Dissertations / Theses on the topic 'Propulsão alternativa'

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2017-03-16T13:17:39Z No. of bitstreams: 1 Claudinilson Alves Luczkiewicz_.pdf: 1630762 bytes, checksum: 2bfd6665aa09c3c9c751c44c759f2463 (MD5)
Made available in DSpace on 2017-03-16T13:17:39Z (GMT). No. of bitstreams: 1 Claudinilson Alves Luczkiewicz_.pdf: 1630762 bytes, checksum: 2bfd6665aa09c3c9c751c44c759f2463 (MD5) Previous issue date: 2017-02-07
UNISINOS - Universidade do Vale do Rio dos Sinos
Esta pesquisa objetiva explorar a alternativa de propulsão automotiva elétrica e apresentar uma proposta de utilização de equipamentos industriais produzidos em larga escala que possam ser inseridos no subsistema de propulsão de um veículo elétrico com características populares, para, dessa forma, oferecer uma alternativa de rápida inserção dos veículos em centros urbanos. As características de potência e torque da alternativa proposta foram investigadas através da dinâmica longitudinal veicular e dos equipamentos existentes comercializados. São avaliadas três configurações de propulsão, sendo um propulsor elétrico conectado de forma única, com dois propulsores independentes conectados nas rodas traseiras e com quatro propulsores independentes conectados diretamente nas rodas. Foram avaliados também aspectos econômicos, podendo em certos casos apresentar custos atrativos ao consumidor final. Os principais resultados, de acordo com as características técnicas dos equipamentos, a viabilidade econômica e o peso, demonstram que a potência mínima necessária para o desempenho do subsistema de tração deve ser de 33,70 kW com o consumo de energia de 19,10 kWh, estando distribuído na configuração com dois propulsores independentes conectados nas rodas traseiras.
The objective of this study is to explore the alternative of electric automotive propulsion and present a proposal for the use of industrial equipment ever produced on a large scale that can be inserted to the propulsion subsystem of an electric vehicle with popular features, and thus offer an alternative fast integration of vehicles in urban centers. The power and torque characteristics of the alternative proposal were investigated for longitudinal vehicle dynamics and its equipment sold. Three driving settings are evaluated, and an electric thruster connected in a unique way, with two independent propellers connected to the rear wheels and four independent drivers directly connected to the wheels. It is also observed the characteristic of economic viability may present attractive costs to the final consumer. The main results, according to the technical characteristics of the equipment, economic viability and weight, show that the minimum power required for the performance of the traction subsystem should be 33.70 kW with energy consumption of 19.10 kWh and distributed in the configuration with two independent propellers connected to the rear wheels.

O presente trabalho aborda análises de sistemas de propulsão e manobra para comboios fluviais, e seus efeitos na manobrabilidade dos comboios. Analisam-se o sistema de propulsão convencional (propulsor mais leme), o sistema azimutal e o equipamento de proa auxiliar combinado com cada um destes sistemas de propulsão. Apresenta-se a modelagem matemática dos sistemas de propulsão e manobra citados, os quais serviram de base para implementação de um simulador computacional utilizado para obtenção dos resultados desta dissertação. As forças e momentos hidrodinâmicos são obtidos através do método das derivadas hidrodinâmicas para as simulações próximas à velocidade de serviço do comboio, enquanto para simulações em baixa velocidade utilizou um método semi-empírico baseado no princípio de cross-flow. Inicialmente, efetuou-se a validação do simulador com resultados da literatura para o caso do comboio com propulsão convencional. Em seguida, o modelo foi adaptado para os demais tipos de sistemas de propulsão e manobra propostos. Os resultados obtidos mostram que há uma maior eficiência do sistema de propulsão azimutal e do equipamento na proa para manobras em baixas velocidades, o que se torna adequado sua aplicação em comboios fluvial, pois essas embarcações navegam em velocidades menores se comparadas a outros tipos de embarcações.
The present work deal with analysis of propulsion and maneuvering systems for pusher-barge system, and results on the maneuverability of convoys. It analyzes the conventional propulsion system (rudder plus propeller), the azimuth system and combined auxiliary equipment bow with each of these propulsion systems. Presents the mathematical modeling of propulsion and maneuvering systems mentioned, which served as the basis for implementation of a computational simulator used to obtain the results of this dissertation. The hydrodynamic forces and moments are obtained by the method of hydrodynamic derivatives for simulations about service speed, while for simulations at low speed used a semi - empirical method based on the principle of cross-flow. Initially, performed the validation of the simulation results with the literature for the case of pusher-barge system with conventional propulsion. Then the model was adapted to other types of propulsion and maneuvering systems proposed. The results show that there is a greater efficiency of azimuth propulsion system and equipment in the bow to maneuver at low speeds, which makes it suitable for application in river transport, because these vessels navigate slower speeds compared to other types of vessels.

