The doctoral thesis deals with utilization of hydroforming technology for manufacturing of a new type of solar absorber, which has directly flow meandering structure and a structured surface consisting of pyramidal elements. Austenitic stainless steel X5CrNi18-10 is used as a material for absorbers production. At the beginning of the thesis, a literary research is performed, which is focused on particular methods of hydroforming technology, their applicability for this problem, forming limits determination and usability of numerical simulation. Based on the literature study, the production technology was developed by using parallel hydroforming technology and it was optimized by using a numerical simulation in the ANSYS software. Hydroforming parameters for two variants of the structured surface with pyramidal cavities with apex angle of 90° and 60° were determined from the calculations and the material tests.

Le contexte du réchauffement climatique entraîne un développement des technologies CSP (Concentrated Solar Power). La réduction des coûts de production de ces technologies passe par une amélioration de la durabilité et de l'efficacité des composants des centrales solaires. Les températures de fonctionnement élevées du CSP (250-600°C) nécessitent d'employer des absorbeurs spectralement sélectifs afin de limiter les pertes par radiation. Cette thèse propose une architecture originale d'absorbeurs sélectifs stables à haute température sous air en combinant un dépôt de TiAlN en couches minces avec un réseau de diffraction. L'ajout d'une texturation de surface augmente l'absorption solaire du dépôt par un effet d'absorption et de gradient des indices optiques effectifs conduisant à une augmentation du rendement photothermique de l'absorbeur. Dans ce mémoire, la modélisation du comportement optique des absorbeurs texturés, les méthodes de fabrication du réseau de diffraction ainsi que le dépôt des couches minces par PVD et PECVD seront abordés et les mesures expérimentales seront comparées aux modélisations. L'analyse des absorbeurs texturés fabriqués confirme un gain de rendement photothermique pouvant atteindre +3% ainsi qu'une stabilité thermique remarquable à 500°C sous air jusqu'à 300 h de recuit / The global warming context reinforces the development of CSP technologies. Cost reduction of CSP requires the improvement of component durability and efficiency. The solar absorbers should be spectrally selective since the high working temperatures of CSP plants increase the radiative thermal losses. This thesis proposes an original, spectrally selective absorber structure combining TiAlN based coatings and diffractive gratings. The surface texturing provided by the diffractive gratings improves the solar absorption of the thin coating by an effective optical index gradation effect leading toincreased photothermal efficiency. In this thesis, the modeling of the textured absorber’s optical behavior, fabrication methods of diffractive gratings, as well as layer deposition by PVD/PECVD will be discussed. Experimental measurements will be compared to the theoretical modelling. The experimental analysis of textured absorbers confirms the increase of photothermal efficiency by almost 3%, as well as a good thermal stability at 500°C in air for 300 hours of annealing

