Masters Degrees (Mechanical Engineering)

Permanent URI for this collectionhttps://hdl.handle.net/10413/6862

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Performance comparison between gas generator and electrically pumped rocket engines under ablative and regenerative cooling.
(2024) Silver, Jordan.; Brooks, Michael John.; Snedden, Glen Campbell.; Cooper, Ryan William Neil.
In recent years, there has been a dramatic advancement in the global satellite industry, with new technologies allowing for smaller and more powerful satellites to be developed. Despite this, South Africa and other African countries developing satellite technologies still depend on foreign launch services as there is no indigenous capability in Africa, incurring additional costs and delays. Against this backdrop, the University of KwaZulu-Natal’s (UKZN) Aerospace Systems Research Institute (ASRI) is pursuing the development of a two-stage Commercial Launch Vehicle (CLV) to provide South Africa with a sovereign launch capability. ASRI is currently developing the booster engine for CLV - the South AFrican FIrst Rocket Engine (SAFFIRE). The booster stage will utilize a cluster of nine of the SAFFIRE engines, and the second stage will use a vacuum derivative of the SAFFIRE engine called SAFFIRE-V and will give CLV the envisioned payload capacity of 200 kg to a 500 km Sun Synchronous Orbit (SSO). Although the design of the SAFFIRE engine is largely complete in terms of injector design, combustion chamber and nozzle geometry, and thrust output, the feed cycle responsible for delivering the propellants to the combustion chamber is undecided. In this report, the gas generator and electropump cycles are under consideration to supply propellants to the SAFFIRE and SAFFIRE-V chambers. In addition, although the chambers are currently ablatively cooled, ASRI remains interested in the possibility of using regenerative cooling. This study, therefore, considers the gas generator and electropump cycles under both cooling methods to identify which SAFFIRE engine combination can provide the best performance for CLV. To measure the performance of each engine combination, the payload mass capabilities of a hypothetical CLV are calculated using results attained from 1- dimensional simulations run in Flownex®, models coupled with Mass Estimating Relationships (MER) that evaluate the components that make up a two-stage liquid rocket engine. The performance comparison found that each engine configuration exceeded the set payload capacity of 200 kg. For the electropump cycle, the ablative and regenerative engines achieved payload masses of 303 kg and 290 kg, respectively. The gas generator performed even better due to a lower dead mass than the electropump cycle, achieving payload masses of 392 kg and 386 kg, respectively. For both cycles, the ablatively cooled rocket engines had better payload capabilities than the regeneratively cooled engines due to a regeneratively cooled engine having a smaller expansion ratio. When the expansion ratios were made the same, the regeneratively cooled engines achieved a payload capacity of 308 kg and 405 kg for the electropump and gas generator cycles, respectively, due to the increased thrust from the heated fuel, which has an increased energy density, producing more thrust. When the dead mass of the electropump cycle was decreased by ejecting the depleted battery packs for each engine stage during the launch, the electropump payload deficit decreased from 98 kg to 29 kg for the ablative engines and 96 kg to 32 kg for the regenerative engines. Based on this study, the best performing SAFFIRE engine configuration is a gas generator cycle with ablative cooling, giving the conceptual CLV rocket a payload of 392 kg to 500 km Sun Synchronous Orbit.
Development of an injector test rig for shear thinning gel propellants.
(2024) Mdhluli, Thabang.; Brooks, Michael John.; Velthuysen, Timothy Johnathan.
This work describes the development of an injector test rig to characterise the behavior of shear-thinning gelled rocket propellants. The work falls under a broader program of research into gel propellants conducted by the Aerospace Systems Research Institute (ASRI). Gels represent a new class of propellant for rocket propulsion applications. They offer potential advantages over conventional liquid and solid propellants but their behaviour through injector orifices is poorly understood. Consequently, there is no standardised design procedure for gelled propellant injectors, although computational fluid dynamic (CFD) methods have shown potential. The aim of this research was to design, build and commission an injector test rig utilising single-element impinging injectors to generate experimental data on gel sprays such as breakup length, and droplet size. The rig is intended to inform gel injector design methodologies by providing experimental data against which CFD-generated simulations can be compared and refined. MATLAB® image processing tools were used to analyse spray sheet images and quantify the resulting fluid structures generated by the test rig. The study included the design and manufacture of the propellant/simulant feed system, injector insert, injector manifold, frame and propellant/simulant supply tank. Two adjustable converging injection orifices were used to form spray sheets at 45°, 60° and 90° impinging angles. For testing purposes, two water-based simulants were formulated using hydrocolloid xanthan and guar gum gelling agents at 0.5, 1.0 and 1.5 wt%. Rheological characterisation of the gels was performed to verify their shear-thinning behavior using a rotational rheometer. Spray sheets were then generated at injector pressure drops in the range of 140 kPa to 1400 kPa. A MATLAB® model of the system was developed to establish control parameters for the desired outputs and the rig was controlled via a LabVIEWTM application. The rig provides a platform for further research into the behavior of gelled rocket propellants, with an intended focus on hydroxylamine nitrate (HAN) and ammonium dinitramide (ADN).
Research and development of a hybrid kinematic platform, with associated control methodology, for several low degree of freedom serial kinematic manipulators.
(2023) Kelly, Bryan Sherwood.; Bright, Glen.; Padayachee, Jared.
