Browsing by Author "Kuppuswamy, Ramesh"

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    Open Access
    Development of high efficiency high speed permanent magnet generator
    (2019) Richmond, Colin; Kuppuswamy, Ramesh
    Renewable energy technology is steadily gaining importance in the energy market because of the limited nature of fossil fuels, as well as the political pressures to reduce carbon emissions. To ensure sustainable development, adequate and affordable energy should be made available to satisfy the demand of electric energy. The High Speed Permanent Magnet (HSPM) generator is designed and developed and is expected to deliver 10 kW output power as well as to achieve a speed of 30000 RPM, however, to achieve a compact and efficient design with lower excitation losses, magnetizing currents and rotor losses requires the HSPM generator to be operated at high rated speeds of approximately 30000 RPM. However, at high speeds these machines produce a substantial amount of heat. This makes the thermal management of these machines difficult and complicated, which leads to demagnetization and the reduction of the output power and shortens the lifetime of the critical components such as the bearings. This thesis presents the design and development of the HSPM generator. It also identifies the heat generated by means of electromagnetic, mechanical and core losses. The development of an adequate cooling system (cooling jacket) is presented to avoid hot spots in the generator and thermal damage to the magnets, resulting in demagnetization. The use of pressurized oil air particles as a lubrication method for the bearings of the generator is also considered to avoid: thermal damage and starvation at the rolling element and to address the predominant concern of effectively cooling the HSPM generator ball bearings at elevated speeds. The HSPM generator is designed and developed to operate at a maximum speed of 30000 RPM to deliver 10 kW output power and is subjected to 80~92°C temperature rise with an idle power consumption of ~2kW, enough to cause hot spots on the generator, demagnetization of the magnets and severe impact to the rolling elements of the bearings. The developed cooling jacket and the newly developed oil air mist lubrication arrangement enables the control of the temperature rise of the generator and the temperature rise at the rolling element, respectively. A steady state analysis was also carried out at motor maximum power output to determine its safe operation with the objective of finding an optimal operating condition by performing a parametric study on the effect of cooling. A 3D steady state model of a 10-kW electric permanent magnet machine was generated and investigated with one cooling jacket layout. The end windings and bearings were not considered to simplify the motor model. Numerical analysis is performed with two different coolant flow rates, no flow and maximum flow (3.5 m3 /h) with special emphasis on the maximum motor temperature. The analytical calculations for the role of coolant flowrate on heat transfer characteristics for a high speed generator, showed that the convection heat transfer coefficient increases with an increase in flowrate (0.3 – 3.5 m3 /hr), while the numerical simulations showed that the maximum coolant flowrate conditions achieved lower temperature generation (27.9°C at the front bearing) throughout the generator compared to no coolant flowrate (43.7°C at the front bearing). The detailed understanding of the effects of these parameters on the generator’s temperature field will help in validating the performance of the generator with actual results.
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    Open Access
    Flexible Media Polishing Machine for Ti-6Al-4V Components
    (2022) de Jongh, Quintin Oliver; Kuppuswamy, Ramesh; George, Sarah
    New-age components (notably those in the bio-medical and aerospace industries) are often manufactured from hard to machine materials such as Ti-6Al-4V and tungsten carbide and have extreme surface finish requirements. Flexolap polishing offers a technique to achieve these requirements, and minimizes the disadvantages encountered by other polishing techniques. The aim of this dissertation is that of designing and developing a working Flexolap polishing machine (and associated abrasive compound) suitable for the South African manufacturing industry (and any industry with a lack of financial means and skills for advanced manufacturing). This aim was affirmed by developing models to characterize the Flexolap polishing process, as well as by using experimental analysis to verify the process viability and compatibility with Ti-6Al-4V (and subsequently, other easier to machine materials). A thorough literature review is presented with the most important conclusions of optimal polishing conditions (high hydration, high media impinging velocity and a 45º polishing angle) and applicable modelling methods (momentum, critical values, and vibrational analysis). Two models (empirical and analytical) and a supporting simulation model are presented for force control and stipulation of required conditions for ductile regime polishing to occur. A third model is presented later in the dissertation and classifies the viscoelastic nature of the designed abrasive as well as its damping effect as the compounded media is hydrated (the media-workpiece interaction becomes more underdamped). The results of all modelling processes provide proof that effective polishing can be achieved at designed working conditions (times of less than 10 minutes to desired surface roughness and contact stresses less than that for brittle failure but greater than that required to induce ductile regime polishing). The process of creating/building the Flexolap machine is described through design and development. Process calculations to support design include belt and pulley calculations, bearing calculations, steady abrasive/air flow calculations and weld strength calculations. Experimental techniques include gathering force data (using a dynamometer) and finding surface properties (using a profilometer and various microscopes). This led to gathering a large set of results which were used to study the process viability. Analysis is based on surface roughness and texture change over time (or change over other parameters), as well as the changes in force over parameters such as media hydration, media diamond concentration and media velocity. Experimental results display trends of polishing forces decreasing with an increase in hydration, while surface roughness decreases in a logarithmic manner (with a great initial decrease before reaching a convergence point). Surface texture is also shown to improve with a lesser presence of asperities and a more uniform texture overall (with greater hydration levels). Higher impinging velocities lead to lower surface roughness being achieved quicker while higher diamond concentration tends to create higher roughness at higher impinging velocities. Medium-high media hydration (30%), higher impinging velocities (31.4 m/s) and a polishing angle of 45º are proven to be the most effective polishing conditions. The study was successful in proving the viability and effectiveness of the Flexolap polishing technique while also providing pertinent experimental and theoretical data towards the further study of the process. The expected benefits the outcomes of this study provide to industry are: an easy to learn finishing process that can easily integrate into a finishing or manufacturing workshop (thus upskilling operators), an efficient and cost effective means of polishing hard to machine materials (reducing cycle time and cost), and a framework of polishing machine that can be easily adjusted to meet industry needs for example: size/shape of workpiece and automation of the process. This study was embarked on due to the lack of inexpensive and easy to operate polishing methods available in South Africa, particularly because raw titanium is often exported for processing due to the low availability of advanced manufacturing equipment for the material in South Africa as well as the low level of operator experience in advanced manufacturing machinery.
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    Surface texture enhancement of SLS processed turbine blades using a mix of flexible media and abrasives
    (2022) Titus, Matthew; Kuppuswamy, Ramesh
    Additive manufacturing technologies such as Selective Laser Sintering of Grade 5 Titanium has been used extensively within the aerospace industry as it allows for the fabrication of complex shapes with minimal material wastage. With the increased use of complex shapes, newer polishing technologies need to be developed to accommodate the fabrication technological advancements. This dissertation proposes a novel abrasive flow polishing technology that can lower polishing times as well as limiting damage that polishing may have on a component due to excessive forces. This is achieved by the addition of a flexible media to the abrasive particles to achieve more desirable properties of the polishing media. The technology has been partially developed with further design requirements being investigated by means of explicit dynamic simulations within the Ansys package. The simulations include an asperity made of Grade 5 titanium, a SiC abrasive particle and, an HDPE particle as the flexible media. These simulations have tested process parameters such as abrasive size, asperity size and impact velocity. These simulations have shown that addition of the flexible media can increase the material removal rate of process by up to 200% due to a vibratory motion that was observed of the abrasive particle. These results are promising in showing that the proposed abrasive flow polishing technology can improve the material removal rate of the current aero lapping technology due to the addition of the flexible media. Preliminary testing for this technology has shown that the developed system is within a 22% performance range of similar literature. However, the verification of these simulations and findings needs to be completed through thorough testing of the physical technology.