Since the late 19th century, the average temperature on Earth has risen by approximately 1.1 °C because of the increased carbon dioxide (CO2) and other man-made emissions to the atmosphere. The transportation sector is responsible for approximately 33% of the global CO2 emissions and 14% of the overall greenhouse gas emissions. Therefore, increasingly stringent regulations in the European Union require CO2 emissions to be lower than 95 gCO₂/km by 2020. In this regard, improvements in internal combustion engines (ICEs)must be achieved in terms of fuel consumption and CO2 emissions. Given that only up to 35% of fuel energy is converted into mechanical power, the wasted energy can be reused through waste heat recovery (WHR) technologies. Consequently, organic Rankine cycle (ORC) has received significant attention as a WHR technology because of its ability to recover wasted heat in low- to medium-heat sources. The Expansion machine is the key component in ORC systems, and its performance has a direct and significant impact on overall cycle efficiency. However, the thermal efficiencies of ORC systems are typically low due to low working temperatures. Moreover, supersonic conditions at the high pressure ratios are usually encountered in the expander due to the thermal properties of the working fluids selected which are different to water. Therefore, this thesis aims to design an efficient radial-inflow turbine to avoid further efficiency reductions in the overall system. To fulfil this aim, a novel design and optimisation methodology was developed. A design of experiments technique was incorporated in the methodology toexplorethe effects of input parameters on turbine performance and overall size. Importantly, performance prediction modelling by means of 1D mean-line modelling was employed in the proposed methodology to examine the performance of ORC turbines at constant geometries. The proposed methodology was validated by three methods: computational fluid dynamics analysis, experimental work available in the literature, and experimental work in the current project. Owing to the lack of actual experimental works in ORC-ICE applications, a test rig was built around a heavy-duty diesel engine at Brunel University London and tested at partial load conditions due to the requirement for a realistic off-high representation of the performance of the system rather than its best (design) point, while taking into account the limitation of the engine dynamometer employed. Results of the design methodology developed for this projectpresented an efficient single-stage high-pressure ratio radial-inflow turbine with a total to static efficiency of 74.4% and an output power of 13.6 kW.Experimental results showed that the ORC system had a thermal efficiency of 4.3%, and the brake-specific fuel consumption of the engine was reduced by 3%. The novel meanlineoff designcode (MOC) was validated with the experimental works from three turbines. In comparison with the experimental results conducted at Brunel University London, the predicted and measured results were in good agreement with a maximum deviation of 2.8%.

Les véhicules électriques (VE) ou les véhicules électriques hybrides (VEH) offrent de nombreux avantages par rapport aux véhicules à moteur à combustion interne classiques. Selon les tendances récentes, la demande en VE(H) efficaces devrait augmenter considérablement. Pour une gamme haute puissance, la technologie des moteurs à aimants permanents a été le choix privilégié dans les véhicules électriques hybrides. La demande croissante de moteurs à haut rendement est en corrélation directe avec la demande d'aimants puissants (NdFeB ou SmCo) utilisant des terres rares. La disponibilité et la production des terres rares sont très critiques particulièrement pour les terres rares lourdes. L'objectif de cette thèse de doctorat est donc de concevoir un moteur Halbach à rotor extérieur pour une application VE(H) avec recyclage et réutilisation faciles des aimants. En outre, le projet vise à étudier et à proposer la fabrication d'un aimant Halbach utilisé dans les moteurs de forte puissance pour application VE.Tout d'abord, la fabrication d'un aimant Halbach utilisant un aimant NdFeB fritté avec et sans liant a été étudiée. L'étude montre que la fabrication d'une configuration de Halbach à l'aide d'un aimant collé est beaucoup plus facile et plus rentable que la fabrication d'un aimant fritté. La caractérisation d'un aimant NdFeB lié utilisé pour fabriquer un aimant Halbach a également été réalisée. Diverses voies de recyclage des aimants frittés et liés ont été analysées; on peut en déduire que les aimants collés sont beaucoup plus faciles à recycler, de manière rentable et respectueuse de l'environnement. La thèse propose également un moyen de recyclage pour l'aimant collé utilisé dans le moteur.Deuxièmement, un moteur à aimant Halbach collé a été conçu en modélisation éléments finis 2D et 3D. Pour obtenir un moteur très efficace et compact, on a utilisé un bobinage à pas fractionnaire. Les propriétés de l'aimant Halbach ont été calculées à l'aide du modèle éléments finis et comparées au modèle analytique. Les résultats obtenus par les deux approches étaient similaires. De plus, l'impact des combinaisons nombre d’encoches-pôles sur les pertes moteur et le couple a été