Doctoral Degrees (Mechanical Engineering)

Permanent URI for this collectionhttps://hdl.handle.net/10413/6861

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Sustainable energy efficiency and energy security in developing countries: a case study of airports in South Africa.
(2022) Joseph, Jerusha Sarah.; Inambao, Freddie Liswaniso.
When looking at the penetration of energy efficiency into the built environment and progress in the decrease in reliance on fossil fuel sources for energy generation, there is a definite challenge in obtaining the priority it requires to arrest the exponential increase in carbon emissions. Energy being key to economic development and improvement of the human way of life, developing countries face unique challenges to secure and sustain low carbon energy sources and effectively inculcate energy efficiency. This study aimed to present a solution in the form of an engineering approach entrenched in the three dimensions of business sustainability, i.e., environmental, social, and economic, to ensure that efforts towards energy efficiency and energy security in developing countries are effective and sustained in reducing carbon emissions. This solution was implemented in a live environment for nine airports in South Africa, and the results are presented in the form of case studies. The thesis investigated the global context of the climate change challenge and the global trends regarding carbon emissions from energy generation. The barriers that developing countries face with respect to achieving energy efficiency and energy security are presented together with the focuses required to overcome the barriers. Energy efficiency is investigated from the point of resource extraction to the point of energy end use, investigating energy conversion efficiencies, showing its best-matched end-use, resulting in the determination of principles for energy efficiency from component to system to infrastructure ecosystem. The principles developed were used to write an energy efficiency policy for all new infrastructure adopted at Airport Company South Africa’s (ACSA’s) nine airports in South Africa. An approach to interpreting onsite low carbon energy sources and their generation potential using available commercial technologies is proposed. Principles are created to determine an optimum low carbon energy mix that is suitable to available resources, business focus, operating environment and efficiently matching the site energy demand. The resulting energy mix based on these principles is presented as a case study for ACSA’s airports. The technologies identified for implementation to reduce energy consumption of the airports as well as their carbon footprint through the energy mix are tested for their financial viability using an economic model run via Microsoft Excel. These initiatives are SMART (specific, measurable, achievable, relevant, timed) in that they are specifically chosen for an organisation in a developing country, measurable in economic return and environmental benefit, achievable for the business, relevant to the airports’ geographical location and timed to map a pathway to carbon neutrality in electricity consumption for the airports by 2030. To ensure that the principles defined are sustained through the necessary changes in legislation, personnel and technologies, a set of key factors that underpin energy efficiency and energy security were determined and are presented. A case study of the implementation of these factors for airports in South Africa are presented. The thesis concludes with leveraging the fourth industrial revolution for innovative engineering solutions, presenting smart solutions to close the large development time gaps required for building human capacity, engineering capability and costly storage technologies to mature due to inherent intermittency of renewable energies. The results of the study and its implementation show that the solutions presented for energy efficiency and a low carbon energy mix are realistic and successful, while being grounded in sound scientific and engineering principles and sustained through inevitable changes. This is evident in the various strategies, company policies, technical guidelines and other programmes being approved and implemented by the senior management of the organisation that owns and operates the nine South African airports presented in this case study. The findings of the implementation show that a low carbon energy mix makes business sense, provides energy security and that achieving carbon neutrality is possible through the adoption of carbon offsetting. The “acid test” showing the solution presented in this thesis is being implemented for the nine airports in South Africa is that it still remains as a valid and a business focus even in the financial crisis faced by the aviation industry since the COVID-19 pandemic.
Combustion studies of hybrid nanoadditive doped waste cooking oil biodiesel and its blends in compression ignition engine.
(2021) Maverengo, Hilton.; Inambao, Freddie Liswaniso.
South Africa, among the developing nations in sub-Saharan Africa lacks technologies for converting crude biooil into biodiesel to run fuel CI engines. The country has also struggled to identify a suitable feedstock that can be used for biodiesel production. This research was therefore aimed at analysing the suitability of mixed waste cooking oil (WCO) biodiesel doped with hybrid nano particles as a viable fuel for diesel engines. The utilization of WCO as feedstock for biodiesel is garnering attention since it does not impact on the food supply chain and provides a solution to the challenges associated with its disposal. Biodiesel acceptance has been hampered by three main issues. These are related to higher production costs linked to feedstock, higher nitrogen dioxide emissions, and a lack of economic evaluation of technologies incorporating different alcohols and catalysts. This research performed investigations to develop solutions to circumvent all these challenges. Regarding high feedstock cost, WCO was identified to present an easily available solution since it is acquired at a low cost and its usage helps to solve the disposal problem. Manufacture, assessment, and engine testing of biodiesel from WCO was conducted to evaluate its viability as a potential feedstock for biodiesel. From the derived results, WCO oil has higher oil yields and excellent fuel properties and therefore is a viable feedstock to create biodiesel. Transesterification, a biodiesel creation measure, was performed utilizing methanol and NaOH or KOH as catalysts. This feedstock showed some favourable engine exhaust emission behaviour, but on engine performance considerable shortfalls were noted when evaluated against fossil diesel (FD) fuels. Lower brake thermal efficiency and higher fuel consumption were noted when the neat fuel blends with fossil diesel were tested in two-cylinder compression ignition engines. Higher NOx emissions were also noted with WCO and its blends when evaluated against FD. Three options are available to dealt with the above problems, namely, engine modification, exhaust after-treatment, and fuel reformulation. Fuel reformulation is the most promising due to its easy implementation and cheaper cost. The researcher’s search for the most relevant solution resulted in identification of hybrid nanoparticles consisting of cerium oxide and aluminium oxide as the most appropriate solutions. WCO biodiesel and its blends were doped with nanoparticles and tested in two-cylinder compression ignition (CI) engines and results compared with those of FD. From the experimental analysis, addition of hybridized nano additives