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Rotordynamic Characterization of Tilting-Pad Bearings With Eight Pads in Vertical Rotors 
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.ORCID-id: 0000-0002-4185-2395
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.ORCID-id: 0000-0001-6016-6342
Vattenfall AB Research and Development, SE 814 26 Älvkarleby, Sweden.
2022 (Engelska)Ingår i: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 144, nr 1, artikel-id 010902Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

It has been documented that stiffness and damping for a four-pad bearing are dependent not only on the magnitude of the load but also on the position of the rotor in the bearing. However, eight-pad bearings are not commonly employed on horizontal turbines, and the presence of several pads in the bearing will decisively affect the dynamics of the system. This paper evaluates the stiffness and damping coefficients of tilting-pad bearings with eight pads and explores the main frequencies acting on the forced response of a vertical rotor. The bearing properties were modeled as a function of eccentricity and position in the stationary coordinate system by Navier–Stokes equations whose results are taken from commercial software. The simulated unbalanced response is compared to experimental results; the changing position of the shaft produces a periodic stiffness and damping, which is dependent on the number of pads. Cross-coupled coefficients influence is discussed, showing that their absence makes an accurate model for the mean values. The results indicate that simulation of vertical rotors with eight-pad bearings can be simplified which allow more effective simulations and dynamic analysis. 

Ort, förlag, år, upplaga, sidor
American Society of Mechanical Engineers (ASME) , 2022. Vol. 144, nr 1, artikel-id 010902
Nyckelord [en]
tilting-pad bearing, vertical rotor
Nationell ämneskategori
Teknisk mekanik
Forskningsämne
Maskinkonstruktion
Identifikatorer
URN: urn:nbn:se:ltu:diva-86562DOI: 10.1115/1.4051803ISI: 000720985000005Scopus ID: 2-s2.0-85121689564OAI: oai:DiVA.org:ltu-86562DiVA, id: diva2:1584425
Forskningsfinansiär
EnergimyndighetenLuleå tekniska universitet
Anmärkning

Validerad;2022;Nivå 2;2022-01-01 (johcin)

Tillgänglig från: 2021-08-12 Skapad: 2021-08-12 Senast uppdaterad: 2024-04-19Bibliografiskt granskad
Ingår i avhandling
1. Dynamic Modeling of Hydropower Generators
Öppna denna publikation i ny flik eller fönster >>Dynamic Modeling of Hydropower Generators
2022 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Modeling the dynamics of hydropower generators has been the aim pursued by many studies, as providing a reliable model would lead to more cost-effective designs. Hydropower generators comprise many parts, tilting-pad bearings, shaft, rotor rim, and stator among them, that contribute to the system's nonlinearities. In this thesis, the dynamics of hydropower generator is studied first by characterizing tilting-pad bearings. Multiple pad bearings are common in the industry; an eight-pad tilting-pad bearing has been studied on vertical rotors. Previous studies have shown that multiple pad bearings display stiffness and damping coefficients dependent on eccentricity and position. A model for eight-pad tilting pad bearings has been proposed and compared to experiments. The effect of cross-coupled phenomena was also investigated.

On the other hand, the generators are not rigid bodies, and the flexibility of either rotor rim or stator influences the distribution of the magnetic field, thus the force distribution. An uneven force distribution endangers the integrity of the machine. This thesis also proposes a model for a generator with flexible rotor rims and rigid stators using Lagrange equations, considering the centrifugal and Coriolis effects, the electromagnetic interaction between rotor and stator, and static and dynamic eccentricities. This model was tried 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.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå University of Technology, 2022. s. 119
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Nationell ämneskategori
Teknisk mekanik
Forskningsämne
Maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-88896 (URN)978-91-8048-016-1 (ISBN)978-91-8048-017-8 (ISBN)
Presentation
2022-03-03, C305, Luleå Tekniska Universitet, Luleå, 09:00 (Engelska)
Opponent
Handledare
Projekt
Swedish Hydropower Centre - SVC
Tillgänglig från: 2022-01-24 Skapad: 2022-01-24 Senast uppdaterad: 2023-09-05Bibliografiskt granskad
2. Dynamic Models for Mechanical Analysis of Synchronous Hydropower Generators
Öppna denna publikation i ny flik eller fönster >>Dynamic Models for Mechanical Analysis of Synchronous Hydropower Generators
2024 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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. 

Ort, förlag, år, upplaga, sidor
Luleå: Luleå University of Technology, 2024
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Nyckelord
Rotordynamics, Hydropower, Generator, Curved Beam, Tillting-Pad Bearing
Nationell ämneskategori
Teknisk mekanik
Forskningsämne
Maskinkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-105169 (URN)978-91-8048-548-7 (ISBN)978-91-8048-549-4 (ISBN)
Disputation
2024-06-14, B192, Luleå University of Technology, Luleå, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2024-04-22 Skapad: 2024-04-19 Senast uppdaterad: 2024-05-16Bibliografiskt granskad

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