étudié, en particulier les pertes Joule (compte tenu de toutes les contraintes de conception). Différentes stratégies pour utiliser des aimants recyclés à faible rémanence sont également présentées. L'utilisation d'un aimant recyclé avec une augmentation de la longueur axiale du moteur pourrait être le meilleur choix compte tenu de différents facteurs, notamment la fabrication de l'aimant Halbach. Sur la base de différentes études paramétriques, une conception du moteur a été proposée et un prototype a été construit. Il a été montré qu'un aimant Halbach de grande puissance pouvait être construit de manière économique avec un aimant NdFeB collé. La densité de flux d'entrefer du rotor, mesurée sur le prototype, est en étroite concordance avec les valeurs calculées.De plus, la méthodologie WIRE (Weighted Index of Recycling and Energy) a été présentée pour comparer différentes conceptions de moteurs en fonction de leur performance et de leur recyclabilité. La méthode développée produit deux indices basés sur-Facilité de recyclage du moteur en ce qui concerne le matériau, le montage et le démontage des aimants.-Impact d'un aimant recyclé sur la consommation d'énergie d'un moteur pendant sa durée de vie.En utilisant ces deux indices, on peut facilement analyser les avantages et les inconvénients des différentes conceptions sur la base de la recyclabilité et de l'efficacité énergétique. La conception proposée a été évaluée à l'aide cette méthode et on montre que le moteur est facile à monter et à démonter. De plus, l’assemblage moteur (sans colle) permet une extraction facile des aimants et une réutilisation directe. L'indice énergétique évalué du moteur montre l'impact de l'utilisation d'un aimant recyclé et sa viabilité pour les applications VE dans différents scénarios / Electric vehicles (EVs) or Hybrid electric vehicles (HEVs) offer many advantages over the conventional IC engine vehicles. According to recent trends, the demand for efficient (H)EVs is expected to grow significantly. For a high-power range, permanent magnet based motor technology has been the preferred choice for motors deployed in (H)EVs. Growing demand of highly efficient motors is in direct correlation to the demand of strong magnets (NdFeB or SmCo), which uses rare earth elements (REE). The availability and supply of REEs specially heavy REEs is very critical. Therefore, the aim of this doctoral thesis is to design an outer rotor Halbach motor for a (H)EV application with easy recycling and reuse of the magnet. Further, the project aims to investigate and propose the manufacturing of a Halbach magnet used in a high power motor EV applications.Firstly, the manufacturing of Halbach magnet using a sintered and a bonded NdFeB magnet was investigated. The study shows that the manufacturing of Halbach array using a bonded magnet is much easier and more cost effective than the sintered magnet. The characterisation of a bonded NdFeB magnet used for manufacturing a Halbach magnet was also performed. Various recycling routes for both sintered and bonded magnets were analysed and it can be inferred that bonded magnets are much easier to recycle in a cost effective and environment friendly manner. The thesis also proposes the recycling route for the bonded magnet used in the motor.Secondly, a motor with bonded Halbach magnet was designed using 2D and 3D FEM. To achieve a highly efficient and compact motor, fractional slot tooth coil winding was used. The properties of Halbach magnet was calculated using FEM model and benchmarked against the analytical model. The results obtained from the two approaches were in close agreement. Further, the impact of slot pole combinations on motor losses and the subsequent torque were investigated, specifically eddy loss (considering all the design constraints). Different strategies to use recycled magnet with lower remanence is also presented. It is shown that using a recycled magnet with increased axial length of the motor could be the best choice considering different factors, specially manufacturing of the Halbach magnet. Based on different parametric studies a design of the motor was proposed and prototype was built. It was demonstrated that a high power Halbach magnet could be built economically using a bonded NdFeB magnet. The airgap flux density of the rotor, measured on the prototype is in close agreement with the calculated values.Additionally, WIRE (Weighted Index of Recycling and Energy) methodology was presented to benchmark different motor designs on the basis of performance and recy- clability. The method developed produces two indices based on:• Ease of motor recyclability considering material, assembly and disassembly of magnets.• Impact of a recycled magnet on the energy consumption of a motor during its operational lifetime.Using both the above indices, one can easily analyse the pros and cons of different motor designs on the basis of recyclability and energy efficiency. The proposed motor design was evaluated using the developed method and it is shown that the motor is easy to assemble and disassemble. In addition, the motor assembly (glue free) enables easy magnet extraction and direct reuse. The evaluated energy index of the motor shows the impact of using a recycled magnet and its viability for EV applications in different scenarios.