Letecká doprava jako všechny ostatní dopravy podílí na produkci emisí skleníkových plynů, což je hlavní důvod změn klimatu. Disertační práce je zaměřena na možnost využití alternativního zdroje energie (paliva, motor) v letectví, aby se snížily emise produkované letadel. Oblast,na která již pracuje je všeobecné letectví, zejména letadel kategorie LSA a VLA. Tři možnosti, alternativní zdroj energie, budou diskutovány. První používá LPG palivo, další je elektrické motory, a poslední přidání katalyzátoru a výfukového systému. U každého z nich bude uvedeno výhody a nevýhody, hlavní změnu pohon letadla nebo výfukového systému a různé výkonnosti letadla v důsledku těchto změn.

The subject of the thesis is to identify and assess the current status of electromobility in the Czech Republic and proposal of partly strategiy and recommendations for company Mercedes-Benz Czech Republic s.r.o. in this area. The theoretical part deals with the definition of the theory of strategic management process, especially the analysis of the external and internal area and methodologies of creation strategy. The practical part describes the characteristics of the Mercedes-Benz Czech Republic s.r.o., direct analysis of the electromobility and internal analysis of the company. Finally, there is a summary SWOT analysis and strategy formulation and recommendations in the area of electromobility for the company.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, 2006.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
Technology transitions require the formation of a self-sustaining market through alignment of consumers' interests, producers' capabilities, infrastructure development, and regulations. In this research I develop a broad behavioral dynamic model of the prospective transition to alternative fuel vehicles. In Essay one I focus on the premise that automobile purchase decisions are strongly shaped by cultural norms, personal experience, and social interactions. To capture these factors, I examine important social processes conditioning alternative vehicle diffusion, including the generation of consumer awareness through feedback from driving experience, word of mouth and marketing. Through analysis of a simulation model I demonstrate the existence of a critical threshold for the sustained adoption of alternative technologies, and show how the threshold depends on behavioral, economic and physical system parameters. Word-of-mouth from those not driving an alternative vehicle is important in stimulating diffusion. Further, I show that marketing and subsidies for alternatives must remain in place for long periods for diffusion to become self-sustaining.
(cont.) Results are supported with an analysis of the transition to the horseless carriage at the turn of the 19th century. In the second Essay I explore the co-evolutionary interdependence between alternative fuel vehicle demand and the requisite refueling infrastructure. The analysis is based on a dynamic behavioral model with an explicit spatial structure. I find, first, a bi-stable, low demand equilibrium with urban adoption clusters. Further, the diffusion of more fuel efficient vehicles, optimal for the long run, is less likely to succeed, illustrating the existence of trade-offs between the goals of the early stage transition, and those of the long-run equilibrium. Several other feedbacks that significantly influence dynamics including, supply and demand, and supply-coordination behaviors, are discussed. In Essay three I examine how technology learning and spillovers impact technology trajectories of competing incumbents - hybrid and radical entrants. I develop a technology lifecycle model, with an emphasis on technology heterogeneity. In the model, spillovers can flow to the market leader and can be asymmetric across technologies. find that the existence of learning and spillover dynamics greatly increases path dependence. Interaction effects with other feedbacks, such as scale economies, are very strong. Further, superior radical technologies may fail, even when introduced simultaneously with inferior hybrid technologies.
(cont.) I find that the existence of learning and spillover dynamics greatly increases path dependence. Interaction effects with other feedbacks, such as scale economies, are very strong. Further, superior radical technologies may fail, even when introduced simultaneously with inferior hybrid technologies.
by Jeroen J.R. Struben.
Ph.D.

Atmospheric carbon dioxide and pollution due to the burning of fossil fuels is increasing. Many scientists attribute global warming to the rising levels of carbon dioxide and other pollutants, some of which also pose risks to health. These can be reduced by the more efficient use of conventional fuels and the development of non-polluting energy resources. Fuel cells offer a highly efficient and low polluting method of generating electricity, and are under development for both the power generation and transport sectors. There is a need to assess (a) emissions from fuel cells using various fuels and (b) ways of introducing such technology to transportation in the near future. Fuel consumption, energy and emissions from the production and use of fuels (hydrogen, methane, propane, petrol, diesel, alcohols and rape methyl ester) are calculated per kilowatt hour of fuel cell output over a range of efficiency. These are compared with those for internal combustion engines with advanced exhaust control and for the recharging of battery driven vehicles. The results, which are applicable to both transport and power generation, enable the best low pollution fuels to be selected and are used to calculate through life emissions for public transport buses. Fuel cells are an ideal solution to reduce pollution from transport, but their commercial development in this field is further away than that for stationary applications. Thus, a transition stage is recommended where fuel cell electrical power stations, based on existing demonstrators, are used to recharge fleets of battery driven vehicles during the development of mobile fuel cell systems. These fleets include public transport and commercial vehicles. Also, fuel cell power stations could provide energy for electric trains. A combined system is proposed where electric trains recharge battery driven commercial vehicles during long journeys. The above proposals would enhance fuel cell development, introducing them alongside current transport systems, possibly using the same fuel.

