No (1754)
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1754
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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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
Final Report of the Centre of Excellence for Nonlinear Dynamic Behaviour of Advanced Materials in Engineering
Parma, Slavomír; Gabriel, Dušan
2022 - English
This final report presents the CeNDYNMAT Center of Excellence, which was established at the Institute of Thermomechanics of the Czech Academy of Sciences in 2016 and ended in 2022. The report summarizes the most important scientific results of the center. It also gives an overview of the main outcomes and developments of the project, including budgeting, purchasing instrumentation, international cooperation and organization of conferences and summer courses.
Keywords:
nonlinear dynamic behavior; advanced materials; metal plasticity
Available at various institutes of the ASCR
Final Report of the Centre of Excellence for Nonlinear Dynamic Behaviour of Advanced Materials in Engineering
This final report presents the CeNDYNMAT Center of Excellence, which was established at the Institute of Thermomechanics of the Czech Academy of Sciences in 2016 and ended in 2022. The report ...
Problematics of aerodynamic damping calculation from measured data of 5-blade cascade
Šnábl, Pavel; Pešek, Luděk; Prasad, Chandra Shekhar; Chindada, Sony
2022 - English
Aerodynamic damping as a function of inter-blade phase angle (IBPA), so called S-curve, is crucial for assessment of aeroelastic stability of blade cascades, e.g. turbines, compressors, etc.\nFor constructing the S-curve, the motion-induced controlled flutter is introduced to the bladesof the cascade. As decribed in [1], two testing methods exist: aerodynamic influence coefficient\n(AIC) approach and travelling wave mode (TWM) approach. In TWM approach, all blades in a row oscillate with the same frequency and amplitude with various IBPAs. The response is\nmeasured only on the reference blade. With this approach, several measurements with different IPBAs are needed to construct the S-curve. On the other hand, AIC uses single oscillating\nblade and principle of linear superimposition of aerodynamic influence responses measured on all blades in a cascade. The result of one single measurement can be used for estimation of\naerodynamic damping for any IBPA. In the past year a new 5-blade cascade with rotating symmetrical NACA 0010 profiles was designed and built. The blades of the cascade were placed further apart and thus we are now able to reach stall flutter. Also, the suspension of the blades and sensors were significantly improved. Now, our goal is to evaluate S-curves using AIC approach for different flow conditions and oscillation frequencies.
Keywords:
aerodynamic damping; S-curve; blade cascade
Available at various institutes of the ASCR
Problematics of aerodynamic damping calculation from measured data of 5-blade cascade
Aerodynamic damping as a function of inter-blade phase angle (IBPA), so called S-curve, is crucial for assessment of aeroelastic stability of blade cascades, e.g. turbines, compressors, etc.\nFor ...
Aerodynamic Measurements on Transonic Compressor Blade Cascades KR-D-5 and KR-D-6
Šimurda, David; Hála, Jindřich; Luxa, Martin
2022 - English
This report contains results and evaluation of aerodynamic measurements conducted on two variant transonic compressor blade cascades with MCA profile (KR-D-5) and DCA profile (KR-D-6).
Keywords:
compressor blade cascade; experiment; transonic flow; MCA profile; DCA profile
Available at various institutes of the ASCR
Aerodynamic Measurements on Transonic Compressor Blade Cascades KR-D-5 and KR-D-6
This report contains results and evaluation of aerodynamic measurements conducted on two variant transonic compressor blade cascades with MCA profile (KR-D-5) and DCA profile (KR-D-6).
Topical Problems of Fluid Mechanics 2022
Šimurda, David; Bodnár, T.
2022 - English
Proceedings consist of papers presented during the conference Topical Problems of Fluid Mechanics 2022. \n
Keywords:
experimental fluid mechanics; mathematical modelling; CFD; turbulence; stratified fluid; multiphase flow; vortex structures; supersonic flow
Available at various institutes of the ASCR
Topical Problems of Fluid Mechanics 2022
Proceedings consist of papers presented during the conference Topical Problems of Fluid Mechanics 2022. \n
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