Segui questo link per vedere altri tipi di pubblicazioni sul tema: Electron heat engine.

Tesi sul tema "Electron heat engine"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili

Scegli il tipo di fonte:

Vedi i top-17 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Electron heat engine".

Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.

Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.

Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.

1

Humphrey, Tammy Ellen Physics Faculty of Science UNSW. "Mesoscopic quantum ratchets and the thermodynamics of energy selective electron heat engines". Awarded by:University of New South Wales. Physics, 2003. http://handle.unsw.edu.au/1959.4/19186.

Testo completo
Abstract (sommario):
A ratchet is an asymmetric, non-equilibrated system that can produce a directed current of particles without the need for macroscopic potential gradients. In rocked quantum electron ratchets, tunnelling and wave-reflection can induce reversals in the direction of the net current as a function of system parameters. An asymmetric quantum point contact in a GaAs/GaAlAs heterostructure has been studied experimentally as a realisation of a quantum electron ratchet. A Landauer model predicts reversals in the direction of the net current as a function of temperature, amplitude of the rocking voltage, and Fermi energy. Artifacts such as circuit-induced asymmetry, also known as self-gating, were carefully removed from the experimental data, which showed net current and net differential conductance reversals, as predicted by the model. The model also predicts the existence of a heat current where the net electron current changes sign, as equal numbers of high and low energy electrons are pumped in opposite directions. An idealised quantum electron ratchet is studied analytically as an energy selective electron heat engine and refrigerator. The hypothetical device considered consists of two electron reservoirs with different temperatures and Fermi energies. The reservoirs are linked via a resonant state in a quantum dot, which functions as an idealised energy filter for electrons. The efficiency of the device approaches the Carnot value when the energy transmitted by the filter is tuned to that where the Fermi distributions in the reservoirs are equal. The maximum power regime, where the filter transmits all electrons that contribute positively to the power, is also examined. Analytic expressions are obtained for the power and efficiency of the idealised device as both a heat engine and as a refrigerator in this regime of operation. The expressions depend on the ratio of the voltage to the difference in temperature of the reservoirs, and on the ratio of the reservoir temperatures. The energy selective electron heat engine is shown to be non-endoreversible, and to operate in an analogous manner to the three-level amplifier, a laser based quantum heat engine. Implications for improving the efficiency of thermionic refrigerators and power generators are discussed.
Gli stili APA, Harvard, Vancouver, ISO e altri
2

Kalua, Tisaye Bertram. "Analysis of factors affecting performance of a low-temperature Organic Rankine Cycle heat engine". Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/17844.

Testo completo
Abstract (sommario):
Organic Rankine Cycle (ORC) heat engines convert low-grade heat to other forms of energy such as electrical and mechanical energy. They achieve this by vaporizing and expanding the organic fluid at high pressure, turning the turbine which can be employed to run an alternator or any other mechanism as desired. Conventional Rankine Cycles operate with steam at temperatures above 400 ℃. The broad aspect of the research focussed on the generation of electricity to cater for household needs. Solar energy would be used to heat air which would in turn heat rocks in an insulated vessel. This would act as an energy storage in form of heat from which a heat transfer fluid would collect heat to supply the ORC heat engine for the generation of electricity. The objective of the research was to optimize power output of the ORC heat engine operating at temperatures between 25℃ at the condenser and 90 to 150℃ at the heat source. This was achieved by analysis of thermal energy, mechanical power, electrical power and physical parameters in connection with flow rate of working fluid and heat transfer fluids.
Gli stili APA, Harvard, Vancouver, ISO e altri
3

Johansson, Anton, e Martin Drangel. "Measurements and Modelling for Heat Transfer Corrected Exhaust Gas Temperatures in a Gasoline Engine". Thesis, Linköpings universitet, Fordonssystem, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-157637.

