Reduced modal model of bladed turbine wheel for study of suppression of self-excited vibration by dry-friction contacts

0541968 - ÚT 2022 RIV PL eng C - Konferenční příspěvek (zahraniční konf.)
Pešek, Luděk - Šnábl, Pavel - Prasad, Chandra Shekhar
Reduced modal model of bladed turbine wheel for study of suppression of self-excited vibration by dry-friction contacts.
14th International Conference on Dynamics of Rotating Machines : SIRM 2021. Gdaňsk: IMP PAN, 2021 - (Žywica, G.; Szolc, T.), s. 371-380. ISBN 978-83-88237-98-0.
[SIRM 2021 International Conference on Dynamics of Rotating Machines /14./. Gdaňsk (PL), 17.02.2021-19.02.2021]
Grant CEP: GA ČR(CZ) GA20-26779S
Institucionální podpora: RVO:61388998
Klíčová slova: blade * flutter * travelling wave * Van der pol model
Obor OECD: Applied mechanics

Because three-dimensional finite element computational programs of fluid and structural dynamics are very expensive and require large computational power to simulate fluid-structure problems in machines where a largefluid domain and complex solid bodies need to be discretized, we aim at development and application of reducedorder modelling (ROM) of flutter oscillations in turbine bladed wheel dynamics [1]. Though such ROM approaches are lower fidelity, yet they can bring interesting knowledge about dynamic behaviour of bladed wheelsystems. In this contribution, we deal with the exploitation of modal synthesis method (MSM) [2-4] as a tool for ROM modelling of dry-friction damping effect on self-excited vibrations due to aero-elastic instability. The MSM, proposed for the bladed wheel dynamics’ applications recently in [5], is extended herein to study anon-linear dynamics of an industrial turbine wheel of 66 blades with inter-blade connections by tie-boss dryfriction couplings [6]. In the bladed wheel model, neighbouring blades are interconnected by rigid arms that are on one side fixed to one blade and are in friction contact on their free side with the other blade. The point contact pairs of two neighbouring blades overlap in undeformed state of the cascade. The relative contact displacements due to blade cascade deformation are calculated from kinematics of relative blade motions. For evaluation of friction forces in contacts the modified Coulomb friction law is used [7]. The aerodynamic excitation arises from the spatially periodical flow of steam through the stator blade cascade. The forced nozzle excitation causes instability and/or increase of self-excited oscillations [8-10]. For description of post-critical dynamic behaviour of the bladed wheels at self-oscillations, semi-analytical approach based on theVan der Pol model was proposed [11-13]. We considered two types two types of Van der Pol model related to a) absolute blade movement: b) relative inter-blade movement in our previous works. From the flutter theory of blade cascades both movements are important for flutter origin. In this study, however, the effect of the self-excited vibrations related to case a) was considered only. The analysis is oriented on the narrow frequency range and a case when a slip motion is prevailing in the contacts. The calculations by MSM is computationally very efficient and the effect of the friction damping on the self-excited oscillations with respect to magnitude of normal contact forces is analysed.
Trvalý link: http://hdl.handle.net/11104/0320671