Mechanical Engineering Commons^™

Characterization Of Fast Flames For Turbulence-Induced Deflagration To Detonation Transition, Jessica Chambers

Electronic Theses and Dissertations

One of the fundamental mechanisms for detonation initiation is turbulence driven deflagration to detonation transition (TDDT). The research experimentally explores the propagation dynamics demonstrated by fast deflagrated flames interacting with highly turbulent reactants. Fast flames produce extremely high turbulent flame speeds values, increased levels of compressibility and develop a runaway mechanism that leads to TDDT. The flame structural dynamics and reacting flow field are characterized using simultaneous high-speed particle image velocimetry, chemiluminescence, and Schlieren measurements. The investigation classifies the fast flame propagation modes at various regimes. The study further examines the conditions for a turbulent fast flame at the boundary …

A Study On The Plasticity And Fracture Of Aisi 4340 Steel Under Different Loading Conditions Considering Heat Treatment And Micromechanics, Sami Ghazali

Electronic Theses and Dissertations

Accurate predictions of material strength under different loading conditions with large plastic deformation and ductile fracture are of great importance. This dissertation aims to develop an essential understanding of ductile fracture of AISI 4340 steel alloy using both empirical and micromechanics based models. For this purpose, 29 specimens of different geometries with different heat-treatments were designed to investigate the effects of stress states. These specimens are: (a) 13 round bars with different notches (axial symmetric tension); (b) 13 flat grooved specimens with different grooves; (c) 3 small round cylinders. Mechanical tests up to fracture were conducted on these specimens to …

Energy-Optimal Guidance Of An Auv Under Flow Uncertainty And Fluid-Particle Interaction, Demuni Singith De Zoysa Abeysiriwardena

Electronic Theses and Dissertations

The work presented gives an energy-optimal solution to the guidance problem of an AUV. The presented guidance methods are for lower level control of AUV paths, facilitating existing global planning methods to be carried out comparatively more efficiently. The underlying concept is to use the energy of fluid flow fields the AUVs are navigating to extend the duration of missions. This allows gathering of comparatively more data with higher spatio-temporal resolution. The problem is formulated for a generalized two dimensional uniform flow field given a fixed final time and free end states. This allows the AUVs to navigate to certain …

Mechanisms Of Flame Extinction For Bluff Body Stabilized Flames With Influences Of Pressure Gradient Tailoring, Anthony Morales

Electronic Theses and Dissertations

Flame extinction continues to hinder the performance of combustion technologies used in propulsion systems and power generating turbomachinery. Within these applications, there is a crucial need to improve energy output while minimizing harmful environmental impacts. Lean combustion helps attain these goals by minimizing fuel costs and reducing NOx emissions. However, operating at lean conditions increases the likelihood of flame extinction; the flame becomes more susceptible to hydrodynamic instabilities which can induce global blowout and termination of the combustion process. The work in this thesis is focused on identifying the mechanisms of flame extinction and controlling these mechanisms via pressure gradient …

Flutter Stability Of Shrouded Turbomachinery Cascades With Nonlinear Frictional Damping, Alex Torkaman

Electronic Theses and Dissertations

Prediction of flutter in shrouded turbomachinery cascades is difficult due to i) coupling of aerodynamic drivers and structural dynamics of the cascade through shrouds, and ii) presence of nonlinear dry friction damping as a result of relative motion between adjacent shrouds. An analytical framework is developed in this dissertation to determine flutter stability of shrouded cascades with consideration of friction damping. This framework is an extension to the well-established energy method, and it includes all contributing factors affecting stability of the cascade such as aerodynamic excitation and the stabilizing effects of dry friction damping caused by nonlinear contact forces between …

A Localized Blended Rbf Collocation Method For Effective Shock Capturing, Michael Harris

Electronic Theses and Dissertations

Solving partial differential equations (PDEs) can require numerical methods, especially for non-linear problems and complex geometry. Common numerical methods used today are the finite difference method (FDM), finite element method (FEM) and the finite volume method (FVM). These methods require a mesh or grid before a solution is attempted. Developing the mesh can require expensive preprocessing time and the quality of the mesh can have major effects on the solution. In recent years, meshless methods have become a research interest due to the simplicity of using scattered data points. Many types of meshless methods exist stemming from the spectral or …