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 137-139).
In an effort to develop submarine designs that deliver reduced size submarines with equivalent capabilities of the current USS VIRGINIA (SSN-774 Class) submarine, a joint Navy/Defense Advanced Research Projects Agency (DARPA) called the Tango Bravo (TB) program was initiated in 2004 to overcome technology barriers that have a large impact on submarine size and cost. A focus area of the TB program is propulsion concepts not constrained by a centerline shaft. This thesis investigates the operational impacts that a conceptual propulsion configuration involving the use of azimuthing podded propulsors has on a submarine. Azimuthing pods have been used commercially for years, with applications on cruise ships being quite common although their use on large naval platforms has been nonexistent to date. The use of such systems on a submarine would allow for the removal of systems related to the centerline shaft; freeing up volume, weight, and area that must be allocated and potentially allowing the submarine designer to get outside the speed-size-resistance circular path that results in large, expensive platforms. Potential benefits include having the pods in a relatively undisturbed wake field -possibly increasing acoustic performance as well as improving operational maneuvering characteristics. For this thesis a submarine maneuvering model was created based on analytical techniques and empirical data obtained from the DARPA SUBOFF submarine hullform. This model was analyzed for two configurations: ** A centerline shaft configuration utilizing cruciform control surfaces for yaw and pitch control; ** A podded configuration utilizing pods for propulsion as well as yaw and pitch control. The maneuvering characteristics for each configuration were investigated and quantified to include turning, depth changing, acceleration, deceleration, and response to casualties.
by Brian D. Heberley.
Nav.E.and S.M.

A dual, double-acting propulsion system is analyzed to determine how efficiently it can convert the potential energy available from liquid nitrogen into useful work. The two double-acting pistons (high- and low-pressure) were analyzed by using a Matlab-Simulink computer simulation to determine their respective mechanical efficiencies. The flow circuit for the entire system was analyzed by using flow circuit analysis software to determine pressure losses throughout the system at the required mass flow rates. The results of the piston simulation indicate that the two pistons analyzed are very efficient at transferring energy into useful work. The flow circuit analysis shows that the system can adequately maintain the mass flow rate requirements of the pistons but also identifies components that have a significant impact on the performance of the system. The results of the analysis indicate that the nitrogen propulsion system meets the intended goals of its designers.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-03-10T11:01:44Z No. of bitstreams: 1 texto completo.pdf: 1917304 bytes, checksum: a9477d6e6ed5a86abb04c7cfc3729333 (MD5)
Made available in DSpace on 2017-03-10T11:01:44Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1917304 bytes, checksum: a9477d6e6ed5a86abb04c7cfc3729333 (MD5) Previous issue date: 2005-07-18
Fundação de Amparo à Pesquisa do Estado de Minas Gerais
Neste trabalho, estudou-se o uso de motores alternativos para a propulsão de um microtrator agrícola utilizado no revolvimento de café no terreiro. Alternativas de energia usadas na propulsão permitem o uso do microtrator em diferentes funções, elevando o índice de mecanização das lavouras brasileiras. Foram implementados e ensaiados três diferentes tipos de motores:, um motor elétrico de corrente alternada (MCA), um de corrente contínua (MCC) e um de combustão interna, de ciclo “Otto” (MCI), montados sobre o chassi de um microtrator utilizado no revolvimento de frutos de cafeeiro em terreiros de secagem. Também foram realizados ensaios de tração, cujos resultados foram confrontados com um modelo, para simulação do comportamento dinâmico trativo. Na montagem do microtrator MCA, empregou-se um motor elétrico trifásico de corrente alternada, alimentado pela rede de energia elétrica convencional por meio de cabos. O microtrator MCC foi impulsionado por um motor de corrente contínua e, neste caso, a energia necessária para a movimentação do sistema era armazenada em baterias de chumbo ácido que acompanham o protótipo. O microtrator MCI, por sua vez, recebeu um motor à combustão interna, dois tempos, a gasolina. As forças de tração máximas para as diferentes montagens foram medidas, demonstrando- se que o sistema MCC é capaz de desenvolver uma força de tração maior que os demais sistemas, obtendo-se os seguintes resultados: 1,66 kN para o MCA, 2,02 kN para o MCC e 1,61 kN para o MCI. Os resultados experimentais comprovaram que os 8aumentos da força, da potência na barra de tração e do coeficiente de tração resultam em um incremento da patinagem dos microtratores utilizados. Verificou-se que, para as três fontes de propulsão, o aumento na velocidade de deslocamento do microtrator demandou maior força para o revolvimento, o mesmo ocorrendo quando se elevou a altura da camada de frutos no terreiro. O modelo adotado para simulação gerou, menores valores para a força, a potência e o coeficiente de tração, quando comparados aos valores experimentais, sendo especialmente adequado à simulação do comportamento trativo do microtrator MCC.
The use of alternative engines for the propulsion of an agricultural microtractor in revolving the coffee on the yard was studied. The alternative sources of energy used in the propulsion allow for the use of microtractor in different functions, therefore rising the mechanization index of the Brazilian agriculture. The following types of engines were implemented and assayed three different engine types: one alternating-current electric engine (MCA), one direct-current electric engine (MCC), and one internal- combustion engine of the Otto-cycle type (MCI). These engines were assembled on the chassis of a microtractor used in revolving the coffee cherries on drying yards. Traction assays were also accomplished, from which the results were confronted with a model for simulation of the dynamic tractive behavior. In assembly of the MCA microtractor, an alternating-current, three-phase electric engine fed by conventional electrical network through cables was used. The MCC microtractor was impelled by a direct- current engine; in this case, the energy needed for the system movement was stored in acid-lead batteries with which the prototype is provided. The MCI microtractor was added with an internal-combustion, two-stroke cycle, gasoline engine. The maximum tractive forces for the different assemblies were measured, so showing that the MCC system is able to develop a higher tractive force than the other systems, as the following results were obtained: 1.66 kN for MCA, 2.02 kN for MCC, and 1.61 kN for MCI. The experimental results proved that the increases in the power, drawbar horsepower, and traction coefficient result into an increased skidding of the microtractors used. For those three propulsion sources, the increase in the displacement speed of the microtractor required higher strength for revolving, and the same occurred when the height of the coffee cherry layer in the yard was increased. The model adopted for simulation rather generated lower values for the force, potency, and coefficient of traction, compared to the experimental values, although it is was especially adequate for simulating the tractive behavior of the MCC microtractor.
Tese importada do Alexandria