Industry has placed focus on efficiency and flexibility, for this reason it is beneficial to propose a method in which serial manipulators can be reoriented into a parallel system when needed. This reorientation allows industry to implement less robotic manipulators, which reduces cost and space requirements; while still being able to receive the benefits that are associated with serial and parallel robotic manipulators. This research focuses on the development of a hybrid kinematic platform that consists of the combination of several low degree of freedom Serial Kinematic Manipulators (SKM) into a Parallel Kinematic Manipulator (PKM). Special attention was placed on the initial selection of the serial manipulators to be combined into a hybrid SKM PKM platform. The aim of the hybridization is to create the ability to have several serial manipulators that can operate within a collaborative workspace for tasks that require dexterity, such as assembly operations. As well as, become an individual parallel mechanism to perform tasks that require increased rigidity, such as machining. Several desktop models were produced via rapid prototyping methods. An electronic system that included stepper motors, limit switches, Arduino, RAMPS breakout board and motor drivers were installed onto each RobotArm. Several design optimizations were implemented to improve the potential of the final platform. Full serial kinematic analysis was performed on the individual serial RobotArms, including full 3D forward and inverse derivations via a geometric approach. A parallel inverse kinematic derivation was performed for the combined system, which includes a rotation matrix. The rotation matrix was required due to the added degrees of freedom that became available in the combined hybrid kinematic platform. The kinematics were used for the control system that were implemented via Arduino and a Python GUI. The kinematics also allowed for investigation into the workspace, and the singularities present in that workspace. Both the workspace and the singularity plots were performed via Monte Carlo randomization scripts performed in Octave/MATLAB and Python. Testing was then performed to identify how well the platform works as individual collaborative serial manipulators as well as a single combined hybrid platform. The tests focused on the accuracy and repeatability present within the different combination of the platform. It was found that the combined hybrid kinematic platform outperformed the individual serial kinematic manipulator in accuracy as well as displaying a lower level of deflection to load. The combined hybrid kinematic platform was able to achieve three further degrees of freedom compared to the individual serial kinematic manipulator. The results obtained validate the research question of whether it is possible to combine several low degree of freedom serial kinematic chains into a single hybrid platform and how such a platform would be controlled.
Design and manufacturing methods for fused deposition modelling in additive manufacturing for the South African railway industry.
(2022) Toth, Ashley Dillon.; Padayachee, Jared
Additive Manufacturing, commonly known as 3D printing, is a transformative technology that has seen rapid adoption in well-established industrial environments due to its increasing reliability and associated economic value. It’s adoption within the South African industry has been driven by the biotechnical/medical, aerospace and automotive industries, with limited adoption in the railway industry. The rolling stock and rail infrastructure consists of numerous systems and components that may benefit from the technology within the railway environment. This study explores utilizing additive manufacturing technology as an additional technique to create functional railway-related components. The study aims to develop tools, methods, and processes for designing and manufacturing functional end-use railway parts, ultimately allowing the industry to derive the economic benefits of additive manufacturing. The study is limited to using the Fused Deposition Modelling technique and polymer materials. Firstly, the available physical and digital manufacturing workflow techniques are identified through literature with recommendations for best practices. Secondly, the research proposes a Multi-Criteria Decision-Making methodology based on the Analytic Hierarchy Process to identify potential railway-related parts that may benefit from the Fused Deposition Modelling additive manufacturing process. The methodology is validated through case studies found in literature. Thirdly, a novel method to optimise the infill design is presented for improving the strength of the 3D printed parts, thereby making the parts more suitable for the railway environment. The method is based on combining Finite Element Analysis and Bi-directional Structural Optimisation Topology Optimisation. Lastly, the study presents a custom-developed application built using Visual Basic and Excel. The application is built upon a generic design process to aid railway design engineers in effectively using the Fused Deposition Modelling technology to create functional 3D printed parts. The research concludes with a case study of a roof scoop and air vent, which was identified, redesigned, optimised, and manufactured using Fused Deposition Modelling. The part was used as a replacement component on a railway inspection vehicle. Compared to the existing design, an 18,7 % reduction in shear stress was achieved for the 3D printed design.
Performance assessment of a zeolite heat store.
(2021) Muhammad, Sheik.; Smith, Graham Douglas James.; Klein, Peter.
Abstract: According to the Department of Mineral Resources and Energy, the industrial sector in South Africa is the largest consumer of energy. Waste heat recovery can significantly reduce costs and carbon emissions in industry. In addition, energy supply does not always match demand and it is therefore necessary to investigate efficient ways of storing thermal energy. Sorption based thermochemical heat storage provides high energy densities while minimizing losses when utilised for long-term heat storage. To commercialize sorption storage systems, additional research and experimentation is required to validate numerical models of heat and mass transfer within the system to allow for accurate design calculations. A lab-scale prototype was developed to analyse the thermal storage characteristics of zeolite 13X in an open (non-pressurized) sorption system. The test unit consists of a packed (pellet) bed reactor, heating system, blower, and humidifier. Thermocouples, humidity sensors, and mass-flow meters were used to determine the mass and energy balances in the system. The experiments that were conducted involved a reversible reaction between zeolite 13X and water vapour in air. During the charging (desorption) process, the zeolite pellets were dehydrated by hot air which was heated using an electric heater. During the discharging (adsorption) process, humidified ambient air was supplied to the reactor bed, which rehydrated the zeolite pellets, resulting in hot dry air exiting the reactor bed. The packed bed was charged at three different temperatures (130 oC, 160 oC and 200 oC). It was discharged at three different values of relative humidity (25%, 70% and 100%,) and mass-flow rates (90 kg/h, 126 kg/h and 177 kg/h). The maximum amount of energy absorbed by the bed was 13.64 kWh (at 200 oC) and the maximum amount of energy released was 11.56 kWh at 100% relative humidity during discharging. This equates to a storage efficiency of 85% and an overall efficiency of 57% for the process. The highest temperature lift achieved was 107 oC during adsorption and the maximum energy storage density was 148 kWh/m3. By decreasing the regeneration temperature, the energy storage capacity was decreased and the desorption time was increased. A lower inlet humidity (during discharging) lowered the temperature lift and energy efficiency and increased the adsorption time. A lower flow rate also led to a lower efficiency and increased the adsorption time. The potential of zeolite 13X for long term storage was confirmed as a relatively high energy storage efficiency of 72% was achieved, for a period of 5 months between charging and discharging, in an open reactor. The application of zeolite for drying processes in industry was demonstrated using ceramic casting moulds. An average drying rate (water removal) of 0.67 kg/h was achieved. The moisture adsorption capacity of zeolite 13X was also investigated and a maximum of 286 gwater/kgzeolite was adsorbed at a relative humidity of 85%. The performance of the system was analysed by comparing the experimental results to calculations and models from previous studies. The next step is to develop and test a pilot-scale rig in a small-scale ceramic factory.
Development of liquid propellant tanks for a suborbital launch vehicle.
