Mechanical Engineering Commons^™

Pressurized Combustion Product Temperature Measurement Using Integrated Spectral Band Ratios, Scott Cutler Egbert

Theses and Dissertations

With increasing global power demands, there is a growing need for the clean and efficient use of fossil fuel resources. Gas turbine engines are a commonly used means for generating power; from the propulsion of aircraft to electricity on municipal grids. Measuring the temperature within a turbine combustor or at a turbine inlet could provide numerous advantages related to engine control, durability, efficiency, and emissions and yet this relatively straightforward task has eluded turbine engine manufacturers, primarily because of the high temperatures and pressures, harsh environment, and limited access. Optical emissions measurements are of particular interest for this task as …

An Experimental Study Of Thrust Augmentation With Asymmetrical Nozzle Driven Pulsed Ejector, Orlando Rodriguez

Theses and Dissertations

With the emergence of V/STOL vehicles and unmanned aircrafts has come the resurgence of thrust augmentation through an ejector. The use of an ejector has many benefits such as being lightweight and simple design to manufacture. In this study a hot steady jet and a cold steady/unsteady jet was tested. The hot steady jet was produced by a JetCAT PX-180 rxi with a two-inch diameter nozzle exit. The hot steady jet was compared to the cold free steady and unsteady cases. The cold jet was tested under free steady and unsteady condition, as well as steady and unsteady ejector conditions. …

Assessment Of Some Of The Common Practices Used In Scheduling Highway Projects, Jennifer Reyes

Theses and Dissertations

There are several factors documented in the literature that can affect the accuracy of estimated project durations in highway construction, such as weather, location, and soil conditions. Recently, the Texas Department of Transportation (TxDOT) raised a concern regarding some of the practices used when estimating the contract time for projects. This research presents an assessment of the effect that two practices identified have on the estimated project duration. These two practices include: 1) the estimated lead/lag times in project schedules and 2) scheduling with only critical or controlling activities. The effect of these practices is measured, primarily, by using four …

An Atomistic Approach For The Survey Of Dislocation-Grain Boundary Interactions In Fcc Nickel, Devin William Adams

Theses and Dissertations

It is well known that grain boundaries (GBs) have a strong influence on mechanical properties of polycrystalline materials. Not as well-known is how different GBs interact with dislocations to influence dislocation movement. This work presents a molecular dynamics study of 33 different FCC Ni bicrystals subjected to mechanical loading to induce incident dislocation-GB interactions. The resulting simulations are analyzed to determine properties of the interaction that affect the likelihood of transmission of the dislocation through the GB in an effort to better inform mesoscale models of dislocation movement within polycrystals. It is found that the ability to predict the slip …

Energy Harvesting Techniques To Power Onboard Railway Bearing Condition Monitoring Systems, Jacob Nathaniel Bensen

Theses and Dissertations

Limitations of the standard wayside hotbox detection system as a method to identify failing railway bearings severely inhibit the reliability and safety of rail transport. An onboard bearing condition monitoring system would address and ameliorate the issues present in the current detection system. The onboard system would provide more frequent and reliable information regarding bearing condition. For the system to succeed in reducing maintenance time and preventing bearing failure, a method of providing the system with sufficient energy to power its instrumentation is necessary. The instrumentation location environment poses a significant challenge. The device must be placed on the steel …

Functional Porous Polydimethlysiloxane As Piezoresistive And Piezoelectric Materials, Taissa Rose Michel

Theses and Dissertations

In this paper, polydimethylsiloxane (PDMS), carbon nanotubes (CNTs), and zinc oxide (ZnO) were combined to create functionalized piezoresistive and piezoelectric sensors for pressure sensing and energy harvesting. Samples were foamed to show that the increased deformability of the foam sensors makes them suitable for a range of applications including dexterous robotics, tactile sensing, energy harvesting, and biosensing. Uniform dispersion of CNTs was achieved with chloroform as the solvent. Samples were foamed using chemical blowing and scaffolding but granulated sugar at 70% porosity resulted in foamed samples with the most consistent mechanical properties. Samples underwent tensile and compressive testing for their …

