The main idea is focused on the diagnostics of a specific hydraulic system, i.e. sensing the physical quantities of the hydraulic circuit with a tank and a centrifugal pump driven by an asynchronous motor. It is a system of pipes connected to the pump, where due to its work it creates a water flow and a pressure increase. In practice, this issue is also addressed in the energy and nuclear industries. Primary circuits in some cases cannot be designed or modified to be able measure locally the pressure value. It is necessary to measure this quantity indirectly - from the motor currents. The main idea of the work is to diagnose the system by an indirect method - specifically to detect the state of the hydraulic circuit (pressure, flow) from the values that we are able to measure and detect damage in advance. In the second part of the thesis is the application of the parts of a specific hydraulic system in the simulation environment MATLAB Simulink. The model of the hydraulic circuit contains mathematical-physical relations that simulate the course of the mentioned experiment. The results of the simulation are compared with the results of the experiment. The model also investigates the simulation of a fault condition, when we supply pressure pulsations to the hydraulic circuit. It is these changes in the hydraulic part that affect the characteristics of the pump and the asynchronous motor, so we are able to diagnose this system.

The diploma thesis deals with pressure pulsations in pipeline system with dynamic muffler. There is presented original geometry of side-branch resonator. Pressure pulsations are solved by a created mathematical model, numerical simulations and verified by an experimental approach. The influence of dynamic and bulk viscosity is involved in derived governing equations. A system of nonlinear equations is solved by genetic algorithm and frequency dependent relationship of bulk viscosity of air is determined afterwards. The correct function of used pressure sensors is tested. The processing of experimental data is performed by the fast Fourier transform with coherent sampling. Finally, a comparison of analytical, numerical and experimental approaches is introduced for different geometric variants of presented muffler.

This diploma thesis deals with axial thrust existence in a double suction pump rotor. Axial thrust appears especially in low flow rates modes. The aim of this work is finding information about this issue and deriving mathematical model of calculation which will be subsequently applied on experimental data received from double suction pump measurement in laboratory. It is important to examine the whole dynamics of axial thrust development and find its cause of formation in measured double suction pump.

We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

No description available.

No description available.

Les garnitures mécaniques sont utilisées dans de multiples applications pour réaliser l'étanchéité autour d'arbres en rotation. Ces composants peuvent fonctionner efficacement pendant plusieurs années en conditions stables, mais leur durée de vie est significativement réduite lorsque les conditions varient. L'objectif de ce travail de recherche est de développer et d’utiliser un banc d'essais et code de calcul pour étudier l'impact de pulsations de pression, d’inversions de pression et du chargement dynamique résultant sur les performances de garnitures mécaniques ayant des faces mésalignées et présentant des défauts de planéité.Le solveur fluide d'un modèle numérique de garnitures mécaniques a été étendu aux conditions transitoires. Un module résolvant la dynamique des forces et des moments a été ajouté afin de prédire le déplacement axial et les déplacements angulaires de la face montée de manière flexible. Afin de caractériser les performances de garnitures, un banc d'essais générant des pulses de pression a été instrumenté et des méthodes de mesure de perte de volume d'huile et d'entrée d'eau mises en place.Des garnitures mécaniques à faces parallèles puis mésalignées, fonctionnant sous pulsations et inversions de pression, ont été testées expérimentalement et simulées. Seules de très faibles augmentations d'eau dans l'huile ont été observées, sans augmentation au cours du temps, et sans fuite d'huile mesurable. Les faibles valeurs d'entrées d'eau sont dues à la faible épaisseur de film et à la courte durée des inversions de pression. Une garniture mécanique expérimentale à fort défaut de planéité a aussi été testée. Contrairement aux autres paramètres, le défaut de planéité semble augmenter significativement la fuite et promouvoir les entrées d'eau et pourrait ainsi être à l'origine de certaines défaillances. / Face seals are mechanical devices used to seal rotating shafts in numerous applications. While they can operate efficiently under steady conditions for years, they tend to fail prematurely when operating in severe, or rapidly varying conditions. The focus of this research work is the development and use of an experimental and a numerical method to investigate the impact of pressure pulses, pressure inversions and induced dynamic loading on the performance of mechanical face seals exhibiting face misalignment and waviness.The fluid solver of a state-of-the art face seal numerical model was extended to transient conditions and a module solving the dynamics for the axial and angular degrees of freedom of the flexibly-mounted stator added. A system-level experimental setup generating pressure pulses was instrumented and methods to characterise face seal performance in terms of oil volume loss and ingression of water outer-fluid selected and implemented.Face seals, with flat and misaligned faces, operating under pressure pulses and pressure inversions were experimentally tested and simulated. They show only slight increase of water in the oil, no increase over time, and no measurable oil leakage. The low water ingression is due to low film thickness combined with the short duration of pressure inversions. An exploratory face seal of high waviness was also experimentally tested. Contrary to the other parameters, the waviness appears to significantly increase the leakage and promote water ingression and could thus be at the origin of some seal failures.