improved BTE by a maximum value of 6.22 % compared to FD fuel when evaluated against load. A maximum decrease in BSFC of 10.20 % was noted with hybrid nano fuel WCO20A50C50 compared to FD fuel. A significant reduction in NOX of 25.62 % was found compared to FD. CO, unburnt hydrocarbons (UBHC) and smoke opacity were reduced by 36.8 %, 27.8 % and 17.68 % respectively compared to FD. WCO20A50C50 produced the most superior characteristics of all the fuels tested in this research. To understand the combined impact of hybrid nanoparticles and other engine conditions on performance and emissions, design of experiments (DOE) using the response surface method (RSM) was performed to model and optimize WCO20 performance and emissions parameters. This was accomplished by utilizing a variable compression engine and selecting three variables, namely, hybrid nanoparticle blends (fuel blend), compression ratio (CR) and load as input parameters, while the analyzed responses were brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), nitrogen oxides (NOX), unburnt hydrocarbons (UBHC), carbon monoxide (CO) and smoke. The outcomes from this investigation showed that RSM is a viable technique for improvement of the parameters of biodiesel blends doped with nanoparticles in diesel engines. Considering the intricacy of biodiesel production measures, process development, technical assessment, and advancement of biodiesel according to the entire chain, is fundamental for improving its performance and increasing its global adoption. A detailed biodiesel process flow design was developed and economic assessment incorporating material performed. The designed plant is expected to produce 16.88 tons per annum. The cost of biodiesel was evaluated based on researched cost variables and plant data which resulted in a biodiesel production cost of ZAR10.10 per kg giving a total production cost of ZAR10,100.00 (US$673.33) per ton. A CaO ethanolysis catalysed process was shown to be the most appropriate process for WCO production – the reaction was faster and produced a high yield. South Africa, among the developing nations in sub-Saharan Africa, has a huge capacity to produce its own renewable fuels but at present there is an absence of localized and effective applicable techniques for converting crude bio-oil into biodiesel to run fuel CI engines. Therefore, the discoveries of the present doctoral study are important because they demonstrate that it is viable to convert WCO to biodiesel and that its properties can be enhanced with the addition of nano particles, thereby demonstrating that its performance is even better than that of FD. Furthermore, a more sustainable CaO catalysed ethanolysis, with superior yields and locally produced in comparison to methanolysis, has been effectively developed and evaluated, as per the objectives of the thesis.
The impact of disruptive technology on the manufacturing process, and productivity, in an advanced manufacturing environment.
(2022) Salawu, Ganiyat Abiodun.; Bright, Glen.; Onunka, Chiemela.
Disruptive technology plays a critical role in the performance of mechatronic systems in an advanced manufacturing environment. Robots were used to perform pick and place task in a virtual manufacturing environment. Newton-Raphson model, renewal theorem and queuing theory were used to model the disruptive technology and develop decision-making algorithms in an advanced process. The motion of the conveyor belt system starved modeled and simulated to determine suitable design parameters that were compatible with the tasks of the pick and place robot. MATLAB and Engineering Equation Solver (EES) were used to determine static solutions and simulated solutions to the pick and place problem in the advanced manufacturing process. The results from the simulations were used to develop suitable task-dependent operational conditions in the advanced manufacturing environment. The simulation results were used to determine the optimal conveyor speeds required for the robotic tasks. Comparing the throughput rate of the developed system with the simulated system indicated that optimal productivity was achieved when the decision-making algorithms were implemented at the early stages of the manufacturing process.
Studying the feasibility of hydroprocessing used cooking oil into hydrogenation derived renewable diesel from local feedstock and catalyst.
(2021) Pelemo, Josiah.; Inambao, Freddie Liswaniso.; Onuh, Emmanuel Idoko.
Identifying and developing heterogeneous catalysts capable of mild-cracking used cooking oil (UCO) into hydrogenation-derived renewable diesel (HDRD) or green diesel production has posed a considerable challenge to commercialization of this fuel type in the energy sector. HDRD has received wide acceptance as alternative renewable energy that guarantees a pollutant-free environment, sustainability, renewability, and possesses a high degree of compatibility with compression ignition (CI) engine with little or no retrofitting needed. This research focuses on the feasibility of locally sourced UCO and catalysts for hydrogenation into green diesel. The objectives of this research are to produce a biofuel for CI engine using biowaste catalyst and UCO as a feedstock. Various studies have highlighted the benefit of UCO as a feedstock for biofuel production. UCO was collected from takeaway outlets. The samples were prepared by the in-situ hybridization method, heated on an electric heater fitted with a magnetic stirrer kept at 110 ⁰C and agitating speed of 50 rpm. The novel approach of in-situ hybridization of waste cooking oil was investigated. The outcome of the investigation showed that hybridization of the samples caused an increase in iodine value from 80.4 cg/g to 100.2 cg/g, affected kinematic viscosity, saponification value, and density, but did not affect cetane number, higher heating value, and acid value. The results are evidence that hybridization is a viable technique for improving the quality of existing feedstock and creating high-quality feedstock for the production of HDRD. Bio-based thermal power plant fly ash (BBTPPFS) was sourced locally from an ESKOM power plant in South Africa, pulverized, and developed into a fine powder, while SiO2, Al2O3, and CaO were procured from a commercial supplier. The samples were reinforced in various proportions and subjected to thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) characterization processes. The results revealed that SiO2 reinforced with BBTPPFS showed adequate properties that render it viable as a potential low-cost green catalyst for hydrogenation and capable of mild cracking to achieve a green diesel range C15-C18. The properties of locally sourced catalyst and feedstock were evaluated; experimental results revealed that the BET surface area, pore-volume, and micropore volume of fly ash reinforced with SIO2 showed high catalytic viability because of its capability to withstand temperatures up to 950 °C. Also, the addition of SIO2 to BBTPPFS showed a significant percentage increment in quartz, calcite, and mullite. This property is further evidence of its viability as a potential local catalyst for hydrogenation. HDRD were produced from hydro-processed used cooking oil using a locally sourced fly ash catalyst. The properties of HDRD were measured according to the ASTM standards and compared with green diesel. In terms of fuel quality, engine performance, and emission outcome, HDRD showed high yield and exhibited excellent fuel properties. The results from the engine test and combustion performance in a diesel engine are compatible with results from a CI engine, and meet acceptable performance and emission standards.