Application And Evaluation Of Full-Field Surrogate Models In Engineering Design Space Exploration, Christopher Murray Thelin

Theses and Dissertations

When designing an engineering part, better decisions are made by exploring the entire space of design variations. This design space exploration (DSE) may be accomplished manually or via optimization. In engineering, evaluating a design during DSE often consists of running expensive simulations, such as finite element analysis (FEA) in order to understand the structural response to design changes. The computational cost of these simulations can make thorough DSE infeasible, and only a relatively small subset of the designs are explored. Surrogate models have been used to make cheap predictions of certain simulation results. Commonly, these models only predict single values …

Performance Analysis Of A Parabolic Trough Solar Collector, Feras Abdullah Mohammed Alghamdi

Theses and Dissertations

Solar energy technologies are growing vastly in both developed and developing countries. The parabolic trough solar collector (PTSC) technology is the most widely used system among concentrated solar technologies. In this thesis, three models were developed to investigate the performance of the PTSC; these models are 2D & 3D numerical models and 1D analytical model. Each model considers three absorber tube configurations, vacuum annulus, air-filled annulus, and bare absorber tube. The specifications of the Luz LS-2 PTSC were used throughout the study. Since the study considers the 3D model, a realistic non-uniform heat flux distribution around the receiver tube was …

Redeployment And Demonstration Of The Video Guidance Sensor For Proximity Maneuvers, Xiangyi Li

Theses and Dissertations

This paper presents the redeployment and demonstration of the Photogrammetric Video Guidance Sensor (PVGS) as a position and attitude sensor for proximity maneuvers and formation flight of small spacecraft. The original PVGS was developed to use a smartphone as its hardware and an Android application as its software; however, this paper provides a possibility for using a smaller and cheaper single-board computer, Raspberry Pi as new hardware, and for using a Java program run in Linux as its software. We finally achieved the approximate performance compared to the original PVGS. At the current stage, a PID controller was supposed to …

Development Of Prognostics Techniques For Surface Defect Growth In Railroad Bearing Rolling Elements, Nancy De Los Santos

Theses and Dissertations

One of the major causes of failure in railroad bearings used in freight service is rolling contact fatigue (RCF). RCF is due to subsurface inclusions which are a result from impurities in the steel that is used to fabricate the bearings. Once the bearings initiate subsurface fatigue cracks, they will then propagate upward and initiate spalling of the rolling surfaces. These spalls will begin small and continuously propagate with operation as this induces additional crack forming and spalling. Studies have indicated that bearing temperature is not a good indicator of spall initiation. In many cases, the temperature of the bearing …

Impact Of Cycloalkanes On Ignition Propensity Measured As Derived Cetane Number In Multi-Component Surrogate Mixtures, Dalton Odell Carpenter

Theses and Dissertations

Cycloalkanes are one type of hydrocarbons present in real jet fuels. The distinct cyclic structure of the cyclo-alkanes impacts the chemical kinetic behavior differently compared to n- and iso-alkanes. At high temperatures, thermal decomposition reactions dominate, producing n-alkyl radicals similar to the oxidation reactions of n-alkanes thus promoting the reactivity. Whereas in low temperatures, the presence of the ring structure essentially suppresses the formation of alkylhydroperoxy radicals (QOOH) from alkylperoxy radicals (RO2), thus exhibiting similar reactivity to iso-alkanes. In previous generations of surrogate fuels, the cyclo-alkane functional group were largely ignored due to low levels of cycloalkanes in traditional jet …

Enhancing Thermal-Hydraulic Performance Of Parallel And Counter Flow Mini-Channel Heat Sinks Utilizing Secondary Flow: A Numerical And Experimental Study, Amitav Tikadar

