Ústav termomechaniky

Nejnovější přírůstky:
2020-03-19
09:41
Fyzikální modelování a tvorba havarijního softwaru
Chaloupecká, Hana ; Kluková, Zuzana ; Jakubcová, Michala ; Kellnerová, Radka ; Jurčáková, Klára
Zpráva popisuje postup řešení na dvouletém projektu TAČR TJ01000383.\nV prvním roce řešení jsme se zabývali nalezením vztahu mezi charakteristikami krátkodobých a dlouhodobých úniků plynu pro městskou zástavbu na základě databáze COST ES1006. Dále jsme se zabývali úniky krátkodobých a krátkodobých plynů pro případ rurálního povrchu. Z naměřených dat jsme vytvořili bezrozměrnou databázi I. \nV roce 2019 jsme dále navázali na řešení v předešlém roce. Zaměřili jsme se na rozptyl krátkodobých a dlouhodobých úniků plynu v industriální oblasti. Změřená data byla zpracována a byla z nich vytvořena bezrozměrná databáze II.. Databáze I. a II. byly využity pro validaci modelu. Byl vytvářen software coby hlavní konečný cíl projektu.\n

Úplný záznam
2020-02-28
11:29
The measurement of the heterogeneous particles in the steam
Bartoš, Ondřej ; Hrubý, Jan ; Ždímal, Vladimír ; Kolovratník, Michal ; Jiříček, I. ; Moravec, Pavel ; Zíková, Naděžda
The aim of this extended abstract is to reveal the work done as cooperation between several institutions which was presented and published in recent years (Kolovratník, 2014). The formation of droplets in low-pressure steam turbines has a significant impact on the efficiency of energy conversion due to the strongly nonequilibrium nature of this process . The condensed water also erodes the turbine blades. A very important question is to what extent heterogeneous nucleation contributes to the phase transition process . In the case of heterogeneous nucleation , the number of droplets depends only on the number of h eterogeneous particles in the system, whereas in the case of homogeneous nucleation, the number of created droplets is determined rather by the expansion rate - in a faster expansion, greater supersaturation and more droplets are formed until the released condensation enthalpy quenches the nucleation.\nThe specific number of droplets (number of droplets per unit mass of steam) formed in the turbine can be determined by optical probes, developed first by Walters and later in the Czech Republic improved by Petr and Kolovratník. Until recently, no information was available on the relative importance of heterogeneous nucleation in forming these droplets.

Úplný záznam
2020-01-23
14:06
Acoustic emission sources from fast dislocation motion
Hora, Petr ; Machová, Anna ; Červ, Jan ; Uhnáková, Alena
Acoustic emission from the fast dislocations emitted from an edge crack in 3D bcc iron crystal is studied via atomistic simulations by molecular dynamics technique. Acoustic emission patterns arising from the fast dislocation motion in molecular dynamics are visualized via the local kinetic energies of individual atoms and further modeled as a moving source of the stress waves in the anisotropic continuum.

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2020-01-23
14:06
NDT in Progress 2019
Převorovský, Zdeněk
Already 10th International Workshop NDT in Progress 2019 was organized by the Czech Society for NDT (CNDT) along with the Institute of Thermomechanics of the Czech Academy of Sciences under auspices of ACADEMIA NDT International and European Federation for NDT. This unique biennial Workshops series started in 2001 with the primary aim to get together experienced NDT world experts with young people and students from various academic and industrial branches, allowing them to deeply discuss the latest state-of-the-art and progress in nondestructive testing and evaluation methodologies (NDT/NDE/SHM/CM) and new trends in both research and application areas. \nMain topics of the Workshop covered (not only):\n•Acoustic & ultrasonic methods; acoustic emission; guided waves; phased arrays.\n•Radiographic methods; infrared & terahertz waves testing.\n•Electromagnetic & magnetic methods; optical methods & defects imaging.\n•Signal & Image processing; nonlinear methods; inverse problems; time reversal.\n•Structural health and condition monitoring (SHM/CM).\n•Numerical simulations and modeling in NDT/NDE.\n•NDT for Industry 4.0 and additive manufacturing.\n

Úplný záznam
2020-01-23
14:06
Development of Vibration Equipment for the Production, of Polycomponent Phytomixtures
Yanovych, V. ; Duda, D. ; Rubanenko, O. ; Uruba, Václav
One of the most important stages of the technological process of manufacturing complex pharmaceutical mixtures is the grinding of pre-dried phytosteramines with a gradual sifting and giving it a homogeneous consistency of up to 97-98% with additional pharmaceutical ingredients due to mixing.