Testo completo
Abstract (sommario):
This thesis is treating the modelling of a thermocouple (tc) to compensate forheat transfers due to convection, radiation and conduction when performingtemperature measurements in an SI-engine. An experiment plan was developedwhich covered experiments in an stc-rig and on a 4-cylinder SI-engine. The measurementsin the stc-rig was mainly to develop the model, while the measurementsin the engine lab was mainly to examine the characteristics of the engineand evaluate the modelled tc.Measurements with an exposed thin tip tc in the stc-rig showed a symmetricaltemperature profile in the pipe. By examining how the 1.5 mm tc behaved inthis environment with known gas temperature profile, the obtained knowledgecould be applied to cross-sectional measurements in the SI-engine. It was foundthat the temperature profile in the engine deviated from the temperature profilemeasured in the stc-rig. The temperature was higher near the top of the pipethan in the center and lower part. In the horizontal direction, the temperaturewas found to be constant.Conclusions drawn from measurements in the engine lab points to that the crosssectionaltemperature and mass flow profiles have a strong connection with theengine’s operation point. The cross-sectional profiles, along with respective profileover time, is crucial when estimating the energy content of an exhaust gaspulse.The inverted sensor model with optimized parameters could estimate the meanvalue of the measured gas temperature during stationary runs within 6 degC.
Gli stili APA, Harvard, Vancouver, ISO e altri
4

Ahmed, Mahbub. "Investigation on the flame dynamics of meso-combustors". To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
5

Farrall, Simon. "A study in the use of fuzzy logic in the management of an automotive heat engine/electric hybrid vehicle powertrain". Thesis, University of Warwick, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387380.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
6

Thornberg, Nils, e Kraft Jonas Eriksson. "Physically Based Modelling for Knock Prediction in SI Engines". Thesis, Linköpings universitet, Fordonssystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149020.

Testo completo
Abstract (sommario):
The high demand for an increase in performance and at the same time loweringthe emissions is forcing the automotive industry to increase the efficiency of thevehicles. This demand lead to a problem called knock, which often is the limitingfactor when increasing the efficiency of the engine. Knock occurs when theunburned gases inside the combustion chamber self-ignites due to the increasingpressure and temperature.This thesis investigates if it is possible to predict knock with a physicallybased knock model. The model consist of several sub-models such as pressuremodel, temperature model and knock model. The models are built by using measureddata and the goal is to get an independent knock prediction model that canfind the limited ignition angle that will cause knock.The results shows that an analytic pressure model can simulate a measuredpressure curve. But when it comes to predicting knock, there is an uncertaintywhich can be improved by changing the modelling strategy and making the modelsmore accurate.
Gli stili APA, Harvard, Vancouver, ISO e altri
7

Cruz, Ricardo Wilson Aguiar da. "Avaliação da introdução de cogeração no sistema isolado do interior do estado do Amazonas". [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265238.

Testo completo
Abstract (sommario):
Orientadores: Silvia Azucena Nebra e Elizabeth Ferreira Cartaxo
Tese (doutorado) - Universidade Estadual se Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-04T02:01:08Z (GMT). No. of bitstreams: 1 Cruz_RicardoWilsonAguiarda_D.pdf: 17244783 bytes, checksum: a03d0eedccd3e72d383d8e704276c5cf (MD5) Previous issue date: 2004
Resumo: Neste trabalho procurou-se apresentar um panorama da geração isolada de energia elétrica pelo Sistema CEAM, quanto às suas características técnicas e econômicas, e do mercado de conservação de pescado do interior do Estado do Amazonas, como bases para desenvolver um método que permita avaliações da introdução de cogeração nessas usinas, visando a produção de mo e gelo, como forma de elevação da lucratividade. Para tanto é mostrado que uma usina autônoma produzindo apenas energia elétrica no cenário interiorano amazonense não tem como ser lucrativa no cenário atual. Foi utilizado como ferramentas básicas elementos da teoria dos motores de combustão interna sob carga variável, teoria das máquinas de remgeração por absorção água-amônia e métodos termoeconômicos baseados na primeira e segunda lei da Termodinâmica. O quadro típico das usinas do interior é mostrado por dados coletados em visitas a cinco usinas, sendo duas delas de outros estados que não o Amazonas, mas que conservam características comuns com as usinas amazonenses. O mercado de pescado é discutido sobre dados bibliográficos. E, do cruzamento desses quadros, são inferidas características da interdependência entre remgeração industrial e energia elétrica
Abstract: This investigation shows a panorama of the isolated power generation of the Amazon State CEAM System regarding its technical and economic characteristics, as well as the problems of the refrigeration facilities of the tishing industry of inland the State, focusing to develop methods to evaluate the introduction of cogeneration in the generation system to the enhance its protitability. Meanwhile, it is shown that a autonomous power station can not expect to become protitable in the Amazonian nowadays scenario if it uniquely produces electric energy. To achieve this objective the main theoretical background were elements of the theory of internal combustion engines under variable charge, the theory of aquammonia absorption refiigeration devices, and methods belonging to thermoeconomics based on tirst law and second law of thermodynamics. A typical profile of the stations of the CEAM System is showed by collected data on tive autonomous power stations among the Northern Brazilian autonomous power grid. The tive power stations preserve common characteristics among them. The market of the tishing industry is showed by bibliography surveyed data. These data made possible to infer the profound relationship between refiigeration and electric energy
Doutorado
Planejamento de Sistemas Energeticos
Doutor em Planejamento de Sistemas Energéticos
Gli stili APA, Harvard, Vancouver, ISO e altri
8