Theses and Dissertations

Continual growth of hydraulic and thermal boundary layers along stream wise direction in conventional straight fin mini-channel heat sink causes gradual deterioration of their thermal performance. To enhance thermal-hydraulic performance by breaking and redevelopment of the boundary layers, this research aims to introduce a novel inter-connected mini-channel sinks. Two inter-connectors were positioned transversely between two adjacent mini-channels, which segmented the flow domain into three zones. Secondary flow was generated through the inter-connectors utilizing the pressure difference of the adjacent channels resulting in hydraulic and thermal boundary layers disruption and hence enhanced thermal-hydraulic performance of the mini-channel heat sink was achieved. …

3d Topology Optimization Of Spatially Reinforced Composites, Luis G. Bahamonde Jácome

Theses and Dissertations

Topology optimization is a numerical design tool used to generate structural concepts that present optimal load paths for a given set of functional requirements. This functional generative design capability has been used to lightweight high performance structures with 1D, 2D and 3D stress states. On the other hand, fiber-reinforced composites are the perfect candidate material to use in high performance structures due to the tailorability of their stiffness and strength properties. Although numerical tools that simultaneously tailor the composite material properties while optimizing the structural topology exist, these tools are inherently limited to 1D and 2D stress states.

This work …

Mechanical Characterization And Non-Destructive Evaluation Of SicF/SicM Composites For Nuclear Applications, Donald J. Mccleeary

Theses and Dissertations

The SiC_f/SiC_m composite material is a promising candidate for accident tolerant fuel cladding in light water reactors and for structural elements in high temperature reactors. The material demonstrates exceptional toughness when compared to monolithic ceramics. It is critical to characterize the mechanical behavior, internal damage and ultimate strength of these composites under relevant loading conditions. In this thesis, the author developed and improved several mechanical characterization and non-destructive evaluation methods and applied them to SiC_f/SiC_m composites. Impulse excitation (IE) analysis of damaged SiC_f/SiC_m composite disks following controlled impact testing shows a …

A Model For Condensation Heat Transfer In Hydrophobic-­Hydrophilic Surfaces, Abdulwahab E. Alhashem

Theses and Dissertations

The primary focus of this research is to provide a validated model for a comprehensive understanding of hydrophobic-­‐hydrophilic condensation on patterned-­‐ hybrid surface. Establishing the model requires the modeling of fully dropwise condensation (DWC) before applying modifications to evaluate heat transfer performance of patterned-­‐hybrid condensation surface.

The model for fully DWC consists of defining expressions for heat transfer through a single drop, maximum radius of the drop and drop-­‐size distribution which all are primarily based on the work in the literature. In this work the author utilized a proposed modified version of the simulation for drop-­‐size distribution for fully DWC, …

A Coastal Estuarine Ensemble Forecasting System, Peyman Taeb

Theses and Dissertations

This research has been conducted in an effort to reduce the computational costs associated with high-resolution coastal estuarine modeling in ADCIRC. It was proposed that model scalability will be significantly enhanced if the conventional single-domain technique is replaced by a nesting method. Preliminary testing indicated the potential for 50% to more than 80% simulation runtime reduction (depending on the study site) by implementing a nesting technique. Once the concept was proved, the development of an operational, ensemble-based forecasting system, exclusively for the east coast of Central Florida and the IRL system, was implemented. The system, referred to as Ensemble Multistage, …

Surrogate Formulation Based On Chemical Functional Group Analysis, Stuart Nates

Theses and Dissertations

Chemical kinetic characteristics of real fuels exhibit high-dimensional complexity due to the excessive number of molecules and molecular classes. As a method of projecting this high-dimensional complexity, which is pertinent to real fuels, to the low-dimensional description, either a surrogate approach or detailed experiments have been utilized, can guide the construction of chemical kinetic models for real fuel. Although the validity of the surrogate approach has been extensively demonstrated by a wide range of canonical experiments for whole fuel/air mixtures, the use of empirical fuel property indicators still worries whether or not the surrogate mixture truly captures the more complex …

Developing An Interview Protocol For An Engineering Design Capstone Course To Measure Student Motivation And Engineering Identity, Mckenzie Clark

