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Vibrations of blades bunches
Půst, Ladislav ; Pešek, Luděk
Paper describes a mathematical model for analysing the dynamic characteristics of five-blades bunch with different damping connections among individual blades. The connections of blades by means of special rubber elements either with the fixed contact with neighbouring blades or with one-sided slip is presented. Systems with dry friction connections among blades by means of direct contacts or by inserted dry friction elements are described as well. As an example of analysis results, response curves of five-blades-bunch excited on first blade at different dry friction force in the first bending resonance is shown. Elaborated analysis create the basic theoretical background for evaluation of measurement on experimental bladed disk set in the laboratory of Institute of Thermomechanics of ASCR and it is also applied for evaluation of effectiveness of methods for suppression of forced vibration of blades.
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Investigatiom of friction on a beam-blades model
Půst, Ladislav ; Veselý, Jan ; Horáček, Jaromír ; Radolfová, Alena
Results of measurements of damping and friction properties of a couple of turbine blades modeled by a couple of cantilever prismatic beams with perpendicular branches provided by friction surfaces made of material T671- Böhler or coating of wolfram carbide are presented. The dependences of energy lost, coefficients of dry friction and equivalent linear damping coefficients on amplitudes of vibrations, on frequency in the range 10 – 40 Hz and on normal forces were shown. Revided regression relation can be used at damping elements designed of turbine blades.
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Computational model of a blade couple conected by a damping element
Půst, Ladislav ; Horáček, Jaromír
Couple of turbine blades is analysed on a simplified computational model of two cantilevers undamped beams connected on its free ends by a damping element, which is either linear one or has Coulomb friction characteristic. The end of one beam is excited by harmonic force. Derived expressions for amplitudes of vibrations are completed by response curves records. The model of combined dry and viscous damping but corresponds to the experimental results. A more exact computational model with eccentric frictional contacts and a structural modification of blades are proposed as well.
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Kapalinový tlumič pro lávky
Pirner, Miroš ; Urushadze, Shota
The new type of passive tuned liquid damper (TLD), which relies on the motion of liquid inside a movable rectangular tank with two degrees of freedom (horizontal displacement and rotation). The authors study the influence of vessel horizontal motion and rotation on the damping of the vertical and horizontal vibrations of the footbridges. Experimental solution consists in the determination of the magnitude of the excitation force of the shaking table required under resonance during the harmonic excitation of the vessel the dimensions of which correspond with the dimensions of the girder of the footbridge.
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