Este trabalho trata da questão da redução de consumo de combustível fóssil em instalações de máquinas de navios. É um tema de grande interesse no momento, devido ao alto custo operacional e à emissão de poluentes decorrentes do processo da combustão desses derivados de petróleo. Apresenta-se, inicialmente o cenário atual e tendências futuras das instalações propulsoras convencionais que usam óleo pesado ou Diesel. Em seguida, são examinadas alternativas propostas para redução de consumo de combustíveis fósseis nos navios, que são enquadradas em três categorias. A primeira delas envolve possíveis melhorias de projeto para redução da demanda de energia. As outras categorias se referem ao emprego de fontes alternativas de energia, que introduzem uma força propulsora adicional, reduzindo o empuxo requerido do hélice, ou uma potência suplementar no eixo propulsor. Em ambos os casos há também uma redução de demanda de potência requerida do motor Diesel. Na seqüência, são apresentados e discutidos fundamentos termodinâmicos, com ênfase nas análises energética e exergética, como ferramentas para avaliação das máquinas dos navios. A análise exergética, diferentemente do enfoque apenas energético, é a ferramenta mais apropriada para tratar as questões ligadas ao meio ambiente, pois a própria definição de exergia está relacionada com o ambiente de referência. Finalmente, utilizando dados de um navio porta contêineres da frota nacional, é exercitado um exemplo de aplicação com as análises termodinâmicas do motor de propulsão; são também avaliadas e simuladas as diversas alternativas de melhorias e novas fontes de energia, que visam a redução de consumo de combustível fóssil.
This work addresses the issue of reduction of fossil fuel use on ship machinery. Presently it is an interesting topic due to high operational cost and the pollution emissions generated by the combustion process. Initially, it is introduced the present scenario and future trends regarding conventional ship machinery that use heavy or diesel fuel oil. In the sequence, the proposed alternatives for reducing the use of fossil fuel on ships are presented and examined. These alternatives are classified into three categories. The first category comprises possible improvements to the design of ships for reduction of total energy demand. The other categories refer to the use of alternative energy sources, that produce and additional force on the ship reducing the required propeller thrust; or a supplementary power added to the propulsion shaft. For both cases there is also a reduction in the power required from the Diesel engine. Afterwards, the pertaining thermodynamics theory is revised and discussed with focus on the energy and exergy analysis as aid tools for evaluation of ship machinery. The energetic analysis, different from the sole energetic focus, is the most applicable tool to be employed for environmental issues as the self definition of exergy relates to an environment reference. Finally, using data from a typical container ship belonging to the national fleet, an application example using the thermodynamic analysis is performed to the propulsion main engine; as well as it is also simulated several alternative conditions for improvements and new energy sources, aiming to the reduction of fossil fuel consumption.

L'objectif des travaux présentés dans ce mémoire concerne la commande en poussée de propulseurs électriques marins. Afin de simplifier le problème, l'étude se limite aux véhicules sous-marins autonomes (AUV) ou commandés à distance (ROV).

La première partie de ce mémoire présente la modélisation des propulseurs ainsi que plusieurs commandes en poussée issues de la littérature. La majorité de ces commandes est basée sur l'inversion des modèles avec parfois une boucle de régulation
intermédiaire.

Dans une deuxième partie, une commande originale est proposée. Elle repose sur trois éléments : l'observation du couple hydrodynamique, l'estimation de la poussée par modèle inverse et l'utilisation de correcteurs de type PID. Une étude comparative avec les commandes existantes est menée en simulation.

