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Rotor dynamics of asynchronous generator fast fixed with water turbine
Blažek, Petr ; Donát, Martin (referee) ; Dušek, Daniel (advisor)
This Master’s thesis deals with rotordynamics analysis of asynchronous generator rigid coupling with water turbine shaft. The purpose of this thesis was to determine influence of connection of generator with water turbine by rigid coupling to reactions in bearings. This problem was solved in two ways. The first option focused on model without influence of inaccuracies whereas there were inaccuracies included in the second option. The problem was solved by computational modeling by software Ansys.
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Numerical simulation of of human voice propagation through the vocal tract and in the space around the body
Batelka, Jiří ; Hájek, Petr (referee) ; Švancara, Pavel (advisor)
This master's thesis handles description of the source-filter theory of voice production, anatomy of larynx, possible approaches to voice production modelling and selected works using these approaches in first chapter. Brief description of selected quantities used in acoustics and model creation follows. Models of only the head and head with female and male torso are created, including mesh testing to determine suitable element size. Models created in this thesis focus on description of voice propagation primarily in front of body and on influence of torso on sound propagation. Inclusion of torso results in fluctuations in frequency domain in range from 1 000 Hz to 8 000 Hz, more pronounced near lower frquencies. In transverse plane the presence of torso manifests in lower SPL in front of mouth and higher SPL on the sides for several frequencies. Regions with decrease of SPL in front of mouth are coindicent with frequencies, where higher SPL on sides in comparision with direction in front of the mouth is evident. These observations are in agreement with other works. No significant differences were observed between models with different torsos in the transverse plane. Below the transverse plane differences between models with different torsos can be observed, for example for some frequencies decrease in SPL isn't observed in front of mouth in directivity diagrams for model with male torso.
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Simulation of Noise Emitted by a Single-stage Gearbox
Motl, Daniel ; Hadaš, Zdeněk (referee) ; Lošák, Petr (advisor)
The level of noise and vibration of gearboxes is one of the most important parameters for today´s customers. This thesis deals with mathematical acoustic behavior modelling and its contribution to the gearbox design using finite element method. The process is presented at three computations models. Two of those were validated with experimental measurement. Acoustic analysis were performed with software FFT ACTRAN.
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Reconstruction of the cable suspended footbridge in Kroměříž
Liška, Jaroslav ; Kulhavý,, Tomáš (referee) ; Klusáček, Ladislav (advisor)
The Diploma thesis deals with the reconstruction design of a footbridge in the city of Kroměříž, Czech Republic. The footbridge would serve as safe transport for pedestrians over the Morava river. The main objective of the thesis is to conceive two or three reconstruction designs. The most suitable one will be opted for and elaborated in more detail. Eventually, strengthening of the bridge by means of additional prestressing using mono-strand post-tensioning systems is picked as the best solution of the planned reconstruction. The monostrand post-tensioning system is led under the deck, the cross section being outside. External cables are anchored in concrete blocks built around existing supports. Load-generated internal forces are calculated on a spatial bar model with non-linear first-order analysis. The calculation is executed using the finite element method in the midas Civil programme. The chosen reconstruction design is then assessed against load capacity limit states, and functionality. Also, the designed reconstruction is assed for dynamic effects. Results are compared with existing structure, and verified against the real-time tensometric measurement-obtained data. Dimensions, assessment of load-bearing structure, and structural details are all made according to valid Eurocodes.
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Computational modelling of noise inside cabin of aircraft VUT 100 Cobra
Prnka, Jiří ; Houfek, Lubomír (referee) ; Švancara, Pavel (advisor)
This master’s thesis deals with the computational simulation of low-frequency noise inside the cabin of small commercial airplane VUT 100 Cobra. For this low-frequncy range deterministic methods: Final Element Method (FEM) and Boundary Element Method (BEM) are used for simulation of the dynamic behaviour of the object. FEM has been used to compute eigenmodes and eigenfrequences of the structure of the aeroplane cabin and of the acoustic space inside cabin. Then response to harmonic excitation of engine represented by unit forces in place of contact has been computed. Obtained velocities on the surface of the cabin are then used as the basis for the noise calculation inside the cabin using BEM. After that effect of some construction modifications on sound level inside cabin are evaluated by computational modelling.
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Optimisation of electric vehicles gearbox housing with focus on emitted noise
Fürich, Adam ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This thesis deals with the vibration and noise of the gearbox for an electric vehicle. The gearbox itself acts as an emitter of unwanted noise caused by vibration excitation of the internal components of the gearbox. It is therefore necessary to deal with a complex unit such as the gearbox at system level as soon as it is being designed. This can be achieved using analytical tools and software. In this thesis, in order to evaluate the validity of the designed gearbox, a procedure is developed using both technical experiment and numerical simulations. The effect of the bolt preload is not overlooked for the following computational modelling dealing with the radiated noise of the gearbox. The results obtained from the performed technical experiments were then evaluated and compared with the results of the computational models. In this way, it is possible to compare the different approaches, their limitations and weaknesses. Furthermore, the thesis deals with design modifications that are analyzed using computational modeling. The thesis is concluded with a brief description of the application of each approach and an evaluation of the gearbox design modifications.
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Compensation of Nonlinearities in AC Motor Control Algorithms
Buchta, Luděk ; Kuchař,, Martin (referee) ; Glasberger,, Tomáš (referee) ; Blaha, Petr (advisor)
Analysis of the dead-time effect and other nonlinearities of the voltage source inverter was carried out in the introduction of the doctoral thesis. Three compensation strategies for vector controlled PMSM were proposed based on the analysis. The voltage disturbance observer with cost function of current errors is based on the model of PMSM, known machine parameters and easily measurable quantities. The second observer which estimates the dq- axes currents and the value of the voltage error with one parameter only is designed based on the harmonic analysis and Kalman filter algorithm. The third method combines an adaptive approach with feedback and voltage disturbance observer that is based on the PMSM model. Furthermore, the two compensation methods for vector controlled induction motor were proposed. In the first case, the standard compensation strategy is extended by a harmonic compensator that suppresses the residual 6th harmonic component in dq- axes currents. The last strategy detects the polarity of the estimated phase currents that are obtained by the Kalman filter. All compensation strategies have been verified by MATLAB/Simulink simulations and by experiments on real drives.
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Study of Power Plant Connection to Power Network
Sýkora, Martin ; Kurfűrst, Jiří (referee) ; Paar, Martin (advisor)
It is necessary to judge the influences of producers on the electric compounds while creating electrical energy or during the regulation of those existing. These analyses are sorted out by so called studies of connectivity. These calculations analyze the degree of connection of the producer and the standby unit during a break-down. The results of this report are several recommendations for creating such unit and succeeding steps leading to secure the stability and safety of the electric compound operation. The aim of this thesis is to discuss about software for PC solutions for static and dynamic network model, to draft power outlet into a network of generating high voltage, to complete a study of connectivity with respect to all the distortion factor, as increased voltage, inrush current at startup, flicker, harmonic currents, interference ripple, contribution to short-circuit current, reactive power control options, and demands for compensation.
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