Development and fabrication of functionally graded aluminium metal matrix composite for automobile component applications.
(2021) Owoputi, Adefemi Oluwaniyi.; Inambao, Freddie Liswaniso.; Ebhota, Williams Saturday.
In recent times, interest in aluminium matrix composites (AMCs) have garnered traction over conventional aluminium alloys as the material of choice in the manufacturing of components for various engineering applications. Engineering components developed from single-element material are increasingly less favored over materials engineered from two or more elements. The rise in the demand for a multifunctional engineering material to exhibit opposing yet complementary engineering properties at different spatial positions within the material due to functionality requirements, has birthed several innovative fabrication processes. This study focuses on the development and fabrication of functionally graded aluminiummetal matrix composite (FGAMMC) through the liquid metallurgy route for proposed automobile component production. Industrially produced A356 aluminium alloy and silicon carbide powders (Al-SiC) was adopted as the base matrix and reinforcement materials for the fabrication of the metal matrix composites. Centrifugal casting technique was used to fabricate seven samples of Al-SiC functionally graded aluminium metal matrix composites with varied reinforcements particle size and weight percent addition. Samples A, B, and C contained 1 wt.%, 3 wt.%, and 5 wt.% of SiC of size 7 μm reinforcement, respectively, while samples E, F, and G had 1 wt.%, 3 wt.%, and 5 wt.% of SiC of size 15 μm reinforcement respectively. Sample D with no reinforcement additions served as the control sample for the experiment. Microstructural characterization showing the elemental composition and reinforcement distribution of silicon carbide particles within the matrix of the cast composite was carried out using optical microscopy (OM), optical emission spectroscopy (OES), energy dispersion xray (EDX), and scanning electron microscopy (SEM). The influence of SiCp on the mechanical, wear behavior and thermal properties of the cast aluminium composites were determined by subjecting the cast samples to mechanical, tribological, and thermal tests. Sample C with 5 wt.% and 7 μm of SiC particle reinforcement recorded improved hardness,compressive strength, Young's modulus, shear strength, and shear modulus of 112.7 HV0 1, 3107 MPa, 6.39 GPa, 14.4 GPa, and 9.29 GPa, respectively. Tribological analysis show an increase in the cast composites' wear resistance and frictional coefficient proportional to the frequency of contact between the counterface ball of the tribometer and the dispersed SiC reinforcements in the composites' matrices. Thermogravimetric analysis showed the weight loss and heat flow rates exhibited by the cast samples as the temperature was increased from 25 °C to 1000 °C in an Argon environment. Although negligible weight loss was recorded for all the cast composites within the experimental temperature boundary, sample C with 7 𝜇m
Implementation of CFD and remote sensing technology to investigate the suitability of telecommunication mast for wind resource assessment in southern Africa.
(2021) Okorie, Maduako Emmanuel.; Inambao, Freddie Liswaniso.
Abstract available in PDF.
Designing a photovoltaic-microbial fuel cell (pv-mfc) renewable hybrid system based on public-private partnership and other South Africa’s policies: a case study Umhlathuze municipality.
(2021) Nhleko, Melusi Velolwenkosi.; Inambao, Freddie Liswaniso.
Abstract available in PDF.
Effect of flexible supports on the frequencies of nanobeams with tip mass and axial load for applications in atomic force microscopy (AFM)
(2020) Moutlana, Malesela Kenneth.; Adali, Sarp.
This aim of this investigation is to describe the mechanical performance of a beam (probe) used in dynamic atomic force microscopy (dAFM) which can be utilized in scanning the topographical features of biological samples or "pliable" samples in general. These nanobeams can also be used to modify samples by using high frequency oscillating contact forces to remove material or shape nano structures. A nanobeam with arbitrary boundary conditions is studied to investigate different configurations and the effects of the relevant parameters on the natural frequencies. The nano structure is modelled using the Euler-Bernoulli theory and Eringen's theory of nonlocal continuum or first order stress-gradient theory is incorporated to simulate the dynamics of the system. This theory is effective at nanoscale because it considers the small-scale effects on the mechanical properties of the material. The theory of Nonlocal continuum is based on the assumption that the stress at a single point in the material is influenced by the strains at all the points in the material. This theory is widely applied to the vibration modelling of carbon nanotubes in several studies. The system is modelled as a beam with a torsional spring boundary condition that is rigidly restrained in the transverse direction at one end. The torsional boundary condition can be tuned, by changing the torsional spring stiffness, such that the compliance of the system matches that of the sample to prevent mechanical damage of both the probe tip and the sample. When the torsional spring stiffness is zero, the beam is pinned and when the stiffness is infinite, the beam is a cantilever. In the first case, a mass is attached to the tip and a linear transverse spring is attached to the nanobeam. The mass and spring model the probe tip and contact force, respectively. In the second case, at the free end is a transverse linear spring attached to the tip. The other end of the spring is attached to a mass, resulting in a single degree of freedom spring-mass system. When the linear spring constant is infinite, the free end behaves as a beam with a concentrated tip mass. When the mass is infinite, the boundary condition is that of a linear spring. When the tip mass is zero, the configuration is that of a torsionally restrained cantilever beam. When tip of the nanobeam vibrates, the system behaves like a hammer and chisel. The motion of the tip of the beam and tip mass can be investigated to observe the tip frequency response, force, acceleration, velocity and displacement. The combined frequencies of the beam and spring-mass systems contain information about the maximum displacement amplitude and therefore the sample penetration depth.
Effects of pyrolyzed municipal solid waste feedstocks as energy sources for non-road diesel engine, combustion, performance and emissions characteristics using biodiesel blended ratios.