Investigation Of Oxy-Fuel Combustion Behind Reflected Shockwaves, Owen Pryor

Electronic Theses and Dissertations

Supercritical carbon dioxide has brought about new questions on the chemical kinetics of several small hydrocarbon fuels and the effects of carbon dioxide as the primary diluent on the different fuels. This report presents work on the ignition delay times and several species time-histories of methane, ethylene and syngas over a range of conditions. All experiments were conducted behind reflected shock waves using two different shock tubes. The ignition delay times were measured using a GaP photodetector to measure the emission of light. The species time-histories were measured using single laser spectroscopy. The effect of CO2 as a diluent on …

Bio-Inspired Visual Servo Control Of A Picking Mechanism In An Agricultural Ground Robot, Sinem Gozde Defterli

Electronic Theses and Dissertations

For a recently constructed disease detection agricultural ground robot, the segregation of unhealthy leaves from strawberry plants is a major task of the robot's manipulation subsystem in field operations. In this dissertation, the motion planning of a custom-designed picking mechanism in the ground robot's subsystem is studied in two sections. First, a set of analytical, suboptimal semi-analytical and numerical algorithms are studied to solve the inverse kinematics problem of the handling mechanism in firm circumstances. These premeditated approaches are built on the computation of the joint variables by an identified 3D position data of the target leaf only. The outcomes …

Investigation Of A Self-Powered Fontan Concept Using A Multiscale Computational Fluid-Structure Interaction Model, Kyle Beggs

Electronic Theses and Dissertations

Congenital Heart Disease (CHD) occurs in about 1\% (40,000) of newborn babies each year in the United States alone. About 10.9\% (960) of whom suffer from Hypoplastic Left Heart Syndrome (HLHS) - a subset of CHD where children are born with a single-ventricle (SV). A series of three surgeries are carried out to correct HLHS culminating in the Fontan procedure where venous flow returns passively to the lungs. The current configuration for the Fontan results in elevated Central Venous Pressure (CVP), inadequate ventricular preload, and elevated Pulmonary Vascular Resistance (PVR) leading to a barrage of disease. To alleviate these complications, …

Electrospray And Superlens Effect Of Microdroplets For Laser-Assisted Nanomanufacturing, Eduardo Castillo Orozco

Electronic Theses and Dissertations

Nanoparticles of various materials are known to exhibit excellent mechanical, chemical, electrical, and optical properties. However, it is difficult to deposit and transform nanoparticles into large two-dimensional and three-dimensional structures, such as thin films and discrete arrays. Electrospray technology and laser heating enable the deposition of these nanoparticles through the dual role of microdroplets as nanoparticle carriers and superlenses. The main goals of this dissertation are to delineate the electrospray modes, to achieve subwavelength focusing, and to enable a process for the deposition of nanoparticles into microlayers and discrete nanodots (a nanodot is a cluster of nanoparticles) on rigid and …

Detailed Understanding Of Flow, Heat Transfer, And Pressure Drop Behavior In A Square Channel With 45 Deg Ribs, Lumaya Ahmed

Electronic Theses and Dissertations

Internal Duct Cooling (IDC) with rib turbulators is one of the common cooling techniques applied inside the turbine airfoils. It is very important for the gas turbine industry to design and develop an optimized cooling channel that maximizes the amount of heat removed, while simultaneously minimizing the pressure drop for a target overall cooling effectiveness. Angled ribs perform superior to the transverse ribs due to additional secondary flow associated with them. However, they result in a highly non-homogenous heat transfer distribution, which is a manifestation of the complex, turbulent flow field inside the channel. It is very important to comprehend …

Brain Stethoscope: A Non-Invasive Method For Monitoring Intracranial Pressure, Md Khurshidul Azad

Electronic Theses and Dissertations

Monitoring intracranial pressure (ICP) is important for patients with increased intracranial pressure. Invasive methods of ICP monitoring include lumbar puncture manometry, which requires high precision, is costly, and can lead to complications. Non-invasive monitoring of ICP using tympanic membrane pulse (TMp) measurement can provide an alternative monitoring method that avoids such complications. In the current study, a piezo based sensor was designed, constructed and used to acquire TMp signals. The results showed that tympanic membrane waveform changed in morphology and amplitude with increased ICP, which was induced by changing subject position using a tilt table. In addition, the results suggest …

