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

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388998%3A_____%2F21%3A00541968" target="_blank" >RIV/61388998:_____/21:00541968 - isvavai.cz</a>

Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

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

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

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

Popis výsledku anglicky

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.

Druh

D - Stať ve sborníku

CEP obor

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OECD FORD obor

20302 - Applied mechanics

Projekt

<a href="/cs/project/GA20-26779S" target="_blank" >GA20-26779S: Výzkum nestabilit dynamického stall flutteru a jejich následků na aplikace turbostrojů pomocí matematických, numerických a experimentálních metod</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2021

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název statě ve sborníku

14th International Conference on Dynamics of Rotating Machines : SIRM 2021

ISBN

978-83-88237-98-0

ISSN

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e-ISSN

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Počet stran výsledku

10

Strana od-do

371-380

Název nakladatele

IMP PAN

Místo vydání

Gdaňsk

Místo konání akce

Gdaňsk

Datum konání akce

17. 2. 2021

Typ akce podle státní příslušnosti

EUR - Evropská akce

Kód UT WoS článku

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