Browsing by Author "Veale, Kirsty Lynn."

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Aerodynamic modelling and further optimisation of solar powered vehicle.
(2016) Lawrence, Christopher Jon.; Bemont, Clinton Pierre.; Veale, Kirsty Lynn.
Computational fluid dynamics was used to optimise the aerodynamics of a solar powered vehicle via the addition of airflow alteration devices that interact with the boundary layer airflow. These features were designed, manufactured and applied to the vehicle while ensuring that the bulk geometry remained unmodified. The modifications had to be added to the vehicle non-invasively, and had to allow for removal during race conditions. The solar vehicle raced in both the Sasol Solar Challenge (SASC) which took place in September 2014 and the Bridgestone World Solar Challenge (WSC) which took place in September 2015. Aerodynamic drag is the single largest energy loss experienced by a solar vehicle; it is therefore essential that the aerodynamics of these vehicles be highly refined if they are to be competitive. The UKZN solar vehicle placed first in South Africa in the SASC and 13th in the WSC - indisputably outstanding results. The features to be refined were chosen to reduce aerodynamic drag caused by the wheel spokes as well as the canopy due to these being high turbulence zones and having high curvatures respectively. The principles applied were to reduce turbulence caused by the wheel spokes by adding to the wheel geometry, and adding turbulence to the canopy airflow through the use of a technique commonly known as flow tripping. While turbulence caused by the wheels is undesirable, the turbulence added by flow tripping is desirable as it reduces the size of the separated region of airflow behind the canopy, allowing for a net reduction in aerodynamic drag. Wheel geometry alteration was done via the addition of smooth and dimpled covers, so as to mitigate the turbulence caused by the wheel spokes. Many techniques were considered to trip the airflow on the canopy, it was found that vortex generators of specific geometry and dimensions would reduce drag more effectively. Another airflow altering device, a NACA duct, was designed and manufactured. This duct was placed on the canopy to allow airflow into the driver compartment which enabled adherence to race rules and allowed for driver cooling and ventilation. Each wheel cover was manufactured from two layers of carbon fibre to allow a net gain in efficiency with regards to rolling resistance and drag reduction when considering weight added by the wheel covers. The vortex generators and NACA duct were 3-D printed using ABS plastic. The wheel covers and NACA duct were applied to the car for the World Solar Challenge while only the wheel covers were applied for the Sasol Solar Challenge. The vortex generators were not applied due to the efficiency gain from the application being uncertain at the time of the race. A gain in aerodynamic efficiency with the addition of wheel covers to a front wheel was shown through CFD testing. The drag was reduced by approximately 0.5 Newtons (5 %) relating to translational forces and 0.02 Newtons per meter (44 %) percent with regards to rotational forces. The addition of vortex generators resulted in a drag reduction ranging from approximately zero to three percent when considering straight airflow and crosswinds respectively.
Design and development of the Phoenix-1B hybrid rocket.
(2017) Balmogim, Udil.; Brooks, Michael John.; Veale, Kirsty Lynn.; De La Beaujardiere, Jean-Francois Pitot.
In August 2014, South Africa’s first university-based hybrid rocket, Phoenix-1A, was launched at the Overberg Test Range near Cape Agulhas. The vehicle suffered nozzle and parachute failures during flight which, together with a reduced oxidiser load, reduced the nominal design apogee of 10 km to 2.5 km. The aim of this research was to improve on the design and performance of the prototype demonstrator and thereby develop a workhorse hybrid sounding rocket, named Phoenix-1B, to serve as a reliable platform for future hybrid rocket research at the University of KwaZulu-Natal (UKZN). Analysis of Phoenix-1A shortcomings served as the starting point for the new design, which utilises a paraffin wax and nitrous oxide propellant combination. The focus of this research was the propulsion system, with specific attention being paid to the nozzle and injector designs. In addition, an aerodynamic study was applied to the 1 m long ¾ parabolic nose cone and four tapered swept fins. Final design of the aluminium oxidiser tank and combustion chamber bulkheads incorporated finite element analyses to ensure an operational safety factor greater than 1.5. The oxidiser tank and combustion chamber assemblies were pressure tested to 80 and 60 bars respectively. A key output of the present work is an analysis of the effect of aluminium loading in the paraffin wax fuel grain, which indicated a potential rocket mass reduction of 23 kg when transitioning from a pure paraffin grain to one containing 40% aluminium by mass. The analysis also indicated that combustion temperature rises with aluminium loading, increasing from 3300 K for pure paraffin to 3600 K for 40% aluminised fuel. Consequently, an iterative transient thermo-structural analysis was conducted on the nozzle, resulting in an optimised design able to sustain the higher operating temperatures as well as mitigate the risk of failure as seen with Phoenix-1A. The final manufactured composite nozzle has a throat diameter of 32 mm, an expansion ratio of 6.38, and a length of 156 mm. The nozzle has a steel casing which provides structural support to the silica phenolic insulation and graphite throat insert. A two phase CFD analysis, coupled with analytical mass flow rate models, was used to configure the axial injector and reduce the potential for combustion instabilities associated with the nitrous oxide flow. The Phoenix-1B motor has a design thrust of 5 kN to propel the fully loaded vehicle, with a mass of 70 kg, a length of 4.3 m and a diameter of 164 mm, to an altitude of 16 km.
