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Masters Degrees (Mechanical Engineering)

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

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Browsing Masters Degrees (Mechanical Engineering) by SDG "SDG9"

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    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).
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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.
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    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.