(2022) Mchunu, Vulinhlanhla Salvation.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
Having developed several hybrid sounding rockets, the Aerospace Systems Research Group (ASReG) at the University of KwaZulu-Natal is currently investigating the development of an indigenous launch vehicle for micro satellites. As part of this effort, a liquid propellant rocket engine called the South African First Integrated Rocket Engine (SAFFIRE) is in the advanced design phase. SAFFIRE combusts liquid oxygen and kerosene propellants to generate thrust. Following ground tests, the first version of the SAFFIRE engine will be incorporated into a single-stage launch vehicle to test its flight performance during the suborbital flight. This study aimed to develop a design procedure and subsequent engineering designs for propellant tanks suitable for use by this launch vehicle, known as the Suborbital Test Vehicle (STEVE). The liquid oxygen and kerosene propellant tanks were designed according to NASA propellant tank design guidelines based on the mechanical properties of half-hard 301L stainless steel – the alloy selected as the material of construction for both tanks. This material has various advantageous characteristics, including its compatibility with liquid oxygen, its high strength once work-hardened and its increased strength and ductility at cryogenic temperatures. As part of the study, comprehensive material testing was conducted to establish a suitable tank welding procedure and to evaluate the achievable weld efficiency. For the best performing welding procedure assessed, mean weld efficiencies with respect to yield strength and tensile strength were determined to be 70 % and 81 %, respectively. A trial propellant tank was fabricated using the selected welding procedure and subsequently subjected to a destructive hydrostatic pressure test. The outcomes of this test provided a clear indication of the modes and progression of tank failure and served to inform final design work. In terms of propellant tank layout, a tandem configuration with the liquid oxygen tank positioned above the kerosene tank was selected, in order to improve the stability characteristics of the vehicle and to minimise total feedline length. To reduce vehicle drag and mitigate aerodynamic heating effects, the liquid oxygen feedline was configured to pass coaxially through the kerosene tank via a tunnel tube. The incorporation of elliptical tank ends in both tank designs was dictated by pre-existing tooling made available by the tank end manufacturer. Based on these design characteristics, the anticipated tank loading conditions and the mechanical properties of the as-welded 301L stainless steel alloy, a minimum wall thickness requirement of 2 mm was determined for both tanks via finite element analysis.
Low-cost sensory glove for human-robot collaboration.
(2020) Bright, Tyrone William John.; Adali, Sarp.; Athol-Webb, Avern Malcom.
Human Robot Collaboration (HRC) is a technique that enables humans and robots to co-exist in the same environment by preforming operations together. HRC has become a vital goal for industry to achieve progress towards the fourth industrial revolution (Lotz, Himmel, & Ziefle, 2019) as it focuses on creating advanced production/manufacturing plants that have high levels of productivity, efficiency, quality and automation. Sensory gloves can be used to enhance the Human Robot Collaboration environment in order to achieve progress towards Industry 4.0. It can provide a safe environment where humans and robots can interact and work in conjunction. However, challenges exist in terms of cost, accuracy, repeatability and dynamic range of such devices. The project researched and developed a low-cost sensory glove to enable a user to collaborate with an industrial robot in a production environment. The sensory glove was used to provide a process whereby humans could collaborate with the robot through physical interaction under safe conditions. The sensory glove used IMU sensors in order to track the orientation of the user’s hand accurately. An algorithm was developed and designed to extract the data from the glove and create a simulated three-dimensional render of the hand as it moved through free space. This involved the design and development of an electronic system architecture that powers the glove. A control system was developed to enable the extraction of data and create the simulated three-dimensional hand model. It produced the image that the robot would sense when interacting with the worker. Testing was conducted on the cost, accuracy, dynamic range, repeatability and potential application of the system. The results showed that it was an innovative and low-cost method for humans and robots to collaborate in a safe environment. The apparatus established a process whereby humans and robots could perform operations together.
Renewable energy powered reverse osmosis system for seawater desalination.
(2022) Ojo, Olufisayo Emmanuel.; Inambao, Freddie Liswaniso.
Desalination is one of the most successful procedures for freshwater supply from seawater in the world. Reverse osmosis (RO) is a major technology in the business of seawater desalination because of its ability to produce excellent potable water of highest quality from the seawater source with low energy consumption compared to other technologies. Freshwater is a prerequisite for life and procreation. Water as an essential commodity is used in every phase of human life, ranging from domestic activities such as drinking, cooking, washing, etc., to innumerable industrial and agricultural purposes such as power generation. Today's increasing demands for freshwater by the world population cannot be met by the available fresh water in our ecosystem. This is why numerous technologies for seawater desalination have been established and advanced over the years to augment/satisfy the ever-increasing global demand for freshwater. One such technological development is the use of computer-based modeling for the design and system analysis of the RO treatment process for optimum performance. The hands-on modeling of an efficient full-scale reverse osmosis (RO) system may be daunting work due to the RO systems’ operating conditions which continually fluctuate due to cyclical variations in seasons and progressive fouling of the membrane during long-term filtration. The RO plants design, the cost of capital estimation (CAPEX), and operation expenses (OPEX) for large projects have become important factors for potential investors and consulting engineers to bear in mind for pre-construction planning and proper evaluation. This study reviews existing seawater reverse osmosis (RO) desalination protocols, covering key areas such as pretreatment, RO treatment, and post-treatment of seawater desalination for best performance, with emphasis on solar energy powered RO systems for seawater desalination. This study also models an RO desalination plant using ultrafiltration and IX polishing for feed water pretreatment and post-treatment respectively using the W.A.V.E. software program for design efficiency. The success of seawater desalination using RO technology is predicated upon an efficient feed water pretreatment and post-treatment regime. The use of an ultrafiltration system in combination with filtration has been tested and adjudged to generate excellent quality feed water for the RO system, notwithstanding the quality of the raw seawater. The model framework depicted in this study can serve as a guide for design engineers in providing effective tools for the design of an efficient RO system while maintaining an acceptable balanced hydraulic performance with considerable cost savings. For the experimental study, the physical experiment was conducted at the Victoria and Alfred (V & A) Waterfront Desalination Plant in Cape Town, South Africa. The experiment was aimed to investigate and quantify the effects of feed water temperature, pressure, salinity, and pH parameters on RO membrane elements. The raw data collected were processed and analyzed to establish the working principle of SWRO, and at the same time develop a relationship model based on the identified system parameters for a better understanding of SWRO operation. The modeling results are validated against the experimental result to evaluate RO system performance. This financial analysis covering capital expenditures CAPEX and operational expenditure (OPEX) of a traditional seawater reverse osmosis (SWRO) desalination plant was conducted. The key parameters involved in the determination of life cycle costs of seawater desalination were listed and analyzed. The parameters include water quality characteristics, production or plant capacity, location, energy consumption, materials, maintenance, operation, RO module costs, chemicals, and award year. For clarity, a 2 MGD SWRO plant was designed using WAVE software, and the design result was used to calculate the lifecycle cost of producing a unit (m3/d) of potable water in Lagos, Nigeria, deploying a curve fit approach and pertinent water economic analysis tools to develop a reliable life cycle cost for RO systems with acceptable levels of accuracy, based on verifiable and practical parameters
Development of a titanium sheet manufacturing process via direct powder rolling and spark plasma sintering.
