Engineering Commons^™

Carbon-Based Nanostructured Materials As Electrode In Lithium-Ion Batteries And Supercapacitors, Zhuo Yao

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Carbon-based nancomposites attract much attention as electrode materials in electrochemical energy storage systems due to their low-cost, extraordinary high electrical and thermal conductivity, super high surface area etc. In this research, graphene nanosheets (GNS) and their nanocomposites with manganese oxides (GNS/MnOx) or silicon nanowires (GNS/SiNWs/CF) are studied for their applications in Li-ion batteries and supercapacitors. GNS powders are synthesized via a chemical oxidation of nature graphite followed by appropriate reduction process. GNS/MnOx composites are synthesized rendering MnOx nanoparticles embedded on the surfaces of GNS. SiNWs grown in carbon fibers are mechanically mixed with GNS powders. The impacts of the manganese …

Design And Fabrication Of An Eddy Current Brake Dynamometer For Efficiency Determination Of Electric Wheelchair Motors, Wesley Brin

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Electric wheelchairs have a considerable impact on improving the quality of life for the millions of disabled persons around the world. These modern pieces of technology offer freedom and mobility for disabled persons to interact with the world outside of their homes. The goal of this project is to assist in advancements of conventional electric wheelchairs. This includes replacing the heavy, bulky, and inefficient lead acid batteries and worm gear drive systems with lithium-ion batteries and wheel hub motors in order to decrease weight and size, and increase efficiency. This master thesis research is focused on designing, fabricating, and testing …

Design And Improve Energy Efficiency And Functionalities Of Electrical Wheelchairs, Dewei Guan

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There are millions of people who have lost their abilities to walk and wheelchairs offer the ONLY opportunities for their interactions with people and environments outside their houses. These individuals are becoming more and more eager to adapt modern technologies on their wheelchairs to improve quality of social life and the life of freedom. However, most available electric wheelchairs, driven by traditional lead-acid batteries and gear motors, are heavy and bulky in design with low energy efficiency, limited travel radius, and scarce communication/navigation functionalities. This project is to design and prototype an electric wheelchair that is lighter, more flexible in …

Synthesis And Characterization Of Graphene Oxide/Sulfur Nanocomposite For Lithium-Ion Batteries, Aaron Joseph Blake

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The growing need for clean and efficient energy storage systems has recently peaked due to concerns of climate change and increased global energy consumption. However, efficiently integrating renewable resources such as solar and wind energy into society will require a complex electrical energy storage (EES) system capable of storing and expending significant amounts of energy. A battery based on the lithium/sulfur couple can yield a theoretical specific energy of 2600Wh/kg, which is about five times higher than that offered by present Li-ion batteries, and hence, is a promising and attractive technology. Despite recent developments in addressing various issues inherent to …

Steps In The Development Of A Full Particle-In-Cell, Monte Carlo Simulation Of The Plasma In The Discharge Chamber Of An Ion Engine, Bryan James Penkal

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The design and development of ion engines is a difficult and expensive process. In order to alleviate these costs and speed ion engine development, it is proposed to further develop a particle-in-cell (PIC), Monte-Carlo collision (MCC) model of an ion engine discharge chamber, which has previously been worked on by the Wright State Ion Engine Modeling Group. Performing detailed and accurate simulations of ion engines can lead to millions of dollars in savings in development costs.

In order to recognize these savings more work must be done on the present day models used to simulate ion engine performance. The work …

Bull's-Eye Structure With A Sub-Wavelength Circular Aperture, Masoud Zarepoor

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This research focuses on improving the spatial resolution of terahertz (THz) imaging. Using a sub-wavelength aperture in a metal ground plane is the most common way to improve the spatial resolution, but a sub-wavelength aperture has low radiation transmission. To increase the radiation transmission of a sub-wavelength aperture, periodic circular grooves were put in the metal around the aperture. The sub-wavelength circular aperture and the periodic circular grooves around it are known as the bull's-eye structure. The bull's-eye structure shows high radiation transmission at its design frequency, and it also has sub-wavelength spatial resolution. This research designed the bull's-eye structure …

Structural-Acoustic Analysis And Optimization Of Embedded Exhaust-Washed Structures, Ryan N. Vogel

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The configurations for high speed, low observable aircraft expose many critical areas on the structure to extreme environments of intense acoustic pressure loadings. When combined with primary structural and thermal loads, this effect can cause high cycle fatigue to aircraft skins and embedded exhaust system components. In past aircraft design methods, these vibro-acoustic loads have often been neglected based on their relatively small size compared to other thermal and structural loads and the difficulty in capturing their dynamic and frequency dependent responses. This approach is insufficient for effective advanced designs of complex aerospace structures, such as internal ducted exhaust systems …

Computational Modeling Of Graphene Oxide Exfoliation And Lithium Storage Characteristics, Reza Mortezaee

