A method to obtain the linear dynamic coefficients for journal bearing in vertical rotors
Industrial Lubrication and Tribology
ISSN: 0036-8792
Article publication date: 3 October 2019
Issue publication date: 14 January 2020
Abstract
Purpose
The infinitesimal perturbation (IP) method is commonly used in calculating stiffness and damping of journal bearing in horizon rotor systems. The boundary condition (BC) for the perturbed pressure is assumed being zero at leading edge of film, although it is usually not zero because of nonzero pressure gradient. This assumption is sufficiently accurate for most purpose in horizon rotors. However, for journal bearing in vertical rotor-bearing systems, the BC with the assumption in IP method will bring in significant errors in calculating linear dynamic coefficients. This paper aims to propose a method to obtain the dynamic coefficients of journal bearing in vertical rotors.
Design/methodology/approach
The stiffness and damping are approached based on IP method and the modified BC of perturbed pressure. As it is difficult to predict perturbed pressure at leading edge at a fixed coordinate system using IP method, a dynamic coordinate system is introduced in this method, of which the origin on circumferential direction is defined as the leading edge of film.
Findings
The effectiveness and accuracy of proposed IP method in dynamic coordinate (IPMDC) system are verified by comparing the obtained results with analytical solutions. The comparison shows that the results from IPMDC present a good agreement with the analytic solutions.
Originality/value
The proposed method can be applied in obtaining linear dynamic coefficients of journal bearing in vertical rotors with high precisions. Instead of the usual nonlinear analysis of vertical rotors, this method provides a feasibility of predicting the instability threshold of vertical rotor-bearing systems via linear models.
Keywords
Acknowledgements
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by the National Natural Science Foundation of China (NO.11672179, NO.11272204).
Citation
Chen, C., Jing, J. and Cong, J. (2020), "A method to obtain the linear dynamic coefficients for journal bearing in vertical rotors", Industrial Lubrication and Tribology, Vol. 72 No. 1, pp. 38-45. https://doi.org/10.1108/ILT-04-2019-0144
Publisher
:Emerald Publishing Limited
Copyright © 2019, Emerald Publishing Limited