(2022) Moosa, Fathima.; Bemont, Clinton Pierre.
The intention of this research was the improvement of titanium processing in South African industry. South Africa currently has limited ability to efficiently process its titanium reserves and the results of this research, combined with other work in the associated research consortium, has the potential to lead to significant positive economic impact. A novel method of titanium processing, combining the processes of direct powder rolling (DPR) and spark plasma sintering (SPS), was explored in the course of this research. A rolling mill was designed using modelling and simulation techniques, manufactured based on the resulting design, and the DPR-SPS process parametrically tested on the rolling mill using commercially pure titanium powder. The mechanical aspects of this project included experimental testing on a range of titanium powder samples to determine the properties of the powder, modelling of the rolling mill behaviour using MATLAB, 3D modelling of the proposed and iterated rolling mill frame design and its components using Siemens NX and OnShape, finite element analysis of the rolling mill frame and auxiliary components using Siemens NX, and manufacture and parametric testing of the mill for titanium powder compaction. The electrical aspects of this project included connecting and programming a variable speed drive and AC motor to control the speed of the mill rolls, simulating the behaviour of the integrated SPS-type sintering circuit using Simulink, designing a suitable method for safely and effectively transmitting the large SPS current to the rotating rolls, and building and testing the circuit for titanium compact spark plasma sintering. The manufactured direct powder rolling mill compacts titanium powder into strip through a pair of rolls, measuring 350mm diameter and 50mm width. Each of the rolls is mounted on the same shaft as a worm-driven gear. A 5.5kW three phase AC motor drives the worm shafts, which have opposing threads to ensure the rolls rotate in opposing directions. The worm and gear arrangement serves to both evenly transmit the drive power to both rolls, and to increase the torque from the motor to the rolls. The motor is controlled using a variable speed drive – this allows the roll speed to be adjusted as necessary, to optimise the consolidation process. The bearings used on the roll and worm shafts were designed and manufactured using an insulating bearing material to ensure the current used for sintering is not instead transmitted through the steel rolling mill frame. Flexible couplings with polymeric inserts isolate this current from the motor and between each worm gear. The minimum density of the green compact required for further handling was determined empirically as being greater than 65 % of the theoretical density of titanium. The mill was designed for an optimal density of 81%. The density range achieved by varying the parameters of roll speed, number of passes through the mill, and roll gap, was 55 – 84%. It is expected that the strip density may be greatly increased with implementation of the improvements and parameter changes identified. The spark plasma sintering circuit sinters the titanium either during the direct powder compaction process (simultaneous DPR-SPS), or following it (sequential DPR-SPS) during re-rolling through the same set of rolls used for compaction. A number of electrical circuits with different output types were designed for the SPS process; one of these was built and tested towards proof of concept of the DPR-SPS process. The tested circuit uses a DC source to apply a sintering current through the titanium sample. Application of the SPS current to the titanium resulted in a theoretical density increase of 11 –14% compared to DPR only, depending on whether the processes were performed sequentially orsimultaneously This multidisciplinary project employed a broad range of combined materials, mechanical and electrical design and analysis methods. The resulting mill can be used as is for further parametric testing, improved as will be discussed for the same process, or adapted to a range of different applications.
Buckling of woven fibre and graphene platelet reinforced nanocomposite laminates.
(2021) Sewnath, Kiren.; Adali, Sarp.; Drosopoulos, Georgios A.
Composite materials are known for exhibiting high specific stiffness, strength and light weight. Their properties can be optimized by designers for a specific application. They currently have many applications in various industries such as aerospace, automotive and building industries. Fibre reinforced polymer composites are a large portion of the composite material market. The use of such materials has many advantages. Recently, nanosized reinforcements such as carbon nanotubes and graphene nanoplatelets have also been used as filler materials in composites. Graphene is one of the strongest materials available today and exhibits excellent mechanical properties. The study presented here is an investigation into the buckling of a woven glass fibre and graphene nanoplatelet reinforced epoxy composite. A laminate analogy is utilised. The analytical equations governing these types of laminates are presented and incorporated into Matlab, a computer simulation software that makes use of matrix implementations. The programme is then used to investigate the effects of various design parameters on the buckling load, by generating 2D and 3D graphs. In this study, a laminate analogy is used for the woven glass fibres whereby undulation of the fibres is neglected, and the composite is regarded as an assembly of cross-ply laminates with woven fibres orientated at 90° to each other. The Halpin-Tsai equations are used to incorporate the graphene nanoplatelets into the epoxy matrix. The laminate that is investigated consists of 4 plies, each reinforced by woven glass fibres and graphene nanoplatelets. The laminate is symmetric about its midpoint, such that the two outer layers are identical, and the two middle layers are identical. Layer thicknesses are non-uniform and the reinforcements are distributed non-uniformly in the layers. The thickness ratio of the laminate is defined as the ratio of the total width of the outer layers to the entire laminate thickness. The governing equations of classical laminate theory for buckling of a simply-supported rectangular plate under biaxial loading are used to predict the critical buckling load of the laminate. The bending-twisting coupling terms are neglected. The results generated display the influence of various design parameters on the buckling load. The design parameters investigated are the woven glass fibre volume fraction, woven glass fibre orientation, woven glass fibre balancing coefficient, graphene platelet weight fraction, laminate thickness ratio and laminate aspect ratio. The results show that the graphene nanoplatelets have a greater effect on the buckling load than the woven glass fibres. High graphene content can obscure the effect of the woven fibre orientation and laminate aspect ratio on the buckling load. At low graphene contents, a more concentrated fibre distribution in a single direction (warp or weft) is preferred for the buckling load. At higher graphene content, a more evenly balanced distribution is preferred. Furthermore, for high thickness ratios, more focus must be placed in the reinforcements in the outer layer of the laminate for a cost-effective design.