(2021) Maroa, Samwel Semakula.; Inambao, Freddie Liswaniso.
Biodiesel oil blending is not a new concept in the study of biofuels and production. Blending is a chemical process of two or more different feedstocks comingled in varying proportions in the production of a new oil or fuel blend possessing different physico-chemical properties. Since fuel properties and the physico-chemical configuration of each feedstock vary from source to source, blending improves and enhances these properties. Therefore, the combination of different feedstocks enhances and improves properties of the initial parent feedstock, by adapting to improved and high-quality attributes. Worldwide, the sources of biodiesel production has been centred on edible and non-edible plants such as sunflower, canola, soybean, moringa, Jatropha, and so on. However, in the recent past, there has been a renewed shift into biomass and other recycled waste sources for biodiesel production and utilization. Waste to energy is a critical area of research and study in this present work as it intends to fill in these gaps by emphasising the shift to biodiesel production from non-plant-based sources. This shift will increase food security by discouraging the contribution of commercial farming for the production of biodiesel. This work contributes to improving environmental protection by reducing pollution from municipal solid waste found in landfills and other waste management sites. Waste resources such as waste cooking oil, waste engine oil, waste tyre oil and waste plastic oil converted into energy provide many alternatives in reducing wastage. By promoting use of these resources, this study aims at increasing environmental awareness and sustainability by using waste as an energy resource. This focus will open up socio-economic opportunities in recycling besides the academic and research impacts. By employing blending strategies using these waste feedstocks (engine oil, cooking oil, plastic oil and waste tyre oil using pyrolysis thermal processes), the study will improve the initial poor chemical properties which will confer improved engine performance with emissions reduction especially those dealing with sulfur and other contaminants from municipal solid waste streams. The production of pyrolyzed municipal solid waste (MSW) oil will be ex-situ and in-situ (the former means after production while the later means before production of biodiesel). This research work will assist in determining standard procedures and sequencing to obtain working ratios of the blending processes and techniques of biodiesel production.
Research, development and testing of brake pad materials from biomass-based nanocomposites.
(2021) Ige, Oluwafemi Ezekiel.; Inambao, Freddie Liswaniso.
Many variables affect braking systems in the automotive industry, including component geometry, brake materials, component interactions, and various operating conditions. The current research trend in the automotive industry is to use waste as raw material for nanocomposite materials in automobile applications. A novel bio-based hybrid nanocomposite (BHN) brake pad has been developed and investigated to serve as a functional replacement for metallic, ceramic, and hazardous asbestos-based brake pad materials. Carbon-based nanocomposites such as carbon nanospheres, carbon nanotubes, carbon nanosheets, and carbon nanofibers, etc., have attracted wide attention from researchers since their discovery. Carbon nanospheres (CNSs) are among the novel carbon nanostructures distinguished for their potential use in many areas, for instance lithium-ion batteries, electrodes in super capacitors, different parts of automobiles and adsorbents. In this study, CNSs were synthesized from palm kernel fiber (PKF) activated carbon using a simple physical activation method under CO2. The BHN consisted of a matrix of carbon nanomaterials from PKF which acted as the filler material, epoxy resin which acted as the binder material, together at a nanoscale to produce brake pad. The temperature effect on synthesized nanomaterials was investigated using transmission electron microscopy (TEM), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), Fourier transform infrared microscopy (FTIR), and thermo-gravimetric analysis (TGA). The SEM results showed the highest purity, and the largest number of CNSs were formed at a synthesis temperature of 1000 °C. The tribological properties of BHN brake pads were studied and compared with conventional (CON) brake pad material. The BHN brake pads exhibited low wear rate compared to the CON brake pads, while the coefficient of friction (COF) of the BHN brake pad samples (0.3 to 0.5) were within the SAE J661 CODE standard. The results showed that the brake pad performance differed with each pad formulation. The BHN brake pad material had excellent performance in most of the analyses when compared to the CON brake pad material. The mechanical properties of the BHN brake pad such as compressive strength, compressive modulus, hardness and impact strength were tested. The nanocomposite material showed a higher impact strength and compressive strength compared to the (CON) brake pads. The hardness of the material of the two brake pads was statistically akin. Furthermore, the performance of oil and water absorption, thermal stability as well as degradation of the BHN brake pad were determined. The results showed that the BHN brake pad material had low oil absorption rate and low moisture water absorption rate. The BHN brake pad showed thermal stability within the range 300 °C to 400 °C, which are within the standard temperature range. Result from SEM analysis carried out on the worn surfaces of the BHN brake pads reveals a tougher structure than SEM of the worn surfaces of the CON brake pads. Dynamic mechanical analysis (DMA) results showed that at a temperature between 55 °C and 105 °C, the 𝑇𝑎𝑛 𝛿 magnitude of BHN was higher due to the loss modulus supremacy over the storage modulus. In addition, in the temperature range 105 °C to 190 °C, the storage modulus and the loss modulus was as low as that of the CON, and the BHN 𝑇𝑎𝑛 𝛿 magnitude reduced. Excellent mechanical and tribological properties of BHN brake pad was achieved at 0.3 % CNS.
Hybrid nanoshell reinforced plant fiber biocomposite.
(2020) Gbadeyan, Oluwatoyin Joseph.; Adali, Sarp.; Glen, Bright.; Sithole, Bishop Bruce.
Abstract available in PDF.
Design and testing of a composite material for modelling wind turbine blade structures in tropical region.
(2018) Tefera, Getahun Akulu.; Adali, Sarp.; Bright, Glen.; Davidson, Innocent Ewean.
