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Survey of the use of propane as refrigerant R290 in cooling circuits and heat pumps
Aminian, Ali; Prokopová, Olga; Vinš, Václav
2022 - anglický
The technical report presents a review on the application of propane as refrigerant R290 in cooling circuits and heat pumps (HVAC). Safety risks of R290 used in HVAC are addressed according to ANSI/ASHRAE and EN standards. Comparison of thermophysical properties of propane with other refrigerants, solubility and miscibility of propane in compressor oils and heat transfer in condenser and evaporator are discussed. The main aim of the study is to provide an overview about the potential use of propane in the cooling circuit and heat pump for the hydrogen bus developed by the SOR Libchavy company.
Klíčová slova:
cooling circuit; heat pump; hydrogen bus; refrigerant
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Survey of the use of propane as refrigerant R290 in cooling circuits and heat pumps
The technical report presents a review on the application of propane as refrigerant R290 in cooling circuits and heat pumps (HVAC). Safety risks of R290 used in HVAC are addressed according to ...
Identification of material constants of rubber damping segments by modal analysis for railway rubber-resilient wheels
Šulc, Petr; Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav
2022 - anglický
In this paper, an experimental and numerical modal analysis is described to assess two rubber compounds for the damping segments of a railway wheel. The subject of this comparison is materiál parameters such as Young’s modulus and loss factor for both compounds in the frequency range up to 6.5 kHz. From this comparison, an idea of the damping, stiffness and durability of these rubber segment materials inside these wheels is obtained.
Klíčová slova:
modal analysis; rubber; railway wheel; damping segment
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Identification of material constants of rubber damping segments by modal analysis for railway rubber-resilient wheels
In this paper, an experimental and numerical modal analysis is described to assess two rubber compounds for the damping segments of a railway wheel. The subject of this comparison is materiál ...
Measurement on Compressor Cascade KOBRA
Luxa, Martin; Šimurda, David
2022 - anglický
The report contains results and evaluation of conducted optical (shadowgraph and schlieren technique) and pneumatic measurements on the profile cascade intended for the tip section of the first rotor row compressor blade.
Klíčová slova:
compressor cascade; transonic flow; optical measurement; pneumatic measurement
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurement on Compressor Cascade KOBRA
The report contains results and evaluation of conducted optical (shadowgraph and schlieren technique) and pneumatic measurements on the profile cascade intended for the tip section of the first rotor ...
Two-way fluid structure interaction study of aero-engine compressor blade vibration under air excitation
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Maturkanič, Dušan; Hodboď, Robert
2022 - anglický
In this paper, we provide a numerical method via FEM software (ANSYS) using two-way Fluid-Structure Interaction (FSI) solver to estimate the blade’s vibration where the force used to excitation is a continuous air jet. This will help to provide data to diagnostic blade condition and health monitoring and a bridge toward a precise study of the blade’s dynamic under rotation and the estimation of blade’s displacement to define the amplitude and the frequency that occurs under different types of excitation which is a pillar for the process of machine condition and health monitoring.
Klíčová slova:
two-way fluid structure interaction (FSI); air excitation; blade tip displacement
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Two-way fluid structure interaction study of aero-engine compressor blade vibration under air excitation
In this paper, we provide a numerical method via FEM software (ANSYS) using two-way Fluid-Structure Interaction (FSI) solver to estimate the blade’s vibration where the force used to excitation is a ...
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 ...
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 ...
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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