Multi-point static dexterous posture manipulation for the stiffness identification of serial kinematic end-effectors.
(2020) Singh, Akshay Pradeep.; Bright, Glen.; Padayachee, Jared.
The low stiffness inherent in serial robots hinders its application to perform advanced operations due to its reduced accuracy imparted through deformations within the links and joints. The high repeatability, extended workspace, and speed of serial manipulators make them appealing to perform precision operations as opposed to its alternative, the CNC machine. However, due to the serial arrangement of the linkages of the system, they lack the accuracy to meet present-day demands. To address the low stiffness problem, this research provided a low-cost dexterous posture identification method. The study investigated the joint stiffness of a Fanuc M10-iA 6 Degree of Freedom (DOF) serial manipulator. The investigation involved a multivariable analysis that focused on the robot’s workspace, kinematic singularity, and dexterity to locate high stiffness areas and postures. The joint stiffness modelling applied the Virtual Joint Method (VJM), which replaced the complicated mechanical robot joints with one-dimensional (1-D) springs. The effects of stress and deflection are linearly related; the highest stress in a robot’s structure is distributed to the higher load-bearing elements such as the robot joints, end-effector, and tool. Therefore, by locating optimal postures, the induced stresses can be better regulated throughout the robot’s structure, thereby reducing resonant vibrations of the system and improving process accuracy and repeatability. These aspects are quantifiably pitched in terms of the magnitude differences in the end-effector deflection. The unique combination of the dexterity and the stiffness analyses aimed to provide roboticists and manufacturers with an easy and systematic solution to improve the stiffness, accuracy, and repeatability of their serial robots. A simple, user-friendly and cost-effective alternative to deflection measurements using accelerometers is provided, which offers an alternative to laser tracking devices that are commonly used for studies of this nature. The first investigation focused on identifying the overall workspace of the Fanuc M-10iA robot. The reachable workspace was investigated to understand the functionality and potential of the Fanuc robot. Most robotic studies stem from analysing the workspace since the workspace is a governing factor of the manipulator and end-effector placement, and its operations, in a manufacturing setting. The second investigation looked at identifying non-reachable areas and points surrounding the robot. This analysis, along with the workspace examination, provided a conclusive testing platform to test the dexterity and stiffness methodologies. Although the research focused on fixing the end-effector at a point (static case), the testing platform was structured precisely to cater for all robotic manufacturing tasks that are subjected to high applied forces and vibrations. Such tasks include, but are not limited to, drilling, tapping, fastening, or welding, and some dynamic and hybrid manufacturing operations. The third investigation was the application of a dexterous study that applied an Inverse Kinematic (IK) method to localise multiple robot configurations about a user-defined point in space. This process was necessary since the study is based on a multi-point dexterous posture identification technique to improve the stiffness of Serial Kinematic Machines (SKMs). The stiffness at various points and configurations were tested, which provided a series of stiff and non-stiff areas and postures within the robot’s workspace. MATLAB®, a technical computing software, was used to model the workspace and singularity of the robot. The dexterity and stiffness analyses were numerically evaluated using Wolfram Mathematica. The multivariable analyses served to improve the accuracy of serial robots and promote their functionality towards high force application manufacturing tasks. Apart from the improved stiffness performance offered, the future benefit of the method could advance the longevity of the robot as well as minimise the regular robot maintenance that is often required due to excessive loading, stress, and strain on the robot motors, joints, and links.
Multiscale nanocomposites and laminates reinforced by carbon nanotubes and fibres.
(2020) Zeeman, Morné.; Adali, Sarp.
The addition of nanomaterials to conventional composites as reinforcement results in a new generation of composites, namely, multiscale composites. Multiscale composites comprise of reinforcements from two or more different length scales such as macro, micro and nano hence the name multiscale. Developing a computational modelling approach which analyses the flexural response of nanocomposites at the nanoscale, which is not restricted by time scales, would benefit future studies in the field of nanotechnology. The dissertation details the analysis of carbon nanotube reinforced composites. The key focus areas include micromechanical modelling of both two and three phase nanocomposites along with their applications to structural elements. Furthermore, the flexural behaviour of a simply supported hybrid plate element subjected to a uniform transverse pressure is analysed under various conditions. Firstly, both carbon and glass fibre reinforced composites are investigated along with a nanomaterial such as carbon nanotubes (CNT) to form a multiscale epoxy composite. Modelling techniques such as Mori-Tanaka and Halpin-Tsai approaches are furthered in order to investigate the mechanical properties of both two-phase and three-phase composites. The results obtained from these models are compared to theoretical and experimental results available in the literature. Secondly, the material properties obtained are then used to investigate the bending behaviour of a CNT/fibre/polymer cross-ply laminate by incorporating micromechanical modelling techniques with structural mechanics. Numerical results are then obtained and used to study the effect of various problem parameters such as agglomeration, different fibre reinforcements, material layup and nanotube diameter. The numerical results given in this study provides a quantitative analysis of the effects of different types of CNT parameters, fibre reinforcements and the volume fractions on the static behaviour of laminated composites.
Fused deposition modelling (FDM) to fabricate a transitional vertical take-off and landing (VTOL) unmanned aerial vehicle (UAV) for transportation of medical supplies in underdeveloped areas.
(2020) Harcus, Matt Brandon.; Bright, Glen.