Reis, Joaquim Antônio dos [UNESP]. "Projeto e montagem de um sistema compacto de cogeração: aplicação da análise exergoeconômica". Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/106421.

Testo completo
Abstract (sommario):
Made available in DSpace on 2014-06-11T19:35:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-04Bitstream added on 2014-06-13T18:47:03Z : No. of bitstreams: 1 reis_ja_dr_guara.pdf: 3822491 bytes, checksum: c9fd5a88d775153288d737de07be90be (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho desenvolve o projeto, aqui entendido como a seleção das unidades que atendam às exigências de obtenção de eletricidade, calor e frio, e a montagem de um sistema de cogeração que usa um motor de pequeno porte associado a uma máquina de absorção e trocadores de calor que satisfarão tais exigências de uma maneira a mais econômica possível, isto é, otimizado em termos de custos. Aplicando-se um método de obtenção dos custos associados à exergia, cria-se um quadro de custos exergéticos para a obtenção de cada produto, e a soma de cada custo constitui o que chama-se de custo de manufatura exergética. O estudo demonstra que é possível aplicar esse método e identificar os pontos de deficiência de um sistema térmico como o mostrado e ,com isso, tomar medidas que venham a melhorar seu desempenho. Essa otimização física não se utiliza de conhecidos algoritmos de otimização matemática, utilizando-se de dados físicos e termodinâmicos medidos, O método permite identificar a forma operacional (basicamente a rotação do motor) que apresente os menores custos. A compreensão dos aspectos gerais da cogeração, das tecnologias envolvidas, com suas vantagens e desvantagens, torna possível aplicar a avaliação exergética associada a conceitos econômicos,e, com essa análise, tomar-se medidas que melhorem o desempenho do sistema em estudo.
This work develop the design of a cogeneration system with a small internal combustion engine coupled with an absorption refrigeration unit utilised in the production of a refrigeration effect, heating effect and electrical power generation with the utilization of exhaust waste heat, in a most possible economic way, i.e., optimized within limits of costs. By developing a method of costs associated to exergy, raises an exergetic costs for each unit, and the total costs is called manufacture exergetic cost. This study demonstrate that the appliance of this method identify the failures in the system and indicate where applies measures that improves its performance. This optimization do not utilizes mathematical algorithms, it is a physical optimization that use thermodynamics and physical data. The objective of this method is to identify the operational form that introduces the smaller cost. This compact cogeneration system have an internal combustion engine coupled with two heat exchangers and an absorption engine. The comprehension of general aspects of cogeneration technologies, its advantages and disadvantages turn possible to apply the exergetic evaluation associated with economic concepts to improve the performance of the system.
Gli stili APA, Harvard, Vancouver, ISO e altri
9

Reis, Joaquim Antônio dos. "Projeto e montagem de um sistema compacto de cogeração : aplicação da análise exergoeconômica /". Guaratinguetá : [s.n.], 2006. http://hdl.handle.net/11449/106421.

