자료유형  

 학위논문

Control Number  

0017160907

International Standard Book Number  

9798382652085

Dewey Decimal Classification Number  

621

Main Entry-Personal Name  

Maimani, Fares.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of Southern California., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

131 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-11, Section: B.

General Note  

Advisor: Ronney, Paul.

Dissertation Note  

Thesis (Ph.D.)--University of Southern California, 2024.

Summary, Etc.  

요약This work investigates the use of chemical fuels like hydrogen and propane for small scale power generation. Chemical fuels' high specific energy makes them promising for applications with stringent power system requirements. We focus on two projects: one employing hydrogen with catalytic combustion for powering microrobots, and another utilizing propane in proton exchange membrane fuel cells (PEMFC) for portable power. Microrobots at the subcentimeter scale have the potential to perform useful complex tasks if they were to become energy independent and could operate autonomously. The vast majority of current microrobotic systems lack the ability to carry sufficient onboard power to operate and, therefore, remain tethered to stationary sources of energy in laboratory environments. Recent published work demonstrated that chemical fuels can react under feedback control on the surfaces of tensioned shape-memory alloy (SMA) nickel-titanium (NiTi) wires coated with platinum (Pt) catalyst. Combining catalytic combustion of fuels with high energy densities with the high work densities of SMA wires is a promising approach to provide onboard power to microrobots. In this work, we present a novel 7-mg SMA-based miniature catalytic-combustion engine for millimeter-scale robotic actuation that is composed of a looped NiTi-Pt composite wire with a core diameter of 38 µm and a flat carbon-fiber beam with a length of 13 mm. This beam acts as a leaf spring during operation. The proposed design of the engine has a flat and narrow geometry, functions according to a periodic-unimorph actuation mode, and can operate at frequencies as high as 6Hz and lift 650 times its own weight while functioning at 1Hz, thus producing 39.5 µW of average power in the process. For the purposes of design and analysis, we derived a model of the heat transfer processes involved during actuation, which combined with a Preisach-model-based description of the SMA wire dynamics, enabled us to numerically simulate the response of the miniature system, and thus predict its performance in terms of frequency and actuation output. The suitability for microrobotics and functionality of the proposed approach is demonstrated through experimental results using a custom-built fast-response high-precision system of fuel delivery. Low-temperature direct hydrocarbon PEMFC offer a viable solution for portable power generation, with capacities under 100W. These cells provide a practical alternative to hydrogen PEMFC due to the ease of storage and handling of hydrocarbons. Moreover, they exhibit a potential energy density advantage of 10 to 50 times over traditional batteries. Despite their potential, challenges such as low power densities and the occurrence of an extinction phenomenon-wherein the cell stops producing power-remain. To address these issues, we developed a custom experimental setup to explore the dynamics and control of direct propane PEMFC, utilizing three distinct membrane electrode assemblies with varying platinum catalyst configurations. Our findings diverge from prior studies, showing sustained open circuit voltage and power generation capabilities with high purity propane alone. The study investigates the deactivation and activation dynamics under varied conditions, including current density, fuel flow rate, catalyst specifics, cell temperature, and operational modes. Current density was found to be the critical factor influencing cell behavior, while increasing the temperature significantly enhanced performance by accelerating activation and decelerating deactivation. Experimentally, we demonstrated that the direct propane PEMFC achieves power densities on the scale of 10 mW/cm2 at 85 ◦C. Additionally, we examined the impact of ethylene and hydrogen additives in propane on cell dynamics. Based on the experiment observations, we formulated a dynamical model to capture the direct propane cell dynamics. This model informed the development and evaluation of two control strategies: on-off control and model predictive control, aimed at enhancing average power output. Simulation and experimental validation of these strategies demonstrated an increase in average power density by 59%, underscoring the effectiveness of active feedback control in optimizing direct propane PEMFC performance.

Subject Added Entry-Topical Term  

Mechanical engineering.

Subject Added Entry-Topical Term  

Energy.

Subject Added Entry-Topical Term  

Design.

Subject Added Entry-Topical Term  

Engineering.

Index Term-Uncontrolled  

Catalytic combustion

Index Term-Uncontrolled  

Hydrocarbons

Index Term-Uncontrolled  

Fuel cells

Index Term-Uncontrolled  

Microrobots

Index Term-Uncontrolled  

Energy density

Index Term-Uncontrolled  

Portable power

Added Entry-Corporate Name  

University of Southern California Mechanical Engineering

Host Item Entry  

Dissertations Abstracts International. 85-11B.

Electronic Location and Access  

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Control Number  

joongbu:656271