Theses and Dissertations

This thesis examines the process of developing an effective in-depth interview protocol to measure student motivation and engineering identity. Several methods were employed during the creation, refining, and analysis portions of this study to ensure reliability and validity of the qualitative research instrument. In a multifaceted course such as senior capstone design, it is integral to ensure students are receiving a value adding experience. In most universities across the United States, senior capstone design is a multiple semester sequence where design is heavily emphasized and students are encouraged to test their skills, both technical and nontechnical, by solving and implementing …

Advancing Numerical Calculation Of Mixed Sized Sediment Transport And Morphology Change, Irene Margaret Watts

Theses and Dissertations

Numerical modeling of sediment transport and morphologic change has become a powerful tool for studying and working in the coastal zone. Numerical calculation can assist in a broad range of projects from regional sediment management to beach nourishment as well as evaluating environmental aspects of dredging and placement and implications to water quality and turbidity. Success in application of these tools is partially dependent on the quality of characterization of the sediments in the field. These parameters could include grain size, mineralogical composition, specific gravity and fall velocity. Sediment transport formulations are sensitive to the spatial representation of the sediments …

Quantifying Appearance For Opaque Surfaces Using Spectral Bidirectional Reflectivity, Christopher Richard Brooks

Theses and Dissertations

Quantifying the appearance of a surface is an important aspect in quality control. Becauseobjects at room temperature emit negligible amounts of radiation into the visible spectrum, aspectsof their appearance may be quantified using reflected light. Therefore, the appearance of opaquesurfaces may be quantified using measurements of the spectral, bidirectional reflectivity. However,measuring the spectral, bidirectional reflectivity of even one point at every set of incident andreflected directions is a time intensive process that is infeasible for quality control.The objective of this work was to determine whether a limited number of spectral, bidirectionalreflectance measurements may be used to characterize the appearance of …

The Conversion Of Manual Machining Equipment Into Smart, Connected Systems With Real-Time Monitoring And Issue Identification Capabilities, David Lee Williams

Theses and Dissertations

With the advent of the fourth industrial revolution, information technology and manufacturing systems are merging to form what is now known as Smart Manufacturing. However, with this newer technology being integrated with newer pieces of machining equipment, companies with legacy equipment occasionally are in a bind since these machines were not designed or built with the fundamental components of smart manufacturing systems: unified connectivity, real-time monitoring, and issue identification. The purpose of this research is to provide a solution for converting manual machining equipment into smart systems with these fundamental components of smart manufacturing. The pieces of equipment that were …

Design, Fabrication And Testing Of A Pressurized Oxy-Coal Reactor Exhaust System, Aaron Bradley Skousen

Theses and Dissertations

One of the challenges facing engineers is to provide clean, sustainable, affordable and reliable electricity. One of the major pollutants associated with coal combustion is CO2. A proposed technology for efficiently capturing CO2 while producing electricity is pressurized oxy-combustion (POC). The first objective of this work is to design, build and demonstrate an exhaust system for a 20 atmosphere oxy-coal combustor. The second objective of this work is to design and build mounts for a two-color laser extinction method in the POC. The POC reactor enables the development of three key technologies: a coal dry-feed system, a high pressure burner, …

Frequency Response And Recovery Of Muscles And Effects Of Wrapping The Lower Leg On Surface Velocity Measurements, Cameron David Smallwood

Theses and Dissertations

This thesis is comprised of two studies. The objective of the first study was to find the frequency response and stiffness of the biceps brachii muscle group during recovery from exercise induced damage and to determine whether these data could be used to track muscle recovery by correlating changes in the frequency response with changes in muscle stiffness. Stiffness moduli were collected using Shear Wave Elastography (SWE) which were then applied to a proportional first mode frequency analysis. Data were collected for the muscle stiffness and frequency response for fifteen subjects (25.6 +- 4.5). By comparing the proportion of the …

Dynamic Radiation Heat Transfer Control Through Geometric Manipulation, Rydge Blue Mulford

Theses and Dissertations

The surface area and radiative properties of an object influence the rate of radiative emission from the object's surface and the rate of radiative absorption into the surface. Control of these variables would allow for the radiative heat transfer behavior of the surface to be manipulated in real time. Origami tessellations, being a repeated pattern of linked, dynamic surfaces, provide a framework by which dynamic control of apparent radiative properties and surface area is possible. The panels within a tessellation form cavities whose aspect ratio varies as the device actuates. The cavity effect suggests that the apparent radiative properties of …