Úplný záznam
2020-01-23
14:06
Anisotropy of Turbulent Flow around an Airfoil
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
The flow around an airfoil is analyzed from the point of view turbulence anisotropy assessment. The turbulent flow-field in the vicinity of an airfoil is populated by vortices, in some locations they tend to regularity in orientation, i.e. to anisotropy. However in the wake behind the plate as well as in the core of the boundary layer on the plate suction side the turbulence is close to isotropic state.

Úplný záznam
2020-01-23
14:06
Effect of Various Boundary Conditions on the Supersonic Flow Through the Tip-Section Turbine Blade Cascade with a Flat Profile
Musil, Josef ; Příhoda, Jaromír ; Fürst, J.
The paper deals with the numerical simulation of 2D compressible flow though the tip-section turbine blade cascade with a flat profile. The OpenFOAM code was used for simulations based on the Favre-averaged Navier-Stokes equations completed by the two-equation SST turbulence model and the gama-Re_th transition model proposed by Langtry and Menter (2009). Calculations were carried out for two nominal regimes with the inlet Mach number M1 = 1.2 and isentropic outlet Mach numbers M2is = 1.7 and 1.9. Simulations of compressible flow with the supersonic inlet were focused on the relation between of the inlet Mach number and the inlet angle given by the unique incidence rule. Further, the effect of the inlet free-stream turbulence and of the outlet isentropic Mach number on the flow filed in the blade cascade was investigated. Numerical results were compared with results of optical and pressure measurements.

Úplný záznam
2020-01-23
14:06
Finite element implementation of creep constitutive model including transient effects
Gabriel, Dušan ; Masák, Jan ; Plešek, Jiří ; Kloc, Luboš ; Dymáček, Petr
A complex creep constitutive model including transient effects was implemented in the finite element code PMD (Package for Machine Design). The material model for P-91-type creep-resistant steel together with computer implementation was verified by means of uniaxial stress loadings. Testing bar was discretized by the finite element method (FEM) and loaded with uniaxial stresses and constant temperatures that were used to demonstrate the analytical solutions in original paper.

Úplný záznam
2020-01-23
14:06
Real-time diagnostics for ROS running systems based on probabilistic patterns identification
Věchet, Stanislav ; Krejsa, Jiří
Autonomous mobile robots consists of various software modules to achieve given goal, including solving complex navigation tasks as localization, mapping or path planning. These tasks are highly dependent on the quality of data measured and gathered from hardware subsystems. Using Robot Operating System (ROS) as integration basis reduces the development effort and time to market. While ROS framework itself is considered as reliable and stable to run even soft real-time tasks, in case of any internal failures on data misreadings can be problematic to debug or even identify the problem for common user. Due to this unpleasant situations we develop a virtual assistant, internally represented as diagnostic expert system, to help users to identify and possibly fix the problem.

Úplný záznam
2020-01-23
14:06
Utilization of Convolution Neural Network Based Road Detection in Mobile Robot Localization
Krejsa, Jiří ; Věchet, Stanislav
Mobile robot on-road navigation requires fusion of both global and local sensory information with an emphasis on the road detection processing. The paper deals with the road detection based on convolution neural networks (CNN) using commonly available tools such as TensorFlow and Keras. The road is defined by its linear boundaries. Network output is formed by the road definition together with classification parameters and serves as a local sensor in Kalman filter based localization. CNN based road detection is currently capable to successfully detect about 90% of images.

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