This dissertation’s work has focused on the design and development of a prototype UAV that aims to facilitate the delivery of emergency medical aid supplies to remote locations within South Africa (SA). This research has conducted a conceptualized design of a tilt-rotor VTOL UAV named Airslipper, which was entirely fabricated using FDM methods. Identification of key performance parameters within the vehicle’s mechatronic design enabled this research to conduct a simultaneous optimization on the propeller-based propulsion system and aerodynamic configuration. Execution of MATLAB’s ‘gamultiobj’ function on two parametrically formulated objective functions resulted in a UAV setup that increased flight endurance by 𝟓8 𝒔𝒔. This improvement amplified the effectiveness of this system and expanded the service radius distance by 𝟏.𝟓1 𝒌m. The outcome of a stability and sensitivity analysis performed on the Airslipper’s aerodynamic surfaces provided critical information that contributed towards the vehicle’s flight characteristics. Findings indicated a stabilized design that exhibited appropriate frequency plots for both longitudinal and lateral stability modes. The addition of a plane analysis, which included viscous and inertial effects, offered essential drag and pressure coefficients, which aided in the final design. This research correspondingly conducted several CFD simulations on an Airslipper model, which allowed this work to examine further the fluid behaviour characteristics endured on the vehicle in both VTOL and Fixed Wing (FW) modes. Simulation findings revealed standard pressure distributions, which confirmed thrust and lift forces for the relevant components without performance compromise. This research proposed to experimentally investigate a correction factor for an FDM fabricated aerofoil that aimed to determine what structural effects were apparent for a printed part with varying FDM parameters. Outcomes demonstrated greater resilience to failure for parts that had reduced layer heights and increased infill percentages. Fabrication of the Airslipper comprised of 99 individually printed parts that encompassed a specific parameter combination which pertained to the design’s importance. Validating the prototype’s functionality was achieved through a series of hover tests that generated suitable data logs plots for the control response, actuator output signals, vibration metrics, and power. This research concluded by discussing the Airslipper’s design and fabrication method with further mentioning of recommendations for potential improvements.
Design, modeling and optimization of a seawater reverse osmosis desalination plant.
(2021) Ncube, Randy.; Inambao, Freddie Liswaniso.
Potable water is one of the major needs for human, animals and plant survival. But recently, due to the growth in population and industrialization, fresh water shortage has escalated to alarming levels particularly in the Middle East and Africa. South Africa has not been spared in this predicament. Recently, Cape-town and its surrounding areas have been hard hit by water shortages and in one of the years, the region almost got to day zero, where all water sources were about to run dry, yet the region is surrounded by vast amounts of sea water. Research and development of several methods to mitigate this problem is still ongoing. Desalination of seawater is one of the several ways which have been used to ease this problem, and Reverse Osmosis (RO) is generally taking over as the preferred technique of desalination because of its generally higher efficiency and better quality of water produced using generally lower energy. Research has also shown that the limitations and concerns of using RO technique on water productivity are membrane fouling and high energy consumption in these plants. Design, modeling and optimization using modelling and simulation softwares and experiments on seawater reverse osmosis (SWRO) desalination plant is one of the ways in which this water shortage crisis may be alleviated. This dissertation seeks to attend to the limitations of the available plants in use through experimentation, coming up with mathematical models and simulations to increase throughput and efficiency of the system. Theoretical data analysis and membrane modeling of a SWRO desalination unit was done on the design and undertaken using Hydranautics Nitto Group Company powered Integrated Membrane Solutions Design (IMSDesign) software, a membrane modeling software that allows users to design a reverse osmosis (RO) system based on Hydranautics membranes. The experiments were done on the Victoria and Alfred (V&A) Waterfront desalination unit, a seawater desalination plant located along the Atlantic Ocean coastal city of Capetown, South Africa. Extracted data from experiments was collected and statistically analyzed using Microsoft excel and different relationships of parameters were plotted. Some of the design input and output parameters that were studied using include feed and permeate TDS, pressure, temperature, pH, energy consumption and conductivity. The effects of different fee parameters were compared against their permeate variables in the month of November 2018, and several relationships and correlations were plotted. Experimental data showed that an increase in feed temperature resulted in a decrease in permeate TDS, whereas and increase in feed pressure resulted in a general increase in permeate TDS. Finding the optimum compromise between the two input variables was done and optimum values were found. Energy efficiency and reducing energy consumption of the plant while not compromising on product quality is also one of the parameters that were studied and the relationships between feed TDS, feed temperature, feed pressure and feed pH against energy consumption were modelled. Modeling and simulation using ROSA and IMSDesign softwares was undertaken and several equations and correlations of specific energy and input temperature, feed temperature and permeate TDS, feed TDs and permeate TDS were produced. Optimization of the V & A desalination plant was performed using experimental data extracted from the plant and some assumed data. Simulation and optimization was accomplished using Water Application Value Engine simulation software and improvements in specific energy consumption, permeate TDS and permeate productivity were observed.
Research, design and investigation of a multiple user mixed reality system.
(2021) Naidoo, Dashlen.; Bright, Glen.; Collins, James Edward Thomas.
Current forms of virtual technology are limited by their single-user capability per device. Additionally, these technologies are listed at expensive price ranges due to the robust technology and processing power required for operations. These were identified as research challenges when a review of virtual technologies was undertaken. Research indicated the need for a system that allowed simultaneous user viewing and interaction without requiring robust hardware or system software. This dissertation researched, designed and investigated a Mixed Reality (MR) System that allows multiple user viewing and interaction with mid-air images. Beam splitter theory was used to deliver the mid-air images on this system. Multiple user viewing was achieved through beam splitter selection of an ASKA3D Plate and the design of a novel system architecture that adjusted system components. A mechatronic actuation system was developed to automate the adjustment of system components that allowed seated and standing viewing within three height ranges. System operation and interaction were allowed through inputs on a laptop. Additionally, the implementation of gesture control was investigated using a web camera or a CaptoGlove™. The testing performed on the manufactured MR System validated the design, actuation methods, viewing method and performance of the system. The laptop’s Operating System (OS) was used to develop an MR game for entertainment testing, display images and videos for visual learning testing and operate SolidWorks™ for engineering design testing. The results of accuracy testing showed that the actuation methods had an accuracy range within the required 45-degree rotations with a highest possible error of 3° and the required vertical movements of 50 mm and 100 mm with a highest possible error of 0.5 mm. The results of repeatability testing showed the actuation methods had coefficients of variance with values less than 0.1, signifying a high repeatability. System performance was evaluated through user testing and proved the system as a tool to facilitate entertainment, education through visual learning and engineering design. Visual learning was found to be the most successful on the MR System with an average percentage rating of 100% and the overall system performance was given a rating of 80%. Actuation testing and user testing validated the hardware design, software design, electronic design and viewing method of the system. The MR System operated as intended showing successful multiple user viewing without requiring robust hardware or software for system operation. The system was limited by the defined interaction method, the lack of multiple user testing and the limited programs used for testing the system’s performance.