Cette thèse est consacrée à l'étude d'amortisseurs passifs non linéaires innovants pour le contrôle de l'instabilité de flottement sur un profil d'aile à deux degrés de libertés. Lorsqu'un profil d'aile entre en flottement, il oscille de façon croissante jusqu'à se stabiliser sur un cycle limite dont l'amplitude peut être significative et détériorer sa structure. Le contrôle a ainsi deux objectifs principaux : retarder l'apparition de l'instabilité et réduire l'amplitude des cycles limites. Avant d'étudier l'influence des amortisseurs passifs, l'instabilité de flottement, et notamment le régime post-flottement, a été étudié. Une expérience de flottement sur une plaque plane a été menée et sa modélisation, prenant en compte le phénomène de décrochage dynamique, a été réalisée. Concernant le contrôle passif, le premier type d'amortisseur étudié est un amortisseur hystérétique réalisé à l'aide de ressorts en alliage à mémoire de forme. La caractéristique principale de tels amortisseurs est que leur force de rappel étant hystérétique, elle permet de dissiper une grande quantité d'énergie. L'objectif principal est ainsi de réduire l'amplitude des cycles limites provoqués par l'instabilité de flottement. Cet effet escompté a été observé et quantifié expérimentalement et numériquement à l'aide de modèles semi-empiriques. Le second type d'amortisseur utilisé est un amortisseur non linéaire de vibration accordé. Il est composé d'une petite masse connectée au profil d'aile à l'aide d'un ressort possédant une raideur linéaire et une raideur cubique. La partie linéaire de ce type d'amortisseur permet de retarder l'apparition de l'instabilité tandis que la partie non linéaire permet de réduire l'amplitude des cycles limites. L'influence de l'amortisseur non linéaire de vibration accordé a été étudiée analytiquement et numériquement. Il a été trouvé que l'apparition de l'instabilité est significativement retardée à l'aide de cet amortisseur, l'effet sur l'amplitude des cycles limites étant plus modeste. / The aim of this thesis is to study the effect of passive nonlinear absorbers on the two degrees of freedom airfoil flutter. When an airfoil is subject to flutter instability, it oscillates increasingly until stabilizing on a limit cycle, the amplitude of which can be possibly substantial and thus damage the airfoil structure. The control has two main objectives : delay the instability and decrease the limit cycle amplitude. The flutter instability, and the post-flutter regime in particular, were studied first. A flutter experiment on a flat plate airfoil was conducted and the airfoil behavior was modeled, taking into account dynamic stall. Regarding the passive control, the first absorber studied was a hysteretic damper, realized using shape memory alloys springs. The characteristic of such dampers is their hysteretic restoring force, allowing them to dissipate a large amount of energy. Their main goal was thus to decrease the limit cycle amplitude caused by the flutter instability. This expected effect was observed and quantified both experimentally and numerically, using heuristic model. The second absorber studied was a nonlinear tuned vibration absorber. This absorber consists of a light mass attached to the airfoil through a spring having both a linear and a cubic stiffness. The role of the linear part of such absorber was to repel the instability threshold, while the aim of the nonlinear part was to decrease the limit cycle amplitude. It was found, analytically and numerically, that the instability threshold is substantially shifted by this absorber, whereas the limit cycle amplitude decrease is relatively modest.

The doctoral thesis deals with utilization of hydroforming technology for manufacturing of a new type of solar absorber, which has directly flow meandering structure and a structured surface consisting of pyramidal elements. Austenitic stainless steel X5CrNi18-10 is used as a material for absorbers production. At the beginning of the thesis, a literary research is performed, which is focused on particular methods of hydroforming technology, their applicability for this problem, forming limits determination and usability of numerical simulation. Based on the literature study, the production technology was developed by using parallel hydroforming technology and it was optimized by using a numerical simulation in the ANSYS software. Hydroforming parameters for two variants of the structured surface with pyramidal cavities with apex angle of 90° and 60° were determined from the calculations and the material tests.

This diploma thesis’s focuses on the mechanical design of fast solenoid throttle valve for DCC semiactive damper. Current DCC dampers work with a time response of over 10 ms, which is not suitable for fast semiactive control of vehicle chassis. The time response needs to be shortened, to improve quality of regulation. The required time response is archived by new fast electromagnetic actuator for original CES valve. The actuator has been accelerated by reducing induction of eddy currents and by reducing weight of moving parts. New valve helped to reduce the time response of damper by 28 % to 8,1 ms. The results proved, that the time response is affected more by speed of the servo effect, which is closing main orifice, than by electromagnetic actuator. There is no more potential in accelerating CES valve by actuator.

This work is focused on the developement of a sensor, which enables to measure the ultrasonic power by heat effect of the mechanical Wales. The princip of two basic kinds of thermoacoustic sensor is descibed here – one level and two level sensor. This work also contains a proposition of these sensors with description of each parts and a trial to find suitable absorber. Achieved results, which support the function of the sensors are presented here by form of graphs and tables. Measuring by thermoacoustic sensors is confronted here with measuring of ultrasonic by hydrophone, which is used as reference measuring.

This semestral thesis focuses on the description of specific renewable resources in the form of thermophotovoltaic cells using selective radiators with micro/nano structures. This work deals with an introduction of renewable resources and specifically focuses on thermophotovoltaic. Thesis describes basic principles, but also influences affecting the proper functioning of these systems. It also focuses on selective radiators, which are created by mikro/nano structures, and factors that can affect their implementation or simulation. Part of the work are also examples of calculations of basic parameters of the structures, which will be used in the simulations. Next chapters are dealing with simulations which are analyzing thermal effects on termophotovoltaic system. Except the analysis itself there is also partial optimalization solving some of the negative thermal effects.