Testo completo
Abstract (sommario):
Resumo: Este trabalho desenvolve o projeto, aqui entendido como a seleção das unidades que atendam às exigências de obtenção de eletricidade, calor e frio, e a montagem de um sistema de cogeração que usa um motor de pequeno porte associado a uma máquina de absorção e trocadores de calor que satisfarão tais exigências de uma maneira a mais econômica possível, isto é, otimizado em termos de custos. Aplicando-se um método de obtenção dos custos associados à exergia, cria-se um quadro de custos exergéticos para a obtenção de cada produto, e a soma de cada custo constitui o que chama-se de custo de manufatura exergética. O estudo demonstra que é possível aplicar esse método e identificar os pontos de deficiência de um sistema térmico como o mostrado e ,com isso, tomar medidas que venham a melhorar seu desempenho. Essa otimização física não se utiliza de conhecidos algoritmos de otimização matemática, utilizando-se de dados físicos e termodinâmicos medidos, O método permite identificar a forma operacional (basicamente a rotação do motor) que apresente os menores custos. A compreensão dos aspectos gerais da cogeração, das tecnologias envolvidas, com suas vantagens e desvantagens, torna possível aplicar a avaliação exergética associada a conceitos econômicos,e, com essa análise, tomar-se medidas que melhorem o desempenho do sistema em estudo.
Abstract: This work develop the design of a cogeneration system with a small internal combustion engine coupled with an absorption refrigeration unit utilised in the production of a refrigeration effect, heating effect and electrical power generation with the utilization of exhaust waste heat, in a most possible economic way, i.e., optimized within limits of costs. By developing a method of costs associated to exergy, raises an exergetic costs for each unit, and the total costs is called manufacture exergetic cost. This study demonstrate that the appliance of this method identify the failures in the system and indicate where applies measures that improves its performance. This optimization do not utilizes mathematical algorithms, it is a physical optimization that use thermodynamics and physical data. The objective of this method is to identify the operational form that introduces the smaller cost. This compact cogeneration system have an internal combustion engine coupled with two heat exchangers and an absorption engine. The comprehension of general aspects of cogeneration technologies, its advantages and disadvantages turn possible to apply the exergetic evaluation associated with economic concepts to improve the performance of the system.
Orientador: José Luz Silveira
Coorientador: Edson Bazzo
Banca: Pedro Magalhães Sobrinho
Banca: Julio Santana Antunes
Banca: Jose Rui Camargo
Banca: Newton Galvão de Campos Leite
Doutor
Gli stili APA, Harvard, Vancouver, ISO e altri
10

Šaroun, Josef. "Projektové řízení výstavby technologického celku". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230034.

Testo completo
Abstract (sommario):
The target of this master thesis is specify the requirements, which come up while summing the investment aim of a new 40MW energetic unit, and show the overall project management. Thesis is divided into two parts. First part deals with project management from the investors point of view. There is also detailed concept study, technological description of piston co-generation units and combined cycle, concept design of calculated variations and their economical analysis. Second part is taken from the point of view of the main supplier. There is defined the range of operations, documents and official permissions needed for successful finish of the civil part of the energetic unit project.
Gli stili APA, Harvard, Vancouver, ISO e altri
11

Kim, Moochan. "Problems on Non-Equilibrium Statistical Physics". Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-8007.

Testo completo
Abstract (sommario):
Four problems in non-equilibrium statistical physics are investigated: 1. The thermodynamics of single-photon gas; 2. Energy of the ground state in Multi-electron atoms; 3. Energy state of the H2 molecule; and 4. The Condensation behavior in N weakly interacting Boson gas. In the single-photon heat engine, we have derived the equation of state similar to that in classical ideal gas and applied it to construct the Carnot cycle with a single photon, and showed the Carnot efficiency in this single-photon heat engine. The energies of the ground state of multi-electron atoms are calculated using the modi ed Bohr model with a shell structure of the bound electrons. The di erential Schrodinger equation is simpli ed into the minimization problem of a simple energy functional, similar to the problem in dimensional scaling in the H-atom. For the C-atom, we got the ground state energy -37:82 eV with a relative error less than 6 %. The simplest molecular ion, H+ 2 , has been investigated by the quasi-classical method and two-center molecular orbit. Using the two-center molecular orbit derived from the exact treatment of the H+ 2 molecular ion problem, we can reduce the number of terms in wavefunction to get the binding energy of the H2 molecule, without using the conventional wavefunction with over-thousand terms. We get the binding energy for the H2 with Hylleraas correlation factor 1 + kr12 as 4:7eV, which is comparable to the experimental value of 4:74 eV. Condensation in the ground state of a weakly interacting Bose gas in equilibrium is investigated using a partial partition function in canonical ensemble. The recursive relation for the partition function developed for an ideal gas has been modi ed to be applicable in the interacting case, and the statistics of the occupation number in condensate states was examined. The well-known behavior of the Bose-Einstein Condensate for a weakly interacting Bose Gas are shown: Depletion of the condensate state, even at zero temperature, and a maximum uctuation near transition temperature. Furthermore, the use of the partition function in canonical ensemble leads to the smooth cross-over between low temperatures and higher temperatures, which has enlarged the applicable range of the Bogoliubov transformation. During the calculation, we also developed the formula to calculate the correlations among the excited states.
Gli stili APA, Harvard, Vancouver, ISO e altri
12

