Mechanical Engineering Commons^™

A Multi Physics Integrated Solution For A High-Pressure Stage Turbine Efficiency And Durability, Sanjay Chopra

Theses and Dissertations

World electricity demand is projected to grow at an annual rate of ~ 2.1% to year 2040₁. EIA projects nearly 50% increase in world energy usage by 2050 led by growth in Asia.[28];[29]. It is predicted that the global electricity demand grows at approximately 1.6 % per year from approximately 2008 and forecasted to approximately 2035, twice the rate of primary energy demand. This raises electricity's usage in total final energy consumption from approximately 19% in 2018 to approximately 24% in 2040. Electricity demand growth is set to be particularly strong in developing economies. .[28];[29];[38] As an enabler, to meet …

Reduced Order Modeling Based On Hybrid Snapshot Simulation, Feng Bai

Theses and Dissertations

Reduced order model (ROM) is an emerging technique for rapid and efficient numerical simulation and computation in science and engineering applications. The ROM consists of two stages: (1) the offline snapshot simulation to produce high-quality snapshot data representative of model trajectories, from which the projection subspace can be extracted and used for ROM construction; and (2) the online simulation to utilize the ROM built in stage 1. The snapshot simulation is traditionally performed with full order model (FOM) and is computationally demanding, which is one of the most critical limiting factors for the development and deployment of ROM in real-world …

Optimizing Heat Pipes With Partially-Hybrid Mesh-Groove Wicking Structures And Its Capillary-Flowing Analysis By Simulation, Guanghan Huang

Theses and Dissertations

Heat pipes are known as efficient two-phase heat transfer devices and widely utilized in thermal management of power plants and electronics. The hybrid mesh-groove wick promises to attain a higher thermal performance of the heat pipe by balancing the permeability and capillarity. However, traditional fully hybrid mesh-groove wick presents considerable condensation thermal resistance due to the condensed quiescent working fluid and thick, saturated wick.

In this study, a novel partially hybrid mesh-groove wick has been proposed to enhance the evaporation of L-shaped copper-ethanol heat pipes. L-shaped heat pipe promotes high-efficient draining of condensed liquid by gravity, while traditional straight-shaped heat …

The Effects Of Noise On Parametrically Excited Systems With Nonlinear Damping, Donghao Li

Theses and Dissertations

Parametric oscillators are a class of resonating systems in which a parameter, such as stiffness in a mechanical system or capacitance in an electrical system, is periodically modulated in order to alter the system response in a desired manner. A resonance effect occurs when the pump frequency is near twice of resonant frequency. Such systems are said to be “parametrically pumped,” and this pump can, above a certain amplitude threshold, destabilize the system in the absence of nonlinearities. Parametric resonance is widely observed in nature and has been employed in a large variety of engineered systems, most notably in micro-electro-mechanical …

Design Of A Pneumatic Soft Robotic Actuator Using Model-Based Optimization, Mahsa Raeisinezhad

Theses and Dissertations

In this thesis, the design and optimization process of a novel soft intelligent modular pad (IntelliPad) for the purpose of pressure injury prevention is presented. The structure of the IntelliPad consists of multiple individual multi-chamber soft pneumatic-driven actuators that use pressurized air and vacuum. Each actuator is able to provide both vertical and horizontal motions that can be controlled independently. An analytical modeling approach using multiple cantilever beams and virtual springs connected in a closed formed structure was developed to analyze the mechanical performance of the actuator. The analytical approach was validated by a finite element analysis. For optimizing the …

Life Cycle Climate Performance Assessment For R1234yf As A Low Gwp Drop-In Alternative For R134a In Domestic Refrigerators, Mohamed Ragab Senosey Khaled Zain

Theses and Dissertations

Aligning with the global movements towards mitigating CO2 emissions and regulations to phase out HFC refrigerants, many low GWP refrigerants are being tested and proposed as fourth-generation refrigerants. R1234yf is a refrigerant with a GWP of less than one and has a high potential to replace R134a, which has a GWP of 1300, and it is the most commonly used refrigerant in domestic refrigerators. In this study, an energy performance evaluation and a life cycle climate performance assessment for R1234yf were conducted and compared to those of R134a based on a baseline domestic defrost refrigerators. Four different charges of R1234yf …