Enfin, la dernière partie concerne la conception d'un banc d'essais. Ce banc d'essais permettra de valider les modèles et les lois de commande utilisés pour la commande en poussée des AUV et des ROV.

L'objectif des travaux présentés dans ce mémoire concerne la commande en poussée de propulseurs électriques marins. Afin de simplifier le problème, l'étude se limite aux véhicules sous-marins autonomes (AUV) ou commandés à distance (ROV). La première partie de ce mémoire présente la modélisation des propulseurs ainsi que plusieurs commandes en poussée issues de la littérature. La majorité de ces commandes est basée sur l'inversion des modèles avec parfois une boucle de régulation intermédiaire. Dans une deuxième partie, une commande originale est proposée. Elle repose sur trois éléments~: l'observation du couple hydrodynamique, l'estimation de la poussée par modèle inverse et l'utilisation de correcteurs de type PID. Une étude comparative avec les commandes existantes est menée en simulation. Enfin, la dernière partie concerne la conception d'un banc d'essais. Ce banc d'essais permettra de valider les modèles et les lois de commande utilisés pour la commande en poussée des AUV et des ROV
This work deals with the thrust control for marine electric thrusters. In order to simplify the problem, we consider the case of the thrusters which equip the Autonomous Underwater Vehicles (AUV) or Remotely Operated underwater Vehicles (ROV). The first part of this work presents the thruster modelling and several thrust controls find in the literature. The most of these controls are based on the inverse models, sometimes with a cascade regulation loop. In a second part an original control law is proposed. This one is based on three parts~: the observation of the hydrodynamic torque, the thrust estimation by the inverse model and the use of PID controllers. A comparative study with the existing control laws is undertaking in simulation. Finally, the last part relates to the design of a thruster test stand. This test will allow to validate the models and the control laws used for the thrust control of AUV and ROV

Les propulseurs de Hall sont l’une des techniques de propulsion fusée par plasma les plus utilisés. Ils possèdent une impulsion spécifique moyenne et un haut rapport poussé sur puissance qui les rend idéal pour une grande partie des applications commerciales et scientifiques. Une de leurs limitations principales est l’érosion des parois du propulseur par le plasma qui réduit leur durée de vie. La topologie dite “d’écrantage magnétique” est une solution proposée pour prolonger cette durée de vie. Elle est ici appliquée à un petit propulseur de Hall de 200W. Dans cette thèse les règles de mise à l’échelle pour les propulseurs de Hall de la gamme de 100 à 200W sont testées expérimentalement. Un propulseur écranté de 200W est comparé avec un propulseur standard similaire. Le comportement des ions dans ces deux moteurs est extrêmement différent. Des mesures de performance ont été réalisées avec des parois en BN-SiO2 et graphite. Le courant de décharge augmente de 25% avec le graphite dans le propulseur non-écranté. Le résultat et un rendement maximum de 38% avec le nitrure de bore mais de seulement 31% pour le graphite. Le propulseur écranté quant à lui n’atteint que 25% de rendement quel que soit le matériau.Cette baisse de performance dans les petits moteurs écrantés peut être attribuée à un mauvais rendement d’utilisation de l’ergol. Analyses des résultats expérimentaux ainsi que la conduite de simulations suggèrent que cela est dû au fait que la zone d’ionisation ne couvre pas l’ensemble du canal de décharge. Un nouveau design pour un petit propulseur de Hall écranté est proposé
Hall thrusters are one of the most used rocket electric propulsion technology. They combine moderate specific impulse with high thrust to power ratio which makes them ideal for a wide range of practical commercial and scientific applications. One of their limitations is the erosion of the thruster walls which reduces their lifespan.The magnetic shielding topology is a proposed solution to prolong the lifespan. It is implemented on a small200W Hall thruster.In this thesis the scaling of classical unshielded Hall thrusters down to 200 and 100W is discussed. A 200W low power magnetically shielded Hall thruster is compared with an identically sized unshielded one. The ion behavior inside the thruster is measured and significant differences are found across the discharge channel.Both thrusters are tested with classical BN-SiO2 and graphite walls. The magnetically shielded thruster is not sensitive to the material change while the discharge current increase by 25% in the unshielded one. The result is a maximum efficiency of 38% for boron nitride in the unshielded thruster but only 31% with graphite.The shielded thruster achieves a significantly lower efficiency with only 25% efficiency with both materials.Analysis of the experimental results as well as simulations of the thrusters reveal that the performance difference is mostly caused by low propellant utilization. This low propellant utilization comes from the fact that the ionization region doesn’t cover all of the discharge channel. A new magnetically shielded thruster is designed to solve this issue

This report is divided into six main chapters. It starts off with an introductory chapter explaining the different propulsion strategies that have been considered during the last semester, and the final propulsion system that has been decided upon. The final propulsion strategy has several demands when it comes to components that have to be implemented and what type of components they should be. The main purpose for me in this project was therefore to meet these demands. Main demands for me were to demonstrate different possibilities when it comes to controlling the lights in the PureChoice vehicle, and to make sure the vehicle had enough energy stored in alternative storage devices in order to have a fully functioning system when it comes to driving the vehicle and managing the safety system onboard. The report continues with five individual chapters explaining how these demands were solved and which components that have been considered and implemented in the final vehicle. All off the chapters start of with an introduction about the topic at hand. They then continue with an explanation about the different components used in the vehicle, and reasoning for why exactly these components were chosen. In order to determine how the components would function in the final propulsion system, laboratory tests were performed on all the involved parts, and these laboratory tests are described at the end of all the chapters. This report includes both theoretical calculations and practical solutions.

