Number of found documents: 3064
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Accuracy of the analytical methods developed for blade tip-timing analysis
Maturkanič, Dušan; Procházka, Pavel; Kozánek, Jan
2021 - English
Within the research of methods for precision solution of rotor blade vibration based on the philosophy of Blade Tip-Timing at the Institute of Thermomechanics AS CR, v.v.i., the effort was concentrated on the decomposition of measured data. This paper describes the accuracy of analytical methods taking into consideration the errors of the measured sensors or the influence of the measurement conditions on the results. Keywords: harmonic function; analytical method; blade vibration; accuracy; error; distortion; frequency Available at various institutes of the ASCR
Accuracy of the analytical methods developed for blade tip-timing analysis

Within the research of methods for precision solution of rotor blade vibration based on the philosophy of Blade Tip-Timing at the Institute of Thermomechanics AS CR, v.v.i., the effort was ...

Maturkanič, Dušan; Procházka, Pavel; Kozánek, Jan
Ústav termomechaniky, 2021

Dynamics of a magnetically excited blade: theoretical and experimental analysis
Tchawou Tchuisseu, Eder Batista; Procházka, Pavel; Mekhalfia, Mohammed Lamine; Hodboď, Robert; Maturkanič, Dušan
2021 - English
This work dealt with the theoretical and experimental analysis of a static blade subjected to a magnetic excitation. The theoretical analysis combines the modeling and design of the blade via ANSYS in whih the modal analysis is done. Both methods showed qualitative agreement of the results. Keywords: turbine blade; magnetic excitation; turbo-machinery; finite element method Available at various institutes of the ASCR
Dynamics of a magnetically excited blade: theoretical and experimental analysis

This work dealt with the theoretical and experimental analysis of a static blade subjected to a magnetic excitation. The theoretical analysis combines the modeling and design of the blade via ANSYS in ...

Tchawou Tchuisseu, Eder Batista; Procházka, Pavel; Mekhalfia, Mohammed Lamine; Hodboď, Robert; Maturkanič, Dušan
Ústav termomechaniky, 2021

Nucleation criteria detection as a mean to investigate metastable state
Celný, David; Span, R.; Vrabec, J.
2021 - English
Focus is given to the core problematic, reaching the nucleation region and sample the relevant data for selected pure substance. This termodynamic condition required for nucleation are found in so called metastable region. Metastable region is found between binodal and spinodal line separating it from the stable and unstable system condition respectively.\nObtaining the data in this area proves to be an experimental challenge, therefore the data has to be gathered using other means. Proposed setup relies two part approach combining equation of state (EoS) and molecular simulation. The computational core is done with molecular dynamics tool combined with on the fly performing decision cluster criterion utilized is already available in previously published work. These cluster criteria ensure that the system is only calculated within targeted conditions and the sampled micro-states remain valid observations. To capture whole metastable region two criteria are present for both cluster and void case as illustrated below. Remaining part utilize the equation of state for the initial system condition sampling of the metastable region by calculating the stability line and predicting the instability line for the LJ fluid as show in Linhart et.al. . These thermodynamic condition probes are evaluated afterwards with the established simulation method. Intermediate result from simulations are collected in form of both Helmholtz energy temperature and density derivatives descriptors as well as time averages of system properties for fluids like LJ, Oxygen and Nitrogen. Keywords: metastable state; equation of state; molecular dynamics; cluster criterion Available at various institutes of the ASCR
Nucleation criteria detection as a mean to investigate metastable state

Focus is given to the core problematic, reaching the nucleation region and sample the relevant data for selected pure substance. This termodynamic condition required for nucleation are found in so ...

Celný, David; Span, R.; Vrabec, J.
Ústav termomechaniky, 2021

Modal analysis of a container with measuring equipment for space mission
Zolotarev, Igor; Bula, Vítězslav
2021 - English
This paper continues investigations of some measuring equipment for space mission. The frequency-modal properties a container with several slots and measured desks are studied. The natural frequencies and corresponded modes obtained using measuring methods are presented for several combinations of the container components. Keywords: modal analysis; natural frequencies; modes of vibration Available at various institutes of the ASCR
Modal analysis of a container with measuring equipment for space mission

This paper continues investigations of some measuring equipment for space mission. The frequency-modal properties a container with several slots and measured desks are studied. The natural frequencies ...

Zolotarev, Igor; Bula, Vítězslav
Ústav termomechaniky, 2021

Acoustic resonances can support self-oscillations of a dynamic system.
Horáček, Jaromír; Radolf, Vojtěch; Košina, Jan; Laukkanen, A. M.
2021 - English
Flutter instability of human vocal folds is a necessary condition for speaking, because airflow induced vibrations of the vocal folds create the voice source. The present study shows that the vocal fold self-oscillations can be strongly influenced by interaction with acoustic resonances of the human vocal tract. Keywords: biomechanics of voice; modelling of human voice Available at various institutes of the ASCR
Acoustic resonances can support self-oscillations of a dynamic system.

Flutter instability of human vocal folds is a necessary condition for speaking, because airflow induced vibrations of the vocal folds create the voice source. The present study shows that the vocal ...

