Mechanical Engineering Commons^™

Optimization Of Shape And Control Of Linear And Nonlinear Wave Energy Converters, Jiajun Song

Dissertations, Master's Theses and Master's Reports

In this dissertation, we address the optimal control and shape optimization of Wave Energy Converters. The wave energy converters considered in this study are the single-body heaving wave energy converters, and the two-body heaving wave energy converters. Different types of wave energy converters are modeled mathematically, and different optimal controls are developed for them. The concept of shape optimization is introduced in this dissertation; the goal is to leverage nonlinear hydrodynamic forces which are dependent on the buoy shape. In this dissertation, shape optimization is carried out and its impact on energy extraction is investigated. In all the studies conducted …

Dynamic Testing: An Experimental Approach To Defect Identification In Additive Manufactured Parts, Aimee Allen

Dissertations, Master's Theses and Master's Reports

Today’s additive manufacturing (AM) industry produces specialized parts at low volume or with complex geometries. Traditional testing methods are effective, but costly and time consuming to perform. The AM industry lacks an optimized testing method for identifying internal defects that occur in parts. The evaluation of multiple parts printed on the same build plate for internal defects using various nondestructive (dynamic) testing techniques is presented. From these experiments, perspective was gained on when and how dynamic testing can be used to find defects. Insight gained from these experiments can help the industry in future testing for internal defects.

3d Printing Of Iron Oxide Incorporated Polydimethylsiloxane Soft Magnetic Actuator, Rasoul Bayaniahangar

Dissertations, Master's Theses and Master's Reports

Soft actuators have grown to be a topic of great scientific interest recently. As the fabrication of soft actuators with conventional microfabrication methods are tedious, expensive, and time consuming, employment of 3-D printing fabrication methods appears promising as they can simplify fabrication and reduce the production cost. Complex structures can be fabricated with 3-D printing such as helical coils can achieve actuation performances that otherwise would not be possible with simpler geometries. In this thesis development of soft magnetic helical coil actuators of iron-oxide embedded polydimethylsiloxane (PDMS) was achieved with embedded 3-D printing techniques. Composites with three different weight ratios …

Multiscale Modeling Of Carbon Fibers/Graphene Nanoplatelets/Epoxy Hybrid Composites For Aerospace Applications, Hashim Al Mahmud

Dissertations, Master's Theses and Master's Reports

Significant research effort has been dedicated for decades to improve the mechanical properties of aerospace polymer-based composite materials. Lightweight epoxy-based composite materials have increasingly replaced the comparatively heavy and expensive metal alloys used in aeronautical and aerospace structural components. In particular, carbon fibers (CF)/graphene nanoplatelets (GNP)/epoxy hybrid composites can be used for this purpose owing to their high specific stiffness and strength. Therefore, this work has been completed to design, predict, and optimize the effective mechanical properties of CF/GNP/epoxy composite materials at different length scales using a multiscale modeling approach. The work-flow of modeling involves a first step of using …

Increasing Access To Pv Technology Through Sustainable Racking: A Review Of Existing Literature And Ground Mounted Fixed Tilt Designs, And What Can Be Done Next, Parijata Prabhakara

Dissertations, Master's Theses and Master's Reports

There is a lack of literature on the structural balance of systems (BOS), also called racking, for ground mount, fixed-tilt solar PV systems. Literature that exists discusses mostly rooftop racking and installations, additional wind loading, and weight considerations imposed on roofs, and little guidance is provided in building codes. The lack of peer-reviewed guidance on design requirements for domestic and large-scale application solar PV racking systems leaves most consumers relying on expensive, patented, off-the-shelf hardware. As PV cell technology and module costs have improved, we can start to focus on PV BOS improvements (particularly racking) and move towards sustainable designs …

Generative Design In Energy Efficient Buildings, Johanna Thill

Dissertations, Master's Theses and Master's Reports

This is an investigative report on the use of generative design and genetic algorithms in the design of energy-efficient buildings. It focuses on a workflow using Project Refinery© and Dynamo© in Revit® for multi-objective optimization and visualization, and Honeybee© for daylighting analysis. The workflow was not about to run completely due to instability in Dynamo, however daylighting analysis and visualizations were produced separately from demonstrations of Refinery. It concludes that while genetic algorithms have potential to be useful in energy-efficient building design, these programs are not yet fully developed and difficult to use without extensive background knowledge and fluency in …