Coal-fired power plants are the largest anthropogenic point sources of CO2 emissions worldwide. About 40% of the world's electricity comes from coal. Approximately 49% of the US electricity in 2008 and 23% of the total electricity generation of Canada in 2000 came from coal-fired power plant (World Coal Association, and Statistic Canada). It is likely that in the near future there might be some form of CO2 regulation. Therefore, it is highly probable that CO2 capture will need to be implemented at many US and Canadian coal fired power plants at some point. Several technologies are available for CO2 capture from coal-fired power plants. One option is to separate CO2 from the combustion products using conventional approach such as chemical absorption/stripping with amine solvents, which is commercially available. Another potential alternative, membrane gas separation, involves no moving parts, is compact and modular with a small footprint, is gaining more and more attention. Both technologies can be retrofitted to existing power plants, but they demands significant energy requirement to capture, purify and compress the CO2 for transporting to the sequestration sites. This thesis is a techno-economical evaluation of the two approaches mentioned above along with another approach known as hybrid. This evaluation is based on the recent advancement in membrane materials and properties, and the adoption of systemic design procedures and optimization approach with the help of a commercial process simulator. Comparison of the process performance is developed in AspenPlus process simulation environment with a detailed multicomponent gas separation membrane model, and several rigorous rate-based absorption/stripping models. Fifteen various single and multi-stage membrane process configurations with or without recycle streams are examined through simulation and design study for industrial scale post-combustion CO2 capture. It is found that only two process configurations are capable to satisfy the process specifications i.e., 85% CO2 recovery and 98% CO2 purity for EOR. The power and membrane area requirement can be saved by up to 13% and 8% respectively by the optimizing the base design. A post-optimality sensitivity analysis reveals that any changes in any of the factors such as feed flow rate, feed concentration (CO2), permeate vacuum and compression condition have great impact on plant performance especially on power consumption and product recovery. Two different absorption/stripping process configurations (conventional and Fluor concept) with monoethanolamine (30 wt% MEA) solvent were simulated and designed using same design basis as above with tray columns. Both the rate-based and the equilibrium-stage based modeling approaches were adopted. Two kinetic models for modeling reactive absorption/stripping reactions of CO2 with aqueous MEA solution were evaluated. Depending on the options to account for mass transfer, the chemical reactions in the liquid film/phase, film resistance and film non-ideality, eight different absorber/stripper models were categorized and investigated. From a parametric design study, the optimum CO2 lean solvent loading was determined with respect to minimum reboiler energy requirement by varying the lean solvent flow rate in a closed-loop simulation environment for each model. It was realized that the success of modeling CO2 capture with MEA depends upon how the film discretization is carried out. It revealed that most of the CO2 was reacted in the film not in the bulk liquid. This insight could not be recognized with the traditional equilibrium-stage modeling. It was found that the optimum/or minimum lean solvent loading ranges from 0.29 to 0.40 and the reboiler energy ranges from 3.3 to 5.1 (GJ/ton captured CO2) depending on the model considered. Between the two process alternatives, the Fluor concept process performs well in terms of plant operating (i.e., 8.5% less energy) and capital cost (i.e., 50% less number of strippers). The potentiality of hybrid processes which combines membrane permeation and conventional gas absorption/stripping using MEA were also examined for post-combustion CO2 capture in AspenPlus®. It was found that the hybrid process may not be a promising alternative for post-combustion CO2 capture in terms of energy requirement for capture and compression. On the other hand, a stand-alone membrane gas separation process showed the lowest energy demand for CO2 capture and compression, and could save up to 15 to 35% energy compare to the MEA capture process depending on the absorption/stripping model used.

This is a study that is focused on developing an individual design methodology for a centrifugal impeller and generating a mixed flow impeller for a small turbojet engine by using this methodology. The structure of the methodology is based on the design, modeling and the optimization processes, which are operated sequentially. The design process consists of engine design and compressor design codes operated together with a commercial design code. Design of Experiment methods and an in-house Neural Network code is used for the modeling phase. The optimization is based on an in-house code which is generated based on multidirectional search algorithm. The optimization problem is constructed by using the inhouse parametric design codes of the engine and the compressor. The goal of the optimization problem is to reach an optimum design which gives the best possible combination of the thrust and the fuel consumption for a small turbojet engine. The final combination of the design parameters obtained from the optimization study are used in order to generate the final design with the commercial design code. On the last part of the thesis a comparison of the final design and a standard radial flow impeller is made in order to clarify the benefit of the study. The results have been showed that a mixed flow compressor design is superior to a standard radial flow compressor in a small turbojet application.

