Title

Smart Journal Bearing with Controllable Radial Clearance, Design and Analysis

Date of Award

2017

Degree Type

Dissertation

Degree Name

Doctor of Engineering, Cleveland State University

Department

Washkewicz College of Engineering

First Advisor

Rashidi, Majid

Subject Headings

Mechanical Engineering

Abstract

This work presents an innovative design concept for a “smart journal bearing” set to operate in a stable hydrodynamic lubrication regime, despite variations in bearing speed, load, and its lubricant viscosity. The concept of controlling of the radial clearance, as presented in this work, is original and has not been proposed and discussed in previous research. The proposed bearing design allows adjusting its radial clearance for an attempt to maintain a stable bearing operation under various operating conditions. The design concept allows adjusting the radial clearance at small increments in the order of 0.001 mm. The proposed work includes a 3D model of the bearing that depicts the structural interactions of the bearing components. The 3D model is employed to conduct finite element analyses to simulate the mechanical behavior of the bearing from a structural point of view. A typical journal bearing was analyzed under a set of design parameters, namely r =1.27 cm (journal radius), c = 0.0254 mm (radial clearance), L=1.27 cm (bearing length), w = 445N (bearing load), µ = 0.028 Pascale-sec. (lubricant viscosity). A shaft speed as 3600 r.p.m was considered, and the mass supported by the bearing, m, is set to be 984.2kg. The Summerfield Number associated with the above bearing design
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parameters turn to be, S = 0.3. These combinations resulted in stable bearing operation. Subsequently, the speed was postulated to increase from 3600 r.p.m to 7200 r.p.m; thebearing was found to be unstable under the new increased speed. In order to regain stability, the radial clearance was increased from c = 0.0254 mm to 0.0358mm. The change in the radial clearance was shown to bring the bearing back to stable an operating condition. This work also presents the dynamic behavior of a Jeffcott rotor supported by two identical proposed smart bearings. Adjusting the radial clearance of the bearings showed that the peak-to-peak vibration amplitude of the rotor disk could be reduced from about 0.08 mm to about 0.03 mm.

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