Number of found documents: 3220
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Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor
Idžakovičová, Kristýna; Haidl, J.; Gebouský, O.; Isoz, Martin
2023 - English
The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the central vortex creation. However, particular industries, such as biotechnology, have an increased need for a sterile environment that often results in the usage of atypical stirred vessel configurations. An example of a commonly equipped atypical stirred vessel is an unbaffled stirred tank with an eccentric magnetically driven impeller. However, there is only a little knowledge about the mixing characteristics of such designs. In this work, we list experimental results for both the standard and atypical stirred vessel configurations. Furthermore, we present a CFD model of the atypical configuration. The model is used to calculate its mixing characteristics that are subsequently compared against our experimental results. It is shown that for the liquid height (H) to the vessel diameter (T) ratio H/T ≲ 1.2, the characteristics of both the standard and atypical designs coincide. For higher liquid heights (i) the characteristics of the atypical design decrease dramatically, and (ii) the characteristics estimates based on approaches developed for the standard configuration become unreliable. Keywords: stirred vessel; eccentric impeller; unbaffled tank; CFD; OpenFOAM; experiment Fulltext is available at external website.
Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor

The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the ...

Idžakovičová, Kristýna; Haidl, J.; Gebouský, O.; Isoz, Martin
Ústav termomechaniky, 2023

Autonomous vehicles lane detection using particle filters
Věchet, Stanislav; Krejsa, Jiří; Chen, K.S.
2022 - English
Lane detection belongs among many others crucial tasks which an autonomous vehicles traveling in urban roads need to take care of. We present a lane detection method which uses particle filters combined with visual information from onboard camera to control the vehicles direction. Our initial experiments shows promising results as applied and tested in urban roads with focus on real-time data processing. Keywords: mobile robot; signal processing; measurement Available at various institutes of the ASCR
Autonomous vehicles lane detection using particle filters

Lane detection belongs among many others crucial tasks which an autonomous vehicles traveling in urban roads need to take care of. We present a lane detection method which uses particle filters ...

Věchet, Stanislav; Krejsa, Jiří; Chen, K.S.
Ústav termomechaniky, 2022

Mobile Robot in the Elevator: What Floor Am i On?
Krejsa, Jiří; Věchet, Stanislav; Chen, K.S.; Havelka, M.; Černil, M.
2022 - English
Wheeled mobile robots in multiple stories buildings have to use elevator to access arbitrary floor of the building. To do so, the control system must be able to detect and access elevator controls and also determine on which floor the elevator stopped. The paper deals with the latter problem, using the fusion of relative floor change detected by onboard accelerometer and absolute floor number detected by the processing of elevator information screen panel image acquired by onboard camera. Bayesian filter is used for data fusion and convolution neural network for image processing. Field tests resulted in 97% correct detection. Keywords: mobile robot; elevator floor determination; Bayesian filtering Available at various institutes of the ASCR
Mobile Robot in the Elevator: What Floor Am i On?

Wheeled mobile robots in multiple stories buildings have to use elevator to access arbitrary floor of the building. To do so, the control system must be able to detect and access elevator controls and ...

Krejsa, Jiří; Věchet, Stanislav; Chen, K.S.; Havelka, M.; Černil, M.
Ústav termomechaniky, 2022

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

Annular impinging jets and an active control of hysteretic effects
Devani, Yogendrasasidhar; Antošová, Zuzana; Trávníček, Zdeněk
2022 - English
An annular air jet with and without flow control was studied experimentally using flow visualization and measurements of the wall pressure and flow velocity by the Pitot and Prandtl probes and the hot-wire anemometer. To investigate flow control swirling effects, eight synthetic jets were generated from the annular nozzle center body.The experiments cover Reynolds numbers 4000–10000 (evaluated from the outer exit diameter of the annular nozzle). For Re<9000, the bistability and hysteresis were identified and two different flow field patterns (A and B) were found under the same boundary conditions. For A pattern, a small recirculation area (bubble) of separated flow is attached to the nozzle center body. For B pattern, a large recirculation area of separated flow bridges entire nozzle-to-wall distance. For higher Re > 9000, the bistability and hysteresis were not found.Flow control swirling effects causes suppression of the hysteresis. Moreover, weak flow control causes that the entire annular jet is forced into a precessing motion. Keywords: annular jet; impinging jet; bistability; hysteresis Available at various institutes of the ASCR
Annular impinging jets and an active control of hysteretic effects

An annular air jet with and without flow control was studied experimentally using flow visualization and measurements of the wall pressure and flow velocity by the Pitot and Prandtl probes and the ...

Devani, Yogendrasasidhar; Antošová, Zuzana; Trávníček, Zdeněk
Ústav termomechaniky, 2022

Aeroacoustic Noise Source Investigation in the Case of the Blade Cascade
Procházka, Pavel P.; Antoš, Pavel; Šnábl, Pavel
2022 - English
The blade cascade consisted of five NACA 0010 profiles is examined in the framework of project dealing with nonlinear dynamic phenomenon related to stall flutter of flexible profiles with pitch degree of freedom in subsonic flow. Various angles of attack (AoA) of the cascade generates different (broadband) aeroacoustic noise. The goal of this article is to describe the existence of possible noise sources using two experimental methods – Particle Image velocimetry (PIV) and hot-wire (HW) anemometry. Keywords: blade cascade; time-resolved PIV; HW anemometry; FFT Available at various institutes of the ASCR
Aeroacoustic Noise Source Investigation in the Case of the Blade Cascade

The blade cascade consisted of five NACA 0010 profiles is examined in the framework of project dealing with nonlinear dynamic phenomenon related to stall flutter of flexible profiles with pitch ...

Procházka, Pavel P.; Antoš, Pavel; Šnábl, Pavel
Ústav termomechaniky, 2022

Temporal, Spatial, and Spatio-temporal correlation of the velocity fluctuations
Jurčáková, Klára
2022 - English
Taylor's hypothesis about frozen turbulence [1] says that if the turbulence intensity is small compared to the mean velocity then the advection of a turbulent flow field past a fixed point can be taken entirely due to the mean flow. This means that in the “frozen turbulent field” spatial and temporal dimensions can be interchanged. Although the main assumption of Taylor's hypothesis is not met in the atmospheric boundary layer (the intensity of turbulence is usually between 10 and 20%) the hypothesis is commonly used to calculate integral length scales of turbulent fields from point measurements. Particle image velocimetry with high temporal resolution (TR-PIV) allows us to analyze both temporal and spatial cross-correlations in the turbulent flow fields and to evaluate obtained results. Keywords: frozen turbulence; wind tunnel; integral length scales; Particle Image Velocimetry Available at various institutes of the ASCR
Temporal, Spatial, and Spatio-temporal correlation of the velocity fluctuations

Taylor's hypothesis about frozen turbulence [1] says that if the turbulence intensity is small compared to the mean velocity then the advection of a turbulent flow field past a fixed point can be ...

Jurčáková, Klára
Ústav termomechaniky, 2022

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