In Situ Characterization Of Fiber-Matrix Interface Debonding Via Full-Field Measurements, Robert Livingston

Theses and Dissertations

Macroscopic mechanical and failure properties of fiber-reinforced composites depend strongly on the properties of the fiber-matrix interface. For example, transverse cracking behavior and interlaminar shear strength of composites can be highly sensitive to the characteristics of the fiber-matrix interface. Despite its importance, experimental characterization of the mechanical behavior of the fiber-matrix interface under normal loading conditions has been limited. This work reports an experimental approach that uses in situ full-field digital image correlation (DIC) to quantify the mechanical and failure behaviors at the fiber-matrix interface. Single fiber model composite samples are fabricated from a proprietary epoxy embedding a single glass …

Fluid-Structure Interaction Of Nrel 5-Mw Wind Turbine, Mohamed Sayed Elkady Abd-Elhay

Theses and Dissertations

Wind energy is considered one of the major sources of renewable energy. Nowadays, wind turbine blades could exceed 100 m to maximize the generated power and minimize produced energy cost. Due to the enormous size of the wind turbines, the blades are subjected to failure by aerodynamics loads or instability issues. Also, the gravitational and centrifugal loads affect the wind turbine design because of the huge mass of the blades. Accordingly, wind turbine simulation became efficient in blade design to reduce the cost of its manufacturing. The fluid-structure interaction (FSI) is considered an effective way to study the turbine's behavior …

Feasibility Study Of Radio Frequency Microelectromechanical Filters For Space Operation, Karanvir Singh

Theses and Dissertations

Piezoelectric contour mode resonator technology has the unique advantage of combining low motional resistance with the ability to define multiple frequencies on the same substrate. Contour mode resonators can be mechanically coupled together to form robust band-pass filters for the next generation of GPS satellites with extreme size reduction compared to electrically coupled filters. Piezoelectric zinc oxide (ZnO) contour mode resonators have the potential for monolithic integration with current ZnO transistor further reducing size, power consumption, and cost of filter modules. Barium strontium titanate (BST) contour mode resonators have incredible frequency tunability due to the fundamental nature of the thin …

A Self-Tunable Piezoelectric Energy Harvester, Ashraf Hussein

Theses and Dissertations

In this study, a new technique to harvest energy using inertial vibration energy harvesters is introduced. A triple-layer piezoelectric beam with a self-tunable frequency was developed in order to respond to variable-frequency excitations, thereby maintaining the beam in a state of resonance for maximum power output. The tuning mechanism managed to change the natural frequency of the beam in the range of 2.27 ���� to 6.25 ����. In this case, the output voltage could be raised from 12�� to 23��.

A mathematical model was developed to investigate the natural frequency, the output voltage, and the output power of the beam …

Secondary Resonances Of Electrostatically Actuated Mems And Nems Circular Plates, Julio S. Beatriz

Theses and Dissertations

Two methods are used in the investigation, which are the Method of Multiple Scales (MMS) and the Reduced order Model (ROM) with up to 6 modes of vibration. The MMS is done in three ways, one based on soft excitation and the other models based on the usage of the bookkeeping parameter, ε, in the electrostatic term. These are referred to as the 1 term no ε, and the 2 term no ε, which allow it to model hard excitation. The influence of the number of terms in the Taylor expansion is explored.

These methods are used to investigate the …

Novel Coating Methods On Centrifugally-Spun Polymer Fibers For Applications In Lithium-Ion Batteries, Jonathan G. Ayala

Theses and Dissertations

The work presented in this thesis focuses on the processing, characterization, and electrochemical results of centrifugally spun composite carbon fiber electrodes for application as anode material in lithium-ion batteries. The work is presented as a compilation of two major projects. First, the use of novel Co3O4 wet coatings to increase the capacity of carbon fibers produced from Polyacrylonitrile (PAN). In this work, PAN fibers are produced via the Forcespinning method, and were heat treated by oxidation in air at 200 °C for four hours, and subsequent carbonization at 600 °C for six hours. The electrochemical performance of the Co3O4/C composite-fiber …

Centrifugally-Spun Ceramic/Carbon Composite Fibers And Their Use As Anode Materials In Li-Ion Batteries, Gabriel Gonzalez

Theses and Dissertations

The work in this thesis focuses in the study of Centrifugally Spun Short Fiber Composites and their Implementation as Alternate Anode Material in Li-Ion Batteries. Due to their high theoretical capacity, abundance, and environmental friendliness, metal oxides have been widely studied as alternate anode materials for lithium ion batteries (LIBs). In this research work, the processing of SnO2 and SnO2/TiO2 ceramic short fibers as well as flexible and porous metal oxide carbon fibers (FPMOCFs) by centrifugal spinning followed by an optimized coating technique is reported. In addition, the electrochemical performance of the composites was also investigated and is provided.

