No (3139)
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3139
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Experimental investigation of homogeneous nucleation of water in various gases using an expansion chamber
Lukianova, Tetiana; Lukianov, Mykola; Hrubý, Jan
2022 - English
Nucleation is an integral part of phase transitions and plays an important role in technology. The control of nucleation in devices such as turbines, rocket and jet engines, wind tunnels, and combustion processes is key to achieving efficient, ecologically sound operation. Our paper presents information about a modernized experimental setup used for homogeneous water nucleation research.\nThe main goal of the study is an analysis of the influence of carrier gas on homogeneous nucleation.The experimental setup based on an expansion chamber has been used for research of homogeneous nucleation over several decades and has undergone various technical improvements. In the Institute of Thermomechanics, the setup was been completely disassembled and cleaned. Pressure transducers, laser, and the data acquisition system have been replaced with modern parts. After that, the chamber was assembled, and thoroughly tested and calibrated.Our investigations were carried with argon and nitrogen as carrier gases in a range of nucleation temperatures 220 – 260 K, pressure range 80-150 kPa, at several concentrations of water vapour. The results thus obtained are consistent with literature data.The findings suggest that this experimental approach is useful for homogeneous water nucleation research.
Keywords:
homogeneous nucleation; pulse chamber; nucleation rate
Available at various institutes of the ASCR
Experimental investigation of homogeneous nucleation of water in various gases using an expansion chamber
Nucleation is an integral part of phase transitions and plays an important role in technology. The control of nucleation in devices such as turbines, rocket and jet engines, wind tunnels, and ...
Current status of natural refrigerants for heat pumps in an electric bus
Aminian, Ali; Vinš, Václav
2022 - English
The technical report provides a survey on the current status of hydrocarbons, with special focus on propane (R290), used as natural refrigerants in air‐conditioning units and heat pumps. Due to the\nexpected phase‐down of halogenated refrigerants planned in the regulation of the European Parliament no. 2022/0099/COD, alternatives such as hydrocarbons, carbon dioxide or ammonia are\nmost probably to be used in EU in the near future. A review of recent developments of HVAC units for residential use and for electric vehicles operated with natural refrigerants is presented.
Keywords:
heat pump; electric bus; refrigeration
Available at various institutes of the ASCR
Current status of natural refrigerants for heat pumps in an electric bus
The technical report provides a survey on the current status of hydrocarbons, with special focus on propane (R290), used as natural refrigerants in air‐conditioning units and heat pumps. Due to ...
Experimental evaluation of cyclic strain curves of 08Ch18N10T steel for ÚJV Řež, a. s.
Štefan, Jan; Parma, Slavomír
2021 - Czech
This research report presents the results of low-cycle fatigue tests conducted on 08Ch18N10T material for ÚJV Řež, a. s. in November 2021. Cyclic strain curves as well as the information on strain hardening rate are provided in the report. Tato výzkumná zpráva je protokolem o testech nízkocyklové únavy provedených na materiálu 08Ch18N10T v rámci zakázky pro ÚJV Řež, a. s. v listopadu 2021. Ve zprávě jsou prezentovány cyklické deformační křivky daného materiálu a údaje o rychlosti cyklického deformačního zpevňování.
Keywords:
low-cycle fatigue; strain hardening; austenitic stainless steel
Available at various institutes of the ASCR
Experimental evaluation of cyclic strain curves of 08Ch18N10T steel for ÚJV Řež, a. s.
This research report presents the results of low-cycle fatigue tests conducted on 08Ch18N10T material for ÚJV Řež, a. s. in November 2021. Cyclic strain curves as well as the information on strain ...
Torque and Flow Field Optical Measurements of The Single Blade Under Stall Flutter
Procházka, Pavel P.; Uruba, Václav; Šnábl, Pavel
2021 - English
The single blade NACA0010 was exposed to the incoming flow inside a channel with rectangular cross-section. The blade was investigated for three different working regimes. The first configuration was for fixed blade. The second regime was for fluttering blade due to flow instabilities and the last one was performed for blade under force excitation. The flow field was measured using Particle Image Velocimetry. A force transducer and a small rotary encoder were used to evaluate the force ratios.
Keywords:
blade cascade; time-resolved PIV; FFT; torque
Available at various institutes of the ASCR
Torque and Flow Field Optical Measurements of The Single Blade Under Stall Flutter
The single blade NACA0010 was exposed to the incoming flow inside a channel with rectangular cross-section. The blade was investigated for three different working regimes. The first configuration was ...
Increasing Ejector Efficiency via Diffuser Shape Optimization
Kubíčková, Lucie; Isoz, Martin; Haidl, Jan
2021 - English
An ejector is a technologically simple and yet wide-application fluid machine. While it has favorable characteristics for a signifficant number of technological processes, its main downside is probably its high operational energy demands. The present paper is an initial result of an ongoing research aimed at improving energy e ciency of the ejector via optimization of its geometry. In the paper, we focus mostly on presenting a general multi-objective optimization framework usable for an ejector shape optimization. The approach applicability is illustrated on a simpli ed problem comprising only a single phase flow in an ejector mixing tube and diffuser. Nevertheless, the achieved simulation and optimization results are validated against experimental data. The proposed optimization method itself is based on multi-objective evolutionary algorithms (MOEAs) combined with computational fluid dynamics (CFD) for evaluation of the vector-valued objective function.
