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Running flutter waves in blades cascade
Půst, Ladislav ; Pešek, Luděk
The simplified mathematical model of dynamic properties of bladed cascade excited by wakes of flowing steam from the stationary cascade is derived. Interaction of this kind of forced excitation with aero-elastic self-excitation described by Van der Pol formula causes origin of flutter and its. running waves. It is shown that the velocity, direction of flutter running waves and mode of vibration depend on the blades’ number ratio and on kind of self-excitation forces on individual blade or on inter-blade distance.
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Modelling of running waves in turbine blades cascade
Půst, Ladislav ; Pešek, Luděk
Dynamic properties of blades in the blade cascade excited by steam flow from the stationary bladed disk are investigated with the aim to explain origin and behaviour of running waves. It is shown that one of the most important reasons for existence of running waves is the running periodic forces from steam wakes due to different numbers of blades of stationary and rotating wheels. On a simplified computational model of disk with closed 10-blades bundle are presented resulting velocities, theirs directions and modes of forced running waves. The effect of these forced running waves on the existence of flutter waves will be shortly mentioned as well.
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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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Vibration of blade bunch forced by delayed excitation
Půst, Ladislav ; Pešek, Luděk ; Radolfová, Alena
Response of the five-blade-bunch linked in the shroud by means viscous-elastic damping connections and excited by running harmonic forces is investigated. This type of excitation corresponds to the real excitation in the steam or gas turbine with different number of rotor and stator blades. After ascertaining of phase delay between neighbouring blades, the different dynamic properties of isolated and closed five-blade bunch are shown and analysed in this contribution. Recommendation how apply ascertained results for evaluation of experimentally gained data from dynamic measurements on bladed disk is added.
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