Date of Award

12-2009

Document Type

Thesis

Degree Name

Master of Engineering (ME)

Legacy Department

Mechanical Engineering

Advisor

Daqaq, Mohammed F.

Committee Member

Bruce , David A.

Committee Member

Pisu , Pierluigi

Abstract

Estimating the concentration of gases including carbon monoxide (CO) in the hydrogen fuel exiting the reformer and entering the fuel cell is imperative. A high concentration of CO can cause fuel-cell catalyst poisoning, which permanently destroys the cell. Current practices call for utilizing expensive and bulky spectral analyzers to achieve this task. In addition to their high cost, these methodologies, undoubtedly, hinder the portability and self-containment of the cell. To overcome these problems and achieve the desired objectives of a portable, self-contained, and real-time measurement module, this thesis presents and experimentally investigates a new enabling technology based on utilizing an array of microcantilever sensors to detect minute concentrations of CO in the fuel cell. Results of this study indicate that microcantilevers can be spin coated with homogenous layers of copper-exchanged Y zeolite (CuY). This zeolite is capable of adsorbing CO over a range pressures and fuel cell operating temperatures. As a result of this adsorption, the sensor experiences a shift in its resonance frequency, which can be measured and related to the concentration of CO. It is determined that maximum adsorption capacity of the sensor occurs at 40 oC using CuY zeolite that is loaded with 10 wt% Cu. Furthermore, experimental findings indicate that the sensitivity of the sensor increases as the number of zeolite layers is increased up to a certain threshold (4 layers). Beyond this threshold, adding more layers will only result in a less sensitive sensor. In the experiments described in this thesis, a maximum repeatable shift of 275 Hz in the first modal frequency of the microcantilevers is measured. Ultimately, such frequency shifts can be
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related to the concentration of CO in the gas mixture, allowing closed-loop, real-time control and diagnosis of the flow of gases into and out of the fuel cell. This can help avoid fuel-cell starvation and prevent catastrophic deactivation of the necessary fuel cell catalyst.

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