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Influence of pad compliance on nonlinear dynamic characteristics of tilting pad journal bearings
KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).ORCID-id: 0000-0002-7914-1636
Luleå University of Technology, Department of Engineering Sciences and Mathematics.
KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinkonstruktion (Avd.).
2013 (engelsk)Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 57, s. 46-53Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The effect of pad compliance on the dynamic response of tilting pad journal bearings is investigated. Pad compliance is varied by changing pivot geometry and Young's modulus of pad backing and pad liner. Two pad support configurations are considered: one that allows only circumferential tilt and another one that allows both circumferential and axial tilts. Journal orbits, oil film pressure and oil film thickness are compared and discussed. It is shown that higher pad backing compliance significantly increases the journal orbit size and results in an increase in oil film pressure while oil film thickness is decreased. With a compliant liner, oil film pressure is decreased while oil film thickness is increased. Tapers at the pad edges are essential to increase the global minimum oil film thickness in compliant liner bearings.

sted, utgiver, år, opplag, sider
2013. Vol. 57, s. 46-53
Emneord [en]
Tilting pad journal bearing, Compliance, Line pivot, Ball-socket pivot
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-107432DOI: 10.1016/j.triboint.2012.07.005ISI: 000311474800006Scopus ID: 2-s2.0-84864545767OAI: oai:DiVA.org:kth-107432DiVA, id: diva2:575889
Merknad

QC 20130109. Updated from submitted to published.

Tilgjengelig fra: 2013-01-09 Laget: 2012-12-11 Sist oppdatert: 2018-01-12bibliografisk kontrollert
Inngår i avhandling
1. Nonlinear Isoviscous Behaviour of Compliant Journal Bearings
Åpne denne publikasjonen i ny fane eller vindu >>Nonlinear Isoviscous Behaviour of Compliant Journal Bearings
2012 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Plans to shut down nuclear power plants in some European countries as well as increased electricity production by wind and solar power will increase the work load on hydroelectric power plants in the future. Also, due to the power grid regulations, hydroelectric power plants undergo more frequent start-ups and shut-downs. During such transient periods, a large amplitude shaft motion can occur, especially in the power plants with vertical shafts. Large shaft motion is not desirable because it can lead to a machine failure. Furthermore, performance limitations of conventional white metal or babbitted bearings call for the development of new bearing designs. An outstanding tribological performance can be achieved by introducing compliant polymer liners. At the same time, bearings with compliant liners may alter rotor-bearing system dynamic behaviour compared to the systems with conventional white metal bearings. The research approach of this thesis is to employ nonlinear analysis to provide further understanding of the compliant bearing dynamic response to synchronous shaft excitation.

Plain cylindrical journal bearings with different compliant liner thicknesses were analysed using a nonlinear approach. The numerical model was verified with an in-house developed code at steady state conditions. Results obtained by the numerical models showed good agreement. After verification of the numerical model for fixed geometry journal bearings, models for tilting pad journal bearings were developed. Results for the tilting pad journal bearing with three pads with line pivot geometry were compared with published data in dynamic conditions. A good agreement was obtained between the two numerical models. The effect of pad pivot geometry on bearing dynamic response was investigated. Vertical and horizontal shaft configurations were compared in terms of the effect of preload factor, pivot offset, tapers and pad inclination angles. Influence of the viscoelastic properties of compliant liners was also studied. All these factors significantly affect bearing dynamic response. It is shown how these factors should be selected to control the journal orbit sizes. It was also shown that the compliant liner provides lower maximum oil film pressure and thicker minimum oil film thickness in the bearing mid-plane in both static and dynamic operating conditions.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2012. s. 40
Serie
TRITA-MMK, ISSN 1400-1179 ; 2012:06
Emneord
Compliant Journal Bearings
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-91490 (URN)978-91-7501-285-8 (ISBN)
Presentation
2012-03-29, B242, Brinellvägen 85, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Prosjekter
Swedish Hydropower Centre
Merknad