Modeling And Analysis For Driveline Jerk Control, Prince Lakhani

Dissertations, Master's Theses and Master's Reports

In modern-day automotive industry, automotive manufacturers pay keen attention to driver’s safety and comfort by ensuring good vehicle drivability, feel of acceleration, limiting jerk and noise. The vehicle driveline plays a critical role to meet these criteria. By using high-fidelity simulation tool such as AMESim®, it is now possible to accurately model the vehicle driveline to be tested for different scenarios. With Simulink®, one can develop an efficient torque-based control system to limit the driveline oscillations and the generated noise. So, a joint simulation is used which provides a platform to evaluate the estimators and control system while considering the …

Kinesthetic Learning Experience Simulation Using An Online Intervention To Improve Hands-On Ability, David Leach

Dissertations, Master's Theses and Master's Reports

Students enrolled in mechanical and manufacturing engineering programs employ differing levels of mechanical aptitude and practical hands-on ability. Many students lack practical experience tinkering with mechanical devices and mechanisms prior to entering their post-secondary years. Student attention spans in traditional classroom environments appear to be decreasing with the ever-increasing addiction to immediate gratification provided by electronic devices, gaming software, and social media platforms. The question is then raised whether or not modern engineering students have the ability to improve mechanical aptitude by simulating a kinesthetic or tactile learning experience through an online tutorial. This project describes the development and testing …

Development Of Bosch Rate Of Injection Measurement Procedure And Results, Tyler Menucci

Dissertations, Master's Theses and Master's Reports

Recent developments in internal combustion engine technology have shown that gasoline compression ignition (GCI) combustion modes provide a viable pathway to meet future emission regulations. Lower octane middle distillate gasoline like fuels have also been formulated for GCI combustion applications and have shown similar benefits of improved fuel conversion efficiency and a reduction in particulate matter and nitrogen oxide emissions. As these gasoline like GCI fuels have not been well studied, characterization of their rate of injection (ROI) will be beneficial to supplement injector spray characterization measurements and the development of computational fluid dynamic simulations. A fuel collection method and …

Commercialization Of The Carbon Nanotube Thermophone For Active Noise Control Applications, Steven A. Senczyszyn

Dissertations, Master's Theses and Master's Reports

The rate of commercialization for technology developed in junction with academic institutions has risen dramatically over the past 30 years. Since the introduction of the Bayh-Dole Act in 1980, the amount of intellectual property owned by academic institutions has increased exponentially, and with that, there has also been an increase in the number of university spinouts generated. However, the increase of spinouts does not match the rate of increase in intellectual property. The National Science Foundation has created the Innovation Corps (I-Corps) program to help bridge this gap and provide academic professionals and students the tools necessary to commercialize technology …

An Experimental And Computational Study Of Fuel Spray Interaction: Fundamentals And Engine Applications, Le Zhao

Dissertations, Master's Theses and Master's Reports

An efficient spray injection results in better vaporization and air-fuel mixing, leading to combustion stability and reduction of emissions in the internal combustion (IC) engines. The impingement of liquid fuels on chamber wall or piston surface in IC engines is a common phenomenon and fuel film formed in the spray-piston or cylinder wall impingement plays a critical role in engine performance and emissions. Therefore, the study of the spray impingement on the chamber wall or position surface is necessary.

To understand the spray-wall interaction, a single droplet impingement on a solid surface with different conditions was first examined. The droplet-wall …

Design Optimization And High Cycle Fatigue Analysis And Of A Differential Case, Praveen Bulusu Surya Naga

Dissertations, Master's Theses and Master's Reports

Lightweight Innovations for Tomorrow (LIFT) is a consortium with several industries, universities and research institutes. It is operated by the American Lightweight Materials Manufacturing Innovation Institute (ALMMII). One of their projects, melt 5a, is to develop high silicon ductile iron (DI) alloys with improved mechanical properties and thin walled DI castings. These alloys have high strength to weight ratio compared to that of standard ductile iron (7003). Using these alloys, components can be re-designed that are much lighter which results in improved fuel efficiency, and reduced manufacturing costs and emissions. I

