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International Journal of Rotating Machinery
Volume 2014 (2014), Article ID 309767, 10 pages
http://dx.doi.org/10.1155/2014/309767
Research Article

Experimental and Numerical Simulation of Unbalance Response in Vertical Test Rig with Tilting-Pad Bearings

1Hydro Power, ÅF, 80320 Gävle, Sweden
2Mechanical and Hydraulic Engineering, Vattenfall R&D, 814 26 Älvkarleby, Sweden
3Mechanics of Solid Materials, Luleå University of Technology, 97187 Luleå, Sweden

Received 31 July 2013; Accepted 7 October 2013; Published 6 January 2014

Academic Editor: Jerzy Sawicki

Copyright © 2014 Mattias Nässelqvist et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In vertically oriented machines with journal bearing, there are no predefined static radial loads, such as dead weight for horizontal rotor. Most of the commercial software is designed to calculate rotordynamic and bearing properties based on machines with a horizontally oriented rotor; that is, the bearing properties are calculated at a static eccentricity. For tilting-pad bearings, there are no existing analytical expressions for bearing parameters and the bearing parameters are dependent on eccentricity and load angle. The objective of this paper is to present a simplified method to perform numerical simulations on vertical rotors including bearing parameters. Instead of recalculating the bearing parameters in each time step polynomials are used to represent the bearing parameters for present eccentricities and load angles. Numerical results are compared with results from tests performed in a test rig. The test rig consists of two guide bearings and a midspan rotor. The guide bearings are 4-pad tilting-pad bearings. Shaft displacement and strains in the bearing bracket are measured to determine the test rig’s properties. The comparison between measurements and simulated results shows small deviations in absolute displacement and load levels, which can be expected due to difficulties in calculating exact bearing parameters.