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Flow and heat transfer between the rear side of a turbocharger turbine wheel and the bearing housing
Kalugina, Marina ; Novotný, Pavel (referee) ; Vacula, Jiří (advisor)
The objective of the bachelor’s thesis is to determine the heat balance at the point between the back of the turbine wheel and the bearing housing. The findings concerning the fluid flow and heat transfer in small channels of a rotor-stator system were derived from previously published works. The main focus of this study is the heat exchange between the heated air and the rotor wall. Calculations are applied to the turbine wheel of a real turbocharger to investigate convective heat flow at different local radii. Furthermore, a thermal resistance system is implemented in the stator section to explore potential methods for improving heat dissipation.
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Disc friction of centrifugal pumps
Homola, Tomáš ; Klas, Roman (referee) ; Rudolf, Pavel (advisor)
This diploma thesis discusses the issue of the fluid flow instabilities due to rotating discs. It also deals with the calculation of axial force in centrifugal pumps and pressure distribution on cover and support disc of the impeller. Computational simulation of rotating disc is presented with the aim of capturing flow instabilities. Next computational simulation focuses on modelling a gap between the support disc (rotor) and the stator part of the pump for three different geometries, where axial force, pressure distribution on the support disc and loss torque are calculated for each of three models. Obtained results are then compared with the experiment in the conclusion
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Disc friction of centrifugal pumps
Homola, Tomáš ; Klas, Roman (referee) ; Rudolf, Pavel (advisor)
This diploma thesis discusses the issue of the fluid flow instabilities due to rotating discs. It also deals with the calculation of axial force in centrifugal pumps and pressure distribution on cover and support disc of the impeller. Computational simulation of rotating disc is presented with the aim of capturing flow instabilities. Next computational simulation focuses on modelling a gap between the support disc (rotor) and the stator part of the pump for three different geometries, where axial force, pressure distribution on the support disc and loss torque are calculated for each of three models. Obtained results are then compared with the experiment in the conclusion
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ELECTROCHEMICAL DETECTOR WITH ELECTRODES ARRAY AND ROTATING DISK
SAJDLOVÁ, Zuzana
The thesis deals with the testing and optimization of hydrodynamic conditions of the electrochemical detector, which consists of a flow cell containing the electrochemical sensor with an array of electrodes. The flow cell includes a rotating disc-shaped component, which allows radial flow of analytes along the sensor electrodes. This principle imitates the rotating disk electrode, with the difference that here the electrodes are immobile. Hydrodynamic phenomena in this case are similar to RDE. Therefore, the theoretical part of my work deals with hydrodynamics and mass transfer for the well-described case of rotating disk electrode. It was found that in the current set-up under certain conditions, an analyte flowed back from the output cell channel to the sensor, even at the laminar flow. This causes a nonlinear response of the electrodes and their low reproducibility. The solution is to reduce the distance between the rotation component and the electrodes surface and reduce flow speed of analyzed liquid towards the sensor. A novel type of sensor with annular electrodes was designed and tested. It showed four times higher conversion rate of the analyte compared with the originally used AC9 electrochemical sensor having electrodes in the form of full circles lying on a circumference of a common circle. Based on calculations, conversion of the analyte on the plane electrode can be increased up to 100% when using this annular sensor, adjusting flow cell and reducing of the input flow rate. The detector was connected to the liquid chromatograph and its function was tested on two substances - ascorbic acid and dopamine. For the current detector these parameters were set: dynamic range, linearity, noise, detection limit, time constant and the temperature range at which the detector can be operated.
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