QC 20120319

Tilgjengelig fra: 2012-03-19 Laget: 2012-03-16 Sist oppdatert: 2018-01-12bibliografisk kontrollert
2. Dynamic Performance and Design Aspects of Compliant Fluid Film Bearings
Åpne denne publikasjonen i ny fane eller vindu >>Dynamic Performance and Design Aspects of Compliant Fluid Film Bearings
2015 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Due to government regulations together with health and safety reasons, there are increasing demands on reducing hazardous polluting chemicals from fossil fuel power plants. Therefore, more efforts are imposed on using renewable resources such as water, wind, solar and tide to produce clean/green electricity. On top of that, there is another increasing demand from Original Equipment Manufacturers (OEMs) to operate power plants with higher load while keep the power loss to the minimum. These requirements drive conventional fluid film bearings to its mechanical and temperature limits. This calls for the development of new bearing system designs. An outstanding tribological performance such as low start-up and break-away friction, excellent resistance to chemical attack and anti-seizure properties, can be achieved by introducing compliant polymer liners. At the same time, bearings with compliant liners may alter rotor-bearing system dynamic behaviour compared to the systems with conventional white metal bearings. The research approach of this thesis is to implement compliant liner on bearing surface, impose synchronous shaft excitation and investigate the effect of bearing design parameters on bearing dynamic response.

Plain cylindrical journal bearings with different compliant liner thicknesses were analysed using a FEM approach. The numerical model was compared with an in-house developed code based on the finite difference method (FDM) for a bearing operated at steady state conditions. Results obtained by the numerical models showed good agreement. After verification of the numerical model for fixed geometry journal bearings, models for tilting pad journal bearings were developed. Dynamic behaviour of the tilting pad journal bearing with three pads with line pivot geometry was compared with published data. A good agreement was obtained between the two numerical models. The effect of pad pivot geometry on bearing dynamic response was investigated. Vertical and horizontal shaft configurations were compared in terms of the effect of preload factor, radial clearance, pivot offset, and pad inclination angles. Influence of the elastic properties of compliant liners was also studied. All these factors significantly affect bearing dynamic response. It is shown how these factors should be selected to control the journal orbit sizes. Misalignments in compliant tilting pad journal bearings were analysed for load between pivots and load on pivots with consideration of thermal effects. Significant improvements in bearing performance were obtained with compliant bearings compared to white metal bearings. Furthermore, different polymer materials (PTFE, UHMWPE, pure PEEK and PEEK composite) were characterized using Frequency Response Function (FRF). It was shown that as the excitation frequency increased the equivalent stiffness was more or less constant while equivalent damping decreased exponentially. PTFE had similar equivalent stiffness compared to PEEK. As for equivalent damping, PTFE had slightly higher damping compared to PEEK or UHMWPE. Oil film thickness, oil film temperature and loads on tilting pad journal bearing were measured on 10 MW Kaplan hydroelectric power machine. Test results were compared to FEM model. It was shown that stiffness of the supporting structure may be more important to machine performance than the stiffness of the bearing alone.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2015. s. 56
Serie
TRITA-MMK, ISSN 1400-1179 ; 2014:13
Emneord
Compliant bearing, dynamic performance, design aspects
HSV kategori
Forskningsprogram
Maskinkonstruktion
Identifikatorer
urn:nbn:se:kth:diva-163560 (URN)978-91-7595-398-4 (ISBN)
Disputas
2015-04-22, Sal Gladan, Brinellvagen 83, KTH, Stockholm, 13:00 (engelsk)
Opponent
Veileder
Prosjekter
Swedish Hydropower Centre
Forskningsfinansiär
Swedish Energy Agency
Merknad

QC 20150409

Tilgjengelig fra: 2015-04-09 Laget: 2015-04-08 Sist oppdatert: 2018-01-11bibliografisk kontrollert

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