Humphrey, Tammy Ellen. "Mesoscopic quantum ratchets and the thermodynamics of energy selective electron heat engines /". 2003. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20040202.140246/index.html.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
13

Lloyd, Caleb C. "A low temperature differential stirling engine for power generation : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering in the University of Canterbury /". 2009. http://hdl.handle.net/10092/2916.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
14

Sushma, B. R. "N-Radical Injection For Augmenting The Nox Removal In Diesel Engine Exhaust By Electric Discharges". Thesis, 2005. http://etd.iisc.ernet.in/handle/2005/1484.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
15

Kumar, Bijendra. "No/Nox Removal In Diesel Engine Exhaust Under Different Energizations And Reactor Configurations". Thesis, 2008. http://hdl.handle.net/2005/716.

Testo completo
Abstract (sommario):
In India, with the increase in the number of industries and vehicles the environment is getting more and more polluted. More than industries it is the rapid growth of vehicles which causes serious environmental crisis in the form of air pollution and has become alarming particularly in cities. The industrial and vehicular growth cannot be neglected, as the country’s economic and social well being is largely dependent on them. But this should not come at the cost of our health and eco system. The industrial and vehicular emissions must be controlled in order to keep our air clean. Continued efforts in this direction are being taken up across the globe to investigate an efficient and economical technique. There are many air pollutants being emitted from both natural and manmade sources. The major air pollutants identified as hazardous to human health are nitrogen oxides (NOx), carbon monoxide (CO), particulate matter (PM), volatile organic compounds (VOC), and sulfur dioxides (SOx). Among these, nitrogen oxides are considered to be difficult to remove. The sources of NOx are thermal power plants, stationary and mobile diesel engines, gasturbine engine, ironore sintering plants and various other smallscale utilities. There are conventionally available technologies to remove NOx such as chemical scrubbing, catalysis etc. But these techniques are either difficult to operate or do not bring down the level of NOx to the required norms imposed by the government. The failure of conventional techniques to remove NOx to the expected limit led to the development of alternative nonconventional techniques. Prominent among these new alternative techniques is electric discharge plasma, where the gas is partially ionized and temperature of electrons is considerably higher than that of ions and background gas molecules. Diesel engines are getting popular due to their inherent merits and their number is increasing considerably. Unfortunately, the exhaust of diesel engine being complex with high oxygen content makes the existing pollution control techniques insufficient particularly with regard to removal of NOx. So there is a need for investigating better technology which can effectively abate the pollutants from diesel engine exhaust. Electric Discharge plasma is one such alternative technique which has been very successful in large volumes of flue gas cleaning and hence, its potential is being explored in the cleaning of small volumes of vehicular exhausts, in particular, diesel engine exhaust. In the present work we investigated the relative performance of different electric discharge plasma reactors, with different type of voltages like AC, DC and pulse. The reactors were evaluated for NOx removal efficiency and NO conversion. This research work is a feasibility study to find whether electric discharge plasma can be used more effectively as an alternative technology for the after treatment of diesel engine exhaust in cascade with some cheaper adsorbents, if necessary. The scope of this qualitative experimental study can briefly be summarized as below: . • To study different reactors for NO conversion and NOx removal . • To study the effect of dielectric pellets in enhancing the radical production which in turn will have a bearing on the chemical reactions . • To study the effect of different types of voltages on the cleansing process . • To propose an efficient reactor system subject to the experimental conditions studied.
Gli stili APA, Harvard, Vancouver, ISO e altri
16

Bhattacharya, Tanmoy. "Battery Buffered Stiff Micro Grid Structure For A Variable Speed Slip Ring Induction Machine Based Wind Generation System". Thesis, 2009. http://hdl.handle.net/2005/678.

