Date of Award

Spring 1-1-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Victor M. Bright

Second Advisor

Yung-Cheng Lee

Third Advisor

Kurt Maute

Abstract

A new and comprehensive analytical and numerical model for membrane microcompressors driven axially by a single lead zirconium titanate (PZT) stack actuator incorporating assembly variation errors was developed. The model can be used as a future design aid, to predict dynamic device performance as a function of error severity and as microcompressor dimensions are scaled down from the macro to micro scale. The major conclusion of this work was that since micro compressors can be made adjustable to achieve maximum compression ratio another factor besides assembly variation error reduces the achievable compression ratio. Other contributions included the following. First, an analytical method to predict the maximum pressure to within ~5% of that experimentally measured was developed. Second, a numerical method to predict the maximum pressure to within ~0.6% of that experimentally measured was developed. A useful result found was that for fixed actuator size, smaller membrane radii generate substantially higher pressures. Another useful result was that for fixed actuator size, thicker membranes and membrane materials with higher Young's Modulus can generate substantially higher pressures. Further, maximum pressure is increased more dramatically by decreasing membrane radius than increasing membrane thickness and Young's Modulus. Moreover, an analytical method to predict the compression ratio degradation factor as a function of assembly variation error to adjustable and fixed devices was presented. Covariance analysis was used to determine that the assembly variation error with the most influence on microcompressor performance was the angle of the actuator with respect to the horizontal axis of the device. It was shown that compression ratio is a function of this single net error parameter, and that this function is scale invariant.

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