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research-article

A FEASIBILITY STUDY OF CONTROLLABLE GAS FOIL BEARINGS WITH PIEZOELECTRIC MATERIALS VIA ROTORDYNAMIC MODEL PREDICTIONS

[+] Author and Article Information
Jisu Park

Research Fellow, Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, Seoul, Korea
pjs9701@seoultech.ac.kr

Kyuho Sim

Assistant Professor, Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, Seoul, Korea
khsim@seoultech.ac.kr

1Corresponding author.

ASME doi:10.1115/1.4041384 History: Received June 27, 2018; Revised August 16, 2018

Abstract

This study presents a new concept of controllable gas foil bearings (C-GFBs) with piezoelectric actuators. The C-GFB consists of a laminated top foil, bump foil, and piezo stacks and can simply change the bearing shape or film thickness locally and globally by varying the thickness of the piezo stacks with input voltages. The control schemes are 1) clearance control: the bearing clearance adjusted by changing overall piezo stack thickness, and 2) preload control: the mechanical preload modulated by the thickness expansion of several piezo stacks. Bearing lubrication performance is predicted for four cases of C-GFBs with different bearing clearances and preloads. The piezo stack control generates meaningful differences in the fluid-film thickness and pressure. Clearance control has a great effect on the dynamic force coefficients, but preload control slightly increases. Furthermore, the rotordynamic prediction of a rotor supported on two journal C-GFBs is conducted. As a result, both control mode for C-GFB is found to have a positive effect on rotordynamic amplitudes. Finally, using the orbit simulations, the C-GFB is controlled to have a small bearing clearance and large preload at critical speeds to make it possible to stably pass through the critical speeds. Consequently, it turns out that the C-GFB can improve bearing lubrication and rotordynamic performances by controlling only the input voltage of the piezo stacks. In addition, the C-GFB can be used to form various shapes to meet the operation conditions of an applied system.

Copyright (c) 2018 by ASME
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