Keywords:
CFD; MOEA; ejector; OpenFOAM
Available at various institutes of the ASCR
Increasing Ejector Efficiency via Diffuser Shape Optimization
An ejector is a technologically simple and yet wide-application fluid machine. While it has favorable characteristics for a signifficant number of technological processes, its main downside is ...
TACR TJ04000365: Project EDIMO in the year 2021
Chaloupecká, Hana; Fiala, Roman; Jakubcová, Michala; Kozohorský, Jan
2021 - Czech
The paper describes methods of work on the project TACR TJ04000365 in the year 2021. The paper focuses on the description of the models SWIFT and SPRAY. Furthermore, the creation of a middle-model, which was necessary to develop as one step from many others to be able to merge both models, is described. Finally, the paper is engaged in the trial-run of the merged models. The paper introduces the input parameters and the outputs in the form of concentration maps. The appendix contains sensitivity study of the model SWIFT in respect to the main inputs. Zpráva popisuje postup hlavních prací na projektu TAČR TJ04000365 v roce 2021. Zaměřuje se na popis modelů SWIFT a SPRAY. Dále pak na tvorbu mezi-modelu, který bylo nutné jako jeden krok z mnoha vytvořit pro možnost spojení obou modelů. Nakonec se zaměřuje na zkušební běh spojených modelů, kde zpráva představuje vstupní parametry a konečný výsledek coby koncentrační mapy. Příloha obsahuje citlivostní analýzu výstupů modelu SWIFT na hlavní vstupní parametry.
Keywords:
lagrangian modelling; model SPRAY; model SWIFT
Available at various institutes of the ASCR
TACR TJ04000365: Project EDIMO in the year 2021
The paper describes methods of work on the project TACR TJ04000365 in the year 2021. The paper focuses on the description of the models SWIFT and SPRAY. Furthermore, the creation of a middle-model, ...
Review of methods for the post-processing of topological optimization results
Kopačka, Ján; Ježek, Ondřej; Gabriel, Dušan; Šotola, Martin; Rybanský, David; Maršálek, Pavel; Halama, R.; Tejc, J.; Pašek, M.; Kovář, L.
2021 - Czech
The research report is an output of the sub-project TN1000024/08: Automation and production system optimization in cooperation with MECAS ESI Ltd on the development of methods for post-processing of topological optimization (TO) results. In this report a detailed survey of these methods is introduced as necessary tool for seamless integration of the results TO with subsequent numerical simulations and additive manufacturing. The selected method for post-processing based on a level-set approach using radial basis functions has been implemented and successfully tested on a well-known 2D Messerschmitt-Bölkow-Blohm (MBB) beam test problem. Tato výzkumná zpráva vznikla jako výstup dílčího projektu TN1000024/08: Automation and production system optimization, jehož jedním z cílů je ve spolupráci s firmou MECAS ESI s.r.o. vývoj metod následného zpracování (tzv. post-processing) výsledků topologické optimalizace (TO). V této zprávě je zpracována podrobná rešerše těchto metod jakožto nutného nástroje pro bezproblémové propojení výsledků TO s následnými numerickými simulacemi a aditivní výrobou. Vybraná metoda pro následné zpracování založená na level-set přístupu s pomocí radiálních bázových funkcí byla implementována a úspěšně otestována na známé testovací úloze 2D Messerchimitt-Bölkow-Blohm (MBB) nosníku.
Keywords:
post-processing; topological optimization; MBB test problem
Available at various institutes of the ASCR
Review of methods for the post-processing of topological optimization results
The research report is an output of the sub-project TN1000024/08: Automation and production system optimization in cooperation with MECAS ESI Ltd on the development of methods for post-processing of ...
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 ...
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 ...
Determination of stress wave pulse attenuation in chocolate with different sample thickness
Buchar, Jaroslav; Trnka, Jan; Kober, Jan
2021 - Czech
The report presents the results of an analysis of the attenuation of a mechanical pulse in samples of five types of chocolate, where each type had five different thicknesses. These are data established on the basis of an economic contract between the Institute of Thermomechanics of the Academy of Sciences of the Czech Republic and the Mendel University in Brno. The chocolate samples were loaded using both the Split Hopkinson Pressure Bar (SHPB) and the Hopkinson measuring split bar direct loading method. The measurement results are processed in the time and frequency domains. Ve zprávě jsou uvedeny výsledky studia útlumu mechanického napěťového pulsu ve vzorcích pěti druhů čokolády, kdy každý druh měl pět různých tlouštěk. Jde o údaje stanovené na základě hospodářské smlouvy mezi Ústavem termomechaniky AV ČR a Mendelovy univerzity v Brně. Práce navazují na výsledky dřívějších výzkumů provedených rovněž na základě smlouvy mezi zmíněnými institucemi. Vzorky čokolád byly zatěžovány jak metodou Hopkinsonovy měrné dělené tyče (HMDT), tak metodou přímého zatěžování Hopkinsonovy měrné dělené tyče. Výsledky měření jsou zpracovány v časové i frekvenční oblasti.
Keywords:
chocolate; pulse attenuation; split Hopkinson pressure bar
Available at various institutes of the ASCR
Determination of stress wave pulse attenuation in chocolate with different sample thickness
The report presents the results of an analysis of the attenuation of a mechanical pulse in samples of five types of chocolate, where each type had five different thicknesses. These are data ...
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