In this project, a differential case is being re-designed …

Spray And Combustion Studies Of High Reactivity Gasoline In Comparison To Diesel Under Advanced Compression Ignition Engine Conditions, Meng Tang

Dissertations, Master's Theses and Master's Reports

Gasoline compression ignition (GCI) technology has demonstrated great potentials in improving fuel economy and reducing engine-out NO_x and particulate matter emissions. Development and application of the GCI technology on multi-cylinder engines require both fundamental understandings of the gasoline spray combustion characteristics and accurate numerical tools. Due to the large differences in the thermo-physical and the chemical properties between gasoline and diesel range fuels, differences in the spray combustion characteristics between gasoline and diesel is expected. Reports on the gasoline spray combustion characteristics under conditions relevant to medium to heavy-duty engines are scarce and this dissertation aims to fill in …

Thermomagnetic Convective Cooling Of Hall Effect Thruster, Elizabeth M. Vanheusden

Dissertations, Master's Theses and Master's Reports

This work proposes and shows that thermomagnetic convection could be used in zero gravity to cool components of a Hall-effect thruster. A ferrofluid cavity was develop in the thermal and geometric model of a Hall-effect thruster. Simulations show that with an Ionic Liquid Ferrofluid after two minutes of thruster operations thermomagnetic convection occurs and in zero gravity will produce a larger velocity then natural convection that occurs in earth gravity. However, experiments did not result in heat transfer enhancement due to the limitation of the ferrofluid. Replacement of the Ferrotec EFH1 dispersant with dodecylbenzene did not result in Ionic Liquid …

Optimal Control Of Wave Energy Converters, Shangyan Zou

Dissertations, Master's Theses and Master's Reports

In this dissertation, we address the optimal control of the Wave Energy Converters. The Wave Energy Converters introduced in this study can be categorized as the single body heaving device, the single body pitching device, the single body three degrees of freedoms device, and the Wave Energy Converters array. Different types of Wave Energy Converters are modeled mathematically, and different optimal controls are developed for them. The objective of the optimal controllers is to maximize the energy extraction with and without the motion and control constraints. The development of the unconstrained control is first introduced which includes the implementation of …

Multi-Robot Mission Planning With Energy Replenishment, Bingxi Li

Dissertations, Master's Theses and Master's Reports

Success of numerous long-term robotic explorations in air, on the ground, and under water is dependent on the ability of the robots to operate for an extended period of time. The continuous operation of robots hinges on smart energy consumption and replenishment of the robots. This dissertation addresses the multi-robot system continuous operation problem by developing two mission planning architectures regarding two types of energy replenishment, which can be adapted to different mission scenarios based on mission requirements and available resources.

The first type of energy replenishment utilizes static charging stations to provide a recharging opportunity to primary working robots, …

Analysis Of Injection Parameters Influencing Gasoline Direct Injection Compression Ignition (Gdici) Engine Operation In Ltc Using Naphtha, Devyani Patil

Dissertations, Master's Theses and Master's Reports

A multi-dimensional CFD study using MTU-KIVA-Geq-CHEMKIN code has been carried out for direct injection compression ignition engine combustion fueled with heavy naphtha, light naphtha, and PRF50 in low-temperature combustion (LTC) regime. At constant fueling, combustion characteristics are investigated as a function of injection timing and injection pressure. Further, operating limits of fuel confined by combustion efficiency, noise level (Maximum Pressure rise rate) and emissions at exhaust valve opening (EVO) are evaluated using parametric variation of initial gas temperature, exhaust gas recirculation fraction, boost pressure. Research conducted focuses on ability of fuel to get good combustion which is combustion efficiency > / …

Agile–Stage Gate Management (Asgm): Npd Implementation Practices From Global Firms Developing Complex, Physical Products, John J. Salvato

Dissertations, Master's Theses and Master's Reports

Stage Gate Management (SGM) has been used successfully by global organizations to direct the New Product Development process (NPD) for years, recently a new variant of this venerable approach has emerged. Researchers and firms have begun to intersperse elements of Agile, as popularized for the development of software, to create an Agile – Stage Gate Management (ASGM) hybrid NPD framework. Agile practitioners believe in process waste reduction, an intense focus on customers, and the creation of nimble entrepreneurial project teams, which, for software products, has positively impacted development time to market, resource utilization, and market success, more generally, improved business …

