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Design of electromagnetic of shrouded blades excitation in Erosion stand
Pešek, Luděk ; Vaněk, František ; Bula, Vítězslav ; Cibulka, Jan
The research report was elaborated in frame of the contract with Skoda Power a.s. and Institute of Thermomechanics AS CR, v.v.i.. The aim was to design the electromagnetic excitation of bladed disc in the Erosion stand. In the report the multi electromagnetic excitation design, the production drawings of electromagnets UTM4, their electrical connections and their placement in the stand are presented. Furthermore the methods of electromagnet synchronization for an excitation of the blade and disc vibration modes are discussed. The results of verification tests both in still and rotating states on the test rigs of IT AS CR conclude the report.
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Mathematical model of the support of experimental aerodynamical profile
Kozánek, Jan ; Bula, Vítězslav ; Zolotarev, Igor
In this paper the simple mathematical model of longitudinal and angular vibrating motion of experimental aerodynamical NACA0015 profile is given. With the help of dynamical experiments from complex frequency responses are by least squares fitting method identified complex eigenvalues. The direct identification method defines real coefficient matrices (of order 2) of stiffness, damping and mass of this non-conservative dynamical system. Finally, the comparisons of measured and from mathematical model evaluated responses are given and discussed.
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Awakening of traveling wave of rotor blade wheel by multipoint electro-magnetic excitation
Pešek, Luděk ; Vaněk, František ; Veselý, Jan ; Bula, Vítězslav ; Cibulka, Jan
The analytical expressions for description of traveling waves in rotating blade wheels are presented in the contribution. Both axis-symmetric case of the wheel characterized by multiple eigenvalues and the wheel with imperfection causing the split of this multiplicity are discussed herein. These expressions serve, based on the affinity to the traveling waves, for finding the optimal distribution and time dependences of the excitation forces of the multipoint electromagnetic excitation. The theoretical findings are verified numerically and experimentally on the case of free supported ring in a non-rotating state.
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Contactless Measuring Method of Blade Vibration during Increasing Turbine Operational Speed
Procházka, Pavel ; Vaněk, František ; Cibulka, Jan ; Bula, Vítězslav
A novel method for contactless measurements of turbine blade vibration during increasing or decreasing operational speed is presented. The method is based on the evaluation the time differences of blade tips passing along contactless sensors placed on the stator, and the substitution data correction using a numerical model. The method has been verified both numerically and experimentally. For the experimental research on the model bladed wheel of the Institute of Thermomechanics and subsequent applications in operating conditions, two new types of sensors functioning on the magnetoresistive and induction principle have been developed.
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Zviditelnění nestacionárního proudění kolem vibrujícího profilu: Experimentální uspořádání a předběžné testy
Vlček, Václav ; Horáček, Jaromír ; Luxa, Martin ; Veselý, Jan ; Bula, Vítězslav
The contribution presents the designed aeroelastic model, experimental set-up and preliminary tests of optical measurements of flow field around a vibrating NACA 0017 profile elastically supported in the measurement section of the wind tunnel. The profile can vibrate with two degrees of freedom for translation and rotation. The interferometry method combined with the high speed filming was used for flow visualization of in different phases of the profile motion. The measurements were performed in a subsonic wind tunnel above the airflow velocity for loss of the system stability by flutter, thus the vibration amplitudes were relatively large up to about 7 mm for vertical translation and 16.5 degrees for angle of rotation around the elastic axis. The 52 images of the flow field were recorded during one oscillation period of the profile from which the pressure and velocity can be evaluated in the given time instants.
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Preparation, realization and evaluation of experiment on model test wheel with blades and wedge-shaped friction elements
Pešek, Luděk ; Vaněk, František ; Veselý, Jan ; Bula, Vítězslav ; Procházka, Pavel ; Cibulka, Jan
In the first part of the report the preparation and realization of the experiment on the model test wheel with beam blades having built-in wedge-shaped friction elements. The preparation considered the placement of strain-gauges on the wheel for a deformation measurement, installation of sensors for a friction element displacement observation and the electromagnet for an excitation of resonant vibration at different revolutions. The experiment realization includes both modal analysis of the wheel with and without the friction elements in steady state and analysis of blade vibration at selected revolutions in the range from 60 up to 2100 rpm. Besides the electromagnetic excitation the experiment with the permanent magnet excitation was performed. For evaluation of the friction element influence the comparison method was used when the vibrations of the wheel with the friction elements with the case of the wheel without friction elements at the same test conditions were compare
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New test approach and evaluation of dynamic and thermal parameters of elastomers
Pešek, Luděk ; Vaněk, František ; Procházka, Pavel ; Bula, Vítězslav ; Cibulka, Jan ; Vaněk, Petr
The new test approaches for evaluation of thermo-visco-elastic parameters of elastomers are designed, realized and discussed herein. The main attention is devoted to a kinematic excited rubber beam sample under transient resonant sweep excitation. Mechanical material characteristics, i.e. Young modulus and loss angle, are identified from analytical formulas of FRF function based on measured dynamic loading and response signals. Heat material constants were estimated indirectly by numerical thermo-mechanical FE model and matching numerical and experimental results. The „sweep” regime tests serve for estimation of thermal and mechanical dependences. Long-term tests with cyclic resonant loading enable analysis of material degradation, such as hardening and permanent deformation, due to fatigue. For dynamic tests with pressure pulsation and sudden loading and unloading the high-power electromagnetic pulsater has been developed for damping rubber segments of tram wheels.
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