Number of found documents: 2890
Published from to

Experimentální stanovení ventilačních ztrát ozubeného kola a tepelného zatížení zubu
Kordík, Jozef; Dobiáš, Jiří; Hrubý, Jan
2018 - Czech
Tato zpráva je sepsána v rámci čtvrté etapy řešení výzkumného úkolu TA04011656, „Vývoj rychloběžné planetové převodovky s pružným uložením satelitů pro extrémní obvodové rychlosti”. První část zprávy se věnuje ventilačním ztrátám a jsou zde uvedeny podrobnosti k experimentům, které byly uskutečněny s testovací převodovkou “Alfa II” na zkušebním pracovišti Wikov Gear. Experimenty zahrnovaly měření ventilačních ztrát a měření teplot zubu podél šířky kola. Při experimentech byly testovány tři konfigurace obvodového krytu převodového kola, které se lišily vzdáleností mezi krytem a kolem. Mimoto byl testován i případ bez krytu. V závěru této části je navrženo rozšíření modelu ventilačních ztrát z předešlé zprávy pro reálné geometrie převodového kola s krytem, který je otevřený v místě záběru s pastorkem a v místě odtoku oleje.\nDruhá část zprávy se věnuje tepelnému zatížení boku zubu a prezentuje výsledky experimentů, které se týkaly měření teplot zubu podél šířky kola. Jsou zde rovněž uvedeny detaily k numerickému modelování tepelného zatížení boku zubu. V rámci numerické analýzy (i) byla vyvinuta metodika modelování odvalování boků zubů kola a pastorku po sobě, (ii) byl vytvořen výpočetní model, (iii) byla vyvinuta metodika určování neznámých velikostí některých parametrů výpočetního modelu a (iv) byl vyvinut algoritmus a metodika výpočtu.\n The report is written for the needs of the project no. TA04011656 ("Research and development of new type of high-speed planetary gear unit with the flexible pin technology to support the planet wheels enabling the transmission of high outputs."). The first part of the report targets the topic of windage losses of a rotating toothed wheel, the experiments with testing gearbox “Alfa II” are introduced here, as well. The experiments included measurements of windage losses and temperature measurements along a wheel tooth width. Three geometrical configurations differing in wheel enclosure distance were tested, the case without the enclosure was tested too. The outcome of this part is an extension of the previous windage loss model for real geometry configuration: a wheel with an enclosure opened at place of oil outflow and at place of meshing with pinion.\nThe second part of the report targets the thermal load of a wheel tooth and presents experimental results of measurements of temperature distribution along the tooth. This part also contains the details concerning the numerical modeling of this problematic. The numerical analysis included (i) development of methodology for modeling of tooths meshing, (ii) development of the computational model, (iii) development of methodology for assessment of unknown values of some parameters of the model, (iv) development of algorithm. \n Keywords: widage loss; wheel enclosure; gear box Available at various institutes of the ASCR
Experimentální stanovení ventilačních ztrát ozubeného kola a tepelného zatížení zubu

Tato zpráva je sepsána v rámci čtvrté etapy řešení výzkumného úkolu TA04011656, „Vývoj rychloběžné planetové převodovky s pružným uložením satelitů pro extrémní obvodové rychlosti”. První část zprávy ...

Kordík, Jozef; Dobiáš, Jiří; Hrubý, Jan
Ústav termomechaniky, 2018

Running flutter waves in the model of turbine blades cascade
Půst, Ladislav; Pešek, Luděk
2018 - English
This contribution is connected with the paper on the previous conference, where the origin and properties of forced running waves produced by flowing steam through cascade of stationary and rotating wheels with different numbers of blades in the steam turbine were investigated. Due to the aero-elastic forces of this steam flow, these comparatively small vibrations can excite strong flutter running waves. Presented contribution is oriented on the analysis of dynamic properties of computational model of blades cascade, where the flutter is modelled by two types of Van der Pol self-excitation forces. Keywords: blades cascade; flutter; running waves; self-excitation; number of blades Available at various institutes of the ASCR
Running flutter waves in the model of turbine blades cascade

This contribution is connected with the paper on the previous conference, where the origin and properties of forced running waves produced by flowing steam through cascade of stationary and rotating ...

