Number of found documents: 2932
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Measurements on KR-D-2 Blade Cascade
Šimurda, David; Luxa, Martin; Radnic, Tomáš; Hála, Jindřich
2019 - English
This report contains results and evaluation of aerodynamic measurements conducted on second variant of transonic compressor blade cascade. Keywords: transonic compressor blade; aerodynamic measurements; axial compressor Available at various institutes of the ASCR
Measurements on KR-D-2 Blade Cascade

This report contains results and evaluation of aerodynamic measurements conducted on second variant of transonic compressor blade cascade.

Šimurda, David; Luxa, Martin; Radnic, Tomáš; Hála, Jindřich
Ústav termomechaniky, 2019

Report on the reference densities of water and air employed for the adjustment of vibrating tube density meter
Vinš, Václav; Prokopová, Olga
2019 - English
Zpráva představuje souhrn několika modelů pro určení referenčních hustot čisté vody a vlhkého vzduchu při atmosférickém tlaku, které jsou potřebné k teplotní kalibraci hustoměru s vibrační trubicí Anton Paar DMA 5000 M. Při nastavení přístroje využívaného v Laboratoři termofyzikálních vlastností vzešla řada technických otázek ohledně kalibrace přístroje. Tato zpráva slouží zejména jako podklad k diskuzi se zástupci společnosti Anton Paar. S použitím softwaru pro technické výpočty Matlab byly vytvořeny programy pro výpočet hustoty vody pomocí stavové rovnice IAPWS-95 od Wagnera a Pruße (2002), CIPM standardu od Tanaky a kol. (2001) a vztahu od Spiewecka a Bettina (1992). Pro vlhký vzduch byl sestaven model na základě IAPWS Guideline G8-10 (2010) založeném na stavové rovnici pro suchý vzduch od Lemmona a kol. (2000) a stavové rovnici pro vodu IAPWS-95. Výsledky byly porovnány s CIPM standardem od Picarda a kol. (2008) a zjednodušeným vztahem od Spiewecka a Bettina (1992). V závěrečné části jsou prezentována data naměřená v Laboratoři termofyzikálních vlastností pro čistou vodu v teplotním rozsahu 2 až 50 °C pro různá nastavení referenčních vztahů pro hustoty vody a vlhkého vzduchu použité při kalibraci přístroje.\n Available at various institutes of the ASCR
Report on the reference densities of water and air employed for the adjustment of vibrating tube density meter

Zpráva představuje souhrn několika modelů pro určení referenčních hustot čisté vody a vlhkého vzduchu při atmosférickém tlaku, které jsou potřebné k teplotní kalibraci hustoměru s vibrační trubicí ...

Vinš, Václav; Prokopová, Olga
Ústav termomechaniky, 2019

Influence of tissue changes in superficial lamina propria on production of Czech vowels
Hájek, P.; Švancara, P.; Horáček, Jaromír; Švec, J.
2019 - English
Superficial lamina propria (SLP) is a water-like vocal fold (VF) layer located directly under overlying epithelium. Its material properties affect VF motion and thus resulting spectrum of produced sound. Influence of stiffness and damping of the SLP on sound spectrum of Czech vowels is examined using a two-dimensional (2D) finite element (FE) model of a human phonation system. The model consists of the VF (structure model) connected with an idealized trachea and vocal tract (VT) (fluid models). Five VTs for all Czech vowels [a:], [e:], [i:], [o:] and [u:] were used and their geometry were based on MRI data. Fluid flow in the trachea and VT was modelled by unsteady viscous compressible Navier-Stokes equations. Such a formulation enabled numerical simulation of a fluid-structure-acoustic interaction (FSAI). Self-sustained oscillations of the VF were described by a momentum equation including large deformations and a homogeneous linear elastic model of material was used. Fluid and structure solvers exchange displacements and boundary forces in each iteration. During closed phase VFs are in contact and fluid flow is separated. We can observe that both the damping and the stiffness of the SLP substantially influence the amplitude and frequency of VFs vibration as well as the open time of the glottis.\n Keywords: simulation of phonation; fluid-structure-acoustic interaction; czech vowels; finite element method; biomechanics of voice Available at various institutes of the ASCR
Influence of tissue changes in superficial lamina propria on production of Czech vowels

Superficial lamina propria (SLP) is a water-like vocal fold (VF) layer located directly under overlying epithelium. Its material properties affect VF motion and thus resulting spectrum of produced ...

