Mechanical Engineering Commons^™

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

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

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

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

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

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

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

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

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

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

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

Computational Investigation Of Ethanol And Bifuel Feasibility In Solstice Engine, Adam Michael Blake

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A Gasoline Direct Injection (GDI) engine enables an increased fuel efficiency and higher power output than a conventional Port Fuel Injection (PFI) system. By injecting pressurized fuel straight into each cylinder of an internal-combustion engine, the degree of fuel atomization is increased, as well as the fuel vaporization rate. In order to further harness the effects of direct injection, ethanol is implemented as a fuel. The cooling effect of ethanol fuel droplets changing to vapor inside the combustion chamber facilitates a higher compression ratio, thus increasing engine power and efficiency. Three dimensional computational simulation is used to investigate the feasibility …

Computational Investigation Of A Hinge-Connected Hovering Plate, Zachary Robert Gaston

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A simplified conceptual flapping wing MAV design, capable of hover, is formed from the works of both biologists and engineers, studying the behavior of flying insects and the aerodynamics of flapping flight. With this new model, hovering hinged plates are used to study the effects of passive deflection on aerodynamic performance using two-dimensional Direct Numerical Simulations (DNS) at low Reynolds numbers (Re). The hinge is modeled as a torsional spring at the leading edge, where prescribed motion is applied. The influence of forced-to-natural frequency ratio (hinge stiffness) and stroke-to-chord ratio (leading edge kinematics) are studied, to explore the effects that …

Modeling And Simulation Of A Dynamic Turbofan Engine Using Matlab/Simulink, Scott Michael Eastbourn

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A dynamic, high-bypass turbofan engine has been developed in the modeling and simulation environment of MATLAB/Simulink. Individual elements, including the fan, high pressure compressor, combustor, high pressure turbine, low pressure turbine, plenum volumes, and exit nozzle, have been combined to investigate the behavior of a typical turbofan engine throughout an aircraft mission. Special attention has been paid to the development of transient capabilities throughout the model, increasing model fidelity, eliminating algebraic constraints, and reducing simulation time through the use of advanced numerical solvers. This lessening of computation times is paramount for conducting future aircraft system-level design trade studies efficiently, as …

Measurement Of Static And Dynamic Performance Characteristics Of Electric Propulsion Systems, Aron Jon Brezina

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Today's unmanned aerial vehicles are being utilized by numerous groups around the world for various missions. Most of the smaller vehicles that have been developed use commercially-off-the-shelf parts, and little information about the performance characteristics of the propulsion systems is available in the archival literature. In light of this, the aim of the present research was to determine the performance of various small-scale propellers in the 4.0 to 6.0 inch diameter range driven by an electric motor. An experimental test stand was designed and constructed in which the propeller/electric motor was mounted in a wind tunnel for both static and …

Effect Of Cooling Rate And Mold Counter Pressure On The Crystallinity And Foaming Control In Microcellular Injection Molded Polypropylene Parts, Jeffrey Scott Cousineau

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Microcellular polymer injection molding is a growing industry technique due to its ability to produce dimensionally stable stress free parts while reducing cycle time, material usage, and energy costs. The process was invented by Dr. Nam P. Suh at the Massachusetts Institute of Technology in the early 1980's. The basic idea is to dissolve a supercritical fluid into the polymer melt which will nucleate and expand within the part core after injection during the cooling stage. Microcellular polymer injection molding is becoming increasingly popular in automotive, semiconductor, and industrial applications. While the technique has been widely successful using amorphous polymers, …

Computational Study On Micro-Pilot Flame Ignition Strategy For A Direct Injection Stratified Charge Rotary Engine, Zachary Steven Votaw

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The Office of Security of Defense's Assured Fuels Initiative has recently been pressing for a single fuel battle space. This endeavor requires modifying many of the vehicle power plants currently in operation throughout the Armed Forces. The RQ-7 Shadow, an unmanned aerial vehicle (UAV) utilized by the Marine Corp and Army for reconnaissance purposes, is powered by UEL's AR741 rotary engine and functions on aviation fuel. One effort underway has been focused on developing this rotary engine system to operate on heavy fuels using direct injection technology and charge stratification. Although the rotary engine has many advantages over standard reciprocating …