Půst, Ladislav; Pešek, Luděk
Ústav termomechaniky, 2018

Development, assessment and verification of finite element procedures for contact problems
Gabriel, Dušan; Kopačka, Ján; Masák, Jan; Plešek, Jiří
2018 - English
A frictionless three-dimensional contact algorithm based on the pre-discretization penalty formulation was proposed. The algorithm proved to be robust, accurate and symmetry preserving—no master/slave surfaces have been introduced. It was implemented in the finite element code PMD (Package for Machine Design) for the solution of complex engineering problems. The capability of the algorithm was demonstrated in creep analysis of T-piece of the steam distributor of the CHEMOPETROL heating plant T200. Material properties were described by the probabilistic exponential model with damage. The purpose of the analysis was to compare the original version and the proposed design modification applied to one of T-pieces of the distributor when the proposed contact algorithm was employed to simulate the interaction between the collar and the pipe. Keywords: FEM; contact algorithm; creep analysis; T-piece of the steam distributor Available at various institutes of the ASCR
Development, assessment and verification of finite element procedures for contact problems

A frictionless three-dimensional contact algorithm based on the pre-discretization penalty formulation was proposed. The algorithm proved to be robust, accurate and symmetry preserving—no master/slave ...

Gabriel, Dušan; Kopačka, Ján; Masák, Jan; Plešek, Jiří
Ústav termomechaniky, 2018

Experimental and finite element analysis of composite gun barrels
Mochar, Dominik; Trnka, Jan; Chlada, Milan; Valeš, František; Gabriel, Dušan; Červ, Jan; Vtípil, J.
2018 - English
In this work experimental and numerical investigation of composite gun barrels was studied. The history of the stress-induced deformations located at the center of gun barrels on the outer surface generated by impact loading was measured for six types of barrels. The obtained signals were subsequently evaluated using wavelet transformation. Finally, the finite element analysis in Abaqus and MARC software for optimum composite material M46J was performed. Keywords: composite gun barrels; contact-impact analysis; drop weight tester; air cannon Available at various institutes of the ASCR
Experimental and finite element analysis of composite gun barrels

In this work experimental and numerical investigation of composite gun barrels was studied. The history of the stress-induced deformations located at the center of gun barrels on the outer surface ...

Mochar, Dominik; Trnka, Jan; Chlada, Milan; Valeš, František; Gabriel, Dušan; Červ, Jan; Vtípil, J.
Ústav termomechaniky, 2018

The influence of permanent magnetic rings on the loss power, vibration and stability of vertical rotors
Zapoměl, Jaroslav; Ferfecki, P.; Sudhakar, A.; Kozánek, Jan
2018 - English
Lifting the vertical rotors by permanent magnets is an advanced technological solution for\nreducing energy losses in the supports. The disadvantage of this design is the instable interaction between the magnetic rings, which may destabilize the rotor oscillations. The performed research was focused on the development of computational procedures for analysis of energy losses in the supports of magnetically lifted vertical rotors mounted in rolling element bearings and on analysis of stability of their vibration in a wide range of operating speeds. The computational simulations proved efficiency of the magnetic suspension. Keywords: lifting vertical rotors; magnetic rings; energy losses reduction; vibration stability evaluation Available at various institutes of the ASCR
The influence of permanent magnetic rings on the loss power, vibration and stability of vertical rotors

Lifting the vertical rotors by permanent magnets is an advanced technological solution for\nreducing energy losses in the supports. The disadvantage of this design is the instable interaction between ...

Zapoměl, Jaroslav; Ferfecki, P.; Sudhakar, A.; Kozánek, Jan
Ústav termomechaniky, 2018

Dynamical analysis of bistable mechanical oscillator
Byrtus, M.; Půst, Ladislav
2018 - English
The contribution deals with analysis of dynamical properties of 1 DOF bistable mechanical oscillator. First the mathematical model is formulated. The original mathematical model is approximated by Duffing equation as it is commonly used. These two models are compared and it is shown how they differ in both static and dynamical response. The dynamical response is studied using bifurcation analysis performed by brute force numerical integration in time domain to detect area of interest from dynamical point of view. Such a bistable mechanical system can appear in many technical applications and therefore the proper modelling plays a significant role. Keywords: bistable system; vibration; bifurcation; stability Available at various institutes of the ASCR
Dynamical analysis of bistable mechanical oscillator

The contribution deals with analysis of dynamical properties of 1 DOF bistable mechanical oscillator. First the mathematical model is formulated. The original mathematical model is approximated by ...