Testo completo
Abstract (sommario):
Electric power has become a basic necessity of human life. The major share of electric power comes from fossil fuel which results in global warming and pollution. A share of generated power comes from nuclear power which is equally dangerous. Big hydro projects take away lots of fertile land. The continuous usage of fossil fuel also poses a threat of petroleum and coal getting over in the near future. The only way out of this energy scarcity is to depend more and more on renewable sources like solar, wind and micro-hydro. At present, instead of having preference over any particular source of renewable energy, effort should be made to extract power from every possible energy source available in whatever form it is and use it in an optimal way. Like any renewable energy sources, the wind power contains large potential for harnessing energy that has been well understood hundreds of years ago. The importance of wind power generation has come to focus recently both at installation and research level and lot of activities are being carried out for efficient use of wind energy. There are different types of wind turbine designs available in the literature. But the most commercially used model is the two or three blade horizontal axis propeller type wind turbine. Research has shown that variable speed operation of this type of turbine is advantageous over fixed speed operation in terms of total energy synthesis. The most commonly used machines for wind power conversion are synchronous machine, squirrel cage induction machine and slip ring induction machine (SRIM). Variable speed operation using synchronous machine or squirrel cage induction machine requires large ratings of the power converters. However, SRIM based variable speed wind generator is advantageous over other schemes due to its inherent advantages like lower power rating for the converters, higher energy capture and the flexibility of sharing reactive power between the stator and the rotor. SRIM is used for both grid connected and stand alone applications and have been reported in the literature. The grid connected applications have received major attention in the literature whereas there are only a very few instances of its stand alone counterparts. There are many places both within and outside India where utility grid has not yet reached or the available grid is very weak. Moreover, in many of the places, the transmission line is so long that the losses in the system are extremely high. Isolated wind power generation can be of great advantage in such places where the available wind power is harnessed and utilized locally. This has been the motivation to go for proposing an isolated wind power generation scheme in this thesis. The proposed scheme is designed to supply power to the load even when very low or no wind power is available. Therefore, a battery bank is also a part of the system. The power converter assembly of the proposed scheme has three major components. One is the rotor side converter which is connected to the rotor terminals of the SRIM. The second one is the stator side converter with output LC filter which is connected to the stator side. These two converters share a common DC link which is interfaced to the battery bank through a multi phase bi-directional fly-back DC-DC converter. Fig. 1. Overall block diagram of the proposed stand alone wind power generator Functionally, this thesis proposes a system as shown in Fig. 1, which has primarily two components with multiple energy ports viz. (i) the SRIM is one triple energy port component and (ii) the proposed power conditioner is another triple energy port component. The SRIM device consists of (i) a mechanical energy port that is interfaced with the windmill shaft (ii) an AC port through the stator windings that is interfaced with the micro-grid/load and (iii) a third port which is also an AC port through the rotor windings of the SRIM that interfaces with an AC port of the proposed power conditioner. The proposed power conditioner is another triple energy port device which consists of (i) a DC energy port that interfaces with a battery/accumulator, (ii) an AC port that interfaces with the rotor windings of the SRIM and (iii) another AC port that generates the micro-grid that is connected to the load and the stator port of the SRIM. The proposed power conditioner provides the frame work for managing the energy flow from the mechanical port of the SRIM to the rotor and accumulator as well as from the mechanical port to the stator/load and accumulator. Further, energy interaction can also take place between the stator and the rotor externally through the power conditioner. The power interfaces on all three energy ports of the proposed power conditioner poses several challenges that have been discussed in this thesis. This thesis focuses on developing schemes to solve these challenges as explained below. Speed sensorless control is a natural choice for slip ring induction machine because of the flexibility of sensing both stator and rotor currents. There are different methods proposed in the literature which deal with the speed sensorless control of slip ring induction machine. However, the elimination of the measurement noise in the flux position estimation is not sufficiently addressed. It is important to address this issue as this would lead to deterioration in rotor side control of SRIM if the measurement noise is not eliminated. Primarily, the schemes which use algebraic