Application Of Auto-Tracking To The Study Of Insect Body Kinematics In Maneuver Flight, Shreyas Vathul Subramanian

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There is a need to explain the complex phenomena that underlies the seemingly effortless flight modes of the dragonfly (Infra -order Anisoptera). However, measuring the body kinematics during flight is labor intensive. Thus a robust system was developed that automatically tracks and quantifies the body kinematics of a dragonfly during voluntary and escape take-offs, as well as maneuvers. Ultimately, the tool, which was developed using a custom code in C++ using the open source library OpenCV (Open Computer Vision), would be used to analyze bulk samples of high speed videos providing raw images at the rate of approximately 1000 frames …

Characterization, Stability, And Transport Through Defects In Graphene Nanoribbons, Sri Krishna Divya Pemmaraju

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Graphene nanoribbons (GNRs) constitute a new class of nanostructured materials with unique properties and significant potential for applications. During production of GNRs, defects are generally introduced within the lattice. Assessment of defects' stability and characterization of their effects on GNRs are therefore very important for predicting GNRs performance under realistic circumstances. Here we consider various possible defects, namely the ones caused by removal/addition of carbon atoms from/to the lattice as well as those caused by bond rotation/rearrangement. Our study is based on ab initio geometry optimization and electronic structure calculations. We determine which defects can be stable in graphene nanoflakes …

A Collaborative Computational Framework For Multidisciplinary And Reliability-Based Analysis And Optimization Using Sorcer, Karkada Nagesha Aithala

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In a globalized and highly competitive world of product design, collaboration is a necessity to leverage the expertise available among various engineering teams to meet stringent product specifications and strict product delivery schedules reducing the concept to release time, and hence maintaining a competitive edge in the market. Physical location of teams may span organizational firewalls and different countries. Seamless access must be provided to hundreds of design tools that are utilized by the teams to carry out multidisciplinary analysis, optimization, and reliability studies in order to accurately estimate product performance. Service ORiented Computational EnviRonment (SORCER) is one of the …

Analytical And Experimental Vibration Analysis Of Variable Update Rate Waveform Generation, Joshua F. Mark

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Typical vibration analysis of turbine engine components incorporates the use of a function generator to produce a signal that is routed to an excitation source as the forcing function of the test specimen. These waveforms are constructed by varying the amplitude of the signal over time with a fixed update rate (time increment between samples). This research investigates generating chirp waveforms by storing only one sinusoid of points and using an external timing signal to repetitively send out these stored data points. This results in varying the amplitude of the signal over time as well as the update rate. The …

Effects Of Large-Scale Transient Loading And Waste Heat Rejection On A Three Stream Variable Cycle Engine, Michael William Corbett

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The objective of the research presented in this document was to gain an understanding of the feasibility of extracting large amounts of transient shaft power from a variable cycle engine and to reject waste heat into the third stream bypass duct. This first required the development of a transient engine and controller simulation. After performing basic verification of the model, such as ensuring conservation of mass, tests were run for three missions using a low-efficiency periodic load which both required shaft power and created low quality waste heat. The waste heat generated by that load was lifted by a cooling …

Framework For Cohesive Zone Model Based Multiscale Damage Evolution In A Fatigue Environment, Michael Andrew Thomas

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The focus of this research is to develop a framework to track damage evolution in a structural model subjected to a fatigue environment. This framework incorporates a micromechanical approach of continuous damage modeling, where damage in a homogenized representative microstructure is introduced at the continuum scale through the material constitutive matrix. In this research, damage in the representative microstructure is simulated utilizing cohesive zone models (CZM) whose properties are a function of the magnitude of applied stresses and the resulting separation. In order to minimize the mesh dependence of the cohesive zone model an adaptive meshing technique is employed. A …

A Study On The Effects Of Coil Wedge During Rewinding Of Thin Gauge Metals, Jantzen L. Hinton