Design and optimisation of a composite space frame chassis including experimental and computational analysis.
(2017) Narsai, Mikhail.; Adali, Sarp.; Padayachee, Jared.; Veale, Kirsty Lynn.
Composites are used in lightweight structural designs. In this dissertation, a robust carbon fibre reinforced polymer (CFRP) space frame chassis for a lightweight electric tricycle is produced. In large, most composite research is directed toward flat laminates rather than closed sections. This dissertation addresses the complexities of stresses at joints and buckling (local and global). The space frame design consists of two segments of iterations. The second and more important segment is based on optimisation using NX Nastran finite element analysis (FEA). The final design incorporates the use of steel sleeves to address stress concentrations at joins and local buckling. The design and execution of a new test method was developed to validate FEA results. The test method involves applying compressive stress on tubes fabricated using unidirectional (UD) fibre set at 35°, to induce compressive and shear stresses along the primary fibres. In this way, four major failure criteria were compared: Tsai-Wu, Hoffman, Hill and Maximum Strain. The Hoffman and Tsai-Wu criteria were shown to be accurate and conservative. The Hill criteria showed inaccuracy by having incorrectly high strength ratios, while the Maximum Strain criteria had the highest strength ratio, proving to be the least conservative and most inaccurate. This dissertation shows that certain failure criteria may be used confidently in applications such as filament winding and continuous pulComposites are used in lightweight structural designs. In this dissertation, a robust carbon fibre reinforced polymer (CFRP) space frame chassis for a lightweight electric tricycle is produced. In large, most composite research is directed toward flat laminates rather than closed sections. This dissertation addresses the complexities of stresses at joints and buckling (local and global). The space frame design consists of two segments of iterations. The second and more important segment is based on optimisation using NX Nastran finite element analysis (FEA). The final design incorporates the use of steel sleeves to address stress concentrations at joins and local buckling. The design and execution of a new test method was developed to validate FEA results. The test method involves applying compressive stress on tubes fabricated using unidirectional (UD) fibre set at 35°, to induce compressive and shear stresses along the primary fibres. In this way, four major failure criteria were compared: Tsai-Wu, Hoffman, Hill and Maximum Strain. The Hoffman and Tsai-Wu criteria were shown to be accurate and conservative. The Hill criteria showed inaccuracy by having incorrectly high strength ratios, while the Maximum Strain criteria had the highest strength ratio, proving to be the least conservative and most inaccurate. This dissertation shows that certain failure criteria may be used confidently in applications such as filament winding and continuous pultrusion methods, which are widely used in producing closed sections.trusion methods, which are widely used in producing closed sections.
Design and optimisation of the sector transport, storage and assembly tooling and procedures of the New Small Wheel for the Atlas Experiment.
Sinclair, Peter James.; Bemont, Clinton Pierre.; Yacoob, Sahal.; Veale, Kirsty Lynn.