relation between the estimated rotor current in stator reference frame and the sensed rotor current, are prone to measurement noise. On the other hand, the schemes, which use rotor back-emf integration, are affected by DC drift problems, though they are not much affected by measurement noise. The proposed stator flux position estimation scheme incorporates the benefits obtained from both the above schemes while eliminating the disadvantages inherent to them. The rotor flux position is estimated by integrating the rotor back-electromotive force. The stator flux is then obtained from the rotor flux estimate. This integration mechanism leads to several problems like dc drift and lack of error decaying mechanism. This estimation scheme solves the above problems including reduction in the propagation of noise in the sensed current to the estimated rotor side unit vectors. On the implementation front, this scheme also eliminates the need for differentiating the unit vectors for estimating slip frequency. This makes the proposed flux estimator very robust. The proposed scheme is simulated and experimentally verified. There is an internal DC bus within the proposed power conditioner that manages the energy flow through the three energy ports. The internal DC bus is interfaced to an external accumulator or battery through a power interface called the multi phase bi-directional dc-dc converter. It is generally advantageous to have the motor rated for higher voltages in order to achieve better efficiencies for a given power rating as compared to low voltage motors. This implies higher DC bus voltage. On the other hand, it is advantageous to have the battery bank rated for low voltage in order to improve the volumetric efficiency which is better at lower battery bank voltages. Both these are contradictory requirements. The above problem is solved in this thesis by proposing a multi power port topology using a bidirectional fly-back converter that is capable of handling multiple power sources and still maintain simplicity and features like high gain, wide load variations and lower output current ripple. As a spin-off, the scheme can handle parallel energy transfer from even a eutectic combination of batteries without any additional control circuitry for parallel operation. Further, the scheme also incorporates a novel transformer winding technique which significantly reduces the leakage inductance of the coupled inductor. The proposed multi-port bidirectional converter is analyzed by including non-idealities like leakage inductance. The DC bus voltage regulation requirement is not very stringent because it is not directly fed to any load. Therefore, hysteresis voltage regulation with small proportional correction is used for DC bus voltage control. The proposed converter is built and experimentally verified in the proposed system as well as in a hybrid-electric vehicle prototype. The third port of the proposed power conditioner interfaces with the stator of the SRIM and the load. The stator/load needs to be connected to a stiff micro-grid. The control requirement of the micro-grid is very stringent because, even for a sudden variation in the wind speed or the load, the grid voltage magnitude and frequency should not change. The dynamic response of the grid voltage controller has to be very fast. Moreover, the grid voltage must be balanced in presence of unbalanced loading. This thesis proposes a converter called the stator side converter along with three phase L-C filter at its output to form the micro-grid. A generalized control scheme is proposed wherein the negative sequence components and the harmonics can be eliminated at the micro-grid by means of feed-forward compensators included in the fundamental positive synchronous reference frame alone. The theoretical foundation for this scheme is developed and discussed in the thesis. In isolated locations linear loads constitute a significant percentage of the total load. Therefore, on the implementation front, only the compensation of fundamental negative sequence is demonstrated. One more necessity for compensating the fundamental negative sequence is that, the SRIM offers only leakage impedance to the fundamental negative sequence components resulting in high fundamental negative sequence current even for a small fundamental negative sequence voltage present at the micro-grid. The proposed scheme ensures balanced three phase currents at the SRIM windings and the full unbalanced current is provided from the stator side converter. This scheme is validated both by simulation and experimentation. The proposed power conditioner is integrated and used in the implementation of the entire wind power generation scheme that is proposed in the thesis. The maximum power point tracking of the wind power unit is also incorporated in the proposed system. The simulation and experimental results are also presented. Finally, the engineering issues involved in the implementation of the proposed scheme are discussed in detail highlighting the hardware configuration and the equipments used. The wind turbine is emulated using a chopper controlled DC motor. The shaft torque of the DC motor is controlled to give the Cp−λ characteristic of a typical windmill. The control issues of the DC machine to behave as a wind turbine are also explained. Finally the thesis is concluded by a statement of potentials and possibilities for future work in this research area.
Gli stili APA, Harvard, Vancouver, ISO e altri
17