Horáček, Jaromír; Radolf, Vojtěch; Košina, Jan; Laukkanen, A. M.
Ústav termomechaniky, 2021

Identification of dynamic properties of built electrodynamic shaker
Šnábl, Pavel; Kozánek, Jan; Pešek, Luděk
2021 - English
Electrodynamic shaker was built in our institute for excitation of vibrating blade in a flow field. The shaker consists of permanent magnet and voice coil, 3D printed body, core and cover, and two at suspension rings laser-cutted from Pertinax. For simulation purposes of the whole system, identfication of shaker dynamic parameters was needed. Several identification methods in time or frequency domain were used, and it was shown that the shaker model must contain nonlinear stiffness in order to describe the real system more accurately. Keywords: identification; dynamics; shaker Available at various institutes of the ASCR
Identification of dynamic properties of built electrodynamic shaker

Electrodynamic shaker was built in our institute for excitation of vibrating blade in a flow field. The shaker consists of permanent magnet and voice coil, 3D printed body, core and cover, and two at ...

Šnábl, Pavel; Kozánek, Jan; Pešek, Luděk
Ústav termomechaniky, 2021

Measurement of friction coefficient between damping wire and groove
Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav; Běhálek, V.; Boháč, T.; Tašek, H.
2021 - English
Damping wire is being used on railway wheels for noise suppression. It is inserted into a groove of the wheel and dry friction damping reduces vibrations and thus the noise transmitted by the wheel. For increase of durability of the wire, surface treatment of the groove and the ring must be applied to prevent corrosion. Three combinations of diferent surface treatments were studied during reciprocating motion in a set of measurements with diferent frequencies and normal forces to evaluate friction coeficient. Then, those measurements were repeated after a long-time run to evaluate the change of friction coeficient after the wear of the surfaces. Keywords: tribology; friction; damping wire Available at various institutes of the ASCR
Measurement of friction coefficient between damping wire and groove

Damping wire is being used on railway wheels for noise suppression. It is inserted into a groove of the wheel and dry friction damping reduces vibrations and thus the noise transmitted by the wheel. ...

Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav; Běhálek, V.; Boháč, T.; Tašek, H.
Ústav termomechaniky, 2021

Numerical estimation of blade displacement due to air excitation
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Hodboď, Robert; Maturkanič, Dušan
2021 - English
For the last few years, vibration measurement has taken an intense interest from research activities. For this reason, this article considers, besides vibration measurements, the impact of air forced excitation on blade motion, displacement and vibration through both simulation analysis and The Transformation of mathematical analysis that explain the interaction between fluid (Air) and the structure (Blade) into numerical setup along with FEM analysis through ANSYS Software. 3D Blade was created to meet the same characteristics of the real blade to enable real environment criteria for the simulation. For the last few years, vibration measurement has taken an intense interest from research activities. For this reason, this article considers, besides vibration measurements, the impact of air forced excitation on blade motion, displacement and vibration through both simulation analysis and The Transformation of mathematical analysis that explain the interaction between fluid (Air) and the structure (Blade) into numerical setup along with FEM analysis through ANSYS Software. 3D Blade was created to meet the same characteristics of the real blade to enable real environment criteria for the simulation. Keywords: displacement; Fluid structure interaction (FSI); air; blade Available at various institutes of the ASCR
Numerical estimation of blade displacement due to air excitation

For the last few years, vibration measurement has taken an intense interest from research activities. For this reason, this article considers, besides vibration measurements, the impact of air forced ...

Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Hodboď, Robert; Maturkanič, Dušan
Ústav termomechaniky, 2021

Study of aeroacoustics noise of high-speed aircraft propellers and mitigation of the cause
Prasad, Chandra Shekhar
2021 - English
The project deals with the study of aeroacoustics noise generated by high-speed turboprop propellers and methods to minimize its causes. A reduced order flow solver with aeroacaustic noise capturing characteristics is developed for fast numerical analysis purpose. The acoustical performance will be also studied using flow visualization using article image velocimetry under rotation and acoustics noise will be measured by microphones for both conventional as well as unconventional propeller designs at diferent rotational speeds. Keywords: aeroacoustics; aircraft propellers; tip-vortex interaction; low noise propeller; ROM-CFD/CAA Available at various institutes of the ASCR
Study of aeroacoustics noise of high-speed aircraft propellers and mitigation of the cause

The project deals with the study of aeroacoustics noise generated by high-speed turboprop propellers and methods to minimize its causes. A reduced order flow solver with aeroacaustic noise capturing ...

Prasad, Chandra Shekhar
Ústav termomechaniky, 2021

The new HPC results of 3D FE modelling of dry-friction damping at tie-boss couplings of bladed wheel - 6nd resonant mode
Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
2021 - English
The paper is a direct continuation of our study published in the last colloquium DYMAMESI. This paper deals with the new results of dry-friction damping calculation of the bladed wheel with tie-boss couplings vibrating at a higher resonant mode, i.e. mode with 6 nodal diameters (ND). The numerical solution of the wheel based on 3D finite element method with surface-to-surface dry friction contact model is applied. Due to dry friction contacts and non-linear solution, it leads to HPC computations and long computation times. Therefore, the earlier proposed computational strategy for damping evaluation where the resonant attenuation is computed directly from the defined resonant initial conditions given by the 6ND mode is used. Comparison of experimental and numerical results of dynamical behaviour of the bladed wheel yields a reasonable agreement for the studied vibration mode. Keywords: bladed wheel; dry-friction contacts; damping; tie-boss couplings Available at various institutes of the ASCR
The new HPC results of 3D FE modelling of dry-friction damping at tie-boss couplings of bladed wheel - 6nd resonant mode

The paper is a direct continuation of our study published in the last colloquium DYMAMESI. This paper deals with the new results of dry-friction damping calculation of the bladed wheel with tie-boss ...

Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
Ústav termomechaniky, 2021

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