Cold Start Analysis And Modeling Of A Direct-Injection Gasoline Engine, Yash Borghate

Dissertations, Master's Theses and Master's Reports

In this thesis, two different works related to cold start of a direct-injection (DI) gasoline engine are shown. First, effect of split injection is studied on engine exhaust temperature and hydrocarbon emissions for cold start conditions. Instead of single injection, two injections are done, one injection during the intake stroke and one injection during the compression stroke. Split injection is known to reduce jet wall wetting, thus reducing the hydrocarbon emissions from engine itself. Further, split injection reduces engine cycle-by-cycle variability with respect to the single injection case. Correlations between start of injection for the injection in the intake stroke …

Capillary-Assisted Enhanced Condensation Heat Transfer For Low Surface Tension Liquids, Gnana Vishnu Durgam

Dissertations, Master's Theses and Master's Reports

Extensive research has been carried out over the course of the last few decades to induce dropwise condensation as it offers 5 - 7 times better heat transfer performance compared to filmwise condensation process. A number of methods such as low surface energy hydrophobic coatings, surface modification of hydrophobic surfaces to fabricate micro, nano and hierarchical structures, and the recent incorporation of jumping droplet phenomenon have provided effective means to further enhance the condensation heat transfer. However, existing methods to enhance condensation heat transfer rate fail in the case of low surface tension, highly wetting liquids such as hydrocarbons, cryogens, …

Robotic Mining Digging Core, John Stefan, Ryan Weir

Williams Honors College, Honors Research Projects

The purpose of this design project is to design a digging core for a lunar robot that will collect large amounts of material buried beneath the surface of Mars so one day, astronauts can use those resources. This lunar robot will be competing in the NASA Robotic Mining Competition, where teams from universities around the country display and test their designs. This design must adhere to a newly implemented rule which states that the amount of gravel a robot collects will determine the team score. The layer of gravel is located underneath a layer of Regolith, which simulates the surface …

An Origami-Based Thickness-Accommodating Bistable Mechanism In Monolithic Thick-Sheet Materials, Larry L. Howell, Spencer P. Magleby, Nathan A. Pehrson

Faculty Publications

Origami-based mechanisms can provide useful capabilities in folding large structures to stow in small volumes. However, when using monolithic thick-sheet materials for these types of mechanisms, accommodating the thickness proves challenging. One approach to solve this is to create compliant mechanisms along the fold lines that inherently store energy when actuated and causes the mechanism to tend toward its low energy state. This tendency can be used to create bistable states. We outline a method to use this stored energy to achieve bistable states and name the resulting mechanism an origami-based “Thickness-accommodating bistable interior vertex” (TABIV) in monolithic thick-sheet materials. …

Hydrogen Fuel Cells, Sydney Pilgrim, Skyler Smith

ENgaging Educators in Renewable enerGY (ENERGY): Lesson Plans & Slideshows (2017-2019)

Hydrogen fuel cells are hydrogen powered energy sources. They convert chemical energy into electrical energy by separating water molecules into the two elements that make up water, Hydrogen (2) and Oxygen (1). Hydrogen fuel cells are looking to become a paramount energy producer to avoid consuming fossil fuels for power. Along with the abundance of Hydrogen in the atmosphere being a benefit of using Hydrogen powered fuel cells, the only emission from these energy sources is water vapor. Many car engines only operate at a 20% fuel efficiency, whereas fuel cell powered cars utilize 60% of the energy produced. Although …

Solar Tracking Sustainable Energy Education, Tara Hart, Donita Legonas

ENgaging Educators in Renewable enerGY (ENERGY): Lesson Plans & Slideshows (2017-2019)

Two middle school science teachers collaborated with Georgia Southern lab students to conduct research and experimentation on the benefits of utilizing a dual-axis solar tracking system to assess the amount of voltage received during various times of the day. A smaller similar dual-axis solar tracking system was designed and fabricated to utilize in the teachers’ middle school classrooms in the study of renewable energy and the engineering and design process.