Design, fabrication, experimentation and analysis of high-speed microscale gas bearings
Name
48815694-MIT.pdf
Description
Full printable version
Size
23.98 MB
Format
Adobe PDF
Checksum (MD5)
543282f123bcb4619386cb6e4d4dfc97
Author(s)
Wong, Chee Wei, 1975-
Advisor(s)
Stuart A. Jacobson and Alan H. Epstein.
Date Issued
2001
Publisher
Massachusetts Institute of Technology
Abstract
Microengine Program. The all-silicon device consist of a free-rotating microturbine, with 4.2 mm rotor diameter, enclosed within a five wafer fusion-bonded stack. Of note are the low aspect ratio journal bearing and large journal bearing clearances, primarily limited by microfabrication, from which stable bearing operation must first be demonstrated as viable. Theoretical modeling of the gas-lubricated hydrostatic journal bearing presents design charts, a comparative study of existing predictions and investigation into rotational effects to consider the bearing stiffness during operation. Continued experimental refinements and exploration with our microfabricated rotor achieved rotational speeds up to 1.4 million rpm and peripheral speeds in excess of 300 m/s. Extensive experimental data is presented with analysis, focusing on whirl motion and its harmonic resonances as candidates for instability. Causes of ultimate failure is suggested with recommendations for further improvements. Moreover, in an effort to accomplish self-sustained microbearings, the axial thrust bearing is redesigned for a self-acting spiral groove bearing. The chosen constraint is to incorporate the hydrodynamic thrust bearing with minimal changes to the current device, whilst providing the required load and stiffness. Stability analysis and rarefaction considerations on the optimized design suggests an operating range for the bearing, leading to a hybrid design for ample stiffness during initial operation. The design is then developed into a microfabrication process flow and implemented successfully into the MicroBearing test devices. Experiments on a hybrid bearing were performed to gage the spiral grooves characteristics. A purely hydrodynamic aft thrust bearing device is then tested for operation through low speeds, although the effects of the spiral grooves could not be accurately determined. Finally, transition to a hydrodynamic operating mode for a hybrid bearing is demonstrated.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
Includes bibliographical references (p. [183]-190).
Subjects
Mechanical Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Terms of Use
M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.
Persistent DSpace Link
