. Die beste metodes is deur beide die AVTM en EN aanvaar. Die doel van hierdie studie was om metodes te ontwikkel wat as alternatiewe kan dien tot die wat deur die AVTM en EN voorsgeskryf is. In sommige gevalle is aanpassings tot beide die standaarde (AVTM en EN) en metodes aangebring om die totale en gebonde gliserol-, esteren metanolinhoud te bepaal. Verder is die effek van ‘n water wasstap na transesterifikasie op biodiesel se kouevloei eienskappe gevalueer wat eienskappe soos kinematiese viskositeit, vertroebelingspunt, gietingspunt en digtheid insluit. Die moontlike gebruik van die Jodiumpunt om die bron van die voerstof van ‘n onbekende diesel te bepaal is ook ondersoek. In hierdie studie is ses verskillende oliemonsters van plantaardige oorsprong gebruik wat d.m.v. metanol getransesterifiseer is. Hierdie monsters het palm-, kroon-, sonneblom-, afvalplant-, grondboontjie- en raapsaadolie ingelsuit. Tydens die studie is programmeerbare temperatuur vervlugtiging (PTV) vergelyk met inkolom inspuiting soos deur AVTM D6584/EN14214 vir totale gliserol analise voorgeskryf. Kwantitatiewe resultate het getoon dat die PTV metode nie die verlangde akkuraatheid van ‘n relatiewe standaardafwyking (RS) van 1-4% vir beide vrye en gebonde gliserol kon handhaaf nie. Die akkuraatheid was in die omgewing van 25%, 86%, 25% en 56% vir vrye gliserol (VG), monogliseriede (MG), digliseriede (DG) en trigliseriede (TG), onderskeidelik. Normale fase hoë werkverrigting vloeistofchromatografie met ‘n binêre elueeringsgradiënt is as alternatief tot gaschromatografie (GC) ondersoek om die gebonde gliserolinhoud te bepaal. Al was die GC metode meer sensitief, het die vloeistofchromatografie metode ‘n hoë graad van akuraatheid en herhaalbaarheid getoon met RS% waardes van 0.33, 1.12 en 1.2 wat vir TG, DG en MG, onderskeidelik, verkry is. ‘n Zebron ZB-WAX kolom is vir die EN14103 protokol gebruik. Behalwe vir ‘n groter lengte kon hierdie kolom met spesifikasies soos deur EN14103 voorgeskryf vergelyk word. Met die gebruik van hierdie kolom kon die esterinhoud van miristiensuur (C14:0) tot behensuur (C14:0) bepaal word. ‘n Hoë graad van herhaalbaarheid met RS% waardes van 6.81, 1.91, 7.27, 0.64, 1.18, 1.55, 6.03, 1.96 en 5.21 vir die metielesters van miristien-, palmitien-, stearien-, oleïn-, linoleïn-, linoleen-, aragidoon-, gadoleïen- en behensuur is onderskeidelik verkry. Om die metanolinhoud van die biodiesel te bepaal is soliede fase mikroekstraksie (SFME) m.b.v. gaschromatografie-massaspektrometrie (GC-MS) as alternatiewe tot EN14110 en AVTM D93 ontwikkel. In hierdie metode is daar van poliëtileenglikolvesels (PEG) en gedeutereerde metanol saam met ‘n DB-FFAP kolom (60 mm x 0.25 mm x 0.25 mm) gebruik gemaak. Hierdie metode het ‘n kleiner monstervolume as die EN14214 metode benodig en was sensitief, akkuraat en hehaalbaar wat tot ‘n RS% waarde van 4.82 gelei het. Op grond van die Jodiumwaarde van biodiesel en hul ooreenstemmende voerstowwe het hierdie studie bevind dat die Jodiumwaarde nie gebruik kan word om die voerstof van ‘n onbekende diesel kan voorspel nie. Die effek van ‘n water wasstap na faseskeiding op verskeie kouevloei eienskappe soos kinematiese viskositeit, vertroebelingspunt, gietingspunt en digtheid het van die tipe diesel afgehang. Dit is bevind dat ‘n water wasstap na transesterifikasie ‘n toename in al die kouevloeieienskappe van sonneblomdiesel tot gevolg gehad het. In teenstelling hiermee het slegs die kinematiese viskositeit en digtheid van palm- en afvalplantdiesel vermeerder terwyl hul vertroebelings- en gietingspunte onveranderd gebly het. Die hipotese dat ‘n water wasstap na transesterifikasie tot swak kouevloei eienskappe lei is dus as onwaar bevind aangesien hierdie eienskappe deur die tipe biodiesel bepaal word. Deur ‘n hoogs versadigde biodiesel (lae aantal dubbelbindings) met ‘n minder versadigde biodiesel (hoë aantal dubbelbindings) te vermeng het tot ‘n verbetering van beide die vertroebelings- en gietingspunte gelei. / Centre for Renewable and Sustainable Energy Studies