Currently large wind turbine blades have been installed in several offshore and onshore wind farms around the world, particularly in the desert areas of North East Africa where wind turbine blades and nacelles are affected by elevated temperatures. The aim of this study is to investigate the effect of temperature variation on the mechanical behaviour of composite wind turbine blades installed in tropical wind farms. The blades are constructed from unidirectional carbon fibre/epoxy, glass fibre/epoxy and hybrids of these two composite materials. ASTM standards were taken into account when the composite specimens were manufactured for testing purposes. Short Beam Shear (SBS), Dynamic Mechanical Analysis (DMA) and tensile tests were conducted under increasing temperatures to investigate the mechanical behaviour of composite materials when used for structural modelling of wind turbine blades. Experimental findings revealed that the strength and stiffness properties of composite specimens were reduced when temperatures increased. Betz’s element momentum theory and Glauert’s modelling methods were used to investigate the characteristics of composite wind turbine blades measuring 54m and generating 2MW power. Flap-wise loading was taken into account along the length of the wind turbine blades when they were analysed using the Blade Element Momentum (BEM) theory. The wind turbine blades were developed using carbon fibre/epoxy, glass fibre/epoxy, glass-carbon fibre/epoxy and carbon-glass fibre/epoxy composite materials. The tip deflection of the blades was analysed allowing for different flap-wise and thermal loadings. Simulation results indicated that a glass/epoxy blade has the highest and a carbon/epoxy blade the lowest tip deflection. The values for the tip deflections of the blades show minimal change under thermal loading. To study the mechanical behaviour of the blades under thermal loading, an element-wise approach was developed and the failure index for different composite materials was computed. Tsai-Wu failure criterion was employed to determine the failure index of each composite material under thermal and mechanical loadings. Blades failed when the thermal loading was above 40ºC irrespective of the flap-wise loading. This finding was similar to the experimental results mentioned above. Carbon/epoxy showed non-linear behaviour when the test temperature approached 40ºC. Generally, experimental and numerical results are comparable and can be considered valid. To conclude carbon-glass fibre/epoxy composite wind turbine blades are observed to be a better option for tropical wind farms based on experimental and simulation results. Iqoqa Njengamanje sekufakwe ophephela bomoya abakhulu emapulazini amaningi omoya asolwandle nasezweni emhlabeni jikelele, ikakhulukazi ezindaweni eziwugwadule zaseMpumalangantshonalanga Afrika lapho amazinga okushisa aphakeme enomthelela kophephela bomoya nakuzembozo zezihambisiphephela. Inhloso yalolu cwaningo ngukuhlola umthelela wokuguquguquka kwamazinga okushisa endleleni okusebenza ngayo ophephela bomoya abafakwe emapulazini asezindaweni ezishisa kakhulu. Ophephela bakhiwe ngomabhekanxazonke befayibha yekhabhoni/ ephoksi, ifayibha yengilazi/ephoksi, Kucatshangelwe amazinga e-ASTM ngenkathi kwakhiwa amasampula ayindidiyela ngenhloso yokuhlola. Kwenziwe uhlelo lwe-Short Beam Shear (SBS), Dynamic Mechanical Analysis (DMA) nokuhlola kwamathensayili ngaphansi kwamazinga okushisa anyukayo, ukuhlola indlela ezisebenza ngayo izakhi eziyindidiyela uma zisetshenziselwa ukubona ukuthi singama kanjani isakhiwo sophephela bomoya. Imiphumela yokuhlola iveze ukuthi amazinga amandla nokuqina kwamasampula ayindidiyela kwehlile uma kunyuswa amazinga okushisa. Kusetshenziswe injulalwazi ka-Betz yomthamosivinini kanye nezindlela zika-Glauret zesibonelokulinga ukuhlola izimpawu zophephela bomoya abayindidiyela, abanesikalo esingu-54m futhi esiphehla amandla angu-2MW. Kucatshangelwe isisindo sokuthwala uma ophephela bebheke phansi noma phezulu ngokunjalo nobude bophephela bomoya ngenkathi behlaziywa, kusetshenziswa injulalalwazi i-Blade Element Momentum (BEM). Ophephela bomoya benziwe kusetshenziswa izakhi eziyindidiyela zefayibha yekhabhoni/ ephoksi, ifayibha yengilazi/ ephoksi nefayibha yekhabhoni-ngilazi/ ephoksi. Impebezo yezihloko zophephela ihlaziywe kuvunyelwa okuhlukahlukene kwesisindo sokuthwala netemali, uma ophephela bebheke phansi noma phezulu. Imiphumela yokulingisa ikhombise ukuthi uphephela wengilazi/ ephoksi unempebezo yesihloko ephakene kanti uphephela wekhabhoni/ ephoksi unempebezo yesihloko ephansi. Amavelu empebezo yezihloko zophephela akhombisa uguquko olusesilinganisweni esincane, ngaphansi kokulayishwa kwetemali. Ukucwaninga okwenziwa ngophephela okuphathelene nokusebenza kwemishini uma kulayishwe itemali, kwenziwe ngokuqamba indlela evuna i-elementi, kwase kwenziwa uhlelo lokubala ngekhompyutha inkomba kwehluleka yezakhi eziyindidiyela ezihlukahlukene. Kuthathwe indlelakukhetha kuhluleka kaTsai-Wu ukubona inkomba kuhluleka yesakhi ngasinye esiyindidiyela uma kulayishwe itemali nokusebenza ngemishini. Ophephela behlulekile uma umthamo wetemali ungaphezu kuka-40ºC kungakhathaliseki izinga kulayisha elivuna ukubheka phansi noma phezulu kophephela. Okutholakele bekufana nemiphumela yokuhlola ebalulwe ngenhla. Ikhabhoni/ ephoksi ikhombise indlela okwenza ngayo ophephela engaqondile uma amazinga okushisa okuhlola esondela ku-40ºC. Ezimweni eziningi, imiphumela yokulinga neyezibalo iyaqhathaniseka futhi ingase ibhekwe njengekholakalayo. Ukuphetha, ophephela bomoya abayindidiyela yefayibha yekhabhoningilazi/ ephoksi babonakala beyisu elingalunga kahle emapulazini omoya uma kuthathelwa emiphumeleni yokuhlola nokufanisa.