Hájek, P.; Švancara, P.; Horáček, Jaromír; Švec, J.
Ústav termomechaniky, 2019

Experimental and computer modelling study of glottal closing velocity during phonation
Horáček, Jaromír; Radolf, Vojtěch; Bula, Vítězslav; Šidlof, P.; Geneid, A.; Laukkanen, A. M.
2019 - English
This preliminary study shows that the impact stress between the colliding vocal folds during phonation should not be evaluated from the maximum velocity of the glottal closing because the velocity of the closing diminishes just before the glottal closure. This phenomenon, which can be caused by a pressure cushion effect in the fast narrowing glottal gap, is demonstrated with measurements from high speed camera images recorded from human and on a physical laboratory model for vowel [u:] phonation and on a three-mass computer model employing a Hertz model of impact force. For a more detailed future study of this phenomenon a faster camera has to be used. \n Keywords: impact stress; maximum glottal area delination rate (MADR); High speed imaging Available at various institutes of the ASCR
Experimental and computer modelling study of glottal closing velocity during phonation

This preliminary study shows that the impact stress between the colliding vocal folds during phonation should not be evaluated from the maximum velocity of the glottal closing because the velocity of ...

Horáček, Jaromír; Radolf, Vojtěch; Bula, Vítězslav; Šidlof, P.; Geneid, A.; Laukkanen, A. M.
Ústav termomechaniky, 2019

Simulation of Supersonic Flow Through the Tip-Section Turbine Blade Cascade with a Flat Profile
Musil, Josef; Příhoda, Jaromír; Fürst, J.
2019 - English
The contribution presents results of the numerical simulation of 2D compressible flow through the tip-section turbine blade cascade with a flat profile and the supersonic inlet. The simulation was carried out by the OpenFOAM code using the Favre-averaged NavierStokes equations completed by the two-equation SST turbulence model and the γ-Reθ bypass transition model. Predictions carried out for nominal conditions were focused particularly on the relation between the inlet flow angle and the inlet Mach number. Further, the effect of the shock-wave/boundary layer interaction on the skin friction coefficient was investigated. Numerical results were compared with experimental data. Keywords: supersonic tip-section blade cascade; CFD; transition modelling Available at various institutes of the ASCR
Simulation of Supersonic Flow Through the Tip-Section Turbine Blade Cascade with a Flat Profile

The contribution presents results of the numerical simulation of 2D compressible flow through the tip-section turbine blade cascade with a flat profile and the supersonic inlet. The simulation was ...

Musil, Josef; Příhoda, Jaromír; Fürst, J.
Ústav termomechaniky, 2019

Finite element modeling of the signal propagation in a thin tube and comparison with experimental data
Kruisová, Alena; Kolman, Radek; Trnka, Jan; Mračko, Michal
2018 - English
In finite element modeling of wave propagation problems, both the spatial and temporal discretization lead to dispersion errors. It means that the phase velocity of propagated wave is related to its frequency. In framework of temporal-spatial dispersion analysis, the time step size for implicit time integration method based on the Newmark method is proposed for linear and quadratic serendipity plane finite elements. In this paper, we verify the theoretical dispersion analysis by elastic wave propagation in thin tube, where experimental results are known. Such time step size was used in finite element modeling of the stress wave propagating in this thin steel tube, the results of simulations were compared with experimental results. Keywords: wave propagation; finite element method; dispersion errors Available at various institutes of the ASCR
Finite element modeling of the signal propagation in a thin tube and comparison with experimental data

In finite element modeling of wave propagation problems, both the spatial and temporal discretization lead to dispersion errors. It means that the phase velocity of propagated wave is related to its ...