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With the increase in demand for high quality thin gauge metals improvements to control systems that monitor strip characteristics must first be acquired. During the rewinding of sheet metal, little insight is known as to what stresses are attributed to the actual winding process, not simply those induced by the mill. When winding effects become too severe they will alter control system readings, prompting the need for a rapid model that can predict winding effects and filter them from current control systems. This research develops a new method to determine a 4th order Airy function that predicts the 2D stress …

Computational Investigation Of Optimal Heavy Fuel Direct Injection Spark Ignition In Rotary Engine, Asela A. Benthara Wadumesthrige

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The main objective of this computational study is to investigate the optimum injection and spark parameters for the direct injection spark ignition (DISI) Wankel rotary engine using diesel fuel. Currently only port fuel injected gasoline rotary engines are available in the automotive industry. Compared to reciprocating type engines rotary engine is mechanically simple, less vibrate, have higher power to weight ratio and achieve better performance at high rpm. Due to the inherent low fuel efficiency of rotary engine and increasing gas prices, application of the rotary engine in conventional automobiles is decreasing. This project seeks to introduce DISI technology to …

An Implicit High-Order Spectral Difference Method For The Compressible Navier-Stokes Equations Using Adaptive Polynomial Refinement, Caleb J. Barnes

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A high/variable-order numerical simulation procedure for gas dynamics problems was developed to model steep grading physical phenomena. Higher order resolution was achieved using an orthogonal polynomial Gauss-Lobatto grid, adaptive polynomial refinement and artificial diffusion activated by a pressure switch. The method is designed to be computationally stable, accurate, and capable of resolving discontinuities and steep gradients without the use of one-sided reconstructions or reducing to low-order. Solutions to several benchmark gas-dynamics problems were produced including a shock-tube and a shock-entropy wave interaction. The scheme's 1st-order solution was validated in comparison to a 1st-order Roe scheme solution. Higher-order solutions were shown …

A Study Of The Aerodynamic Behavior Of A Nrel Phase Vi Wind Turbine Using The Cfd Methodology, Yen-Pin Chen

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Wind energy is an abundant natural resource that people have been trying to tap in recent decades. More and more wind turbines are being built to solve the world's energy shortage problem. For a wind turbine, power extracted from the wind by the rotor and the torque applied to the wind turbine blades are important issues in the design process. Thus there is a need to predict the performance of wind turbine blades using computer modeling. This work shows the results of a computational fluid dynamic simulation developed to predict the air flow field and associated aerodynamic quantities around the …

Effect Of Material Anomalies On Fatigue Life Of Turbine Disks, Jace A. Carter

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There is an economic need to extend the fatigue life of turbine engine rotor disks. The probability of failure during the operation life must be quantified as components remain in service beyond their traditional safe-life limit. Fracture mechanics based probabilistic methods are utilized to predict the probability of failure of components containing manufacturing and fatigue anomalies. Total fatigue life is defined in terms of crack initiation and propagation phases. A micromechanical initiation model uses material properties at the micro-scale to characterize the initiation phase, while short and long fatigue-crack growth models predict the crack propagation phase. A Monte Carlo simulation …

Niyama Based Taper Optimizations In Steel Alloy Castings, Daniel A. Gorsky

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In the casting process, regions of shrinkage porosity can be reduced or eliminated through the implementation of taper, or small angled additions of mass on the boundaries of the part design, before risers are placed on the casting. Taper supplements the effect of risers so that a smaller riser volume is necessary to make a casting sound. Typically, taper is determined for a casting by using industry guidelines that were developed for simple two-dimensional simplifications of a complex casting. There is no accepted method of defining taper directly on part geometry aside from using expert opinions to make final decisions …

Computational Modeling And Analysis Of Heavy Fuel Feasibility In Direct Injection Spark Ignition Engine, Suniludaya Simha Moda

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Direct Injection spark ignition (DISI) technology is helpful for the present day engine to increase the fuel efficiency. Power output and the choice of fuel as the demand and scarcity for fossil fuels are increasing. As a new technology DISI engines are employed in some commercial cars like the Pontiac Solstice using gasoline fuel. The advantages of DISI engines like use of different fuels, reduced compression ratio, reduced injection pressure and reduced operating pressures in DISI engines has not been widely tested. As a new technology DISI engines lack experimental results and combustion co-relations that can be directly used as …

