Cette thèse évalue d'abord le potentiel thermodynamique du cycle au CO2 supercritique (sc-CO2) pour une large gamme de température de source chaude et étudie son couplage aux applications nucléaires, 45.7% d’efficacité thermique étant obtenu pour un réacteur à neutrons rapides refroidi au sodium. Des simulations CFD sont réalisées sur un compresseur à échelle réduite et confrontées à une expérience, apportant des éléments de qualification. Des simulations sur un compresseur à échelle 1:1 révèlent des particularités liées à la compression du sc-CO2 au comportement gaz réel, offrant un retour d’expérience pour la conception. Dans ce cadre, une approche de cartes de performance est proposée et validée à l'aide de simulations. Enfin, une étude de la collapse d’une bulle dans le CO2 liquide au voisinage du point critique est réalisée et indique l'absence d’effet destructif de cavitation, ouvrant la voie au fonctionnement du compresseur en phase liquide, lieu optimum de l'efficacité du cycle. / This study first evaluates the thermodynamic performance of the supercritical CO2 (sc-CO2) cycle in a large range of heat source temperature, with a focus on the nuclear applications; a thermal efficiency of 45.7% is reported for a Sodium-cooled Fast Reactor. Second, CFD simulations have been performed on a small scale sc-CO2 compressor and results have been confronted positively with the experimental data. Simulation results on a real scale compressor have then revealed some particularities during the compression of a real fluid, providing feedbacks for the component design. In addition, a reliable performance maps approach has been proposed for the sc-CO2 compressor and validated using the CFD results. Finally, an investigation of bubble collapse in the liquid CO2 near the critical point has disclosed the likely absence of detrimental effects. As such, risks of cavitation damage should be low, favoring the compressor operation in the liquid region for cycle efficiency improvement.

L'objectif de cette thèse est la conception, dans un premier temps, des différentes stratégies de commande pour un générateur hybride composé par une pile à combustible et une source auxiliaire de stockage d'énergie. L'outil des Inégalités Linéaires Matricielles (LMI) est utilisé dans la thèse pour la solution du problème de la commande robuste et multi-variables. Dans un premier temps la commande se consacre à la gestion de la partie électrique de la pile. Des stratégies de commande sont proposées pour les convertisseurs élévateurs du bus continu mais aussi pour le contrôle d'un onduleur de tension conçu pour une opération en mode isolé du réseau. La validation d'une partie du contrôle sous un banc d'essai a été réalisée. Dans un deuxième temps, la commande de la partie fluidique de la pile a été traitée. La gestion de la dynamique de l'air en entrée de la pile est assurée par la commande du débit du compresseur. Le sous-système de compression d'air est régulé pour garantir un certain taux d'excès d'oxygène désiré, ce qui permet d'améliorer les performances de la pile. Une introduction au contrôle des systèmes à paramètres variants (LPV) est aussi présentée. Des études de robustesse des contrôleurs proposés ont été effectuées, et ces caractères robustes sont comparés avec plusieurs méthodes de commande classique, prouvant ainsi l'importance des méthodologies de commande robuste et multi-variables. / The objective of this thesis is the design of several control strategies for a hybrid power generator composed by a fuel cell and an auxiliary energy storage source. The Linear Matrix Inequalities (LMI) tools are extensively used in this dissertation as a solution to the mutivariable robust control problem. As a first approach, the control methodology is consecrated to the electrical power management sub-system of the fuel cell. Different strategies are proposed to control the hybrid boost power converter configuration for DC voltage applications. The methodology is extended to AC islanded applications considering the additional control of a voltage inverter. The validation on a dedicated test-bench, of a part of the proposed control strategies, is presented. In a second approach, the control of the air supply system is addressed. The management of the air dynamic entering the fuel cell is assured by the control of the air flow of a compressor. The air supply sub-system is controlled to keep a desired oxygen excess ratio, this allow to improve the fuel cell performance. An introduction to the control of Linear Varying Parameter (LPV) systems is also presented. Robustness analysis studies are performed, these robust properties are contrasted with several classic control strategies, demonstrating the advantage and the importance of multivariable robust methodologies.

<p>Examensarbetet har finansierats av Interactive Institute Piteå med medel från strukturfondsprojektet LJUDIT. Arbetet har utförts på och handletts av Interactive Institute Piteå.</p> / LJUDIT

This diploma thesis deals with design of air-water heat pump which uses natural refrigerant, propane. In the thesis there are mentioned various types of devices using the source of low-potential heat for heating. The main part of the thesis is the design of the heat pump cooling circuit. In this section, individual components are designed, the calculation and comparison of the heating factor for different operating parameters is performed. Finally, the construction of the coolant circuit and the air exchanger is designed.

This master’s thesis deals with the design and realization of a functional sample power inverter for an electric compressor, which is used in hybrid cars. The electric compressor powered by the inverter is E-compressor by Garrett Advancing Motion. An inverter will be using modern High Electron Mobility Transistors which are based on gallium nitride (GaN). The purpose of this thesis is to find if GaN transistors can be used in E-boosting application.

The aim of diploma thesis is design and lay-out of high pressure pumping station with plunger pumps for splash of scales from slabs of hot-rolled. Theoretic (introduction) part of this thesis contain description of formation of scales and description of ways how it is possible remove these scales. And this part contains also explication of effect of water jet on solid material. The practical part of diploma thesis is focused on design of pumping station including of dimensioning of machinery. Part of this work is also technical documentation for proposed pumping station and specification of main machines and devices.

Tato diplomová práce pojednává o návrhu ložisek kompresoru. Za tímto účelem byl zakoupen speciální program JDynamic. Tento software poskytuje cenný přínos při navrhování kluzných ložisek a s tím spojených problémů. Programové výsledky reálného kompresoru jsou obsaženy v parametrické studii. Byl proveden test reálného kompresru. Modifikace kluzných ložisek byly zaměřeny na snížení ztrát.

This thesis deals with a procedure for determining the complete processing of aerodynamic flow instabilities (rotating stall and surge) in a centrifugal compressor. At small flows the performance of a compressor system is limited by the surge line, which is caused by flow instabilities. Numerical solution is obtained using the method of transfer matrix. This system is simulated through several models with local resistances that represent the dissipation of pressure energy. Pulses are excitated in these models by the pressure jump placed before the centrifugal compressor. From the frequency-amplitude characteristics for the selected range of frequencies and flow the impedance characteristic of the compressor system is determined. We are looking for problematic frequencies in this characteristic that cause flow instabilities in the compressor system.

For air cooling in aircrafts is used an air cycle machine. Recently, there is focusing on incresing efficiency of air cycle and due this are added another rotors. Design of machine with three rotors is performed in this thesis.

This dissertation deals with design of self adjustable discharge valve used in Emerson reciprocating compressors. This work contains research of current state of knowledge, technical analysis of the valve and calculations of basis parameters. Constructional proposal is then presented. Part of the dissertation is manufacturing of prototype and its test. Finally, conclusions for further development are made.