ABSTRACT Developments in the field of microturbine technology and gas turbine driven aircraft has been progressing without much progress in light aircraft predominantly propelled by piston engines. Because of inhibitive maintenance and overhaul costs of such however, propulsion via a gas turbine engine has been proposed with the potential of eventually replacing current engine configurations. Subsequently, the objective was to conceptually design a replacement gas turbine engine in the 150 kW range. A selection of case studies was used to illustrate the changing technologies to illustrate the technological viability of micro-gas turbines for light aircraft. Advantages and disadvantages of both engine types were discussed and a concise description of gas turbine operations and its components was given. A brief overview of fundamentals as well as the transmission layout was also supplied. Three configurations were isolated, namely the single spool design, a twin spool design featuring a free power turbine and the effect of a fuel conserving recuperator. Calculations were performed using Microsoft Excel, which proved sufficient in effectively calculating complex formulae - even under the necessary iterative feed-back conditions the design process demanded. Eventually, variable-specific design criteria were derived regarding the three engine types. Because fuel consumption still proved inhibitive, the effect of recuperation was investigated which yielded a very competitive engine - should the possibility of recuperator technology exist on time. As a result, one particular recuperated, single spool gas turbine engine was successfully identified. Having met all the design criteria sufficiently, this preliminary prototype design was numerically described and put within context of principal, peripheral working components such as a compatible gearbox layout.

A utilização de hidrogénio como combustível está atualmente em constante expansão, em diversos países. Vários órgãos internacionais de estudo de mercado, como a U.S Department of energy (DOE), identificaram recentemente mercados promissores para a implementação de células de combustível, e num desses mercados está presente a utilização de células de combustível em empilhadores. A utilização deste tipo de tecnologia neste ramo, está a ser aplicada com grande ênfase principalmente na América, onde existem também grandes incentivos monetários. Durante a realização desta dissertação foi feita uma revisão do estado da arte da tecnologia de células de combustível. Também se efetuou uma caracterização dos mercados, bem como das condições técnicas e de funcionamento. Na parte final da dissertação é apresentado um estudo viabilidade da implementação da tecnologia de hidrogénio, tanto a nível energético, como a nível económico. Tendo em conta que o desempenho deste tipo de veículos é modulado através de estudos paramétricos, foi criado um modelo em função do número de viagens diárias realizadas por empilhador, que caracteriza o seu gasto energético. Os nossosresultados mostram que de acordo com a carga de trabalho que a cada empresa exige, deve-se dimensionar a frota de empilhadores de forma correta, sendo necessário, em algumas ocasiões escolher o sistema de propulsão que permita obter a maior produtividade. Lembre-se que neste trabalho apenas são abordadas soluções elétricas, ou seja, só são abordados os sistemas de propulsão utilizando baterias e células de combustível.
The use of hydrogen as a fuel is currently expanding, in several countries. The U.S. Department of Energy (DOE) recently identified promising markets for the implementation of fuel cells, and in one of these demands, the use of fuel cells in forklifts is present. The use of this type of technology in this field is being applied with great emphasis mainly in America, where there are also significant monetary incentives. In this dissertation, a review of the state of the art of fuel cell technology was carried out. We also made a characterisation of the market, as well as the technical and operating conditions. In the final part of this study is presented a feasibility study of the implementation of hydrogen technology, both energetically and economically. Taking into account that the performance of this type of vehicle is modulated through parametric studies, a model was created that, based on the number of daily trips performed by forklift, characterises its energetic expenditure. Our results show that according to the workload that each company requires, we must scale the forklift fleet correctly, if necessary, on occasion choose the propulsion system so as to achieve the highest productivity. Remember that in this work only electrical solutions are addressed, that is, only the propulsion systems are approached using batteries and fuel cells.