Le couplage entre un écoulement instable et des résonances acoustiques dans des systèmes de conduites peut conduire à des phénomènes d’oscillations auto-induites. Ce type de phénomènes trouve principalement place dans des conduites latérales fermées, par exemple dans des systèmes de transport ou de compression de gaz. L’objectif de ce travail est d’étudier les oscillations auto-induites dans le cas où le fluide transporté ne se limite pas à un gaz, mais est un mélange de gaz et de liquide. Les pulsations sont mesurées dans des conduites latérales fermées, pour deux types de configurations (en tandem et en croix), avec écoulement d’un mélange variable d’air et d’eau. La position de l’injection d’eau est variable afin d’obtenir plusieurs régimes d’écoulement diphasique. Les résultats indiquent que la présence d’eau a un effet important sur les niveaux de pulsations dans les conduites. Cet effet a pu être attribué à deux mécanismes dus à la présence d’eau : les instabilités de couches de mélange sont modifiées et l’amortissement des ondes acoustiques est amplifié.Le deuxième mécanisme a été quantifié à l’aide de mesures sur un montage expérimental dédié conçu pour avoir un écoulement stratifié. On a observé que, dans tous les cas, la présence d’eau augmente l’amortissement. Cette augmentation a pu être attribuée à la réduction de la section effective de la conduite (due au remplissage partiel par l’eau) et à l’augmentation de la friction turbulente à l’interface entre les phases liquide et gazeuse. / Coupling between flow instabilities and acoustic resonances in ducts with closed side branches leads to Flow Induced Pulsations (FIPs). This is a typical phenomenon in engineering applications (gas transport systems, compressor installations, and chemical plants). The objective of this work is to extend the knowledge about FIPs when the transported medium is not uniquely gas but a combination of gas and (a small quantity of) liquid. For two configurations of double side branches (in tandem and in quasi-cross), the amplitude of pressure pulsations in the side branches was measured for different liquid injection rates. This was repeated with the liquid injection point located at different places to allow different flow regimes at the pipe connections. The results show a strong effect of the water content on the pulsations. On basis of these results and additional measurements, the following hypotheses for the effect of liquid were made: (1) interaction of the liquid with the flow instability and (2) increase of the acoustical damping in the ducts in presence of liquid.The effect of liquid on damping was measured with a dedicated test setup designed to have a stratified flow. It was found that the liquid always increases the acoustical damping, mainly due to the reduction of the effective cross section by the liquid, and because of the increased turbulent friction at the interface between gas and liquid.

The main objective of this Master´s thesis is the appropriate calculation proposal of pressure and discharge conditions in extensive ducts in unsteady flow. The calculation proposal was aimed at the conenction of two commercial programmes. Exacly the programme Ansis Fluent and Matlab, which deals with the connection of onedimensional (1D) calculation in Matlab and multidimensional (2D) calculation in Ansys Fluent programme. This Mastr’s thesis also deals with creation of the independent 1D model (Matlab, method of characteristic) and independent 2D model flow (Ansys Fluent, Inviscid model).

The goal of this diploma thesis is to clarify possibilities of usage of acoustic emission as a hydraulic machinery diagnostics tool. Especially for exposing presence of ruptures or cracks in the parts of machine, assuming changes in acoustic exposure of the part during operation. This clarification is based on series of simple measured experiments, which consist of monitoring the bolt placed in fluid stream inside of a pipe. This bolt was preloaded against inner wall of pipe by appropriate tightening torque. This preload is supposed to simulate effects of the size of rupture. High preload simulates small rupture or none in object and respectively small preload is supposed to simulate big rupture. A group of pressure sensors and accelerometers measures experiments and their evaluations are processed by script created in software MATLAB. Outputs of this script are charts with effective values of respective sensors from the entire record split into individual frequency spectrums. These charts compare spectrums of each configuration to judge effects of parameters changes.