Number of found documents: 3114
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Vysokonapěťový pulzní zdroj a řídící jednotka
Gruber, Jan; Janovec, Jiří; Šonský, Jiří; Němec, Tomáš
2022 - Czech
Zpráva obsahuje popis sestavy vysokonapěťového pulzního zdroje (PPSU) a řídící jednotky (SPCU), které jsou využívány v kombinaci s výbojovou komorou a párem elektrod k aerosolové syntéze nanomateriálů. Uvedena jsou schémata zapojení, seznam elektronických i mechanických součástek, jakožto i popis konektorů a zřetězeného propojení více soustav. Zpráva rovněž obsahuje informace o referenčních parametrech výbojů a popis komunikačního protokolu včetně nastavitelných proměnných. The report contains description of Pulsed Power Source Unit (PPSU) and Spark Control Unit (SPCU), which are utilized in combination with Spark Discharge Chamber and pair of electrodes for aerosol synthesis of nanomaterials. The report includes electronic schematics, list of components, description of connectors and way to chain-link and operate more sets of units. The report also includes information about discharge reference parameters and description of communication protocol and its variables. Keywords: electrotechnics; high-voltage; power transformation; pulse generators Available at various institutes of the ASCR
Vysokonapěťový pulzní zdroj a řídící jednotka

Zpráva obsahuje popis sestavy vysokonapěťového pulzního zdroje (PPSU) a řídící jednotky (SPCU), které jsou využívány v kombinaci s výbojovou komorou a párem elektrod k aerosolové syntéze ...

Gruber, Jan; Janovec, Jiří; Šonský, Jiří; Němec, Tomáš
Ústav termomechaniky, 2022

Vibration mode shape extraction of bladed disk
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Maturkanič, Dušan; Hodboď, Robert
2022 - English
This research paper deals with the experimental protocol followed to visualize the vibration mode shape of an aero-engine bladed disk. This study is based on a comparison between the numerical results obtained through Finite element methods (FEM) using ANSYS software and experimentally using the laser Doppler vibrometer. Therefore the bladed disk was transformed into a 3D virtual environment and structural analysis was performed. The results demonstrate a match between the numerical and the experimental one, this match offers the possibility for using the model for future studies. Keywords: blade disk; mode shapes; laser doppler vibrometer Available at various institutes of the ASCR
Vibration mode shape extraction of bladed disk

This research paper deals with the experimental protocol followed to visualize the vibration mode shape of an aero-engine bladed disk. This study is based on a comparison between the numerical results ...

Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Maturkanič, Dušan; Hodboď, Robert
Ústav termomechaniky, 2022

Approaches to dynamical analysis of rotors with parameters of uncertain magnitudes
Zapoměl, Jaroslav; Kozánek, Jan; Košina, Jan; Cibulka, Jan
2022 - English
In many cases, the rotor configuration or loading characteristics are described by parameters of uncertain magnitude. Several procedures were developed to analyse such systems. This paper deals with the approach based on application of the fuzzy numbers. The investigated mechanical system is a rotor supported by hydrodynamic bearings. The parameters of its loading have uncertain values. Keywords: rotors; uncertain parameters; fuzzy numbers approach Available at various institutes of the ASCR
Approaches to dynamical analysis of rotors with parameters of uncertain magnitudes

In many cases, the rotor configuration or loading characteristics are described by parameters of uncertain magnitude. Several procedures were developed to analyse such systems. This paper deals with ...

Zapoměl, Jaroslav; Kozánek, Jan; Košina, Jan; Cibulka, Jan
Ústav termomechaniky, 2022

Turbine blade linkages in reduced modal synthesis model
Pešek, Luděk; Šnábl, Pavel
2022 - English
The paper is the first stage of our modelling turbine blade linkages in reduced modal synthesis model. The modal synthesis method is used for the dynamic behaviour studies of turbine bladed wheels with frictional inter-blade linkages and in case of the microslips the stiffening effect of the linkages play an important role in wheel dynamics. The paper presents the first results of modal analysis of the wheel when springs were used to substitute the linkages in the modal synthesis model. Keywords: bladed wheel; reduced model; tie-boss; shroud; stiffening Available at various institutes of the ASCR
Turbine blade linkages in reduced modal synthesis model

The paper is the first stage of our modelling turbine blade linkages in reduced modal synthesis model. The modal synthesis method is used for the dynamic behaviour studies of turbine bladed wheels ...