abstract: Scarcity of potable water is one of the major problems faced in the world today. Majority of this problem can be solved if technology is developed to obtain potable water from brackish or saline water. The present desalination methods face challenges such as high costs in terms of energy consumption and infrastructure, physical size of the system, requirement of membrane and high pressure systems and hence have been facing various issues in implementation of the same. This research provides a new low pressure, low energy, portable method to desalinate water without the need for separation membranes, heat or chemical reactions. This method is energy efficient, cost effective, compact, environment friendly and suitable for portable desalination units. This technology, named as Polyphase Alternating current Bi-Ionic Propulsion System (PACBIPS) makes use of polyphase alternating current source to create a gradient in salt concentration. The gradient in salt concentration is achieved due to the creation of a traveling wave which attracts anions on its positive peak (crests) and cations on its negative peak (troughs) and travels along a central pipe thereby flushing the ions down. Another method of PACBIPS is based on Helmholtz capacitor which involves the formation of an electric double layer between the electrode and electrolyte consisting of equal and opposite ions which can be approximated as a capacitor. Charging and discharging this capacitor helps adsorb the ions onto a carbon electrode which has high surface area and electrical conductivity. This desalinates seawater and provides pure water. Mathematical modeling, analysis and implementation of the two methods have been presented in this work. The effects of zeta potential, electric field screening, electric mobility on desalination have been discussed.
Dissertation/Thesis
Masters Thesis Electrical Engineering 2014

Rocket combustors and other high-performance chemical propulsion systems are prone to combustion instability. Recent simulations of rocket combustors using detailed chemical kinetics show that the constant pressure assumption used in classical treatments may be suspect due to high rates of heat release. This study is a exploration on the effects of these extraordinary rates of heat addition on the local pressure field, and interactions between the heat release and an acoustic field.

The full problem is decomposed into simpler unit problems focused on the particular interactions of physical phenomena involved in combustion instability. The overall strategy consists of analyzing fundamental problems with simplified scenarios and then build up the complexity by adding more phenomena to the analysis. Seven unit problems are proposed in this study.

The first unit problem consists of the pressure response to an unsteady heat release source in an unconfined one-dimensional domain. An analytical model based on the acoustic wave equation with planar symmetry and an unsteady heat source is derived and then compared against results from highly-resolved numerical simulations. Two different heat release profiles, one a Gaussian spatial distribution with a step temporal profile, and the other a Gaussian spatial distribution with a Gaussian temporal distribution, are used to model the heat source. The analytical solutions predict two different regimes in the pressure response depending on the Helmholtz number, which is defined as the ratio of the acoustic time over the duration of the heat release pulse. A critical Helmholtz number is found to dictate the pressure response regime. For compact cases, in the subcritical regime, the amplitude of the pressure pulse remains constant in space. For noncompact cases, above the critical Helmholtz number, the pressure pulse reaches a maximum at the center of the heat source, and then decays in space converging to a lower far field amplitude. At the limits of very small and very large Helmholtz numbers, the heat release response tends to be a constant pressure process and a constant volume process, respectively. The parameters of the study are chosen to be representative of the extreme conditions in a rocket combustor. The analytical models for both heat source profiles closely match the simulations with a slight overprediction. The differences observed in the analytical solutions are due to neglecting mean flow property variations and the absence of loss mechanisms. The numerical simulations also reveal the presence of nonlinear effects such as weak shocks that cannot be captured by the linear acoustic wave equation.

The second unit problem extends the analysis of the pressure response of an unsteady heat release source to an unconfined three-dimensional domain. An analytical model based on the spherical acoustic wave equation with an unsteady heat source is derived and then compared against results from highly-resolved three-dimensional numerical simulations. Two different heat release profiles, a three-dimensional Gaussian spherical distribution with either a step or a Gaussian temporal distribution, are used to model the heat source. Two different regimes in the pressure response depending on the Helmholtz number are found. This analysis also reveals that whereas for the one-dimensional case the pressure amplitude is constant over the distance, for the three-dimensional case it decays with the radial distance from the heat source. In addition, although for moderate heat release values the analytical solution is able to capture the dynamics of the fluid response, for large heat release values the nonlinear effects deviate the highly-resolved numerical solution from the analytical model.

The third unit problem studies the pressure response of a fluctuating unsteady heat release source to an unconfined one-dimensional domain. An analytical model based on the acoustic wave equation with planar symmetry and an unsteady heat source is derived and then compared against results from highly-resolved numerical simulations. Two different heat release profiles, a flat spatial distribution with sinusoidal temporal profile and a Gaussian spatial distribution and sinusoidal temporal profile, are used to model the heat source. For both cases, the acoustically compact and noncompact regimes depending on the Helmholtz number are analyzed. While in the compact regime the amplitude of the pressure is constant over the distance, in the noncompact regime the amplitude of the pressure fluctuation is larger within the heat source area of application, and once outside the heat source decays to a far field pressure value. In addition, the analytical model does not capture the nonlinear effects present in the highly-resolved numerical simulations for large rates of heat release such as the ones present in rocket combustors.