Large-Scale Inflatable Structures For Tunnel Protection: A Review Of The Resilient Tunnel Plug Project, Eduardo M. Sosa, Gregory J. Thompson, Gregory M. Holter, John M. Fortune

Faculty & Staff Scholarship

The protection of underground civil infrastructure continues to be a high priority for transportation and transit security agencies. In particular, rail transit tunnels running under bodies of water are susceptible to disruptions due to flooding caused by extraordinary climatic events such as hurricanes or other events resulting from human activities. Several events have taken place in the past decades that have demonstrated the need to mitigate vulnerabilities or, at least, minimize the consequences of catastrophic events. Although it is impossible to prevent all situations that can lead to flooding, damage can be substantially decreased by reducing the area affected by …

Editorial For The Special Issue On Micro/Nano-Chip Electrokinetics, Volume Iii, Shizhi Qian, Xiangchun Xuan

Mechanical & Aerospace Engineering Faculty Publications

No abstract provided.

Fully Compressible Hydrodynamic Simulation Of Non-Equidiffusive Premixed Flames Propagation In Channels, Olatunde A. Abidakun

Graduate Theses, Dissertations, and Problem Reports (ETD)

Premixed combustion remains of fundamental interest in energy generation and propulsion systems as well as in implementation of safety measures for residential and industrial accidental fire explosions. While the fast pace and complex nature of the combustion process has previously necessitated the analytical and computational studies to employ the simplifying assumption of equidiffusivity, when the Lewis number defined as the thermal-to-mass diffusivities ratio is unity , the ongoing advancements in technology and the requirements for efficiently operating combustors over a wide range of conditions make the combustion process more non-equdiffusive ( ) than ever. The impact of non-equidiffusivity on the …

Fast Decision-Making Under Time And Resource Constraints, Kyle Gabriel Lassak

Graduate Theses, Dissertations, and Problem Reports (ETD)

Practical decision makers are inherently limited by computational and memory resources as well as the time available in which to make decisions. To cope with these limitations, humans actively seek methods which limit their resource demands by exploiting structure within the environment and exploiting a coupling between their sensing and actuation to form heuristics for fast decision-making. To date, such behavior has not been replicated in artificial agents. This research explores how heuristics may be incorporated into the decision-making process to quickly make high-quality decisions through the analysis of a prominent case study: the outfielder problem. In the outfielder problem, …

An Examination To Pathways Powering Car Using Clean Energy, Marina Miranda

Graduate Theses, Dissertations, and Problem Reports (ETD)

Traditional vehicles powered by internal combustion engines contribute significantly to increasing emissions of greenhouses gasses (GHG). There has been increasing interest in powering vehicles using green energy include using electricity produced by wind turbine and solar panel. The green electricity can be used to directly charge the Battery Electric Vehicles (BEV), or producing hydrogen as fuel for Fuel Cell Electric Vehicles (FCEV) by converting electrical energy to hydrogen (H₂) through water electrolysis. The low energy density H₂ produced can be stored on board as either compressed H₂ or liquefied H₂.

This research examines the …

Detailed Energy Efficiency Strategies For Converting An Existing Office Building To Nzeb: A Case Study In The Pacific Northwest, Ali Alajmi, Abby Short, Janna Ferguson, Kalina K. Vander Poel, Corey T. Griffin

Mechanical and Materials Engineering Faculty Publications and Presentations

This paper is an attempt to identify a methodology for converting conventional energy consumption buildings to net-zero energy buildings (NZEB). The first step was rather different from the usual energy audit, which is to analyze a facility’s energy consumptions from both macro- and micro-scales. To implement such an approach, a governmental office building (Metro) in Portland, OR, was chosen as a case study. After a building model was validated against a real measurement, it was then used to evaluate different energy efficiency strategies (EESs) so as to reduce the energy consumption. The EESs showed a reduction in energy use intensity …

Utility-Scale Solar Pv Performance Enhancements Through System-Level Modifications, Andrew D. S. Glick, Naseem Ali, Juliaan Bossuyt, Marc Calaf, Raul Bayoan Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

