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The International Colloquium Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2022
Zolotarev, Igor; Pešek, Luděk; Kozień, M. S.
2022 - anglický
The papers of the DYMAMESI are divided into the three sections and focused on the Dynamics of Machines, Interactions and Power Engineering.
Klíčová slova:
dynamics; vibrations of mechanical systems; vibrodiagnostics; energy transformations
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The International Colloquium Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2022
The papers of the DYMAMESI are divided into the three sections and focused on the Dynamics of Machines, Interactions and Power Engineering.
Experimental and numerical evaluation of blade cascade instability using travelling wave mode approach
Chindada, Sony; Šnábl, Pavel; Pešek, Luděk
2022 - anglický
The stability of experimental blade cascade with five NACA 0010 profiles was measured and evaluated with travelling wave mode approach with three inner blades oscilating. The measured moment of the middle blade consist of not only the aerodynamic moment from the flow but also structural moment from the blade dynamics. Two days of obtaining the aerodynamic moment from the measured data are herein presented and the results compared. In addition, numercial simulations were done and the results from 2D CFD analysis in ANSYS are compared with the experimental data.
Klíčová slova:
blade cascade instability; travelling wave mode approach; flutter
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Experimental and numerical evaluation of blade cascade instability using travelling wave mode approach
The stability of experimental blade cascade with five NACA 0010 profiles was measured and evaluated with travelling wave mode approach with three inner blades oscilating. The measured moment of the ...
Developing a coupled CFD solver for mass, momentum and heat transport in catalytic filters
Hlavatý, Tomáš; Isoz, Martin; Kočí, P.
2022 - anglický
Using catalytic filters (CF) in automotive exhaust gas aftertreatment decreases the system heat losses and facilitates the CF regeneration. On the other hand, the CF overall performance is strongly dependent on the catalytic material distribution within it. In the present work, we aim to provide a computational framework to study the dependence of the CF characteristics, i.e. the pressure loss and the conversion of gaseous pollutants, on the catalyst distribution. Previously, we built an isothermal computational fluid dynamics (CFD) model of the flow and conversion of gaseous pollutants inside the CF. However, the reactions occurring inside the CF are exothermic and the assumption of constant temperature proved to be too restricting for real-life applications of the developed isothermal CFD model. Thus, in this work, we extend the framework by the enthalpy balance, which requires combining all the transport equations (mass, momentum and enthalpy) in a single solver. The new and more general solver provides results in good agreement with a well established (1+1)D channel model calibrated on experimental data. Furthermore, it allows studying more complex device-scale geometries of laboratory CF samples.
Klíčová slova:
CFD; catalytic filter; OpenFOAM; gasoline particulate filter (GPF)
Dokument je dostupný na externích webových stránkách.
Developing a coupled CFD solver for mass, momentum and heat transport in catalytic filters
Using catalytic filters (CF) in automotive exhaust gas aftertreatment decreases the system heat losses and facilitates the CF regeneration. On the other hand, the CF overall performance is strongly ...
Estimating rheological properties of suspensions formed of arbitrarily-shaped particles via CDF-Dem
Kotouč Šourek, M.; Isoz, Martin
2022 - anglický
In recent years, new methods combining computational fluid dynamics (CFD) and discrete element method (DEM) have been intensively studied. Usually, these methods are focused on simulations of spherical particles. Nevertheless, this is inadequate for a simulation of a common suspension, the rheology of which is affected by particle shapes. In this work, we leverage the capabilities of an in-house developed CFD-DEM solver to simulate suspensions formed of arbitrarily-shaped particles. Specifically, we simulate a rheological measurement to estimate the suspension viscosity. The CFD-DEM estimates are in very good agreement with available experimental data and correlations proving the new solver capabilities regarding firstprinciples-based simulations of complex non-Newtonian suspension behaviour. The practical potential of suspension simulation is illustrated in a numerical study of the washcoating process in the preparation of a catalytic filter for automotive exhaust gas after-treatment.
Klíčová slova:
CFD-DEM; HFDIB; suspension rheology; OpenFOAM
Dokument je dostupný na externích webových stránkách.
Estimating rheological properties of suspensions formed of arbitrarily-shaped particles via CDF-Dem
In recent years, new methods combining computational fluid dynamics (CFD) and discrete element method (DEM) have been intensively studied. Usually, these methods are focused on simulations of ...
Hybrid fictitious domain-immersed boundary method in CFD-based topology optimization
Kubíčková, Lucie; Isoz, Martin
2022 - anglický
Advances in technological development, especially in 3D printing, allow engineers to design components with almost arbitrary shape and connectivity. Consequently, more and more attention is being directed towards a highly-specialized application-driven component design based on topology optimization (TO). In the present work, we propose a methodology enabling TO of components in contact with flowing fluids. In particular, the optimization itself is based on multi-objective evolutionary algorithms (MOEAs) with the component geometry encoded using a binary representation. The optimization criteria are evaluated via computational fluid dynamics (CFD). The main novelty of the proposed TO framework lies in its robustness and effectiveness achieved by utilizing a single computational mesh for all the tested designs and projecting the specific components shapes onto it by the means of an immersed boundary method. The new methodology capabilities are illustrated on a shape optimization of a diffuser equipped as a part of an ejector. The optimization goal was to increase the ejector energy efficiency. The newly proposed methodology was able to identify a design by roughly 9 % more efficient than an alternative one found utilizing a previously published and less general optimization approach.
Klíčová slova:
HFDIB; topology optimization; CFD; OpenFOAM
Dokument je dostupný na externích webových stránkách.
Hybrid fictitious domain-immersed boundary method in CFD-based topology optimization
Advances in technological development, especially in 3D printing, allow engineers to design components with almost arbitrary shape and connectivity. Consequently, more and more attention is being ...
Experimental investigation of homogeneous nucleation of water in various gases using an expansion chamber
Lukianova, Tetiana; Lukianov, Mykola; Hrubý, Jan
2022 - anglický
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.
Klíčová slova:
homogeneous nucleation; pulse chamber; nucleation rate
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
heat pump; electric bus; refrigeration
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Assessment of Various Converging Inlet Nozzles for Wind Tunnel Using CFD
Kosiak, Pavlo; Radnic, Tomáš; Mamula, Milan; Hála, Jindřich; Šimurda, David; Luxa, Martin
2022 - anglický
A new calibration tunnel intended for pressure probe calibration is being designed at the Aerodynamic Laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences (IT CAS). A critical part of the design is the converging nozzle since it can substantially affect the resulting flow field in the test section. Three types of nozzles were chosen for the CFD investigation: two-sine, Vitoshinski, and Vagt. For each type of nozzle, two configurations were considered: long (645 mm) and short (353mm). Flow of the viscous, compressible fluid through all the variants was simulated using Ansys CFX commercial software. Results proved the Vagt nozzle to have the most uniform velocity profile and zero curvature at its end making it the most suitable for the intended use.
Klíčová slova:
CFD; ANSYS CFX; converging nozzle; wind tunnel design
Dokument je dostupný na externích webových stránkách.
Assessment of Various Converging Inlet Nozzles for Wind Tunnel Using CFD
A new calibration tunnel intended for pressure probe calibration is being designed at the Aerodynamic Laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences (IT CAS). A ...
Torque and Flow Field Optical Measurements of The Single Blade Under Stall Flutter
Procházka, Pavel P.; Uruba, Václav; Šnábl, Pavel
2021 - anglický
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.
Klíčová slova:
blade cascade; time-resolved PIV; FFT; torque
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
CFD; MOEA; ejector; OpenFOAM
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
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