Finally, the last four unit problems focus on the interaction between unsteady heat release and the longitudinal acoustic modes of a combustor. The goal is to assess and quantify how pressure fluctuations due to unsteady heat release amplify a longitudinal acoustic mode. To investigate the nonlinear effects and the limitations based on the acoustic wave equation, the analytical models are compared against highly-resolved numerical simulations. The fourth unit problem consists of the pressure response to a moving rigid surface that generates a forced sinusoidal velocity fluctuation in a one-dimensional open-ended cavity. The fifth unit problem combines an analytical solution from the velocity harmonic fluctuation with an unsteady heat pulse with Gaussian spatial and temporal distribution developed in the first unit problem. The choice of an open-ended cavity simplifies the analysis and serves as a stepping stone to the sixth unit problem, which also includes the pressure reflections provoked by the acoustic boundaries of the duct. This sixth unit problem describes the establishment of a 1L acoustic longitudinal mode inside a closed duct using the harmonic velocity fluctuations from the fourth unit problem. A wall on the left end of the duct is only moved for one cycle at the 1L mode frequency to establish a 1L mode in the initially quiescent fluid. The last unit problem combines the analytical solution of the 1L mode acoustic field developed in the sixth unit problem with an unsteady heat pulse with Gaussian spatial and temporal distribution, and also accounts for pressure reflections. The derivation of the present analytical models includes the identification of relevant length and time scales that are condensed into the Helmholtz number, the phase shift between the longitudinal fluctuating pressure field and the heat source, and ratio of the fluctuating periods. The analytical solution is able to capture with an acceptable degree of accuracy the pressure trace of the numerical solution during the fist few cycles of the 1L mode, but it quickly deviates very significantly from the numerical solution due to wave steepening and the formation of weak shocks. Therefore, models based on the acoustic wave equation can provide a good understanding of the combustion instability behavior, but not accurately predict the evolution of the pressure fluctuations as the nonlinear effects play a major role in the combustion dynamics of liquid rocket engines.

Este trabalho encontra-se inserido no pro jeto SABUVIS I I, sendo o ob jetivo global do pro jeto criar um “cardume” de veículos autónomos de sub-sup erfície biomiméticos. Esse grup o será constituído p or dois tip os de unidades, unidades controladoras cuja função é controlar e co ordenar as restantes unidades p or forma a executar a tarefa pretendida, e as unidades executantes cuja função é executar as ordens das unidades controladoras, p or forma a executar tarefas que p ermitam o cumprimento duma missão, satisfazendo um padrão de requisitos op eracionais. O ob jetivo deste trabalho é desenvolver um protótip o duma unidade executante, começando p elo seu dimensionamento inicial e progredir no sentido de elab orar o seu pro jeto detalhado, incorp orando o dimensionamento do seu sistema energético, do seu sistema de propulsão alternativa e do sistema de variação de flutuabilidade, visando que a unidade custe o menos p ossível dado que, num cenário op eracional, p o derá ser necessário descartar uma destas unidades sem comprometer a capacidade op eracional da força.
This thesis is part of the SABUVIS I I pro ject, and the overall ob jective of the pro ject is to create a swarm of autonomous biomimetic underwater vehicles. This group will consist of two typ es of units, controller units whose function is to control and co ordinate the remaining units in order to p erform the intended task, and the executing units whose function is to execute the orders of the controlling units, in order to p erform tasks that allow the fulfillment of a mission, satisfying a standard of op erational requirements. The ob jective of this pro ject is to develop a prototyp e of an executing unit, starting with its initial dimensioning and progressing towards elab orating its detailed pro ject, incorp orating the dimensioning of its energy system, its alternative propulsion system and the buoyancy variation system, aiming for the minimum cost since, in an op erational scenario, it may b e necessary to discard one of these units without compromising the op erational capacity of the force.

The need for a reduced dependence on fossil fuels is motivated by a wide range of factors: from increasing fuel costs, to national security implications of supply, to rising concern for environmental impact. Although much focus is given to terrestrial systems, over 90% of the world's freight is transported by ship. Likewise, naval warfighting systems are critical in supporting U.S. national interests abroad. Yet the vast majority of these vessels rely on fossil fuels for operation. The results of this thesis illustrate a common theme that hybrid mechanical-electrical marine propulsion systems produce substantially better fuel efficiency than other technologies that are typically emphasized to reduce fuel consumption. Naval and commercial powertrains in the 60-70 MW range are shown to benefit substantially from the utilization of mechanical drive for high speed propulsion; complemented by an efficient electric drive system for low speed operations. This hybrid architecture proves to be able to best meet the wide range of performance requirements for each of these systems, while also being the most easily integrated technology option. Naval analyses evaluate powertrain options for the DDG-51 Flight III. Simulation results using actual operational profile data show a CODLAG system produces a net fuel savings of up to 12% more than a comparable all-electric system, corresponding to a savings of 37% relative the existing DDG-51 powertrain. These results prove that a mechanical linkage for the main propulsion engine greatly reduces fuel consumption and that for power generation systems requiring redundancy, diesel generators represent a vastly superior option to gas turbines. For the commercial application it is shown that an augmented PTO/PTI hybrid system can better reduce cruise fuel consumption than modern sail systems, while also producing significant benefit with regard to CO2 emissions. In addition, using such a shaft mounted hybrid system for low speed electric drive in ports reduces NOx emissions by 29-43%, while CO is reduced 57-66% and PM may be reduced up to 25%, depending on the specific operating mode. As an added benefit, fuel consumption rates under these conditions are reduced 20-29%.
text