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Numerical and experimental study on the dynamic bearing properties of a four-pad and eight-pad tilting pad journal bearings in a vertical rotor 
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0009-0000-8078-5036
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-4185-2395
Vattenfall AB Research and Development, Älvkarleby, SE 814 26, Sweden.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0001-6016-6342
2022 (English)In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 144, no 1Article in journal (Refereed) Published
Abstract [en]

In this paper, the dynamics of tilting pad journal bearings with four and eight pads are studied and compared experimentally and numerically. The experiments are performed on a rigid vertical rotor supported by two identical bearings. Two sets of experiments are carried out under similar test setup. One set is performed on a rigid rotor with two four-pad bearings, while the other is on a rigid rotor with two eight-pad bearings. The dynamic properties of the two bearing types are compared with each other by studying the unbalance response of the system at different rotor speeds. Numerically, the test rig is modeled as a rigid rotor and the bearing coefficients are calculated based on Navier-Stokes equation. A nonlinear bearing model is developed and used in the steady state response simulation. The measured and simulated displacement and force orbits show similar patterns for both bearing types. Compared to the measurement, the simulated mean value and range (peak-to-peak amplitude) of the bearing force deviate with a maximum of 16 % and 38 %, respectively. It is concluded that, unlike the eight-pad TPJB, the four-pad TPJB excite the system at the third and fifth-order frequencies, which are due to the number of pads, and the amplitudes of these frequencies increase with the rotor speed. 

Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME) , 2022. Vol. 144, no 1
Keywords [en]
Bearing Stiffness, Damping Coefficient, Tilting Pad Journal Bearing, Vertical Rotor
National Category
Applied Mechanics
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:ltu:diva-86610DOI: 10.1115/1.4052032ISI: 000720985000020Scopus ID: 2-s2.0-85137204906OAI: oai:DiVA.org:ltu-86610DiVA, id: diva2:1585001
Note

Validerad;2021;Nivå 2;2021-09-01 (johcin)

Available from: 2021-08-16 Created: 2021-08-16 Last updated: 2024-04-22Bibliographically approved
In thesis
1. Nonlinear dynamic analysis of vertical rotors with tilting pad journal bearings
Open this publication in new window or tab >>Nonlinear dynamic analysis of vertical rotors with tilting pad journal bearings
2021 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2021
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
vertical rotor, tilting pad journal bearing, stiffness, damping
National Category
Applied Mechanics
Research subject
Machine Design
Identifiers
urn:nbn:se:ltu:diva-87453 (URN)978-91-7790-946-0 (ISBN)978-91-7790-947-7 (ISBN)
Presentation
2022-02-04, E632, Luleå, 09:00 (English)
Opponent
Supervisors
Projects
Swedish Hydropower Centre - SVC
Available from: 2021-10-11 Created: 2021-10-11 Last updated: 2024-04-08Bibliographically approved
2. Rotordynamic Modeling and Characterization of Support Elements in Vertical Machines
Open this publication in new window or tab >>Rotordynamic Modeling and Characterization of Support Elements in Vertical Machines
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Rotordynamiska Modellering och Karakterisering av Stödelement i Vertikala Maskiner
Abstract [en]

The dynamic properties of rotating machines are highly influenced by supporting elements, such as bearings, seals, damping elements or housings. They play a significant role in regulating the characteristics of the interaction between the rotating and stationary parts of machines. Over the past few years, numerous research studies have been published focusing on the dynamics of such devices across a wide range of applications. The advancement of the research has significantly contributed to enhancing their performance and ensuring the smooth operation of rotating machinery by minimizing excessive vibrations that can lead to catastrophic failure. The research work in this thesis explores the dynamics of supporting elements in vertical rotating machinery, with a particular focus on hydropower applications. In fact, some of the concepts are generic and can be applied to horizontal rotors or any other types of rotating machines. Using numerical simulation and actual measurements, their contribution to the system’s overall performance was investigated. These include the self-induced vibration in vertical application tilting pad journal bearings, and vibration issues observed on a hydropower unit attributed to large bearing clearance. Also, particular attention was given to the influence of the squeeze film damper on the rotor-stator contact dynamics of hydropower units, using tools such as Poincaré maps and bifurcation diagrams.

Moreover, achieving optimal design of such devices requires, among other key aspects, accurate and reliable simulation models to facilitate the prediction and evaluation of their characteristics at any stage in the product development process. In rotordynamic simulations, a common approach for incorporating bearing forces in the system equation is by representing them with stiffness and damping coefficients. For a small vibrational amplitude about a static position, linearized bearing coefficient assumptions can be valid. This is especially applicable for operation under a large radial static load, such as in horizontal rotors, due to the dead weight of the rotor. For vertical rotors, however, the weight of the rotor acts axially, and the radial bearing load is usually low. The bearing coefficients show nonlinearity, making them dependent on the trajectory of the rotor. Therefore, the linear bearing assumption, which is valid for horizontal rotors, does not hold true for vertical rotors. This makes the simulation of a vertical machine more complicated as it typically involves solving the fluid film lubrication model. The classical numerical models can sometimes be computationally demanding and require impractically long computational time. An efficient and fast numerical simulation method which does not significantly affect the accuracy of the result is critical to facilitating the simulation processes effectively. This thesis details the suggested simplifications employed on the bearing models and transformation matrices in the numerical integration procedure. The results from these models were validated using experiments to ensure their reliability.

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
Rotordynamic, Support Element, Bearing, Squeeze Film Damper, Hydropower, Vertical Machine
National Category
Applied Mechanics
Research subject
Machine Design
Identifiers
urn:nbn:se:ltu:diva-105194 (URN)978-91-8048-552-4 (ISBN)978-91-8048-553-1 (ISBN)
Public defence
2024-06-18, B192, Luleå tekniska universitet, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2024-04-22 Created: 2024-04-22 Last updated: 2024-05-17Bibliographically approved

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Benti, Gudeta BerhanuRondon, DavidAidanpää, Jan-Olov

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