Performance of solar PV diminishes with the increase in temperature of the solar modules. Therefore, to further facilitate the reduction in cost of photovoltaic energy, new approaches to limit module temperature increase in natural ambient conditions should be explored. Thus far only approaches based at the individual panel level have been investigated, while the more complex, systems approach remains unexplored. Here, we perform the first wind tunnel scaled solar farm experiments to investigate the potential for temperature reduction through system-level flow enhancement. The percentage of solar irradiance converted into electric power depends upon module efficiency, typically less than 20%. The …

Partnering Undergraduate Engineering Students With Preservice Teachers To Design And Teach An Elementary Engineering Lesson Through Ed+Gineering, Kristie Gutierrez, Stacie I. Ringleb, Jennifer Jill Kidd, Orlando M. Ayala, Pilar Pazos, Krishnanand Kaipa

Teaching & Learning Faculty Publications

Major challenges in engineering education include retention of undergraduate engineering students (UESs) and continued engagement after the first year when concepts increase in difficulty. Additionally, employers, as well as ABET, look for students to demonstrate non-technical skills, including the ability to work successfully in groups, the ability to communicate both within and outside their discipline, and the ability to find information that will help them solve problems and contribute to lifelong learning. Teacher education is also facing challenges given the recent incorporation of engineering practices and core ideas into the Next Generation Science Standards (NGSS) and state level standards of …

A Review Of Problem Structuring Methods For Consideration In Prognostics And Smart Manufacturing, Patrick T. Hester, Andrew J. Collins, Barry Ezell, John Horst

Engineering Management & Systems Engineering Faculty Publications

Successful use of prognostics involves the prediction of future system behaviors in an effort to maintain system availability and reduce the cost of maintenance and repairs. Recent work by the National Institute of Standards and Technology indicates that the field of prognostics and health management is vital for remaining competitive in today’s manufacturing environment. While prognostics-based maintenance involves many traditional operations research-centric challenges for successful deployment such as limited availability of information and concerns regarding computational efficiency, the authors argue in this paper that the field of prognostics and health management, still in its embryonic development stage, could benefit greatly …

Effect Of O2 Concentration In Ambient Mixture And Multiphase Radiation On Pollutant Formation In Ecn Spray-A, Khaled Mosharraf Mosharraf Mukut, Somesh Roy

Mechanical Engineering Faculty Research and Publications

The present study investigates the formation and evolution of soot and NO_X in a high-pressure constant-volume combustion chamber. This work focuses on the effect of multiphase thermal radiation and O₂ dilution in ambient/exhaust gases, some- times also referred to as exhaust gas recirculation(EGR), qualitatively and quantitatively. The spray-A case (n-dodecane as fuel) from Engine Combustion Network (ECN) is used as the target condition. Two different soot modeling approaches have been considered: a semi-empirical two-equation model and a detailed method of moments with interpolative closure (MOMIC) model. A multiphase photon Monte Carlo (PMC) solver with line-by-line (LBL) spectral data …

Structure-Property-Performance Evaluation Of Refractory Metal Incorporated Gallium Oxide Thin Films For Extreme Environment Applications, Anil Krishna Battu

Open Access Theses & Dissertations

An approach is presented to design refractory-metal (RM) incorporated Ga2O3-based materials with controlled structural, mechanical, and optical properties. A model system based on molybdenum (Mo) doped Ga2O3 (GMO) has been considered to elucidate the combined effect of RM-doping and processing parameters on the properties and oxygen sensor performance of GWO nanomaterials. The molybdenum (Mo) content in Ga2O3 was varied from 0 to 11 at% in the sputter-deposited Ga-Mo-O films. Molybdenum was found to significantly affect the structure and optical properties. While low Mo content (≤4 at%) results in the formation of single-phase (β-Ga2O3), higher Mo content results in amorphization. Chemically …

Low Weight Design Of A Pressure-Fed System For A Small Payload Launch Vehicle, Lucero Buendia

Open Access Theses & Dissertations

Carbon fiber reinforced polymer (CFRP) composites have become of great interests to aerospace industries because of their low-cost, lightweight and their tailorable mechanical properties. In aerospace structures, for example, heavy metals have been used in cryogenic fuel and oxidizer tanks for over 50 years. However, weight savings can be substantial if materials such as composites are used instead. From Delta IV heavy-lift launch vehicle it is known that cryogenic composite tanks can save approximately up to 30% of weight in fuel and oxidizer tanks. Although there is a wealth of studies in the mechanical behavior of composites at room temperature, …