Kruisová, Alena; Kolman, Radek; Trnka, Jan; Mračko, Michal
Ústav termomechaniky, 2018

Experimental investigation of fault tolerant converter connected to unbalanced grid
Valouch, Viktor; Šimek, Petr; Škramlík, Jiří
2018 - English
A model of the three-phase voltage converter for simulation of its modes of operation in standard as wellas fault states is presented. The presented model can be used to simulate steady-states and also transients at dc and ac side of the grid-connected converter. Based on simulation, an algorithm was designed to identify and localize a fault in some phase of the three-phase converter. Rules how to modify hardware, and control and modulation strategies to hold the converter in operation after the fault are presented and tested. the algorithm was experimentally verified. Keywords: grid-connected converter; fault identification and localization; reconfiguration Available at various institutes of the ASCR
Experimental investigation of fault tolerant converter connected to unbalanced grid

A model of the three-phase voltage converter for simulation of its modes of operation in standard as wellas fault states is presented. The presented model can be used to simulate steady-states and ...

Valouch, Viktor; Šimek, Petr; Škramlík, Jiří
Ústav termomechaniky, 2018

Influence of excitation frequency and pulse width on blade vibration
Voronova, Evgeniya; Maturkanič, Dušan
2018 - English
The paper describes results of measuring of blade vibration characteristics excitation by one electromagnet at harmonic regime.The measurements were performed in the laboratory of rotational laser vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.\n Keywords: vibration; blade; laser; turbine Available at various institutes of the ASCR
Influence of excitation frequency and pulse width on blade vibration

The paper describes results of measuring of blade vibration characteristics excitation by one electromagnet at harmonic regime.The measurements were performed in the laboratory of rotational laser ...

Voronova, Evgeniya; Maturkanič, Dušan
Ústav termomechaniky, 2018

EXPERIMENTAL ANALYSIS OF BLADED WHEEL MODEL WITH TIE-BOSS COUPLINGS – STEADY AND ROTATIONAL STATES
Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Cibulka, Jan
2018 - English
Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of thenumerical FE model. The pre-stresses in contacts were set and evaluated indirectly by the magnetic torque sensor. Then dynamical tests of bladed wheel under revolutions were performed. The\nelectromagnetic synchronized pulses were used for excitation of forced vibration of the wheel. The Campbell diagram of the wheel with prestressedcontacts was created from the measurement under revolutions. From the attenuation of resonant vibration of the wheel the dampingwas evaluated. Keywords: turbine blade; coupling; dry-friction Available at various institutes of the ASCR
EXPERIMENTAL ANALYSIS OF BLADED WHEEL MODEL WITH TIE-BOSS COUPLINGS – STEADY AND ROTATIONAL STATES

Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of thenumerical FE model. The pre-stresses in contacts were set and evaluated ...

Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Cibulka, Jan
Ústav termomechaniky, 2018

Nonlinear ultrasonic porosimetry of 3D printed metallic parts
Převorovský, Zdeněk; Krofta, Josef; Kober, Jan; Kirschner, A.
2018 - English
Additive manufacturing process optimization requires a feedback from nondestructive testing (NDT) and evaluation. In this contribution are discussed NDT results obtained by nonlinear elastic wave spectroscopy methods to classify presence of defects in Ti-6Al-4V prismatic samples fabricated by electron beam printer. Quantitative calibration of porosity was realized by metallography. The best porosity classification results were obtained by nonlinear wave modulation spectroscopy with chirp excitation and by ESAM (Excitation Symmetry Analysis). Keywords: 3D printing of metals; nonlinear ultrasonics; porosity measurement Available at various institutes of the ASCR
Nonlinear ultrasonic porosimetry of 3D printed metallic parts

Additive manufacturing process optimization requires a feedback from nondestructive testing (NDT) and evaluation. In this contribution are discussed NDT results obtained by nonlinear elastic wave ...

Převorovský, Zdeněk; Krofta, Josef; Kober, Jan; Kirschner, A.
Ústav termomechaniky, 2018

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