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Five-blade bunch with dry friction inter-connection forced by running excitation
Půst, Ladislav ; Pešek, Luděk ; Radolfová, Alena
The vibration of five-blade-bunch linked in the shroud by means dry-friction-elements is investigated. Quasi-stationary response curves are used for analysis of dynamic properties of isolated blade-bunches excited by running harmonic forces. This running wave excitation models the real excitation in the steam or gas turbine with different numbers of rotor and stator blades. Relation between the ratio of these blade-numbers and phase delay between neighboring blades is ascertained and the dynamic responses of isolated five-blade bunch are shown and analyzed in this paper. Gained theoretical results can be used for evaluation of data obtained from dynamic measurements on bladed disk.
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Nonlinear damping in rotating disk
Půst, Ladislav ; Pešek, Luděk
Paper is concerned with the steady state flexural vibrations of imperfect bladed circular disk by analytical and numerical solutions. Disk imperfection results from additional two groups of damping heads fixed on opposite ends of one diameter, which introduces point imperfections in mass, stiffness and nonlinear damping The main aim of this study is to investigate influence of friction damping among adding bladed heads on decrease of resonance amplitudes. Examples based on application of equivalent linearized damping show the properties of such dampers.
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Thermo-mechanical interaction in nonlinear vibrating systems
Pešek, Luděk ; Půst, Ladislav
The interaction between mechanical properties of vibrating system including hardening spring nonlinearity and thermal processes taking place in the rubber-like spring element having high inner damping are studied on one degree of freedom system. Basic differential equations for motion of mechanical system and for heat transfer are solved by numerical simulation.
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Response curves of vibroimpact system
Půst, Ladislav ; Peterka, František
Dynamical properties of 1DOF mechanical system impacting on soft stop are studied at excitation by harmonic force. Soft stop is of Hertzs type with viscous damping. Properties of system are analyzed by means of response curves obtained by simulation of motion at slow variation of excitation frequency. Response curves are completed by phase plane trajectories at selected frequencies and time history record. The influences of clearance in system on the response curves, type and level of oscillations are presented. This paper is in narrow connection with contribution [1], where the regions of various type of oscillations of the same system are analyzed.
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Response curves of parametric excited system
Půst, Ladislav ; Škuderová, Alena
Differential equations of motion of 2DOF system with a periodically variable stiffness controled by the absolute motion of system were derived. Matlab/Simulink was applied for numerical solution. Gained response curves were used to show the influence of structural changes (inertia moments ratio) and of gradient of driving motor characteristic.
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Kmitání tuhého rotoru uloženého v aerodynamických ložiskách
Půst, Ladislav ; Kozánek, Jan
Presented paper is a contribution to the theoretical investigation of one type of aerodynamic bearing developed in Institute of Thermomechanics. Bearing properties were ascertained by numerical solution in the form of evolutive stiffness and damping matrices in the Techlab and used in IT ASCR for analyses of dynamical properties of experimental rotor. Analysis of dynamic properties of rigid rotor supported on aerodynamic bearings was carried out for cases without and with considering of inertia properties of tilting pads.
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