The Effect Of K2co3 Concentration In Kerosene Emulsions On Spray Droplet Sizes For A Magnetohydrodynamic Power Generator, Alejandra Castellano

Open Access Theses & Dissertations

Potassium carbonate (K2CO3) is an effective seeding material to introduce potassium vapor in oxy-fuel combustion to create a conductive plasma. Injecting potassium carbonate before combustion promotes particle volatilization and improves the generation of potassium vapor. This can be achieved by emulsifying a potassium carbonate solution with kerosene. Several studies have investigated creating stable emulsions with kerosene with water by using differing surfactants. However, the effects of using varying concentrations of K2CO3 dissolved in deionized water have not been fully explored. Based on methods of creating successful emulsions, the development of a successful mixture comprised of kerosene and K2CO3 solution is …

Laser Diagnostics Of Compressible And High-Intensity Premixed Methane-Air Combustion Inside A Backward Facing Step Combustor Using High- Repetition Rate Ch-Plif And Piv, Md. Amzad Hossain

Open Access Theses & Dissertations

A novel high repetition rate (10 kHz) planar laser-induced fluorescence (PLIF) diagnostic technique was used for the flame front study. Premixed methane-air combustion was studied at different flow turbulence conditions (Re = 15000, 30000 and 64000; 12CFM, 25CFM and 50 CFM; 10m/s, 20 m/s and 40 m/s) and fuel loading (Փ =0.6 to 1.2). The study used an optically accessible backward-facing step high-speed combustor. Methane-air mixture was supplied to the combustor at atmospheric pressure and standard room temperature (T =25°C). CX-CH PLIF was used to detect the actual flame front structures. The flame dynamics were then correlated to the flow …

An Accelerated Creep Testing Program For Nickel Based Superalloys, Robert M. Mach

Open Access Theses & Dissertations

In order to improve the energy production within the United States, new materials are developed with the goal of increased functionality. These materials are required to perform at extreme pressures and temperatures (up to and beyond 200MPa and 650â??) as well as be sustainable beyond 105 hours. Before developing these materials into components for power generation, mechanical testing is required to better understand the behavior of these materials at various loads and temperatures. The longest of these tests is the conventional creep test which is a real time test that can beyond 105 hours depending on service conditions. Hundreds of …

Velocity Measurements Using A Piezoelectric Plate As A Sensor, Paul Perez

Open Access Theses & Dissertations

In this study, the voltage output from a piezoelectric sensor placed in a test section is used to predict flow velocity changes. The piezoelectric made of PZT is thought to be advantageous due to its fast response time, potential durability at higher temperatures, and self-powered characteristics. Having said that this sensor could be implemented into the Hybrid Performance Project built by NETL to characterize and mitigate the probability of compressor surge and stall. The problem arises because of the added large volume between compressor and gas turbine and resultant changes to system fluid dynamics. The effect of the piezoelectric sensor …

Computational Methods For Creep Modeling, Ricardo Vega

Open Access Theses & Dissertations

Creep is an important phenomenon present in the power generation and aerospace industry. Creep is a mechanism that degrades the quality of a part, such as the turbines used in different industries, when elevated temperatures and loads are applied. Creep damage can cause critical failures that can cost millions of dollars and as such, prevention is important. A multitude of creep models exist to help with design and failure prevention. These models are applied using computational tools which allows the engineer to properly predict the life of a part or other material properties. In this work various creep numerical optimization …

High Pressure High Heat Flux Pool Boiling Test Facility Design To Investigate Nucleation Boiling Heat Transfer Enhancement Using Micro/Nano-Scale Engineered Structures, Omar Hernandez Hernandez Rodriguez

Open Access Theses & Dissertations

Developing efficient heat dissipation technologies is of critical importance towards the development and the commercialization of next-generation compact and high-performance electronic devices, cooling systems, power generation systems and chemical processing units, as well as retrofitting the existing thermal management schemes. As such, phase change heat transfer systems, more specifically boiling heat transfer systems, have attracted significant attention due to their ability to extract a large amount of latent energy stored within the fluid. Pool boiling is an efficient mode of phase change heat transfer processes accompanied by nucleation of vapor bubbles from liquid on to the hot surfaces, bubble growth, …

Development Of A Multi-Axis Wire Embedding Device For A Large Area Thermoplastic Pellet-Fed Additive Manufacturing System, Christopher Jasiel Minjares

Open Access Theses & Dissertations

This research focused on the development and implementations of a six degrees of freedom (6DOF) articulated arm onto a Big Area Additive Manufacturing (BAAM) system to interact with complex 3D geometries. BAAM is a large-scale machine which falls under material extrusion additive manufacturing (AM) - a process that selectively dispenses molten plastic layer-by-layer. The development of the 6DOF articulated arm required a mechanical design which went through several iterations before getting to the final design. Also, implementation of the tool was performed with the help from Cincinnati Incorporated (CI) which is the company that developed the BAAM.