Steel space frames having irregular shapes when subjected to lateral loads caused by wind or earthquakes undergo twisting as a result of their unsymmetrical topology. As a result, torsional moment comes out which is required to be resisted by the three dimensional frame system. The members of such frame are generally made out of steel I sections which are thin walled open sections. The simple beam theory is not adequate to predict behavior of such thin-walled sections under torsional moments due to the fact that the large warping deformations occur in the cross section of the member. Therefore, it is necessary to consider the effect of warping in the design of the steel space frames having members of thin walled steel sections is significant. In this study the optimum design problem of steel space frames is formulated according to the provisions of LRFD-AISC (Load and Resistance factor design of American Institute of Steel Construction) in which the effect of warping is also taken into account. Ant colony optimization and harmony search techniques two of the recent methods in stochastic search techniques are used to obtain the solution of the design problem. Number of space frame examples is designed by the algorithms developed in order to demonstrate the effect of warping in the optimum design.

Coal-fired power plants are the largest anthropogenic point sources of CO2 emissions worldwide. About 40% of the world's electricity comes from coal. Approximately 49% of the US electricity in 2008 and 23% of the total electricity generation of Canada in 2000 came from coal-fired power plant (World Coal Association, and Statistic Canada). It is likely that in the near future there might be some form of CO2 regulation. Therefore, it is highly probable that CO2 capture will need to be implemented at many US and Canadian coal fired power plants at some point. Several technologies are available for CO2 capture from coal-fired power plants. One option is to separate CO2 from the combustion products using conventional approach such as chemical absorption/stripping with amine solvents, which is commercially available. Another potential alternative, membrane gas separation, involves no moving parts, is compact and modular with a small footprint, is gaining more and more attention. Both technologies can be retrofitted to existing power plants, but they demands significant energy requirement to capture, purify and compress the CO2 for transporting to the sequestration sites. This thesis is a techno-economical evaluation of the two approaches mentioned above along with another approach known as hybrid. This evaluation is based on the recent advancement in membrane materials and properties, and the adoption of systemic design procedures and optimization approach with the help of a commercial process simulator. Comparison of the process performance is developed in AspenPlus process simulation environment with a detailed multicomponent gas separation membrane model, and several rigorous rate-based absorption/stripping models. Fifteen various single and multi-stage membrane process configurations with or without recycle streams are examined through simulation and design study for industrial scale post-combustion CO2 capture. It is found that only two process configurations are capable to satisfy the process specifications i.e., 85% CO2 recovery and 98% CO2 purity for EOR. The power and membrane area requirement can be saved by up to 13% and 8% respectively by the optimizing the base design. A post-optimality sensitivity analysis reveals that any changes in any of the factors such as feed flow rate, feed concentration (CO2), permeate vacuum and compression condition have great impact on plant performance especially on power consumption and product recovery. Two different absorption/stripping process configurations (conventional and Fluor concept) with monoethanolamine (30 wt% MEA) solvent were simulated and designed using same design basis as above with tray columns. Both the rate-based and the equilibrium-stage based modeling approaches were adopted. Two kinetic models for modeling reactive absorption/stripping reactions of CO2 with aqueous MEA solution were evaluated. Depending on the options to account for mass transfer, the chemical reactions in the liquid film/phase, film resistance and film non-ideality, eight different absorber/stripper models were categorized and investigated. From a parametric design study, the optimum CO2 lean solvent loading was determined with respect to minimum reboiler energy requirement by varying the lean solvent flow rate in a closed-loop simulation environment for each model. It was realized that the success of modeling CO2 capture with MEA depends upon how the film discretization is carried out. It revealed that most of the CO2 was reacted in the film not in the bulk liquid. This insight could not be recognized with the traditional equilibrium-stage modeling. It was found that the optimum/or minimum lean solvent loading ranges from 0.29 to 0.40 and the reboiler energy ranges from 3.3 to 5.1 (GJ/ton captured CO2) depending on the model considered. Between the two process alternatives, the Fluor concept process performs well in terms of plant operating (i.e., 8.5% less energy) and capital cost (i.e., 50% less number of strippers). The potentiality of hybrid processes which combines membrane permeation and conventional gas absorption/stripping using MEA were also examined for post-combustion CO2 capture in AspenPlus®. It was found that the hybrid process may not be a promising alternative for post-combustion CO2 capture in terms of energy requirement for capture and compression. On the other hand, a stand-alone membrane gas separation process showed the lowest energy demand for CO2 capture and compression, and could save up to 15 to 35% energy compare to the MEA capture process depending on the absorption/stripping model used.