Structural characterisation and response modelling of paraffin-based hybrid rocket motor fuel grains.
(2020) Veale, Kirsty Lynn.; Adali, Sarp.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Bemont, Clinton Pierre.
Abstract available in PDF.
Coupled heat and mass transfer in solar-powered liquid desiccant adiabatic dehumidifier and regenerator for air conditioning applications.
(2020) Oyieke, Andrew Young Apuko.; Inambao, Freddie Liswaniso.
Abstract available in PDF.
Numerical and experimental investigations of optimal fatty acid methyl ester hybrid for enhanced engine performance and emission mitigation in the conventional compression ignition strategy.
(2020) Awogbemi, Omojola.; Inambao, Freddie Liswaniso.; Onuh, Emmanuel Idoko.
The utilization of petroleum-based diesel fuel to power compression ignition (CI) engines has been hampered by inefficient combustion process resulting in unsatisfactory engine performance and emission of hazardous gases. Fatty acid methyl ester (FAME), due to its renewability, biodegradability, and environmentally friendly emissions, has been acknowledged as a viable alternative fuel for CI engines. The application of waste cooking oil (WCO) as feedstock for FAME production did not conflict with food chain, guarantees appropriate disposal of used vegetable oil, and prevents contamination of aquatic and terrestrial habitats. The FAME was produced by transesterification of WCO samples collected from restaurants, catalyzed by calcium oxide derived from chicken eggshell waste powder subjected to high temperature calcination. Properties and fatty acid (FA) composition of the FAME were determined, the fuel used to power an unmodified CI engine, and measure the performance and emission characteristics experimentally. Numerical techniques, including, matrix laboratory, response surface methodology, Taguchi orthogonal, artificial neural network, and multiple linear regression were utilized to unearth the optimal FAME candidate, determine the properties, FA composition, performance and emission characteristics of the newly generated FAME and were found to agree with experimental results. It was discovered that FAME candidate with a concentration of palmitic acid of 36.4 % and oleic acid of 59.8 % produced improved brake thermal efficiency and brake mean effective pressure as well as reduced fuel consumption, and other regulated emissions.
Production, evaluation and testing of bioethanol from matooke peels species as an alternative fuel for spark ignition engine: a case study of Uganda.
(2020) Yusuf, Abdulfatah Abdu.; Inambao, Freddie Liswaniso.
Conversion of new lignocellulose biomass (LCB) waste to energy is an innovative technique for waste valorization and management which reduces environmental pollutions and offers socioeconomic benefits. This has made the LCB to be significant due to its novel behavior towards bioenergy. The aims of this study is to characterize the biomass, evaluate and produce the bioethanol fuels from unique LCB which is matooke peels species, and examined the emissions and combustion effects of low content rates of bioethanol blends with gasoline in a modernized spark-ignition engine. The matooke peels species such as Mbwazirume and Nakyinyika biomass peels, which are pretreated and untreated were characterized to identify its use in bioenergy production. This characterization of biomass was carried out using various analyses such as proximate and ultimate analysis, thermo-gravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometer (EDXS). Experimental findings reveal that the pretreated Mbwazirume biomass exhibits excellent solid fuel properties when compared to untreated Mbwazirume, pretreated and untreated Nakyinyika biomass peels. Bioethanol fuels were produced from Mbwazirume and Nakyinyika biomass peels through a fermentation process using Saccharomyces cerevisiae and analyzed using ANOVA. The study also optimized production variables and determined the models for separate hydrolysis and fermentation (SHF). The properties of the bioethanol were measured according to relevant ASTM standards and compared with the standard ethanol and gasoline. Mbwazirume biomass shows higher bioethanol yields and excellent fuel properties, this serve as a fuel of choice for further experiment. The bioethanol ratios were blend with gasoline at (E0, E5, E10, and E15) used in the development of further experiments on engine and combustion performance, and exhaust emissions test in a modernized TD201 four-stroke petrol engine. The results obtained were computed, modeled, evaluated and analyzed. Results show that the small differences in properties between bioethanol-gasoline blends are enough to create a significant change in the combustion system. These effects lead to behavioral mechanisms which are not easy to analyze or understand, sometimes make it difficult to identify the fundamentals of how blend ratios affect emissions and performance.
Investigation of the thermophysical properties of coconut fibre based green nanofluid for heat transfer applications.
(2018) Adewumi, Gloria Adedayo.; Inambao, Freddie Liswaniso.
Significant resources are being channelled toward research on carbon nanomaterials obtained from biomass precursors because of their overall environmental acceptability, stability, low toxicity and simplistic use. Due to their unique nature, they have excellent thermo-physical properties which include improved thermal conductivity, electrical conductivity and viscosity. In this study, carbon nanotubes and nanospheres were successfully synthesized from coconut fibre activated carbon. The biomass was first carbonized, then physically activated followed by treatment using ethanol vapor at 700 °C to 1100 °C at 100 °C intervals. The effect of synthesis temperature on the formation of the nanomaterials was studied using scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray powder diffraction (XRD), Fourier transform infrared microscopy (FTIR) and thermo-gravimetric analysis (TGA). SEM analysis revealed nanospheres were formed at higher temperatures of 1000 °C and 1100 °C, while lower temperatures of 800 °C and 900 °C favoured the growth of carbon nanotubes. At 700 °C however, no tubes or spheres were formed. TEM and FTIR were used to observe spectral features, such as the peak positions, intensity and bandwidth which are linked to some structural properties of the samples investigated. All these provided facts on the nanosphere and nanotube dimensions, vibrational modes and the degree of purity of the obtained samples. In general, the TEM results showed spheres of diameter in the range 30 nm to 250 nm while the tubes had diameters between 50 nm to 100 nm. XRD analysis revealed that the materials synthesized were amorphous in nature with a hexagonal graphite structure. Experimental measurements of the thermal conductivity, electrical conductivity and viscosity of the synthesized nanomaterials dispersed in 60%:40% ethylene glycol (EG) and water (W) nanofluids containing gum arabic (GA) were performed, considering the effects of temperature and mass fraction. Stability testing of the nanofluids were determined by zeta potential, viscosity and UV spectroscopy measurements of nanofluids for 720 minutes. The green nanofluids prepared were observed to very stable for more than 720 minutes. Also the results of experiments showed that the addition of nanomaterials to the base fluid increased the viscosity and that with the increase in temperature, the viscosity decreased while the electrical conductivity improved when compared to the base fluid. On the other hand, the thermal conductivity results were observed to decrease with the addition of nanoparticles. This decrease observed has been attributed to high thermal boundary resistance, ratio of surfactant and inconsistent size of the nanoparticles.
