Vibration Analysis and Health Diagnosis of Spinning Cyclic Symmetric Rotors with Flexible Bearing and Housing Supports

University Of Washington, Seattle WA

Investigators

Abstract

This research is to study vibration and health monitoring of spinning cyclic symmetric rotors with flexible bearing and housing supports. There are three specific goals. The first goal is to develop a mathematical model to predict ground-based vibration response of a spinning cyclic symmetric rotor with flexible bearing and housing supports. The basic idea is a component mode synthesis allowing the rotor and housing to assume arbitrary geometry. Also, the model will be validated experimentally. The second goal is to develop an efficient algorithm to speed up calculations of the ground-based response. The basic idea is to reduce the order of the governing equation through use of "balanced modes" that do not present coupling between the rotor and the housing. The third goal is to study the feasibility to monitor rotor health via vibration signatures of the housing and bearings. The main focus of the research is cyclic symmetric rotors, which appear very often in rotary machines, such as jet engines and refrigerator compressors. Every rotary machine consists of three basic components: a rotary part (rotor), a stationary part (housing), and multiple bearings that connect the rotary and stationary parts. When a rotor consists of N identical substructures repeating themselves in the circumferential direction, the rotor is called "cyclic symmetric." Examples of cyclic symmetric rotors include wind turbines and propellers. Traditional vibration analyses of cyclic symmetric rotors assume (a) no bearing and housing supports and (b) rotor-based formulations. Recent industrial needs, however, challenge the validity of these two assumptions. With increased material and fuel costs, aviation industry seeks to reduce weight and rigidity of engines, thus increasing coupled rotor-bearing-housing vibration. With increased maintenance costs, industries seek to monitor ground-based machine response to evaluate the health of high-speed rotary systems. The proposed research will not only broaden the knowledge on cyclic symmetric rotors by removing the two major assumptions, but also provide the industry with fundamental understanding to advance its products.