Thesis (MBA)--Stellenbosch University, 2011. / The purpose of the study is to investigate the feasibility and sustainability of producing biodiesel from Jatropha, which contains oil in its seeds by using the Rainbow Biotech economic intervention or also known as the Distributed Food and Fuel Plantation (DFFP) model. The DFFP model is an effective mechanism for producing food and fuel in conjunction with each other, without the biodiesel production influencing the production of food in an adverse way. This is very important, as food security is a high priority for Africa, in order to address the problem of hunger and poverty. Biodiesel produced from Jatropha is an eco-friendly and sustainable alternative to fossil fuel diesel, as it is a carbon neutral fuel. Jatropha cultivation will also create much needed employment in the rural areas of Africa, which has the highest need for socio-economic development on the continent. Jatropha also has the ability to grow on marginal soils and wastelands. Africa has vast open spaces on which Jatropha, as a biodiesel source, can be cultivated without infringing on food production areas. The energy return of the whole production cycle of Jatropha biodiesel is nevertheless a source of much debate. Most stakeholders felt that the energy return is negative. No agreement has yet been reached about whether the energy content of the by-products from biodiesel must be included in the integrated energy balance equation. In order to make biodiesel from Jatropha a sustainable alternative for small farmers in the Southern African Development Community (SADC), government and regional policies will have to support it by promoting it actively. This will generate interest from global biodiesel investors who will then be willing to invest in projects based on the DFFP model of economic development. The DFFP model offers investors economic returns on investment of between 29 and 33 per cent and payback periods of less than four years. It is a very attractive economic development instrument, as it will ensure equitable and sustainable economic and rural expansion in SADC. Ultimately, this model has the potential to create a better life for all the inhabitants on the African continent. Rainbow Biotech (the DFFP model), as an economic development mechanism, will therefore indeed be the next big thing for the SADC in the future.

Thesis (MBA (Business Management))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Through the continual pursuit to reduce wastage through converting unmarketable by-products into a form that can be sold or used, it was established that an opportunity was available to refine poor-quality fish oil into a fuel source for internal use by a company. By commissioning a biodiesel refinery at the pelagic fish-processing facility of Pioneer Fishing (Pty) Ltd, it will be possible to refine the fish oil into biodiesel and easily distribute the fuel to the fishing vessels or the trucks used for the catching and transportation of pelagic fish. South African legislation is promoting small-scale biodiesel plants by reducing the taxes and levies payable on biodiesel sold by those refineries. The aim of this research report is to provide Pioneer Fishing (Pty) Ltd with a business plan to motivate the commissioning of a small-scale biodiesel plant to process the waste fish oil into a useable energy source to fuel the fishing vessels and trucks. / AFRIKAANSE OPSOMMING: Die voortdurende strewe na minder vermorsing deur onbemarkbare neweprodukte in ʼn verhandelbare of bruikbare vorm om te sit, het die geleentheid uitgewys om visolie van ʼn swak gehalte tot ʼn brandstof vir interne gebruik deur ‟n maatskappy te raffineer. Deur ʼn biodieselraffinadery by die diepseevisverwerkingsfasiliteit van Pioneer Fishing (Edms) Bpk in gebruik te neem, sal die afvalvisolie van dié aanleg tot biodiesel geraffineer kan word. Die biodiesel sal betreklik maklik beskikbaar gestel kan word aan die vaartuie en die vragmotors wat vir die vangs en vervoer van die diepseevis gebruik word. Heersende Suid-Afrikaanse wetgewing moedig juis kleinskaalse biodieselaanlegte aan deur ʼn korting toe te staan op die belasting en heffings op die biodiesel van sodanige raffinaderye. Hierdie navorsingsverslag het ten doel om Pioneer Fishing (Edms) Bpk van ʼn sakeplan te voorsien ter motivering van die ingebruikneming van ʼn kleinskaalse biodieselaanleg om die afvalvisolie tot ʼn bruikbare energiebron te verwerk waarmee die visvaartuie en -vragmotors aangedryf kan word.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / abstract / Mechanical Engineering / Doctoral / Doctor of Philosophy

The steady flow model is applied to ablatively accelerated spherical targets for inertial confinement fusion. A parameter study is conducted which identifies regions of good hydrodynamic efficiency. In the limit of very large acceleration the model is seen to become planar and can be used to treat some large aspect ratio shells. A model of charged particle beam driven ablation is presented. The ablation resulting from this form of energy deposition can resemble laser driven albation in some cases, but qualitatively different behavior occurs in certain regimes of the beam power and range. Laser energy deposition by inverse bremsstrahlung is also included. A procedure for descaling the dimensionless results of the steady flow model is presented. This allows for comparison of the model with experiments and numerical simulations.

No description available.