Preliminary design considerations for a commercial launch vehicle upper stage.
(2021) Gyasi-Agyei, Phillip Kwabena Konadu.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
The African small satellite industry (micro and nano satellites in particular) continues to grow with developments in the miniaturization of satellite technology. However, the costs and delays involved with the traditional “piggy backing” satellite launch method is unsustainable for small sat developers and has thus created a niche market for dedicated small satellite launch services. Notably, there is no satellite launch capability whatsoever in Africa, meaning all of the continent’s launch requirements are serviced by foreign providers, incurring additional cost. As its primary objective, the University of KwaZulu-Natal’s (UKZN’s) Aerospace Systems Research Group (ASReG) seeks to enable the establishment of an indigenous small satellite launch capability in alignment with the South African Government’s goals. To this end, ASReG is currently developing the LOX/Kerosene SAFFIRE (South African First Integrated Rocket Engine) to propel a hypothetical two-stage orbital launch vehicle, termed Commercial Launch Vehicle 1 (CLV). The upper stage of the launch vehicle will use a vacuum-expanded variant of SAFFIRE called SAFFIRE-V. The upper stage for both cases must meet the design constraints of a 0.85 mass fraction and a 1.2 m outer diameter. CLV has been envisaged to deliver a 75kg payload to 400 km sun synchronous orbit. This thesis presents a high level analysis focusing on the upper stage of CLV, which intends to guide design decisions by comparing design options based on mass, and develop a methodology for upper stage vehicle design. One of the major design decisions is the type of propellant feed system the vehicle should use; in this regard, the analysis compares an electric pump feed system to a pressure fed system. Another is the selection of propellant tank material, given that the propellant tanks constitute most of the mass of a rocket. Stainless steel (301 and Duplex), aluminium alloy (7075), aluminium-lithium (2195), carbon fibre reinforced plastic (T700/Epoxy), as well as combinations of materials were compared. To perform the preliminary mass analysis, each of the major components/systems of the CLV upper stage were independently designed and the various design options available for each of the components/systems were compared based on mass. These systems and components include: fuel and oxidiser propellant tanks, the propellant pressurization system and the reaction control system. After the individual analyses of the variations of each component, the best suited architectures were modelled in SolidWorks CAD software. The components were then assembled, in CAD. The analysis found that, on a preliminary basis, the Lithium ion (Li-Ion) based electric pump fed upper stages did not meet the mass requirements while Lithium polymer (Li-Po) based upper stages achieved the mass requirements. An upper stage employing stainless steel propellant tanks was found to meet the mass requirements, but only for a pressure fed upper stage. Overall, pressure fed upper stages had lower masses compared to electric pump vehicles. The mass reduction of thin walled, low pressurized, propellant tanks (resulting from using electric pumps) was offset by the mass of the battery packs required to power the pumps.
Optimization of energy conservation measures to improve efficiency in commercial buildings.
(2021) Ismail, Amina.; Inambao, Freddie Liswaniso.
In addition to international energy concerns, South Africa is facing its own electricity generation challenges. Periodic load shedding leads to a decrease in national revenue as the production of goods and services comes to a halt and investor confidence in the country declines. This particularly affects small businesses and contributes to unemployment. Many South African government buildings are old with poor energy management practices. These buildings tend to consume more energy than necessary, making the buildings highly energy intensive, thus compounding the energy demand on the grid. The country’s energy challenge and the lack of energy efficiency in commercial buildings adds to excessive and wasteful consumption of energy, which negatively impacts the environment and the already hurt economy. The aim of this research was to evaluate energy efficiency in a public commercial building and identify the drivers and barriers to energy efficiency to improve energy management practices and ensure electrical and mechanical systems are energy efficient. The outcome from this research indicates that energy consumption can be improved and reduced by using energy efficient technology, implementing energy efficient design techniques for systems design, and incorporating energy conservation measures where possible. Effective energy management of a commercial building involves operation and maintenance of electro-mechanical equipment and continuously improving energy consumption by monitoring the buildings energy use. Another important outcome from this research is that government regulations, building policies and other regulatory documents play an important role in encouraging the implementation of energy efficiency as well as monitoring and improving energy usage. A review of energy efficiency in heating, ventilation, and air conditioning (HVAC) systems indicated that energy efficiency can be implemented from the design stage, where the designer selects energy efficient technology so that energy efficiency of the system is optimised. A review of various articles concluded that energy efficiency of lighting systems and miscellaneous electrical loads (MELs) can be improved by the use of energy efficient light bulbs, occupancy sensors, day/night switches and other novel energy efficient technologies. The review on drivers and barriers to energy efficiency showed that drivers and barriers to energy efficiency can be found in various stages of a building’s life cycle, and in some cases decisions made at the inception stages affect the energy consumption during the operation of the facility. The experimental results showed that the energy conservation measures implemented in the buildings in this study were relatively cost effective and produced a significant improvement in the consumption of electrical energy.
Integrated low-cost reading device targeting the accessibility to quality education for the visually impaired.
(2021) Botha, Ingrid Retha.; Bright, Glen.; Collins, James Edward Thomas.
The movement of society into the Fourth Industrial Revolution introduces a fundamental shift in how Mechatronic devices are implemented in daily life and the workplace. Terms such as ‘efficiency’ and ‘competitive advantage’ bolster the drive to develop technology that sets one company, business or manufacturer apart from the rest. However, is there a possibility that the same technology can be used to unify society by providing equal opportunity within the workplace, academia, and everyday life? This research addresses the position of the South African visually impaired community within Industry 4.0 and how Mechatronic technology can be used to improve current employment statistics and quality of life. The purpose of the research project was to assess the financial and operational viability of a portable text to braille transcription device with focus on the implementation of novel small-scale Dielectric Elastomer Actuators (DEAs). The device was required to transcribe printed characters into braille in real-time. This allowed visually impaired individuals access to books, journals and newspapers without assistance or the need to wait for the production of a braille-embossed printed copy. In addition, the research included an assessment of the current employment and educational circumstances of the blind and visually impaired community of South Africa as well as an investigation of the ideal approach to address multiple key factors using a single device. The design of the selected device was comprised of three major subsystems; the optical character recognition hardware, the software and electronics required to transcribe the characters into a series of voltage outputs and the actuation system of the tactile display. The synthesis and operating conditions of the dielectric elastomer actuators were experimentally assessed. The tactile display was required to be low cost, small-scale, portable, and robust to present a sustainable solution to the challenges presented by the lack of accessible reading material and high cost of commercially available options. Scaled models of the DEA were synthesised. The subsequent experiments included the comparison of elastomer materials, electrode materials, the effect of pre-strain on DEA performance, the effect of different application methods of carbon electrodes and the performance of inflated DEA membranes. The electronic subsystem was simulated to investigate the reaction time of the device. Design challenges included the requirement of a high voltage power supply to actuate the DEA, the insulation of the synthesised membranes, electrical protection of the micro-controller and the incorporation of optical character recognition programmes. This research aimed to assist in the development of actuators with greater portability and scope for miniaturisation than commercially available pneumatic or piezoelectric alternatives while addressing the challenges faced by the visually impaired community of South Africa.