Formulations of optimization under uncertainty (OUU) commonly used in aerospace design—those based on treating statistical moments of the quantity of interest (QOI) as separate objectives—can result in stochastically dominated designs. A stochastically dominated design is undesirable, because it is less likely than another design to achieve a QOI at least as good as a given value, for any given value. As a remedy to this limitation for the multi-objective formulation of moments, a novel OUU formulation is proposed—dominance optimization. This formulation seeks a set of solutions and makes use of global optimizers, so is useful for early stages of the design process when exploration of design space is important. Similarly, to address this limitation for the single-objective formulation of moments (combining moments via a weighted sum), a second novel formulation is proposed—horsetail matching. This formulation can make use of gradient- based local optimizers, so is useful for later stages of the design process when exploitation of a region of design space is important. Additionally, horsetail matching extends straightforwardly to different representations of uncertainty, and is flexible enough to emulate several existing OUU formulations. Existing multi-fidelity methods for OUU are not compatible with these novel formulations, so one such method—information reuse—is generalized to be compatible with these and other formulations. The proposed formulations, along with generalized information reuse, are compared to their most comparable equivalent in the current state-of-the-art on practical design problems: transonic aerofoil design, coupled aero-structural wing design, high-fidelity 3D wing design, and acoustic horn shape design. Finally, the two novel formulations are combined in a two-step design process, which is used to obtain a robust design in a challenging version of the acoustic horn design problem. Dominance optimization is given half the computational budget for exploration; then horsetail matching is given the other half for exploitation. Using exactly the same computational budget as a moment-based approach, the design obtained using the novel formulations is 95% more likely to achieve a better QOI than the best value achievable by the moment-based design.

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Over the past ten years, there has been increased use of electronic power processing in alternative, sustainable, and distributed energy sources, as well as energy storage systems, transportation systems, and the power grid. Three-phase voltage source converters (VSCs) have become the converter of choice in many ac medium- and high-power applications due to their many advantages, such as high efficiency and fast response. For transportation applications, high power density is the key design target, since increasing power density can reduce fuel consumption and increase the total system efficiency. While power electronics devices have greatly improved the efficiency, overall performance and power density of power converters, using power electronic devices also introduces EMI issues to the system, which means filters are inevitable in those systems, and they make up a significant portion of the total system size and cost. Thus, designing for high power density for both power converters and passive components, especially filters, becomes the key issue for three-phase converters. This dissertation explores two different approaches to reducing the EMI filter size. One approach focuses on the EMI filters itself, including using advanced EMI filter structures to improve filter performance and modifying the EMI filter design method to avoid overdesign. The second approach focuses on reducing the EMI noise generated from the converter using a three-level and/or interleaving topology and changing the modulation and control methods to reduce the noise source and reduce the weight and size of the filters. This dissertation is divided into five chapters. Chapter 1 describes the motivations and objectives of this research. After an examination of the surveyed results from the literature, the challenges in this research area are addressed. Chapter 2 studies system-level EMI modeling and EMI filter design methods for voltage source converters. Filter-design-oriented EMI modeling methods are proposed to predict the EMI noise analytically. Based on these models, filter design procedures are improved to avoid overdesign using in-circuit attenuation (ICA) of the filters. The noise propagation path impedance is taken into consideration as part of a detailed discussion of the interaction between EMI filters, and the key design constraints of inductor implementation are presented. Based on the modeling, design and implementation methods, the impact of the switching frequency on EMI filter weight design is also examined. A two-level dc-fed motor drive system is used as an example, but the modeling and design methods can also be applied to other power converter systems. Chapter 3 presents the impact of the interleaving technique on reducing the system passive weight. Taking into consideration the system propagation path impedance, small-angle interleaving is studied, and an analytical calculation method is proposed to minimize the inductor value for interleaved systems. The design and integration of interphase inductors are also analyzed, and the analysis and design methods are verified on a 2 kW interleaved two-level (2L) motor drive system. Chapter 4 studies noise reduction techniques in multi-level converters. Nearest three space vector (NTSV) modulation, common-mode reduction (CMR) modulation, and common-mode elimination (CME) modulation are studied and compared in terms of EMI performance, neutral point voltage balancing, and semiconductor losses. In order to reduce the impact of dead time on CME modulation, the two solutions of improving CME modulation and compensating dead time are proposed. To verify the validity of the proposed methods for high-power applications, a 100 kW dc-fed motor drive system with EMI filters for both the AC and DC sides is designed, implemented and tested. This topology gains benefits from both interleaving and multilevel topologies, which can reduce the noise and filter size significantly. The trade-offs of system passive component design are discussed, and a detailed implementation method and real system full-power test results are presented to verify the validity of this study in higher-power converter systems. Finally, Chapter 5 summarizes the contributions of this dissertation and discusses some potential improvements for future work. / Ph. D.