Study Of Particle Size Effect On The Performance Of Tio2 Nanoparticles As Lubricant Additives On Vegetable Oil-Based Nanolubricants, Dario F. Rodriguez

Theses and Dissertations

Recently there has been an increase in concern regarding the use of petroleum-based lubricants. This has created an interest in readily available biodegradable lubricants such as vegetable oils. This work evaluates the rheological and tribological performance of grapeseed, and sunflower oils altered with 5, 18, and 40 nanometer titanium dioxide (TiO2) nanoparticles at differing concentrations. Block-on-ring tests were performed using the ASTM G-077-05 standard procedure. The effect of nanoparticle size and concentration and shear rate on the viscosity were evaluated and the experimental data was compared to conventional models. Roughness tests were performed on the wear scar of the blocks …

Development And Characterization Of Nanofiber-Based Thermoelectric And Piezoelectric Composites, Julio Enrique Trevino

Theses and Dissertations

This study focuses on the development and characterization of nanofiber-based composites with the goal of developing flexible, lightweight, and cost effective thermoelectric and piezoelectric devices. The following materials were used in the development of the composites: polyvinylidene fluoride (PVDF) with polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), polycarbazole (PCZ), polyacrylonitrile (PAN), functionalized multi-walled carbon nanotubes (MWCNT-COOH), and camphorsulfonic acid (CSA). Blends and in-situ polymerization techniques were utilized to increase the desired thermoelectric/piezoelectric response. Nanofiber systems were produced utilizing the Forcespinning® technique. The morphology, structure, electrochemical, thermal stability, thermoelectric, and piezoelectric performance was analyzed. All of the nanofiber PVDF/CP …

Assessing The Feasibility Of A Biofilter In Medium-To-High Scale Industries, Javier A. Garcia

Theses and Dissertations

The removal of volatile organic compounds, VOCs, from contaminated sources of air stream has become a major air pollution risk. Excessive amounts discharged to the atmosphere are highly risky to human health and to the environmental system. Demand for sustainable VOC control technologies has become crucial for the reduction of emissions. Biological treatments of waste gas streams, such as biofiltration, have proven to be cost effective and environmentally friendly compared to conventional pollution control technologies. The goal of this research is to simulate data for a given biofilter model, and to evaluate if it is economically and environmentally feasible to …

Modeling And Energy Simulation Of A Zero Energy Building: A Case Study For Florida, Mariana Migliori Favaretto

Theses and Dissertations

The study of energy consumption in buildings is an important area of research given the large share of building sector in the worldwide energy usage. The energy consumption of buildings has a high impact on carbon emissions, a greenhouse gas which has proved to play a major role in global warming. In the last decades, global warming has become an increasing concern and worldwide high energy demand have awaken a pressing quest towards improving building energy efficiency. Reducing buildings’ energy usage by implementing energy efficiency measures is one way towards a sustainable future for any country in the world. This …

Flagellation Testing Of Composite Finger Skirts For Surface Effect Ship (Ses) Application, Natalie Marie Holliday

Theses and Dissertations

The objective of this research is to create flagellation data for SES finger skirts. The SES design allows it to have a high tonnage with low draft, little drag, low wavemaking resistance, remarkable carrying capacity, and incredible propulsive efficiency. A SES is a sidehull hovercraft, with air cavity sealing components at the bow and stern. The fingers at the bow collectively make up an elastic, flexible full sealing skirt, dissipating oncoming waves and allowing for the vessel to be self-stabilizing. The problem with SES vessels is that the bow finger skirts wear significantly over a short period of time (~ …

