Afin de modéliser correctement les phénomènes liés à l'évaporation, les numériciens souhaitent obtenir des mesures expérimentales fiables, leur permettant d'améliorer leurs modèles. A l'opposé, de nombreux industriels souhaitent pouvoir réaliser des mesures in situ, avec des techniques expérimentales appliquées aux conditions réelles.C'est dans ce cadre que s'est inscrite cette thèse. L'objectif principal, a été de démontrer la faisabilité, et la stabilité, de mesures en réfractométrie d'arc-en-ciel sur des gouttes uniques en écoulement afin d'obtenir le taux d'évaporation de ces gouttes.L'utilisation d'un dispositif dédié habituellement à la PIV a servi à réaliser des acquisitions de couples d'images, séparées par un délai temporel variable. Une méthode très fine de la mesure de variation de diamètre a été introduite, autorisant la mesure du taux d'évaporation instantané d'une goutte en écoulement par le biais du déphasage de la structure de ripple. / In order to model correctly the evaporation phenomenon, numerical simulations needs to work with reliable experimental data, allowing to improve the existing models. On the other side, industrialists needs to realize in situ measurements, with experimental techniques that apply to real conditions. This is the framework of this thesis. The main work has been to prove that measurements with rainbow refractometry on unique droplets in a flow were possible, obtain the evaporation rate from those measurements, and prove their stability.The use of a specific setup, most of the time used in PIV, allowed us to realize acquisitions of couple images with a temporal delay. A very fine method for the measurement of variation of diameter has been introduced, allowing the measurement of instantaneous evaporation rate of unique droplets in a flow, using the ripple structure phase shift.

This thesis addresses the evolution of nanoscale ripple patterns on solid surfaces during low-energy ion sputtering. Particular attention is paid to the long-time regime in which the surface evolution is dominated by nonlinear processes. This is explored in simulation and experiment. In numerical simulations, the influence of anisotropy on the evolution of the surface patterns in the anisotropic stochastic Kuramoto-Sivashinsky (KS) equation with and without damping is studied. For a strong nonlinear anisotropy, a 90 rotation of the initial ripple pattern is observed and explained by anisotropic renormalization properties of the anisotropic KS equation. This explanation is supported by comparison with analytical predictions. In contrast to the isotropic stochastic KS equation, interrupted ripple coarsening is found in the presence of low damping. This coarsening seems to be a nonlinear anisotropy effect that occurs only in a narrow range of the nonlinear anisotropy parameter. Ex-situ atomic force microscopy (AFM) investigations of Si(100) surfaces sputtered with sub-keV Ar ions under oblique ion incidence show the formation of a periodic ripple pattern. This pattern is oriented normal to the direction of the ion beam and has a periodicity well below 100 nm. With increasing ion fluence, the ripple pattern is superposed by larger corrugations that form another quasi-periodic pattern at high fluences. This ripple-like pattern is oriented parallel to the direction of the ion beam and has a periodicity of around one micrometer. Interrupted wavelength coarsening is observed for both patterns. A dynamic scaling analysis of the AFM images shows the appearance of anisotropic scaling at large lateral scales and high fluences. Based on comparison with the predictions of different nonlinear continuum models, the recent hydrodynamic model of ion erosion, a generalization of the anisotropic KS equation, is considered as a potentially powerful continuum description of this experiment. In further in-situ experiments, the dependence of the dynamic scaling behavior of the sputtered Si surface on small variations of the angle of incidence is investigated by grazing incidence small angle X-ray scattering (GISAXS). A transition from strongly anisotropic to isotropic scaling is observed. This indicates the presence of at least two fixed points in the system, an anisotropic and an isotropic one. The dynamic scaling exponents of the isotropic fixed point are in reasonable agreement with those of the Kardar-Parisi-Zhang (KPZ) equation. It remains to be seen whether the hydrodynamic model is able to show such a transition from anisotropic to isotropic KPZ-like scaling.

This thesis presents the simulation, design, and hardware implementation of a modified multiphase boost converter. Converter design must consider noise imposed on input and output nodes which connect to and influence the operation of other devices. Excessive noise introduces EMI which can damage sensitive circuits or impede their operation. High ripple current degrades battery lifetime and reduces operating efficiency in connected systems such as PV arrays. Converters with high ripple current also experience greater peak conduction loss and require larger components. A two-phase implementation of a modified boost converter demonstrates the input current filtering benefits of the modified topology with increased power capacity. In a 12V to 19V 95W design, the modified multiphase design exhibits a reduced input current ripple of 1.103% compared to the 9.096% of the standard multiphase design while imposing minimal detriment to overall converter efficiency. The modified topology uses two inductors and one feedback capacitance per phase. Larger value inductors generally exhibit lower current ratings as well as larger size. The split inductance of the modified multiphase topology can be designed for occupation of less total volume than the single inductance of the standard multiphase topology.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19687号 / 工博第4142号 / 新制||工||1639(附属図書館) / 32723 / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 斧 髙一, 教授 稲室 隆二, 教授 青木 一生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

No description available.

The objective of this thesis is to determine the feasibility of a novel axial flux variable reluctance machine design. The design aims to compete with prevalent rare-earth permanent magnet machines while also implementing an innovative torque ripple minimization strategy. Given the fundamental operating principles, a selection of dimensions, materials, and excitations are prepared for the machine. Special attention is given to the rotor profile which is crucial to operation. Finite element analysis software is used to evaluate a three-dimensional model in terms of inductance and torque. The ultimate potential of the machine is discussed and recommendations for improvement are proposed.

With solar power and other renewables set to take over the market in the coming decades, maximum power point tracking will be essential to optimizing power output. One underserved topic of research is the effect of inductor current ripple on performance of Maximum Power Point Tracking (MPPT) algorithms. Many new topologies are focused on decreasing the ripple from PV source to increase efficiency and power output. However, not much has been done to show ripple degrading performance of MPPT algorithms. This study uses a boost converter topology to test the performance of constant duty cycle step Perturb and Observe (PO), Incremental Conductance IC, and Constant Voltage (CV) PID over a range of inductor current ripple factor. Inductor current ripple is controlled solely by changing inductance. This study concluded that all three algorithms were quite robust and affected very little over an inductor current ripple factor range of 20% to 40%. One novel finding was increased duty cycle oscillation when the MPPT update and sample speed was faster than the boost converter response.

The delivery of high power and smaller footprints through a non-isolated topology demands for the use of multiphase topology in DC-DC converters. Multiphase reduces the ripple observed on both the input and output waveforms; however, it may not be enough to connect to sensitive power sources such as renewable energy sources. A single-phase modified boost converter demonstrates the ability to acquire very minimal input current ripple by addition of passive components. The expansion to multiphase topology is the next logical step for higher power application while furthering the low input current ripple benefit. In this thesis, the multiphase modified boost topology is compared with the multiphase standard boost topology to explore the benefits and trade-offs of the proposed topology. A 12V input to 19V output at 95W output power multiphase standard and modified boost converters were designed and constructed for the thesis. Results from theoretical calculations, computer simulations, and hardware implementations were then compared to evaluate their performances. Results show that compared to the standard boost, the modified boost yields significantly less input current ripple at 2% under full load condition while maintaining output voltage ripple of 5% and higher than 90% efficiency.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.