Pešek, Luděk; Šnábl, Pavel
Ústav termomechaniky, 2022

Analytické postupy řešení kmitání lopatek pro použití u metody Blade Tip Timing - teoretický popis metody
Maturkanič, Dušan; Procházka, Pavel; Mekhalfia, Mohammed Lamine
2022 - Czech
Práce je zaměřena na analytický přístup k řešení problematiky kmitání lopatek turbíny a kompresoru metodou Blade Tip Timing. Ve zprávě je navržena nová metoda, pro niž byly stanoveny podmínky řešení. Ověření metody bylo provedeno prostřednictvím simulace, kdy byla vyhodnocena spolehlivost, u které byla zadávána správná vstupní data a výpočet probíhal po dostatečně dlouhou dobu, zatímco na základě záměrně zkreslených vstupních dat byla ověřována její přesnost. Součástí zprávy je také vazba výsledků výpočtu frekvence kolísajících otáček, získaných deterministickou metodou, která byla popsána v předchozích pracích, a s nimiž lze dosáhnout přesnějšího výpočtu frekvence a amplitudy kmitání lopatek v reálných podmínkách.\n\n The report focuses on an analytical approach to solving the problem of turbine and compressor blade vibration using the Blade Tip Timing method. The report contains a description of the new method with defined solution requirements. Verification of the method was performed by simulation, where the correct input data was used in the analysis of the reliability of the method when the calculation was repeated at a sufficiently large number of revolutions, while in the accuracy analysis, intentionally distorted input data was used. The report also includes connection to the results of frequency and amplitude calculation for fluctuating speeds obtained by the deterministic method, which was described in previous works aimed at achieving a precise calculation of the frequency and amplitude of blade vibration in real conditions. Keywords: vibration; blade; analytical method; frequency; amplitude; turbine; compressor; sensor Available at various institutes of the ASCR
Analytické postupy řešení kmitání lopatek pro použití u metody Blade Tip Timing - teoretický popis metody

Práce je zaměřena na analytický přístup k řešení problematiky kmitání lopatek turbíny a kompresoru metodou Blade Tip Timing. Ve zprávě je navržena nová metoda, pro niž byly stanoveny podmínky řešení. ...

Maturkanič, Dušan; Procházka, Pavel; Mekhalfia, Mohammed Lamine
Ústav termomechaniky, 2022

Effect of oscillating blade on tonal noise of blade cascade with five NACA 0010 profiles
Šnábl, Pavel; Pešek, Luděk; Radolf, Vojtěch; Antoš, Pavel; Procházka, Pavel; Prasad, Chandra Shekhar
2022 - English
The airfoil tonal noise is a well known phenomenon which appears on single airfoils in moderate Reynolds numbers at low angles of attack. It can appear on small aircrafts, fans, wind turbines etc. In thispaper, it was observed on a blade cascade consisting of five NACA 0010 profiles placed in a closed rectangularchannel with hard walls when for given conditions, i.e. flow velocity and angle of attack, the cascade tunes to one single frequency. During the middle blade oscillation, the single tone splits up to several tones with lower intensity modulated by the excitation frequency. Thus, the oscillation of one blade suppresses the tonal noise generation in the cascade. Keywords: aeroacoustics; blade cascade; trailing edge noise; tonal noise; NACA 0010 Available in digital repository of the ASCR
Effect of oscillating blade on tonal noise of blade cascade with five NACA 0010 profiles

The airfoil tonal noise is a well known phenomenon which appears on single airfoils in moderate Reynolds numbers at low angles of attack. It can appear on small aircrafts, fans, wind turbines etc. In ...

