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Contribution to modelling of bladed model disk with dry-friction contacts in tie-bosses
Pešek, Luděk ; Šnábl, Pavel ; Šulc, Petr ; Půst, Ladislav ; Bula, Vítězslav
The experimental set-up for studying dynamical behavior of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tiebosses based on 3D finite element method with surface to surface dry friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behavior and damping estimation of our bladed wheel design yielded a reasonable agreement. Limitation of the non-linear solution due to dry friction contacts is HPC computations and long computation times. The contribution will deal with the achieved results.\n
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The Effect of Blade Overlap on Aeroelastic Coupling
Procházka, Pavel P. ; Uruba, Václav ; Pešek, Luděk ; Bula, Vítězslav
This experimental study was established to clarify an aeroelastic coupling in the case of rotational periodic bodies. The blade grid was placed behind the outlet of the blow-down wind tunnel. Three of five blades were constructed to allow vertical position changing by the effect of three shakers. Particle Image Velocimetry was used to measure mean-phase velocity and dynamical parameters of the flow. The effect\nof blade enlargement will be introduced as well as the difference between forward and backward wave propagation.
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Classical flutter analysis of low pressure steam turbine blade cascade using 3D boundary element method
Prasad, Chandra Shekhar ; Pešek, Luděk
In this paper study of aeroelastic stability in steam turbine rotor is carried out using boundary element method. A mesh free fluid\nsolver is developed for fast estimation of unsteady aerodynamic loading and to estimate the aerodynamic damping in 3D blade cascade. The aerodynamic damping is estimated in traveling wave mode. The unsteady incompressible flow field is modeled using 3D surface Panel method. The proposed methodology successfully estimates aerodynamic damping with acceptable accuracy the for the aeroelastic (classical \n flutter) analysis of 3D blade cascade. The simulated results are compared with experimental data. The simulated aerodynamic damping shows good agreement with\nexperimental results. The present methodology shows significant reduction in computational time over computational fluid dynamic solvers.
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Influence of variable stiffness in toothed gears on the internal dynamics of the planetary gearbox
Šulc, Petr ; Pešek, Luděk ; Maturkanič, Dušan
This contribution is continuation of the work of above mentioned authors to whom this paper is dedicated. Their latest work dealt with numerical modelling of dynamics of planetary gearboxes with four satellites on flexible pins. They programmed the gear-box model in SIMULINK and now the model is an object of numerical investigations. This contribution describes the numerical model of the planetary gearbox. The numerical simulations are aimed to study an influence of variable stiffness in toothed gears on the internal dynamics of the planetary gearbox.
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Reducing vibration amplitude by means of damping control in support elements of flexible rotors
Zapoměl, Jaroslav ; Pešek, Luděk ; Viet, La Duc ; Savin, L. ; Kozánek, Jan
Damping in the supports of rotors loaded by unbalance has influence on the vibration amplitude and critical speed of rotating machines. To minimize the oscillation amplitude during the rotor acceleration and running over the critical velocity, the damping in the support elements should be reduced. The reduction cannot be sudden but must be distributed in time. This requires to determine the proper moment of time when to start this manipulation and the time of its duration. This paper deals with investigation of the possibility of utilization of controllable squeeze film dampers lubricated by magnetorheological oil to accomplish this manipulation.
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Preliminary identification of damping properties of tonewood
Povolný, J. ; Kozánek, Jan ; Zapoměl, Jaroslav
Besides elasticity parameters, damping of the material is the crucial parameter of the function of a violin and also of other stringed instruments with a wooden soundboard. Assuming tonewood as an orthotropic linear elastic continuum, our aim is to contribute to hypothesis, that each orthotropic elastic constant has its appropriate loss factor - partial dampings. Dynamic experiments are based on the impulse excitation and the steady state harmonic response is calculated by Fourier transform of time-sampled measured signals (excitation and response). Frequency transfer function fitting identification method can determine complex modal and spectral eigen-parameters, mainly eigenfrequencies and eigendampings.
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