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Three-Dimensional Modeling for Mechanical Analysis of Hydropower Generators with Floating Rotor Rim
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-4185-2395
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-5147-683X
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0001-6016-6342
Vattenfall AB Research and Development, 814 70 Älvkarleby, Sweden.
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2024 (English)In: Machines, E-ISSN 2075-1702, Vol. 12, no 4, article id 268Article in journal (Refereed) Published
Abstract [en]

Hydropower generators withstand multiple forces from diverse sources during operation. To ensure their stability and safe performance, numerical tools are developed to characterize their dynamic properties. Traditionally, generators are assumed to be rigid in rotordynamic analyses. However, the measurements in power stations challenge this assumption. This article proposes a novel approach to modeling hydropower generators with floating rotor rims using a three-dimensional (3-D) Finite Element Method, aiming to study their dynamic performance and properties, including natural frequencies, the modes of vibrations, and expansion due to centrifugal and electromagnetic forces, with the goal of improving the reliability of modern designs. Both this approach and employing a two-dimensional (2-D) model using curved beams result in similar in-plane natural frequencies and the expansion of the rotor rim due to centrifugal forces. However, the 3-D model can be used to calculate the out-of-plane natural frequencies and modes, to model the dynamics of complex geometries, and to perform stress evaluation and fatigue analysis.

Place, publisher, year, edition, pages
MDPI, 2024. Vol. 12, no 4, article id 268
Keywords [en]
rotordynamics, FEM, curved beams, hydropower generator, electromagnetic forces, modeling, ring vibration
National Category
Energy Engineering Applied Mechanics
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:ltu:diva-104994DOI: 10.3390/machines12040268OAI: oai:DiVA.org:ltu-104994DiVA, id: diva2:1849294
Projects
Swedish Hydropower Centre-SVC
Note

Full text: CC BY License

Available from: 2024-04-05 Created: 2024-04-05 Last updated: 2024-04-30
In thesis
1. Dynamic Models for Mechanical Analysis of Synchronous Hydropower Generators
Open this publication in new window or tab >>Dynamic Models for Mechanical Analysis of Synchronous Hydropower Generators
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hydropower generators are essential for providing electricity for daily human activities. For that reason, designing and building reliable generators contributes to a sustainable energy supply market. Many studies have sought to model the dynamics of hydropower generators, as providing a reliable model would lead to more cost-effective designs; these models need to consider both operational and faulty conditions. A generator comprises many parts that contribute to its dynamics: tilting-pad bearings, rotor-rim, and stator’s core, which are the ones focused on in this study. Modeling a hydropower generator is a complex endeavor that requires considerable computational resources and is time-consuming. Therefore, this thesis aims to propose models to study and predict the dynamics of hydropower generators, which would be beneficial for manufacturers and operators, reducing the complexity of the design without compromising accuracy. To accomplish this, each mentioned individual part is explored. It starts with characterizing eight-pad tilting-pad bearings on vertical rotors, proposing a model, and comparing the results to experiments. Then it continues by considering the rotor rim in a generator to be flexible and proposing a model for the generator with flexible rotor rims while the stator remains rigid; this is accomplished using Lagrange equations, considering the centrifugal and Coriolis effects, the electromagnetic interaction between rotor and stator, and static and dynamic eccentricities. Reducing the complexity of the rotor rim required assembling 2-D curved beam elements to reproduce its geometry and testing on a generator prototype, discussing the impact of the connecting plates and the magnetic forces on the natural frequencies and the effect of static eccentricity and unbalance. A 3-D Finite Element model of the generator was also proposed, and both simulations focused on the similarities and differences between both approaches.  Furthermore, linear and nonlinear models of the electromagnetic forces acting on the rotor are also considered and applied in the model to study whether the nonlinear behavior in a generator can affect its stability by employing Bifurcation diagrams and Poincaré maps. 

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2024
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Rotordynamics, Hydropower, Generator, Curved Beam, Tillting-Pad Bearing
National Category
Applied Mechanics
Research subject
Machine Design
Identifiers
urn:nbn:se:ltu:diva-105169 (URN)978-91-8048-548-7 (ISBN)978-91-8048-549-4 (ISBN)
Public defence
2024-06-14, B192, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2024-04-22 Created: 2024-04-19 Last updated: 2024-05-16Bibliographically approved

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Rondon, DavidPääjärvi, SimonAidanpää, Jan-OlovJeppsson, Peter

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