Šnábl, Pavel; Pešek, Luděk; Radolf, Vojtěch; Antoš, Pavel; Procházka, Pavel; Prasad, Chandra Shekhar
Ústav termomechaniky, 2022

Identification of the blade tip possition and measurement techniques using the BTT method
Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Mekhalfia, Mohammed Lamine
2022 - English
This paper describes the existing practice in identifying and defining the position of the blade tips and the relevant technique for measuring their vibration during rotation. In connection with the effort to precisely define the position of the vibrating blade, the paper also analysed the possibilities of unambiguous determination of its position. This work creates a parallel branch to signal processing in the complex system of precision measurement and analysis of blade vibration, which was mentioned in previous papers. Keywords: turbine blade; vibration; precision method; modification; harmonic function Available at various institutes of the ASCR
Identification of the blade tip possition and measurement techniques using the BTT method

This paper describes the existing practice in identifying and defining the position of the blade tips and the relevant technique for measuring their vibration during rotation. In connection with the ...

Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Mekhalfia, Mohammed Lamine
Ústav termomechaniky, 2022

Measurement and analysis of vibration and acoustic emissions of a railway wheel under defined dynamic excitations
Pešek, Luděk; Prasad, Chandra Shekhar; Šnábl, Pavel
2022 - English
The paper deals with experimental vibro-acoustics of railway wheel. The methodology for evaluation of effect of vibrational plate dampers was elaborated. The four variants of the wheel was measured and analyse to achieve the optimal solution of the dampers. Keywords: vibro-acoustics; railway wheel; dampers; noise Available at various institutes of the ASCR
Measurement and analysis of vibration and acoustic emissions of a railway wheel under defined dynamic excitations

The paper deals with experimental vibro-acoustics of railway wheel. The methodology for evaluation of effect of vibrational plate dampers was elaborated. The four variants of the wheel was measured ...

Pešek, Luděk; Prasad, Chandra Shekhar; Šnábl, Pavel
Ústav termomechaniky, 2022

Shifted proper orthogonal decomposition and artificial neural networks for time-continuous reduced order models of transport-dominated systems
Kovárnová, A.; Krah, P.; Reiss, J.; Isoz, Martin
2022 - English
Transport-dominated systems are pervasive in both industrial and scientific applications. However, they provide a challenge for common mode-based model order reduction (MOR) approaches, as they often require a large number of linear modes to obtain a sufficiently accurate reduced order model (ROM). In this work, we utilize the shifted proper orthogonal decomposition (sPOD), a methodology tailored for MOR of transport-dominated systems, and combine it with an interpolation based on artificial neural networks (ANN) to obtain a time-continuous ROM usable in engineering practice. The resulting MOR framework is purely data-driven, i.e., it does not require any information on the full order model (FOM) structure, which extends its applicability. On the other hand, compared to the standard projection-based approaches to MOR, the dimensionality reduction utilizing sPOD and ANN is significantly more computationally expensive since it requires a solution of high-dimensional optimization problems. Keywords: model order reduction; shifted POD; CFD-DEM; OpenFOAM Fulltext is available at external website.
Shifted proper orthogonal decomposition and artificial neural networks for time-continuous reduced order models of transport-dominated systems

Transport-dominated systems are pervasive in both industrial and scientific applications. However, they provide a challenge for common mode-based model order reduction (MOR) approaches, as they often ...

Kovárnová, A.; Krah, P.; Reiss, J.; Isoz, Martin
Ústav termomechaniky, 2022

Estimation of damping IN human vocal folds vibration: measurements in vivo and on model
Horáček, Jaromír; Radolf, Vojtěch; Bula, Vítězslav; Košina, Jan; Geneid, A.; Laukkanen, A. M.
2022 - English
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal folds damping is important for testing and further development of mathematical modelling of phonation. The measurements of the damping ratio, based on high-speed videolaryngoscopic registrations, were realized in vivo on a male subject and in vitro using an originally developed silicon replica of the human vocal folds. In both cases the results show remarkable decrease of vibration frequency of the vocal folds and increase of damping ratio D in the phonation offset limiting to the values D=0.12 in vivo measurement and D=0.11 in vitro measurement. The results for vocal folds’ damping are in good agreement with previous measurements performed in humans using different methods. Keywords: phonation offset; high-speed videolaryngoscopy Available at various institutes of the ASCR
Estimation of damping IN human vocal folds vibration: measurements in vivo and on model

This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal folds damping is important for testing and further ...

Horáček, Jaromír; Radolf, Vojtěch; Bula, Vítězslav; Košina, Jan; Geneid, A.; Laukkanen, A. M.
Ústav termomechaniky, 2022

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