Entering of thesis focuses on large-scale solar systems. Large solar-scale system will be used for heating water in public swimming pool. The pool is located in Brno - country. The pool is operated year-round. Great emphasis of the thesis is on the surface heat loss. Evaporation of water from the water surface is also applied in the experimental part of the thesis. In the calculations is used software for modeling the thermal microclimate of buildings and air conditioning design Teruna.

Thesis deals with problems about areas of a non-assembling diagnostics namely resonant adhesive tester according to an EUSAMA methodology. Result of the methodology is a technical condition examination of dampers. However with regard to testing of whole suspension and damping vehicle system are results distorted by influence of testing conditons and another vehical components. Goal of thesis is analysis limits of practical use resonant adhesive tester for a quality checking of mount wheels damping. Problems are solved by a virtual simulation in a program Adams/View where is created a real model of vehical axle of Skoda Roomster TDI 1.4. In the model is consequently simulated possible functional characteristics and abrasions of single components which influence the methodology. Virtual model will be using for research activity of Institute of machine and industrial design Faculty of mechanical ingeneering Brno University of technology.

Les lasers ultra-rapides fibrés sont aujourd’hui incontournables dans de nombreuses applications industrielles et scientifiques du fait de leur stabilité, de leur compacité et des hautes puissances disponibles. Les performances actuelles, rendues accessibles par le développement de fibres à larges aires modales et le concept d’amplification à dérive de fréquence, sont toutefois complexes à mettre oeuvre et limitées par l’utilisation de composants massifs pour les étapes de compression et d’étirement des impulsions. Ces travaux de thèse, à la fois expérimentaux et numériques, avaient pour objectif d’explorer des régimes dynamiques originaux basés sur l’utilisation de fibres actives spécifiques combinant large aire modale et propriétés dispersives adéquates pour la génération d’impulsions ultra-courtes de haute énergie. Les études numériques ont ainsi permis de montrer que des régimes impulsionnels à haute dispersion normale pouvaient être atteints en exploitant les phénomènes de résonnance et de couplage de modes dans des fibres de Bragg ou à profil en W. L’étude de l’influence des paramètres de la cavité laser sur le mécanisme de verrouillage de modes a permis d’identifier des configurations attractives pour la montée en puissance. La mise en oeuvre expérimentale de ces concepts a notamment permis le développement d’une source laser à soliton dissipatif produisant des impulsions énergétiques (38 nJ, 700 fs après compression) à des longueurs d’ondes autour de 1560 nm, record pour ce type d’oscillateur. La réalisation expérimentale de sources ultra-rapides basées sur des fibres actives spécifiques combinées au phénomène de couplage de mode ont permis d’identifier les potentialités et limitations de ces architectures originales à fortes dispersions totales pour la montée en énergie. / Ultrafast fiber lasers represent today a ubiquitous technology in various industrial and research applications thanks to their inherent advantages such as compactness, stability and high power. The best performances to date, mostly relying on large mode area fibers and chirped pulse amplification, however require complex experimental developments and are limited by the use of bulk components for pulse stretching and compression. The experimental and numerical work presented in this PhD thesis aimed at exploring original dynamical regimes based on specific active fibers combining large mode area and high dispersions for the generation of high-energy ultra-short pulses. The numerical studies then showed that pulsed regimes with high normal dispersions could be reached by exploiting resonance and mode-coupling phenomena in Bragg or W-type fibers. Studying the influence of the cavity parameters on mode-locking mechanisms allowed to target attractive configurations for energy scaling. The experimental implementation of this concept allowed the development of a dissipative soliton source delivering record high-energy chirped pulses (38 nJ, 700 fs after compression) at 1560 nm. The realization of ultrafast sources based on specific active fibers combined to mode-coupling phenomena then brought the possibility to identify the potentiality and limitations of these particular architectures with high dispersions for energy scaling.