Production of jet fuel from microalgae biomass cultivated in saline domestic wastewater.
(2018) Bwapwa, Joseph Kapuku.; Trois, Cristina.; Anandraj, Akash.
Jet fuel from crude petroleum oil is known as the most efficient energy carrier for the aviation sector. Environmental concerns and economic pressure drive major industries to adapt to current global revolution towards alternative, sustainable, and clean fuels. In this study conversion of algae biomass to jet fuel is presented as a novel technology of low carbon footprint and a cost-effective jet fuel. In this current study, it is reported that there is a possibility of substantially converting microalgae oil into aviation fuel by adapting and applying the same processes used for the conversion of fossil crude petroleum oil into conventional jet fuel. The drawback, however, remains the low oil output from used species of microalgae and the general operating costs which are still at developmental stages. A part from the introduction and the literature review making respectively chapter 1 and chapter 2, this study, therefore, has focused on the magnification of lipid production and the simplification of the conversion processes in chapter 3. Microalgae cells were physiologically stressed by totally depriving them of all growth nutrients for three days aiming to modify their genetic physiology which in turn will favour the yield of lipid and bio-oil. An elaborate experiment was established from algae biomass cultivation to jet fuel production. The experiment involved biomass cultivation, harvesting and bio-oil extraction using a solvent mixture made of methanol and chloroform. Thermal cracking without catalyst or pyrolysis of crude bio-oil were undertaken to break down the carbon chains in order to complete the fractionation. ASTM methods and standards related to aviation fuels were used to generate the relevant data. The conceptual design with a simplified conversion process undertaken in chapter 4 was established based on the experiment completed in chapter 3. It suggested to cultivate the species in domestic wastewater ponds or use the seawater/saline water because the used species was comfortable in saline or marine environment. Parameters such as density, kinematic viscosity, flash point, freezing point, total sulfur, net heat of combustion and distillation were evaluated during the experiment in chapters 3 and 4. It was found that the majority of parameters analysed regarding the algae-based jet fuel from the laboratory was complying to ASTM standards. However, it will require additional processes such as upgrading and reforming to enhance the quality of jet fuel and improve the level of some parameters such as density and freezing point which were not rigorously complying with ASTM standards. Also, the improvement involves the use of the same additives used for conventional jet fuels for flow ability and freezing at higher altitudes. The scaling up of the production process is still a challenge due to operating costs. In this regard, blending algae-based jet fuel and the conventional jet fuel in 50/50, 80/20 and 20/80 ratios was carried out and evaluated in Chapter 5 and Chapter 6 as an alternative approach for sustainability.
Development of a decision support system for decision-based part/fixture assignment and fixture flow control = Ukusungulwa kohlelo lokuxhaswa kwezinqumo mayelana nokwabiwa kwezingxenye ezakhiwayo kanye nokuhanjiswa kwazo.
(2018) Kasie, Fentahun Moges.; Bright, Glen.; Walker, Anthony John.
ABSTRACT: An intense competition in a dynamic situation has increased the requirements that must be considered in the current manufacturing systems. Among those factors, fixtures are one of the major problematic components. The cost of fixture design and manufacture contributes to 10-20% of production costs. Manufacturing firms usually use traditional methods for part/fixture assignment works. These methods are highly resource consuming and cumbersome to enumerate the available fixtures and stabilise the number of fixtures required in a system. The aim of this study was to research and develop a Decision Support System (DSS), which was useful to perform a decision-based part/fixture assignment and fixture flow control during planned production periods. The DSS was designed to assist its users to reuse/adapt the retrieved fixtures or manufacture new fixtures depending upon the state of the retrieved fixtures and the similarities between the current and retrieved cases. This DSS combined Case-Based Reasoning (CBR), fuzzy set theory, the Analytic Hierarchy Process (AHP) and Discrete-Event Simulation (DES) techniques. The Artificial Intelligence (AI) component of the DSS immensely used a fuzzy CBR system combined with the fuzzy AHP and guiding rules from general domain knowledge. The fuzzy CBR was used to represent the uncertain and imprecise values of case attributes. The fuzzy AHP was applied to elicit domain knowledge from experts to prioritise case attributes. New part orders and training samples were represented as new and prior cases respectively using an Object-Oriented (OO) method for case retrieval and decision proposal. Popular fuzzy ranking and similarity measuring approaches were utilised in the case retrieval process. A DES model was implemented to analyse the performances of the proposed solutions by the fuzzy CBR subsystem. Three scenarios were generated by this subsystem as solution alternatives that were the proposed numbers of fixtures. The performances of these scenarios were evaluated using the DES model and the best alternative was identified. The novelty of this study employed the combination of fuzzy CBR and DES methods since such kinds of combinations have not been addressed yet. A numerical example was illustrated to present the soundness of the proposed methodological approach. Keywords: Decision support systems, case-based reasoning, analytic hierarchy process, fuzzy set