Modal parameters identification of a rotor-journal bearing system using operational modal analysis

Author(s)

Storti, Gustavo Chaves ^[1] ; da Silva Tuckmantel, Felipe Wenzel ^[1] ; Machado, Tiago Henrique ^[1]

Affiliation

^[1] Sch Mech Engn, Lab Rotating Machinery, UNICAMP 200, Mendeleyev St, Postal Box 6122, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: Journal of the Brazilian Society of Mechanical Sciences and Engineering; v. 43, n. 3 FEB 20 2021.
• Web of Science Citations: 0

Abstract

The paper investigates the use of operational modal analysis (OMA) techniques applied directly into a rotating machinery with hydrodynamic journal bearings. OMA has proven to be a strong tool for analyzing the dynamics of large structures, especially to its capabilities in civil engineering; however, its application in rotordynamics is still very incipient. The objective here is to make a broader analysis of how this technique can be used in the universe of rotating machines and how the results become reliable. The application of this technique in rotating machines implies some care due to the inherent operating conditions of the system, especially regarding the presence of harmonic forces. The study emphasizes resonance problems with the early natural modes of the structure and its damping. The main novelty of the paper is to present a simple procedure, tapping throughout the rotor, which made possible the application of OMA to extract the modal parameters with satisfactory results in a system in which the classical EMA steeped sine technique was insufficient to provide a good analysis of the rotor. In this type of system, the hydrodynamic bearings and misalignments caused by the coupling of shaft and motor (something quite common in real systems) may cause difficulty in extracting modal parameters depending on the technique used. However, when applying traditional OMA methods, using both the frequency domain (enhanced frequency domain decomposition) and the time domain (stochastic subspace identification), it was possible to make a good identification of the modal parameters of the rotor, with promising results to encourage a broader modal identification of rotating machinery in operating conditions. (AU)

• FAPESP's process: 15/20363-6 - Fault tolerant identification and control of rotating systems
• Grantee: Katia Lucchesi Cavalca Dedini
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/07454-8 - Proposal of a theoretical-experimental model for rotor-bearing-structure interaction
• Grantee: Tiago Henrique Machado
• Support Opportunities: Regular Research Grants