Inverse Methods For Near-Real Time Estimation Of Surface Heat Flux In Thermal Protection Systems For Space Vehicles, Obinna Oluchukwu Ugochukwu Uyanna

Theses and Dissertations

With the increased goal of manned explorations to outer space, safety during the atmospheric entry/reentry process is paramount as the incident heat fluxes on the surface of vehicle can reach critical values. Thermal Protection Systems (TPS) are therefore essential components in space vehicles as they ensure the safety and protection of the payload and cargo. In order to ensure improved active control capabilities and prolonged used of the vehicle, TPS surface conditions need to be known and determined. Since direct measurement of the surface heat flux using sensors is not feasible, one alternative involves the use of temperature sensors located …

Multi-Degree Of Freedom Position And Attitude Control Of Rings Dipoles Using Electromagnetic Forces And Torques, David Andres Alvarez

Theses and Dissertations

Satellite formation flight (SFF) is likely to transform and advance the scope of space missions in the near future. Some considerable benefits of SFF to a mission include robustness, adaptability, and potential cost savings. However, satellite formations face a fuel expenditure issue: the more spacecraft there are to control, the more fuel will be expended on alignment and maneuvering. A solution to this problem is Electromagnetic Formation Flight (EMFF), which is the application of conductive coils in producing electromagnetic fields that can interact with the fields of other coils in a formation to exchange forces and torques. With three orthogonal …

The Effect Of Simulated Mangrove Forest Width On Shoreline Stabilization At Multiple Tidal Water Levels, James Edward Austin

Theses and Dissertations

Red mangrove (Rhizophora mangle) forests protect hundreds of miles of Florida’s shorelines from erosion and wave damage associated with severe storms and daily wave action. Shorelines are often protected from erosion with man-made structures such as seawalls, revetments, and breakwaters. However, these man-made structures disrupt natural ecosystems and cause scour and erosion in surrounding areas. The presence of mangroves not only prevents erosion but shelters marine life and filters water, promoting ecological health. Mangroves are now being implemented for wave energy reduction and shoreline stabilization, but there is little quantitative data about the precise sediment transport induced or prevented by …

Numerical Modeling Of The Fiber Deposition Flow In Extrusion-Based 3d Bioprinting, Dhanvanth Jaya Talluri

Theses and Dissertations

Extrusion bioprinting involves the deposition of bioinks in a layer-wise fashion to build 3D structures that mimic natural living systems' behavior in tissue engineering. Hydrogels are the most common bioinks, in which their viscosity properties are dependent on the shear-rate, such as Non-Newtonian fluids. Numerical simulation of extrusion bioprinting may help study the flow properties of hydrogels and designing improved bioinks. In this thesis, the instability caused by the shear-thinning or -thickening parameter during extrusion is numerically compared with the theoretical estimations. The process of fiber deposition of hydrogels onto a substrate through the single and coaxial nozzle is done …

Prediction Of Residual Stress And Distortion In Laser Powder Bed Fusion Additive Manufacturing, Bhanuprakash Sairam Kosaraju

Theses and Dissertations

Additive Manufacturing (AM) has its proven advantages to unlock the design space and manufacturing capabilities for complex geometries with lightweights. Distortion is one of the most common defects that occur in Laser Powder Bed Fusion Additive Manufacturing (LPBFAM), which is caused by the significant residual stress during the printing process. This can lead to numerous process iterations to achieve the requisite form and fit tolerances.

In this study, Finite Element (FE) model that utilizes the element birth approach was developed to predict the residual stress and distortion in the LPBFAM process. The methodology leverages a simplified approach where the detailed …

Anisotropic Wave Behavior In Isotropic Material With Orthogonal Surface Perturbation, Khaleda Akter

Theses and Dissertations

Elastic wave propagation in anisotropic media is of great interest in various branches of engineering and applied sciences. In this study, an anisotropic wave propagation behavior in isotropic material with orthogonal surface perturbation is presented. The conventional method of estimating dispersion equations for isotropic material is to apply Helmholtz decomposition on the potential functions for Rayleigh-Lamb wave and Shear Horizontal (SH) waves. However, the presence of isotropic material with orthogonal surface perturbations in two coordinate directions significantly affect the wave propagation behavior due to its direction dependency, and hence, the Helmholtz decomposition of the potential functions cannot be applied to …

