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Application of pulse excitation for forced vibration of selected eigenmode of blade wheel under rotation
Pešek, Luděk ; Bula, Vítězslav ; Cibulka, Jan
Application of pulse excitation for forced vibration of selected eigenmode of blade wheel under rotation. The paper deals with a solution of multipoint electromagnetic pulse excitation of turbine blade wheel under rotation for analysis of its dynamic behaviour. Since a width of electromagnetic pulses should decrease with revolution speed, magnetomotoric forces acting to the blades decrease, too. So, the application of more “high-speed” electromagnets distributed along a circumference of the wheel that multiply the excitation potential seems to be inevitable for such a stiff structure. It, however, requires accurate synchronization of the electromagnets with wheel revolutions and with a dynamic response of the selected blade. Furthermore impulse excitation causes, in general, transient oscillations of many superposed eigenmodes of the wheel. Therefore an attention, herein, was paid to develop an appropriate control algorithm for the pulse excitation of electromagnets and to find a proper strategy of electromagnet interconnections to gain a multiplepoint excitation for excitation of selected eigenmodes.
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The test of the time-difference method for the torsion vibration of the rottating shaft
Pešek, Luděk ; Bula, Vítězslav ; Cibulka, Jan
The contribution deals with testing of the time difference method by using the encoder for evaluation of the torsion vibration of the rotating shaft under dynamic torque moment excitation. The testing of accuracy of this method was first performed on the numerical simulations of the pulse signals and then on the real experimental data gained from the encoder. Then the method was implemented into dSPACE control system for on-line processing. The achieved experimental results are in accordance with the numerical assumptions.
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Experimental analysis of friction coupling in triple blade bundle under rotation
Pešek, Luděk ; Půst, Ladislav ; Bula, Vítězslav ; Vaněk, František ; Cibulka, Jan
In the contribution the experimental analysis of these blades in two opposed bundles under rotation will be presented. One-point electromagnetic synchronized pulse excitation served as a force excitation for analysis of resonant vibration under different revolution speeds. The force level was evaluated from supply current calibrated by dynamic scale measurement. The responses of the blades were measurement by strain-gauges placed on the blades with a slip-ring signal transmission. After sufficient level of first flexural (axial) blade vibration the electromagnetic force was turned off and vibration attenuations were analyzed. The dynamic behaviour of the blades and results of damping are in a good accordance with the numerical modelling.
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Rotational angiography
JAŠAROVÁ, Eva
Digital Subtraction Angiography (DSA) is a special X-ray examination of the blood vessel system. Despite the development of other visual techniques it has not lost its importance so far. In the 1960s and 1970s it developed itself into the most detailed method of visualization of the blood-vessel system. DSA requires much more expensive device and equipment with tools than only ten years ago. The price is equal to the quality and amount of information. DSA further remains the invasive method. One or two-projection system for acquiring the complete picture of blood vessels is the most used technique of record in angiography. Common methodologies require two applications of the contrast medium for the same part of the body. Rotation angiography is a special modern technique for three-dimensional visualization of arteries. It is mainly used for visualization of neck or brain arteries. Its principle is in the application of the contrast medium into the artery, when the examined area is X-rayed and C-arm is continuously turned by 180°. The final angiography can be assessed that we turn the picture step by step. If we display the same area once more without the application of the contrast medium, we get a mask for DSA and both sequences we can subtract. Only one artery is displayed as well as during classic DSA.
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Growing of over - growth tree species
KOSTOHRYZOVÁ, Lenka
The comparison of agronomical practices and land capability of selected deciduous with coniferous wood species, especially fast growing tree species on agricultural land, is the theme of this bachelor work. This work deals with the cultivation of fast growing tree species, the comparison of their growth figures and agricultural techniques. Fast growing tree species were cultivated in these localities: Svatý Jan nad Malší (Chlum nad Malší), Všemyslice- Neznašov and Lesy města Český Krumlov s.r.o. The research was focused on the comparison of yields of deciduous (poplar) with coniferous trees (spruce, larch), agricultural techniques. There is the comparison of yields with yields from the available literature, in conclusion.
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Roman temporary camp and new finds from the Roman Period in Charvátská Nová Ves
Vlach, Marek
In year 2006 during the testing phase of a predictive model project (Institute of Archaeology and Museology, Faculty of Arts, Masaryk University) were encountered traces of the Germanic activities in vicinity of the Roman temporary camp in Charvátská Nová Ves. Using the method of geological probing it was possible to spatially specify exact position of the temporary camp, discovered previously during the aerial survey. The probing also provided information for buildup of simple profile of temporary camp ditch.
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Kinematic system for measurement of dynamic parametes of vibrationg parts under rotation
Pešek, Luděk ; Vaněk, František ; Procházka, Pavel ; Vaněk, Petr ; Cibulka, Jan ; Bula, Vítězslav
Kinematic system for measurement of dynamic parameters of vibrating parts under rotation.In the contribution the research on the improvement of the kinematic measuring system for evaluation of natural and forced vibration of machinery parts under rotation is presented. The improvement was aimed at the sensor part for a continuous movement of rotating and vibrating disk. For this reason the numerical FE model of the physical model of bladed disk was developed and analyzed. Laboratory verification of the new proposed sensor system was performed under an electromagnetic harmonic excitation. By means of strain-gauge measurement that were placed on several disk blades with a slip-ring signal transmission, the dynamics of the rotor was analyzed and the kinematic system was calibrated.
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