Burner Design For A Pressurized Oxy-Coal Reactor, William Cody Carpenter

Theses and Dissertations

The need for electric power across the globe is ever increasing, as is the need to produce electricity in a sustainable method that does not emit CO2 into the atmosphere. A proposed technology for efficiently capturing CO2 while producing electricity is pressurized oxy-combustion (POC). The objective of this work is to design, build, and demonstrate a burner for a 20 atmosphere oxy-coal combustor. Additionally, working engineering drawings for the main pressure vessel and floor plan drawings for the main pressure vessel, exhaust, and fuel feed systems were produced. The POC reactor enables the development of three key POC technologies: a …

Empirical And Theoretical Analysis Of Solar Devices In Public Spaces, Justin Morgan Roberts

Theses and Dissertations

With the debate on global warming and climate change, renewable energy resources, such as solar energy, are being considered. If solar energy is to make a major utility contribution, it will need to be more ubiquitous in today’s society. The research described hereafter analyzes the use of Solar in Public Spaces (SPS). SPS is defined as solar energy used in the public domain to power electronics away from the electric grid. This research specifically examines the viability of integrating solar panels into existing surfaces to charge portable electronics. Viability is evaluated using three criteria: (1) user interaction, (2) technical feasibility, …

Secondary Resonances Of Electrostatically Actuated Mems Cantilevers, Christopher I. Reyes

Theses and Dissertations

In this work the behavior of micro-electromechanical (MEMS) cantilever resonators is investigated. The cantilever resonators are electrostatically actuated with hard AC voltage resulting in nine distinct resonances cases including super and subharmonic resonances. The amplitude frequency and amplitude voltage bifurcation diagrams are obtained for each of the nine resonance cases. Reduced order models (ROMs) are developed to include one and two modes of vibration. Three different methods are used to solve the ROMs namely 1) the method of multiple scales (MMS), which is a perturbation method used for one mode of vibration, 2) the homotopy analysis method (HAM), which is …

A Game Theory Motivated Approach To Analyzing Modularity In Automotive Systems, David John Thiess Jr.

Theses and Dissertations

This paper examines the effect of integrated and modular design on consumers and manufacturers and seeks to determine if there is an optimal design that benefits both. Some consumers perceive the automotive industry to design vehicles with only the company’s benefit in mind, rather than the desires of the consumer. However, the automotive industry seeks to please consumers, while minimizing the cost of production. A game-theoretic based model was developed that was used to determine if there existed a level of modularity for a system that optimized for both the manufacturer and consumer. The game model consisted of two players, …

Hardware-In-The-Loop Testbed For The Dynamics Of Spacecraft Rendezvous And Capture, Stephen Thiam Choy Kwok Choon

Theses and Dissertations

As more satellites are launched into orbit, the amount of space debris objects and defunct satellites in orbit that pose a risk to existing operational space systems is expected to grow. In addition, the risk of collision with defunct systems and space debris increase operational fuel cost for active satellites that have to perform avoidance maneuvers. When a satellite’s propulsion or attitude navigation system malfunction, this may cause the satellite to become defunct, potentially becoming a risk to other active space systems. A way to counter defunct satellite systems, is through robotic on-orbit servicing and active space debris removal as …

Experimental And Numerical Analysis Of The Drag Force On Surfboards With Different Shapes, Omar Lahlou

Theses and Dissertations

The aim of the present study is to define the hydrodynamic resistance of surfboards with different designs. Decreasing the drag acting on a board helps the surfer to attain higher surfing performances. It helps to attain higher speeds and maneuvering for the surfer. In this thesis, theoretical, experimental and computational approaches are used to explain how the drag changes with different surfboard shapes. Four surfboards with varying shapes were towed at different speeds and the resulting force was recorded. Two computational models were developed using Star CCM and Flowsquare to confirm the experimental results. The drag force on the boards …