Byrtus, M.; Půst, Ladislav
Ústav termomechaniky, 2018

Flow Dynamics in the Vicinity of Tandem Buildings
Gnatowska, R.; Kellnerová, Radka; Uruba, Václav
2017 - English
The flow-field in the vicinity of tandem building model in a wind tunnel will be subjected to analysis of dynamics. The model is 3D consisting of the two blocks of different sizes arranged in a streamwise direction. Experiments were performed using time-resolved PIV technique in several measuring planes to capture both spatial and dynamical features. Keywords: PIV experiment; tandem building arrangement; wind tunnel Available at various institutes of the ASCR
Flow Dynamics in the Vicinity of Tandem Buildings

The flow-field in the vicinity of tandem building model in a wind tunnel will be subjected to analysis of dynamics. The model is 3D consisting of the two blocks of different sizes arranged in a ...

Gnatowska, R.; Kellnerová, Radka; Uruba, Václav
Ústav termomechaniky, 2017

Impact of Turbulence Generators on Turbulent Characteristics and Structures
Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk
2017 - English
The turbulent generators are routinely used to produce very turbulent flows. Special type of vertically slenderize spires are applied to enhance turbulent diffusion from the surface upwards in order to increase the boundary layer depth. This paper studies the influence of variable upstream distance of generators on formation of both vortical and non-vortical organized structures within a test section. The 2-component 2-dimensional time-resolved particle image velocimetry measurement of the flow was performed in the wind channel with very rough surface. Intermittent flow dynamics was evaluated by means of higher order moments, vorticity, quadrant and wavelet analysis. The downstream evolution of the flow suggests that equilibrium between roughness- and spires-produced turbulence was reached at the distance of 7 spires height.\n Keywords: turbulence generator; wind channel; vorticity; quadrant analysis Fulltext is available at external website.
Impact of Turbulence Generators on Turbulent Characteristics and Structures

The turbulent generators are routinely used to produce very turbulent flows. Special type of vertically slenderize spires are applied to enhance turbulent diffusion from the surface upwards in order ...

Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk
Ústav termomechaniky, 2017

Application of non-contact vibration measurements on a 48“ blade under low load condition
Kubín, Z.; Liška, J.; Míšek, T.; Procházka, Pavel
2017 - English
The paper describes in detail a Tip-Timing measurement on a combined cycle power plant with a steam turbine power output of 270MW. Newly developed magnetoresistive and optical sensors were used as well as standard eddy-current sensors to measure blade vibration under low load condition and variable back pressure. New hardware solution for the Tip-Timing measurement will is presented as well as results of measurements of relative amplitudes and excited nodal diameters. Keywords: steam turbine; non-contact vibration measurement; magnetoresistive sensor; optical sensor Available at various institutes of the ASCR
Application of non-contact vibration measurements on a 48“ blade under low load condition

The paper describes in detail a Tip-Timing measurement on a combined cycle power plant with a steam turbine power output of 270MW. Newly developed magnetoresistive and optical sensors were used as ...

Kubín, Z.; Liška, J.; Míšek, T.; Procházka, Pavel
Ústav termomechaniky, 2017

Some experimentally determined properties of a profile in case of self-excited oscillations in subsonic flow
Vlček, Václav; Zolotarev, Igor; Kozánek, Jan; Šidlof, Petr; Štěpán, M.
2017 - English
In the wind tunnel of the Institute of Thermomechanics of the AS CR,v .v. i., experiments were realized with the profile NACA0015 in the presence of the self-excited oscillation. The oscillation of the profile with pitch and plunge degrees of freedom was excited by the subsonic air flow. The plunge support had the same elasticity for all experiments, the pitch support had seven different values of elasticity. Within experiments different types of self-excited vibration (flutter, stall flutter, deep stall flutter) were realized. Range of Mach numbers were M=0.08–0.45, when the chord length is used as the characteristic dimension of the profile. The frequency and amplitude characteristics of the oscillating profile were experimentally determined.\n Keywords: airfoil; aeroelasciticy; dynamic stall; stall flutter; limit cycle oscillations; self -excited vibrations Available at various institutes of the ASCR
Some experimentally determined properties of a profile in case of self-excited oscillations in subsonic flow

In the wind tunnel of the Institute of Thermomechanics of the AS CR,v .v. i., experiments were realized with the profile NACA0015 in the presence of the self-excited oscillation. The oscillation of ...

Vlček, Václav; Zolotarev, Igor; Kozánek, Jan; Šidlof, Petr; Štěpán, M.
Ústav termomechaniky, 2017

About project

NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web

Send your suggestions and comments to nusl@techlib.cz

Provider

http://www.techlib.cz

Facebook

Other bases