This report describes the design of the transport, storage and assembly tooling for the sectors of the ATLAS Experiment’s New Small Wheel. This tooling is to be used during the 2018 Large Hadron Collider’s shutdown, Long Shutdown 2. Comprehensive design reports following the Eurocode and CERN’s unique design environment and philosophies are presented. The NSW sector transport tool is an adaption of a previously used ATLAS EO muon transport tool, taking new sector masses, geometries and other transport restrictions into account. A safety document is provided for this tool confirming safety with regards to applied stresses in line with the Euro-code. The document also confirms lifting stability during all of the tool’s intended procedures. The assembly tool allows the sTGC components to be assembled to the Micromegas chambers to create NSW sectors for the New Small Wheel. This tool also provides a platform for repairs and adjustments to be made to the NSW sectors before installation. The NSW sector assembly station is also designed in line with the Euro-code. A floor layout allocating space for transport, assembly and storage procedures in Building 191 of the Meyrin, CERN site is provided as specified by the project requirements. An investigation confirming the validity of the finite element analysis techniques and simplifications used on the Micromegas wedges is conducted and presented. This investigation uses the results obtained from experimental thermal tests and analytical calculations of a Micromegas multiplet mock-up called the MMSW and compares them to finite element analysis results modelled to the same testing conditions. The results obtained from this investigation show that the computational results have an error of 7.6 % when compared to the attained experimental results. Consequently, because the finite element model is created in an identical manner to the one used for the Micromegas wedges, an assumption of similar errors can be applied to future simulations conducted on the Micromegas wedges, using this technique.
Development of a design methodology of a composite monocoque chassis.
(2018) Denny, Jason Andrew.; Adali, Sarp.; Veale, Kirsty Lynn.; Leverone, Fiona Kay.
The concept of the composite monocoque chassis has been implemented in many vehicle designs; however, there is little open-access literature defining the primary considerations when simulating one. The purpose of this research is to develop a methodology for determining the structural integrity of a composite monocoque chassis, through finite element analysis, with the intention of developing a lightweight solar powered vehicle. Factors that influence this methodology include; the definition of the vehicle loading conditions, failure criteria, and important design parameters, chief among which is the torsional stiffness. Chassis design specifications were developed from the 2017 Bridgestone World Solar Challenge rules and regulations as these are the most common and complete specifications for this particular type of vehicle. The primary design criteria considered is the torsional stiffness, which was determined from the application requirements and literature, and resulted in a suitable value of 4000 Nm/deg. Siemens NX Nastran was used to develop a torsional stiffness model, which uses the torsional loading condition, to determine the torsional stiffness value. The design methodology then follows an iterative process where various geometry and layup modifications were considered, under the same loading conditions, with the aim of increasing the torsional stiffness to achieve the required value. Aerodynamic properties were adapted from existing UKZN solar vehicle knowledge; however, this research does not consider the optimisation of the aerodynamic properties of a monocoque chassis. Only a structural simulation was conducted. The ultimate strength of the material was also considered throughout the simulation process, however in all cases the model failed to meet the required torsional stiffness parameter before material failure modes. The door recesses had the most significant effect on the torsional stiffness. By compacting the door recesses the torsional stiffness was increased by 29.04 %. A final torsional stiffness was of 4097 Nm/deg was attained with the implementation of an aluminium honeycomb core. Additionally; an analysis of the mounting points was conducted to ensure that the layup can withstand the concentrated loads at the suspension mounts. This analysis is concerned with the principal stresses, where the principal stresses give insight into the most suitable orientation of the layup. The torsional stiffness model resulted in a maximum principal stress of 81.68 MPa, below the 464.4 MPa tensile strength of the reinforcement material orientated in the direction of the fibres. To verify the significance of the torsional stiffness failure criterion, vertical and lateral bending analyses were conducted. A vertical bending model was developed where the chassis is modelled as a simply supported beam, simulating the squatting and diving of a chassis under acceleration and deceleration respectively. The maximum deflection was 5.28 mm, which is below the vi maximum allowable deflection of 12.29 mm, determined from a maximum deflection ratio of 1/360th of chassis length. A lateral bending model modelled the chassis as a simply supported beam with the maximum stress being analysed. The maximum stress experienced by the chassis under this loading condition was 18.73 MPa, which was 75.8 % less when compared to the maximum stress exhibited by the chassis under the torsional loading condition. Flexural bending tests were conducted on various laminate sandwich structures used in the finite element analysis to validate the simulation material properties. The peak load and mid-span deflection of each specimen was recorded to determine the maximum flexural stress and flexural modulus of elasticity. The flexural stress at specific midspan deflections was compared, under the same loading conditions, to that of the bending stress exhibited by a flexural bend test model finite element analysis conducted in Siemen’s NX Nastran. Graphs of the stress versus midspan deflection were plotted for each specimen layup type and the curves of the simulated and experimental results were compared. In each laminate sandwich structure case, the simulation curve exhibited a linear relationship between the midspan deflection and flexural bend stress and the experimental curve exhibited a linear relationship until the elastic limit of the specimens was reached. Thereafter the curve exhibited an exponential relationship as plastic deformation occurs until the specimen failure. An iterative finite element analysis design methodology was used to develop a composite monocoque chassis. The design process of a composite monocoque chassis is simplified by using finite element analysis to iterate through many different configurations, such as core thicknesses, layup orientations, and geometry features, to customise the properties of the structure. With these properties, it is possible to determine chassis performance. The finite element analysis results illustrated that geometry modifications, such as compacting door recesses, and applying strategic layup orientations, such as implementing a honeycomb core, significantly affected the torsional stiffness of a chassis. In addition, a chassis with sufficient torsional stiffness exhibits sufficient bending stiffness. The methodology presented in this research stands to be supportive in designing a fully composite monocoque chassis for lightweight race vehicle applications.