Preferential Vaporization Potential Of Crude Oils And Its Impact On Flame Flashback Behaviors, Ayuob Al Wahaibi

Theses and Dissertations

As combined cycle gas turbines for power generation operating on light distillate fuels provide a sufficient energy, there is a global trend in using heavy liquids (e.g. HFO, crude oils) for direct-firing in gas turbine. However, using these heavy fuels imposes many challenges due to their wide range of physical/chemical properties, which control near-limit combustion behaviors, such lean blow-out and flashback. In addition, the ignition propensity of these heavy fuels is not reported in crude assays, and utilizing a simple, with small sample, and quick methodology to characterize the ignition propensity is important in determining the fuel quality.

In this …

Instrumentation And Experimentation Development For Robotic Systems, Tristan Kyzer

Theses and Dissertations

Localization of robotic systems is a necessity for control of robotic systems and often requires the use of costly sensors and equipment onboard the robot or installed within a facility. GPS or GNSS sensors are effective for localizing robots in GPSaccessible environments, but do not work as well in dense urban areas or inside fully enclosed buildings, such as factories or warehouses. Sensors such as LiDAR can be costly and require substantial experience and knowledge to utilize as well as potential changes to infrastructure for use. Computer vision-based localization systems offer potential as a localization solution for various applications. A …

Nondestructive Evaluation And Structural Health Monitoring Of Manufacturing Flaws And Operational Damage In Composite Structures, Robin James

Theses and Dissertations

Advanced composite materials have begun to be used extensively in the manufacturing of aerospace structures. Composite aerospace structures can develop complex types of damages during the manufacturing stages and operational lifetime. This creates an indispensable demand for appropriate nondestructive evaluation (NDE) and structural health monitoring (SHM) methods that are tailored to specific types of damage. This dissertation addresses innovative methods for NDE and SHM of manufacturing flaws and operational damage in composite structures.

For the NDE of manufacturing flaws in carbon fiber reinforced polymer (CFRP) composites, an eddy current testing (ECT) NDE method has been developed by conducting multiphysics modeling …

Experimental Investigation Of Single And Two-Phase Heat Transfer Performance In Microchannels With Surface Modifications And Multiple Inlet Restrictors, Saad Kadham Oudah

Theses and Dissertations

Due to shrinking component sizes and faster switching speeds, the volumetric heat generation rates and surface heat flux in many advanced power electronic devices have increased exponentially, creating an urgent need for efficient cooling technologies. It has become particularly challenging to maintain an optimal temperature at the device level. Among advanced cooling techniques, single-phase and two-phase microchannel heat sinks show considerable promise in removing a significant amount of heat from a small surface area. Considered one of the most efficient heat dissipaters, the two-phase microchannel heat sink can handle very high heat flux at a small footprint and requires relatively …

Multimodal Robotic Health In Future Factories Through Iiot, Data Analytics, And Virtual Commissioning, Clint Saidy

Theses and Dissertations

The manufacturing sector is continuously reinventing itself by embracing opportunities offered by the industrial internet of things and big data, among other advances. Modern manufacturing platforms are defined by the quest for ever increasing automation along all aspects of the production cycle. Furthermore, in the next decades, research and industry are expected to develop a large variety of autonomous robots for a large variety of tasks and environments enabling future factories. This continuing pressure towards automation dictates that emergent technologies are leveraged in a manner that suits this purpose. These challenges can be addressed through the advanced methods such as …

Enhanced Flow Boiling And Bubble Dynamics With Hfe7100 & Di Water In Interconnected Microchannels, Jiaxuan Ma

Theses and Dissertations

Flow boiling in microchannels using dielectric fluids is one of the most desirable cooling solutions for high power electronics. Primary two-flow patterns, including bubbly flow, slug flow, and annular flow, have been well established in microchannels. However, it is challenging to promote flow boiling performance, particularly critical heat flux (CHF), due to their unfavorable thermophysical properties. Considering these situations, flow boiling in parallel and isolated microchannels have been extensively studied. In this dissertation, a novel concept that has five parallel microchannels (W=200 µm, H=250 µm, L=10 mm) are interconnected by micro-slots (20 µm wide and 250 µm deep) starting from …