Number of found documents: 3056
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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

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

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

Laminar-Turbulent Transition in View of Flow Separation from Isothermal and Heated Cylinder
Pech, Jan
2020 - English
This work presents insight to the laminar-turbulent transition in flow around cylinder through a numerical simulation, both in isothermal and heated case. The flow is modelled directly as a solution to the Navier-Stokes and Navier-Stokes-Fourier system. Reynolds numbers are considered in range 100-20000, ratio of cylinder-wall and upstream temperature is up to 1.5. Curves representing evolution of separation positions in time provide novel insight to vortex formation. Various regimes are recognized and some of them can be assigned to phenomena described formerly in experiment. Keywords: transition to turbulence; heated flow; cylinder flow; separation angle; Navier-Stokes- Fourier; spectral/hp element method Fulltext is available at external website.
Laminar-Turbulent Transition in View of Flow Separation from Isothermal and Heated Cylinder

This work presents insight to the laminar-turbulent transition in flow around cylinder through a numerical simulation, both in isothermal and heated case. The flow is modelled directly as a solution ...

Pech, Jan
Ústav termomechaniky, 2020

A simple algorithm for probes positioning in BTT systems
Tchawou Tchuisseu, Eder Batista; Procházka, Pavel; Maturkanič, Dušan
2020 - English
The Blade Tip Timing (BTT), a non-contact method for measuring the blade tip displacement through the time of arrival, is studied in this article. This work proposes a simple algorithm based on the minimization of the coherence and the condition number of the sensingmatrix for defining the best probe positioning in the case of synchronous and asynchronous vibrations. Keywords: BTT systems; probe positioning; condition number; coherence Available at various institutes of the ASCR
A simple algorithm for probes positioning in BTT systems

The Blade Tip Timing (BTT), a non-contact method for measuring the blade tip displacement through the time of arrival, is studied in this article. This work proposes a simple algorithm based on the ...

Tchawou Tchuisseu, Eder Batista; Procházka, Pavel; Maturkanič, Dušan
Ústav termomechaniky, 2020

Rázy v potrubí
Luxa, Martin
2020 - Czech
Zpráva se zabývá problematikou rázových vln potrubí, které vznikají při jeho náhlém uzavření. Jsou popsány tři možné teoretické přístupy k řešení a jsou uvedena i řešení praktických úloh. The report deals with shock waves in ducts, which originate as a consequence of sudden closing of quick acting valve. Three methods of solving are described. Selected actual problems of czech power plants are solved. Keywords: water hammer; hydrodynamics; shock wave; aerodynamics Available at various institutes of the ASCR
Rázy v potrubí

Zpráva se zabývá problematikou rázových vln potrubí, které vznikají při jeho náhlém uzavření. Jsou popsány tři možné teoretické přístupy k řešení a jsou uvedena i řešení praktických úloh....

Luxa, Martin
Ústav termomechaniky, 2020

Contribution to HPC FEM calculations of bladed disk dynamics with dry-friction contacts
Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
2020 - English
The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tie-bosses based on 3D finite element method with surface to surface dry-friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behaviour and damping estimation of our bladed wheel design yielded a reasonable agreement. Due to dry-friction contacts and non-linear solution of 3D FE model it, however, leads to HPC computations and long computation times. The contribution deals with description of computational strategy for damping evaluation and achieved results, too. Keywords: bladed wheel; dry-friction contacts; damping; tie-boss couplings Available at various institutes of the ASCR
Contribution to HPC FEM calculations of bladed disk dynamics with dry-friction contacts

The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with ...

Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
Ústav termomechaniky, 2020

Design of experiment for temperature dependence of rubber samples under torsional harmonic load
Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Košina, Jan; Cibulka, Jan
2020 - English
This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a scheme of temperature measurement under torsional dynamic stress. The reason for these measurements is to determine the temperature dependence and sensitivity of the parameters of the thermal outputs. Keywords: heat flow; temperature; Fourier equation Available at various institutes of the ASCR
Design of experiment for temperature dependence of rubber samples under torsional harmonic load

This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a ...

Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Košina, Jan; Cibulka, Jan
Ústav termomechaniky, 2020

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