The development of a paraffin wax/nitrous oxide hybrid rocket slab motor.
(2019) Theba, Raisa.; Veale, Kirsty Lynn.; Bemont, Clinton Pierre.
Slab motors are used to determine and investigate the regression rate characteristics of hybrid rocket propellant combinations. This information is fundamental to the overall design and thus used to determine the payload, altitude and thrust parameters of a rocket. The Phoenix Hybrid Sounding Rocket Programme in the University of KwaZulu-Natal’s (UKZN) Mechanical Engineering Department uses paraffin wax and nitrous oxide in their series of hybrid sounding rockets. The regression rate behaviour of paraffin wax with nitrous oxide has not previously been investigated in slab motors. This study focused on the regression rate behaviour and entrainment mechanism with regards to non-classical fuels including those with metal additives. This was used to gain a greater understanding of the increased regression rates associated with these fuels. The addition of metal additives, such as that of aluminium to fuel grains, was explored since the research suggested that it increases the regression rate of pure paraffin wax by 30%. A hybrid rocket slab motor visualisation test stand was developed to observe and obtain regression rate data. The stand includes a feed system, injector and a combustion chamber. All the components were manufactured using brass and stainless steel materials for their nitrous oxide compatibility, strength, and thermal resistance. Quartz glass windows were incorporated into the combustion chamber design for visualisation purposes. Due to the presence of quartz glass the use of finite element analyses became critical and more complex in order to ensure that the glass could withstand the operating conditions of the slab motor. A side-glass spacer was implemented to minimise the effects of side burning and to observe the influence of regression rate. Tests were conducted at a 130 g/s oxidiser mass flow rate and an atmospheric chamber pressure. A data acquisition system using LabVIEW software was implemented to obtain tank readings for the duration of the burn and to ensure safe motor operation. The regression rate of Sasolwax 0907 fuel was volumetrically determined and observed to be on average 3.74 mm/s. This shows a much higher regression rate than other paraffin wax compositions which have been found to regress at 1.5 mm/s. The characteristics of the entrainment process were validated for the investigated propellants, and the high regression rate mechanism of paraffin wax was observed in the liquid melt layer, droplet entrainment, and roll waves. Tests using aluminised wax fuel grains at atmospheric conditions proved to beunsuccessful with nitrous oxide as the oxidiser. A possible reason for this could be due to the aluminised fuel grains requiring increased heat transfer, therefore not producing sufficient apourisation of the fuel. Moreover, decomposition of the oxidiser appeared to be inhibited by the combination of the oxidiser mass flow rate and the port area which prevented combustion.
Performance characterisation of metal additives in paraffin wax hybrid rocket fuel grains.
(2018) Maharaj, Chikhar Shehan.; Veale, Kirsty Lynn.