Goswami, Himangshu Prabal. "Nonequilibrium Fluctuations, Quantum Optical Responses and Thermodynamics of Molecular Junctions". Thesis, 2016. http://hdl.handle.net/2005/3063.

Testo completo
Abstract (sommario):
Mankind has come a long way since the invention of wheel to accessing information in the quintillionth of a second. At the heart of every invention ever made, there has been only one objective, to ease the way of living. The progeny of this philosophy automatically came to be known as technology. It was technology that led to the design of the wheel for fast human transportation and the same motivation let him design more sophisticated machines. In mankind’s journey to improve technology, it began to learn efficient or correct ways to utilize and understand resources around it, creating a whole new philosophy called science. Ingeniously, it was science that let humans understand what they were made of: matter, to discovering what matter itself was composed of: atoms and what puts these together: forces. Science and technology has been of tremendous comfort for mankind and has helped it evolve throughout history. However, it is not always that science and technology go hand in hand. Technology has always helped man design devices and instruments which often bring physical comfort. Science on the other hand has made sure that loss in manual labor is compensated by increased inquisitiveness. There were times when technology was more developed than science. This was the time when machines were taking mankind by fire, resulting in the first and second industrial revolutions. During that same time, science was develop-ing slowly by increasing human curiosity to learn the way nature functioned at finer details. This led to the discovery of the electron by Joseph John Thomson, who proved the electron to be a negatively charged particle. Consequently, he was awarded the 1906 Nobel Prize in Physics for his work on electricity conduction in gases. Later, his son, George Paget Thomson, counter-proved that electrons are actually waves. He was also awarded the 1937 Nobel Prize in Physics, along with Clinton Joseph Davisson for their discovery of electron diffraction caused by crystals. Despite the ambiguity, mankind today accepts electrons to have dual properties. It is both a wave and a particle. This duality is not limited to electrons but is applicable to all matter, as proposed by Louis de Broglie and is one of the fundamental principles in science. With the help of well-developed technology, mankind can now design machines that allow controlled flow of electrons establishing the world of electronics, allowing faster human communication. The study of electronic properties and its usage in designing efficient devices is what electronics is all about. Electrons are the protagonist of mankind today. The presence of electrons is unanimously accepted by everyone. All physical and chemical processes are a result of electrons getting transported. Electron transfer processes are ubiquitous in nature, be it in photosynthesis or energy production in mitochondria . It is the fundamental process in all chemical reactions and all physical processes related to electricity. Every piece of hi-tech gadget practically uses the electron, and the whole of humanity is being serviced by it. In fact, a life without utilizing the electrons is abysmally mundane. Electronics has evolved from designing the first millimeter sized point contact transistor to silicon chip processors that contain billions of nanosized transistors. Studying electron transport has also led to the discovery of light emission during conduction popularly known as LED, an abbreviation for light emitting diode. Heating up of devices during electron transport forced mankind to study heat transport and design materials that have highly efficient electron transfer processes. Electron transfer is also the basic principle behind the Scanning Tunneling Microscope (STM), Scanning Electron Microscope (SEM) and the Transmission Electron Microscope (TEM) which replaced the conventional idea of using light (photons) as a source to observe matter at the nanolevel. However, mankind is still in the process of developing a technology which exploits both properties of the electron simultaneously. Today, science and technology work together to overcome this barrier. Indeed, science and technology today have come as far as controlling electron transport up to a single atomic level where quantum effects (discretization and interference of states that make up the system) are very pronounced. This branch can be referred to as quantum electronics or quantronics. It is one of the possible alternatives to conventional silicon based electronics, and is made of three separate fields. The first one that exploits the quantum nature of electron transport in nanoscopic systems, is usually called molecular electronics or moletronics. The second involves ex-ploiting the spin of the electron and is termed as spintronics. The third is the most challenging where neither science nor technology has been able to fully grasp the characteristics, i.e utilizing the heat quanta in designing thermal de-vices at the single atomic level. In general, for ultimate exploitation of both the wave and particle characteristics of the electron, a proper comprehension of the quantum effects during electron transport is necessary to design a quantronic device. Also, in any quantronic device, apart from quantum effects, fluctuations in temperature cause changes in the flow of electrons. Since electron flow is a random process, fluctuations need to be analyzed from a statistical point of view. Moreover, to address issues related to efficiency and power of these quantronic devices, a proper understanding of the thermodynamic aspects is required. The aim of the work in the thesis is to theoretically analyze the fluctuations, quantum effects and thermodynamics, that in principle, affect the basic physics and chemistry during electron and heat transport in a specific class of out of equilibrium quantum systems. This class of quantum systems are prototypes for designing quantronic devices, where both wave and particle nature of the electrons are pronounced. These are called molecular junctions or quantum junctions. It will in turn help the field of quantronics in the long run. However, in this thesis, it is the science that I address and not the technological aspects.
Gli stili APA, Harvard, Vancouver, ISO e altri
Offriamo sconti su tutti i piani premium per gli autori le cui opere sono incluse in raccolte letterarie tematiche. Contattaci per ottenere un codice promozionale unico!

Vai alla bibliografia