First, the mechanical …

A High-Temperature Valve Design For A Solid Oxide Fuel Cell/Gas Turbine Hybrid System, Cynthia Morales

Open Access Theses & Dissertations

Systems containing high heat generation require thermal management, especially in a solid oxide fuel cell gas turbine (SOFC/GT) hybrid system. The startup of each system in a standalone configuration may be a trivial approach, but when coupled together, different dynamics are experienced. The SOFC/GT provide high theoretical efficiency due to the ability to recover the extra heat produced by the fuel cell (FC) to drive the gas turbine (GT). After recovering the energy recuperated in the GT, the exhaust gas heats the cathode inlet flow to the FC which is an advantage during nominal operation of the cycle but not …

Oxidation Of Niobium Silicides Obtained By Self-Propagating High-Temperature Synthesis, Frank Anthony Perez

Open Access Theses & Dissertations

Niobium silicide-based composites are promising materials for high-temperature structural applications, such as gas turbines. One attractive method for their fabrication is mechanically activated self-propagating high-temperature synThesis (MASHS). However, oxidation resistance of niobium silicides produced by MASHS has not been studied yet. In this present work, the oxidation of Nb/Nb5Si3 composites obtained by MASHS was investigated by using non-isothermal thermogravimetric analysis (TGA) and differential scanning analysis (DSC). Both techniques have shown that the oxidation starts at about 500 °C and the materials become fully oxidized at 750 â?? 800 °C. Model-based analysis of the TGA data has shown that the Avrami-Erofeev …

Multi-Wavelength Pyrometry For Emissivity Mapping And Accurate Surface Temperature Measurement In Powder Bed Fusion Systems, Md Moinuddin Shuvo

Open Access Theses & Dissertations

Accurate surface temperature measurement within powder bed fusion (PBF) systems during fabrication remains elusive for many reasons, despite the importance of knowing temperature for improving part quality, process control, repeatability and reproducibility, simulation capabilities, and more. Multi-wavelength (MW) pyrometry has been used previously to measure off-axis temperatures of a small region (~2.6mm in diameter) within an electron beam PBF (EBPBF) system. While this small region measurement makes it difficult to get a full field temperature map of the powder bed, it also allows for inline (on-axis) with laser temperature measurements for laser PBF (LPBF) systems. The MW pyrometry technique determines …

Mechanically Activated Combustion Synthesis Of Niobium Silicide Based Composites, Reina Trevino

Open Access Theses & Dissertations

Niobium silicide-based composites are promising materials for high-temperature structural applications, such as gas turbines, but their implementation is hindered by the lack of effective processing methods. Self-propagating high-temperature synThesis (SHS) is an attractive method for fabrication of advanced materials. However, it is difficult to perform SHS of niobium silicides because the melting point of Nb is higher than the combustion temperature, which greatly inhibits Nb-Si reaction. To ignite an Nb/Si mixture and obtain Nb5Si3, the desired phase in niobium silicides, either preheating or mechanical activation of the mixture is necessary. This problem becomes even more critical in the SHS of …

Qualification And Implementation Of A Liquid Oxygen/ Liquid Methane Data Acquisition System, Zachary Welsh Welsh

Open Access Theses & Dissertations

One of the primary goals of the MIRO Center for Space Exploration and Technology Research (cSETR) is the design and testing of liquid oxygen and liquid methane rocket engines. As of this thesis’ time of writing, two engines are currently undergoing testing at the center’s Technology Research and Innovation Acceleration Park (tRIAC), located in Fabens, Texas. The engines vary in scale starting with a 5 lbf Reaction Control Engine (RCE) to a 500 lbf engine dubbed the Centennial Restartable Oxygen Methane Engine (CROME). It was necessary to develop a control and data acquisition system to support these various test campaigns, …