Effect Of Free-Edges On Melt Pool Geometry And Solidification Microstructure In Beam-Based Fabrication Methods, Joy Elizabeth Davis

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Laser and electron beam-based additive manufacturing of Ti-6Al-4V are under consideration for application to aerospace components. A critical concern for these processes is the ability to obtain a consistent and desirable microstructure and corresponding mechanical properties of the deposit. Based on the Rosenthal solution for a moving point-heat source, recent work has developed simulation-based process maps for the thermal conditions controlling microstructure (grain size and morphology) in beam-based deposition of semi-infinite geometries, where a steady-state melt pool exists away from free-edges. In the current study, the Rosenthal solution is modified to include the effects of free-edges. This is accomplished by …

Experimental Studies Of Turbulent Boundary Layers Over A Rough Forward-Facing Step And Its Coarse Scale Resolution Approximations, Huiying Ren

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High spatial resolution PIV experiments are performed in the x-y plane at two different spanwise positions to compare the turbulent boundary layers over smooth and rough forward-facing-steps as well as the rough step's two coarse scale-resolution approximations. The Reynolds number based on the step's mean height, Re_h, is 3450 and the ratio of the boundary layer thickness to the step's height is δ/h = 8. The roughness topography on the top surface of the rough step is replicated from a realistic turbine blade and is intrinsically three-dimensional and highly irregular. The surface topographies of the coarse scale-resolution …

Computational Study Of Direct Fuel Injection In The Rotax 914 Engine, Brad Pollock

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Direct injection spark ignition (DISI) is a fuel delivery method in which the fuel is introduced directly into the combustion chamber of an internal combustion engine. Although direct fuel injection was first pioneered in the early 1920's, it has only recently become a reliable option due to advances made in control systems and injection technology. Direct injection enables increased fuel efficiency and higher power output than a conventional Port Fuel Injection (PFI) system. By delivering pressurized fuel directly into the cylinder, the degree of fuel atomization and the fuel vaporization rate are increased. Hence, the air/fuel mixture can be more …

Stochastic Mistuning Simulation Of Integrally Bladed Rotors Using Nominal And Non-Nominal Component Mode Synthesis Methods, Joseph A. Beck

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Mistuning prediction in integrally bladed rotors is often done with reduced order models that minimize computational expenses. A common model reduction technique used for mistuning applications is the component mode synthesis method. In this work, two modern component mode synthesis methods are used to generate mistuned response distributions that will be used to determine if the two methods are statistically indistinguishable. The first method, nominal mode approximation, assumes an airfoil geometric perturbation alters only the corresponding substructure modal stiffnesses while its mode shapes remain unaffected. The mistuned response is then predicted by a summation of the nominal modes. The second …

Risk Quantification And Reliability Based Design Optimization In Reusable Launch Vehicles, Jason Maxwell King

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Due to the inherent natural variability of parameters with reusable launch vehicles, design considerations without use of a reliability or safety index may be unreliable and vulnerable to vehicle failures. Generally in preliminary air vehicle design little information is known regarding design variable uncertainties, consequently requiring a technique that can quantify epistemic uncertainties. Evidence Theory is employed to accomplish this task resulting in a reliability bound of belief and plausibility. Due to the discontinuous nature of the belief and plausibility function it is necessary to implement a continuous function known as plausibility decision to be used to calculate sensitivities that …

Impact Of Induced Defects On Rotor Life Assessment, Ashley Winfield Whitney-Rawls

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There is an economic need to reduce the conservatisms of current lifing methods and extend component life. Extending component usage increases the probability of failure during operation. Therefore, the risk of continued service must be quantified before life extension concepts can successfully be implemented. The current FAA approved software for the certification of new rotor designs, only accounts for defects present prior to service. Defects due to the handling of components during inspection and material fatigue will induce defects during service and need to be included in any analysis of component life extension. Component life extension analysis of an Inconel …