theory, object-oriented methods, discrete-event simulation, fixtures. IQOQA LOCWANINGO : Ukuncintisana okunezinhlelo eziguquguqukayo kulesi sikhathi samanje sekwenze ukuthi kube nezidingo ezintsha ezinhlelweni zokukhiqiza. Phakathi kwakho konke lokhu izingxenye (fixtures) zingezinye zezinto ezidala izinkinga. Intengo yokwakha uhlaka lwengxenye kanye nokuyikhiqiza kubiza amaphesenti ayi-10 kuya kwangama-20 entengo yokukhiqiza. Amafemu akhiqizayo avamise ukusebenzisa izindlela ezindala zomsebenzi wokwaba izingxenye. Lezi zindlela zidla kakhulu izinsizangqangi futhi kuthatha isikhathi eside ukubala izingxenye ezikhona nokuqinisekisa ukuthi kunesibalo esanele kulokho okumele kube yikho ohlelweni lokusebenza. Inhloso yalolu cwaningo bekungukucwaninga nokusungula i-Decision Support System (DSS) ebe lusizo ekwenzeni umsebenzi wokuthatha izinqumo ngokwabiwa kwezingxenye kanye nokuhanjiswa kwazo ngezikhathi ezimiselwe ukukhiqiza. I-DSS yakhelwa ukusiza labo abayisebenzisayo ukuze basebenzise noma bazisebenzise lapho zingakaze zisetshenziswe khona lezo zingxenye ezibuyisiwe, noma kwakhiwe ezintsha kuya ngokuthi zibuyiswe zinjani lezi ezibuyisiwe nokuthi ziyafana yini nalezo ezintsha. I-DSS isebenzise amasu ahlanganise i-Case-Based Reasoning (CBR), injulalwazi echazwa ngokuthi i-fuzzy, ne-Analytic Hierarchy Process (AHP) ne-Discrete-Event Simulation (DES). I-Artificial Intelligence (AI) eyingxenye ye-DSS isebenzise kakhulu uhlelo lwe-fuzzy CBR luhlangene ne-fuzzy AHP kulandelwa imithetho yolwazi olumayelana nohlobo lomsebenzi. I-CBR isetshenziswe ukumelela lezo zimo zamanani ezingaqondakali nezingaphelele kulezo zingxenye. I-AHP e-fuzzy yasetshenziswa ukuze kutholakale ulwazi kochwepheshe olubeka phambili lezo zingxenye. Ama-oda ezingxenye ezintsha kanye namasampuli asetshenziselwa ukuqeqesha avezwe njengamasha kanye nabekade evele ekhona ngokulandelana kusetshenziswa indlela eyaziwa ngokuthi yi-Object-Oriented (OO) method lapho kubuyiswa izinto noma kunezinqumo eziphakanyiswayo. Izindlela ezijwayelekile zokulandelanisa nokufanisa zisetshenziswe ohlelweni lokubuyisa izinto. Kusetshenziswe isu eliyi-DES ukuhlaziya ukusebenza kwezisombululo eziphakanyiswe yindlela ye-CBR e-fuzzy. Le ndlela iphinde yaveza izimo ezintathu eziphakanyiswe ukuba zibe yisisombululo esibalweni sezingxenye ezihlongozwayo. Ukusebenza kwalezi zimo kuhlungwe ngokusebenzisa indlela ye-DES kwase kuvela inqubo engcono. Ukungajwayeleki kwalolu cwaningo kusebenzise ingxube yezindlela ze-fuzzy CBR ne-DES ngoba lolu hlobo lwengxube belungakaze lusetshenziswe. Kusetshenziswe isibonelo sezibalo ekwethuleni ukusebenza kwale nqubo yokusebenza ehlongozwayo.
Optimisation of welding parameters to mitigate the effect of residual stress on the fatigue life of nozzle–shell welded joints in cylindrical pressure vessels.
(2017) Zondi, Mthobisi Clyde.; Adali, Sarp.; Bemont, Clinton Pierre.
The process of welding steel structures inadvertently causes residual stress as a result of thermal cycles that the material is subjected to. These welding-induced residual stresses have been shown to be responsible for a number of catastrophic failures in critical infrastructure installations such as pressure vessels, ship’s hulls, steel roof structures, and others. The present study examines the relationship between welding input parameters and the resultant residual stress, fatigue properties, weld bead geometry and mechanical properties of welded carbon steel pressure vessels. The study focuses on circumferential nozzle-to-shell welds, which have not been studied to this extent until now. A hybrid methodology including experimentation, numerical analysis, and mathematical modelling is employed to map out the relationship between welding input parameters and the output weld characteristics in order to further optimize the input parameters to produce an optimal welded joint whose stress and fatigue characteristics enhance service life of the welded structure. The results of a series of experiments performed show that the mechanical properties such as hardness are significantly affected by the welding process parameters and thereby affect the service life of a welded pressure vessel. The weld geometry is also affected by the input parameters of the welding process such that bead width and bead depth will vary depending on the parametric combination of input variables. The fatigue properties of a welded pressure vessel structure are affected by the residual stress conditions of the structure. The fractional factorial design technique shows that the welding current (I) and voltage (V) are statistically significant controlling parameters in the welding process. The results of the neutron diffraction (ND) tests reveal that there is a high concentration of residual stresses close to the weld centre-line. These stresses subside with increasing distance from the centre-line. The resultant hoop residual stress distribution shows that the hoop stresses are highly tensile close to the weld centre-line, decrease in magnitude as the distance from the weld centre-line increases, then decrease back to zero before changing direction to compressive further away from the weld centre-line. The hoop stress distribution profile on the flange side is similar to that of the pipe side around the circumferential weld, and the residual stress peak values are equal to or higher than the yield strength of the filler material. The weld specimens failed at the weld toe where the hoop stress was generally highly tensile in most of the welded specimens. The multiobjective genetic algorithm is successfully used to produce a set of optimal solutions that are in agreement with values obtained during experiments. The 3D finite element model produced using MSC Marc software is generally comparable to physical experimentation. The results obtained in the present study are in agreement with similar studies reported in the literature.

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