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Graphene oxide is a two dimensional material obtained by adsorption of oxygen or oxygen-containing groups on graphene. Stacked layers of graphene oxide constitute graphite oxide. These materials have various applications such as a source material for graphene production, transport support for electron microscopy, flexible organic photovoltaic cells and use in Li-ion batteries. Generation of exfoliated graphene oxide from a graphite oxide precursor is achieved relatively easily in solution as compared to graphene exfoliation. In this study we investigate the details of the graphene oxide exfoliation procedure in solution by calculating the Gibb's free energies and reaction rates. We consider two …

Shock Correlation Investigation In A Gaseous Fueled Axisymmetric Scramjet Flowpath, Jaime Omar Larios-Barbosa

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A pressure-based investigation was conducted on a gaseous fueled axisymmetric scramjet flowpath in Research Cell 22 located at Wright Patterson AFB. The investigation followed the work performed by Waltrup and Billig using combustion data to validate the form of the correlation in an attempt to achieve a good predictive tool for isolator length. Two years of axial wall pressure data using Mach values of 1.8 and 2.2 were analyzed in this investigation. The combustion data was shown to follow the same quadratic distribution show in Waltrup and Billig's work with the data being shifted to the right relative to the …

Effect Of Process Variables On Sub-Melt Thermal Behavior And Solid-State Phase Transformations In Beam-Based Additive Manufacturing Of Ti-6al-4v, Heather N. Doak

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The success of laser and electron beam-based fabrication processes for additive manufacture and repair applications requires the ability to control melt pool geometry while maintaining a consistent and desirable microstructure. Previous work has employed a process map approach to link melt pool geometry to solidification microstructure (grain-size and morphology) in beam-based fabrication of Ti-6Al-4V. The current work extends the approach to investigate the effects of process variables on solid-state phase transformations below the solidification temperature through Finite Element Modeling, the 3-D Rosenthal Solution, and experimentation. Process maps for solid-state microstructure could be used to help maintain consistent and reliable mechanical …

Wing Damage Effect On Dragonfly's Aerodynamic Performance During Takeoff, Kuo Gai

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Insect wing damage resulted from living environment or predation commonly happens in nature. This usually results in deterioration of insect's flight performance and as a consequence, the insect needs adjustment of flapping wings to compensate the effect from the wing loss. In this study, a dragonfly (Erythemis simpliciolis) with and without wing loss is chosen to study the change of aerodynamic performance of flapping wings. Three cases including flight with intact wings (IW), flight with one-sided forewing damage (OFD), and flight with double-side forewing damage (DFD) are determined. An integrated study using high-speed photogrammetry, three-dimensional surface reconstruction, and direct numerical …

An Experimental Investigation On The Control Of Tip Vortices From Wind Turbine Blade, Zhe Ning

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Wind turbine dynamics, wake effects and environmental impacts have been identified the most significant research topics needed for wind resource characterization and wind power generation. Among these issues, tip vortices generated from the blade tip have been recognized as a substantial resource for the turbulent wake flow as well as the aerodynamic noise emission from a wind turbine. An experimental study is conducted to characterize the evolution of the tip vortices downstream of a well-designed horizontal axis wind turbine (HAWT) model. In addition to measuring dynamic wind loads (both aerodynamic forces and moments) and power output from the wind turbine …

Analysis Of Laser Induced Spallation Of Electron Beam Physical Vapor Deposited (Eb-Pvd) Thermal Barrier Coatings, David Allen Beeler

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The use of thermal barrier coatings (TBCs) has been an important factor in the efficiency improvements of jet engines due to their ability to withstand the extreme environments within the engine. With this improved resistance, TBCs have also become more difficult to remove without damaging the substrate. Mound Laser & Photonics Center, Inc. (MLPC) has developed an innovative, laser based technique to spall this coating. The intention of this work was to investigate and better understand the removal mechanism. Through experimentation and analysis (such as high speed video, Scanning Electron Microscopy and Energy Dispersive Spectroscopy, semi-logarithmic analysis, and a numerical …

Dynamic Simulation Of Turbine Engine Used With Molten Carbonate Fuel Cell For Power Generation In The Megawatt Range, Carlos Eduardo Gutierrez

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Molten carbonate fuel cells (MCFC) have a high operating temperature of approximately 650° C (1200° F) to achieve sufficient conductivity of its carbonate electrolyte. Therefore, a gas turbine engine coupled with a MCFC is desirable since the turbine engine can be used to provide hot gas to the cathode, and the cathode gas residue can be used to raise the temperature of the natural gas and water vapor mixture (fuel) before it enters the MCFC at the anode. Dynamic models of a hybrid power plant consisting of a gas turbine engine and a MCFC with their respective components were developed …

A Computational Approach To Simulating The Performance Of A 24-Hour Solar-Fuel Cell-Hydrogen Electric Power Plant, Michael K. Gustafson

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World energy demand has risen from about 375 exajoules (EJ) in 1990 to around 600 EJ today. The Energy Information Administration predicts that by the year 2035, this figure will rise to around 800 EJ. This places large stresses on the electric generation infrastructure. Increasingly this demand is being met by renewable energy sources. There are several reasons this is the case. The prices of renewables are dropping quickly and reaching grid parity in more regions. Utilizing renewable energy generation can help achieve energy security: adverse weather or military conflicts are less likely to impact supply routes when energy is …