The Aerospace Systems Research Group (ASReG) at the University of KwaZulu Natal is actively developing sounding rockets in the Phoenix Hybrid Sounding Rocket Programme, for use by the South African scientific community. These sub-orbital launch vehicles use nitrous oxide and paraffin wax as propellants. While paraffin wax offers large performance gains over typical polymeric fuels, due to its high regression rate, further performance gains can be achieved via the use of metal additives such as aluminium powder. The main advantage of using additives such as aluminium is the ability to create a smaller, more compact launch vehicle. This is due to a decrease in the optimal oxidiser-to-fuel ratio brought about by metallisation, which increases overall propellant density. Theoretically, an added advantage is the higher heat of combustion as a result of aluminium combustion. This added heat further increases the regression rate of the solid fuel grain. In order to realise these performance gains, various challenges need to be overcome. Some of these include delayed combustion due to the alumina layer that naturally coats the aluminium particles, slag formation and nozzle erosion. In this study, a laboratory scale hybrid rocket motor was developed to test aluminised paraffin wax fuel grains via a series of hot fire tests. A nitrous oxide feed system was developed, as well as a computer program and associated electronics to control the system remotely and capture data from an array of sensor equipment. Due to time constraints placed on the project, only pure paraffin wax and fuel grains comprising 40 % aluminium by mass were tested. Using specific impulse and characteristic velocity as performance metrics, preliminary data shows little to no gain in performance with aluminised fuel grains due to incomplete combustion of the aluminium. Substantial erosion of the copper nozzles that were used in the aluminium grain tests, due to localised melting, was also noted. Large amounts of aluminium and alumina slag was also found on the nozzles converging face. In order to seek maximum performance gains from aluminium as an additive, it was recommended that the particle size be reduced and stripped of its oxide layer before addition into the solid fuel grain. This will ensure more complete and rapid combustion of the particles before being ejected from the combustion chamber.
Power efficiency of industrial equipment.
(2011) Veale, Kirsty Lynn.; Roberts, Lancian Willett.; Adali, Sarp.
Power conservation has become a high priority to South African industries due to recent environmental assessments and electricity price hikes. This research aims to demonstrate to Industry the many simple and cost effective ways to increase their industrial efficiency with simple modifications, as well as making them more aware of common assembly errors that significantly increase power consumption. This has been accomplished with the design, construction and testing of a test rig capable of producing the desired test results which simulate Industry usage. A test rig was required to test certain energy efficient equipment. This dissertation contains an explanation of the tests required, as well as how they were conducted. These test requirements directed the design outcomes of the test rig. Due to the variety of equipment to be tested, and the accuracy required, the test rig had to be fully adjustable. The design process is explained in this dissertation, along with relevant theory with regard to the testing procedures. The testing procedures were designed to be as accurate as possible. The setup equipment and procedure is briefly explained to ensure an understanding of the capabilities of the test rig. This dissertation contains the results obtained from testing a variety of couplings, belts and motors under different conditions. The results obtained show the difference between the efficiency of a standard motor and that of a high efficiency motor. The efficiency comparison of the Poly V TM, Poly Chain® and SPB V-belts showed very distinct advantages and disadvantages of each belt. The coupling testing was conducted under conditions of misalignment, and resulted in distinct differences in the efficiencies of each coupling at different degrees of misalignments. The couplings tested were the Fenaflex®, the Quick-Flex®, and the Fenagrid® coupling. All results obtained were analyzed and discussed in the relevant sections. The results obtained showed that the high efficiency motor is significantly more efficient than the standard motor at full load, although at low loading, the motor efficiencies were very similar. The coupling tests showed the negative effects misalignment has on the efficiency of the Quick-Flex® and Fenagrid® coupling as well as the capability of the Fenaflex® coupling to withstand the effects of large misalignments without significant efficiency loss. v The belt testing revealed the advantages and disadvantages of each type of belt used. This showed that although the synchronous belt did not lose efficiency with decreased tension, it became unstable, and was difficult to keep on the pulley if not aligned correctly. The V-belts can handle low tension well. Prolonged use of the belts can cause them to stretch, lowering the tension into a “danger zone” that will cause the belts to slip. This slip can damage the belt and pulley. At the lower tension of the V-belt, although the efficiency increases slightly, the vibration of the slack side of the belt is significant, and can be dangerous as the belt could jump off the pulley. The Poly V TM belt has some of the advantages of the V-belt, except that it is unable to maintain its friction at low tension, as the belt width prevents it from being wedged into the grooves like the V-belt. The fluid coupling tests showed that the shock loading on a high inertia system can be significantly reduced with the aid of a fluid coupling. The reduced shock loading can reduce energy consumption, and increase the life of electric motors and the equipment that they drive by preventing excessive overloading.
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.