CFD Modelling and performance evaluation of a forced convection mixed-mode solar grain dryer with a preheater.
(2021) Angula, Johannes Penda.; Inambao, Freddie Liswaniso.
Solar drying of agricultural food products as an art of food preservation has been in existence since the 17th century. In most tropical and subtropical countries, the drying process of harvested agricultural products such as grains is mainly carried out using the method of open-air drying or sun drying to preserve the harvest. With the advances of technology over time, new solar drying methods such as indirect and mixed-mode solar drying are evolving. Mixed-mode solar dryers are among the most efficient solar drying methods for improving the harvest and storage of grains. One of the advances in the development of solar dryers is the use of computational fluid dynamics (CFD) and computer-aided design (CAD) codes to model, simulate, and analyze dryer systems' performance. This study was conducted in two phases. The first phase entailed the use of CAD and CFD codes to model and simulates a forced convection mixed-mode solar grain dryer integrated with a preheater. A 3D model was developed with great accuracy using SolidWorks code and, the CFD simulation was carried out using ANSYS Fluent code. In the second phase, an experiment was conducted using an existing indirect solar dryer which was modified and converted to a mixed-mode solar dryer suitable for the study. The modeling and simulation results were validated against experimental results to evaluate the dryer system' performance. The study was conducted at various airflow speed and preheater temperatures ranging from 0.5 m/s to 2 m/s and 30 ℃ to 40 ℃, respectively. The type of grains used in the experiment were corn grains whereby 72 freshly harvested maize ears/cobs were dried. The study was conducted under the weather conditions of Durban, South Africa, at the University of KwaZulu-Natal. This study aimed to investigate solar drying technologies towards performance enhancement of a forced convection mixed-mode solar grain dryer that incorporated a preheater through modeling and optimization. This approach was followed in order to develop a better understanding of the effects of forced convection and air preheating on airflow distribution and temperature distribution within a solar dryer. The results from both the CFD modeling and experiment were satisfactory, resulting in a correlation with a maximum relative error of 16.3 %. The dryer system's performance results indicated a maximum thermal efficiency of 58.8 % with a corresponding drying rate of 0.0438 kg/hr. The minimum thermal efficiency for the dryer system was 47.7 %, with a corresponding drying rate of 0.0356 kg/hr. The fastest drying time of maize ears was achieved in 4 hours and 34 minutes from an initial moisture content of 24.7 % wb to 12.5 % wb. At the same time, open-sun drying yielded the slowest drying time of 15 hours from an initial moisture content of 27.3 % wb to 12.7 % wb. There was a significant improvement in the dryer system's performance, whose initial efficiency was 36 % when operating as an indirect solar dryer. These results are a clear indication that using a solar dryer system in mixed-mode operation with forced convection and the assistance of a preheater or backup heater can significantly improve drying processes and increase food preservation. The study further presents design concepts of incorporating cost-effective solar thermal energy storage systems that can be implemented to optimize solar dryers. In this case, solar energy can be harvested and stored during peak sunshine hours and made available for usage during off-peak sunshine hours.
Computational fluid dynamic modelling of baffled open volumetric receiver operation.
(2020) Jo Mathew, Mathew.; Pitot De La Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
An Open Volumetric Receiver (OVR) is a type of solar energy receiver that is able to heat atmospheric air volumetrically via a porous absorber exposed to concentrated solar radiation, through which the air flows. OVRs have the potential to attain higher operational efficiency than tubular or cavity type receivers, and they have been extensively investigated for use in concentrating solar power (CSP) plants. In CSP applications, the hot air leaving the OVR is typically passed through a heat recovery steam generator to generate steam for the plant’s steam turbine, after which it is returned to the OVR. Here, it is injected back into the atmosphere near the receiver inlet where some of the warm return air is re-entrained along with fresh air entering it. The amount of air that is re-entrained into the OVR is quantified by the air return ratio, and the higher this ratio, the lower the energy lost from the receiver. One of the factors limiting the operational efficiency of OVRs is fairly poor ARR performance, in the region of 50 % for state-of-the-art OVR designs. This research aims to evaluate the effectiveness of the addition of the vertical air flow baffles in improving the air re-entrained performance of an OVR. The evaluation was carried out numerically using Ansys Fluent Computational Fluid Dynamics (CFD) modelling software. Prior to the core investigation, cold and hot flow validation studies were conducted with respect to a generalized porous absorber and an arrangement of HiTRec-II OVR modules. The corresponding CFD models were successfully validated against experimental data and the methodology used to model the HiTRec-II modules was used to model an arrangement of SolAir OVR modules and modified arrangements incorporating air flow baffles of varying lengths. OVR air re-entrainment performance was evaluated in terms of the module air outlet temperature. The performance of the SolAir modules was evaluated when exposed to wind at varying magnitude and direction. The results from this study were used as a baseline against which the performance predicted for the SolAir modules modified with baffles (of different lengths) could be compared. A comparison of the results indicates that there is a clear increase in mean module air outlet temperature, when air flow baffles are incorporated with the lowest being 2.5 % and highest being 60.7 % increase in the temperature among the wind conditions and baffle lengths investigated for the study. The increase in the temperature also implies an improvement in air re-entrainment and thus OVR efficiency. The results also suggested the existence of an optimal baffle length for the receiver modules, beyond which the air outlet temperature drops and the OVR efficiency deteriorates.

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