Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 18 of 18
Full-Text Articles in Engineering
Commercial Program Development For A Ground Loop Geothermal System: Energy Loads, Gui, Turbulent Flow, Heat Pump Model And Grid Study, Paul A. Gross Ii
Commercial Program Development For A Ground Loop Geothermal System: Energy Loads, Gui, Turbulent Flow, Heat Pump Model And Grid Study, Paul A. Gross Ii
Browse all Theses and Dissertations
The use of the earth's thermal energy to heat and cool building space is nothing new; however, the heat transfer approximations used in modeling geothermal systems, leave uncertainty and lead to over sizing. The present work is part of a Wright State effort to improve the computer modeling tools used to simulate ground loop geothermal heating and cooling systems. The modern computer processor has equipped us with the computation speed to use a finite volume technique to solve the unsteady heat equation with hourly time steps for multi-year analyses in multiple spatial dimensions. Thus we feel there is more need …
Computational Modeling And Analysis Of Heavy Fuel Feasibility In Direct Injection Spark Ignition Engine, Suniludaya Simha Moda
Computational Modeling And Analysis Of Heavy Fuel Feasibility In Direct Injection Spark Ignition Engine, Suniludaya Simha Moda
Browse all Theses and Dissertations
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 …
Niyama Based Taper Optimizations In Steel Alloy Castings, Daniel A. Gorsky
Niyama Based Taper Optimizations In Steel Alloy Castings, Daniel A. Gorsky
Browse all Theses and Dissertations
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 …
Framework For Cohesive Zone Model Based Multiscale Damage Evolution In A Fatigue Environment, Michael Andrew Thomas
Framework For Cohesive Zone Model Based Multiscale Damage Evolution In A Fatigue Environment, Michael Andrew Thomas
Browse all Theses and Dissertations
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 …
Highly Active Porous Catalysts Fabricated By Attachment Of Palladium Nanoparticles On Hierarchical Carbon Structures, Hema Vijwani
Highly Active Porous Catalysts Fabricated By Attachment Of Palladium Nanoparticles On Hierarchical Carbon Structures, Hema Vijwani
Browse all Theses and Dissertations
The effectiveness of metal-based catalysts can be significantly enhanced by increasing the available surface area relative to the volume through the creation of hierarchical nanostructures. The catalyst demonstrated here is palladium, which is a widely recognized heterogeneous catalyst suitable for a variety of industrial applications such as water purification, hydrogen storage, and electrochemical devices. In this study, a novel multi-scale supporting material developed in this group, has been used as support. It consists of micro-porous graphitic carbon with strongly attached carbon nanotubes. This can increase the surface area by orders of magnitude without increasing the size or weight while still …
A Study On The Effects Of Coil Wedge During Rewinding Of Thin Gauge Metals, Jantzen L. Hinton
A Study On The Effects Of Coil Wedge During Rewinding Of Thin Gauge Metals, Jantzen L. Hinton
Browse all Theses and Dissertations
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
Computational Investigation Of Optimal Heavy Fuel Direct Injection Spark Ignition In Rotary Engine, Asela A. Benthara Wadumesthrige
Browse all Theses and Dissertations
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
An Implicit High-Order Spectral Difference Method For The Compressible Navier-Stokes Equations Using Adaptive Polynomial Refinement, Caleb J. Barnes
Browse all Theses and Dissertations
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
A Study Of The Aerodynamic Behavior Of A Nrel Phase Vi Wind Turbine Using The Cfd Methodology, Yen-Pin Chen
Browse all Theses and Dissertations
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
Effect Of Material Anomalies On Fatigue Life Of Turbine Disks, Jace A. Carter
Browse all Theses and Dissertations
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 …
Analytical And Experimental Vibration Analysis Of Variable Update Rate Waveform Generation, Joshua F. Mark
Analytical And Experimental Vibration Analysis Of Variable Update Rate Waveform Generation, Joshua F. Mark
Browse all Theses and Dissertations
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
Effects Of Large-Scale Transient Loading And Waste Heat Rejection On A Three Stream Variable Cycle Engine, Michael William Corbett
Browse all Theses and Dissertations
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 …
Commercial Program Development For A Ground Loop Geothermal System: G-Functions, Commercial Codes And 3d Grid, Boundary And Property Extension, Kyle L. Hughes
Commercial Program Development For A Ground Loop Geothermal System: G-Functions, Commercial Codes And 3d Grid, Boundary And Property Extension, Kyle L. Hughes
Browse all Theses and Dissertations
The rise in fossil fuel consumption and green house gas emissions has driven the need for alternative energy and energy efficiency. At the same time, ground loop heat exchangers (GLHE) have proven capable of producing large reductions in energy use while meeting peak demands. However, the initial cost of GLHEs sometimes makes this alternative energy source unattractive to the costumer. GLHE installers use commercial programs to determine the length of pipe needed for the system, which is a large fraction of the initial cost. These commercial programs use approximate methods to determine the length of pipe mainly due to their …
Graphene Based Anode Materials For Lithium-Ion Batteries, Sree Lakshmi Cheekati
Graphene Based Anode Materials For Lithium-Ion Batteries, Sree Lakshmi Cheekati
Browse all Theses and Dissertations
Improvements of the anode performances in Li-ions batteries are in demand to satisfy applications in transportation. In comparison with graphitic carbons, transition metal oxides as well as graphene can store over twice amount of lithium per gram. Recently, graphene-based anodes for Li-ion batteries are under extensive development. In this research, lithium storage characteristics in graphene oxide (GO), GO/Manganese acetate (GO/MnAc), GO/manganese oxide (GO/MnOx) composites and Nano Graphene Platelets (NGP) were studied. The prepared GO delivered reversible capacities of 706mAh/g with an average columbic efficiency of 87%. Reversible capacities of 533 mAh/g were observed for GO/MnAc composite. GO/MnOx nanocomposite thermal annealed …
The Functionalization And Characterization Of Adherent Carbon Nanotubes With Silver Nanoparticles For Biological Applications, Adam A. Maleszewski
The Functionalization And Characterization Of Adherent Carbon Nanotubes With Silver Nanoparticles For Biological Applications, Adam A. Maleszewski
Browse all Theses and Dissertations
The purpose of this project is to form silver nanoparticles (Ag-NP) attached to a hierarchical substrate for possible use in biological applications. The effectiveness of these Ag-NP-containing devices, including biofilters and biosensors, may be dramatically enhanced by the use of hierarchical structures such as carbon nanotubes (CNT), as they offer a high surface area surface suitable for cell-device interactions, while Ag-NP would be a suitable component in many such devices due to its plasmonic surface properties (e.g. in sensor and directed energy applications) and its anti-microbial properties (desirable for fluid filtration due to its low weight. Meaningful control over the …
Ab Initio Simulations Of Graphene-Based Nanosensor For Detecting No2 And Li, Ahmed Jama Hassan
Ab Initio Simulations Of Graphene-Based Nanosensor For Detecting No2 And Li, Ahmed Jama Hassan
Browse all Theses and Dissertations
Nanosensors, i.e., sensors based on nanomaterials, have the potential of superior performance owing to their size effect, and can have significant effects on detection of pollutants in the environment. Various nanowires have been used in this context. Here we investigate the possibility of NO2 and Li detection using the quantum conductance change in graphene nanoribbon. Quantum conductance modification in graphene nanoribbon upon NO2/Li adsorption was calculated using ab initio methods. The optimized structures of the adsorbed NO2 indicated two different geometries where either nitrogen or oxygen was closer to the graphene lattice. The former resulted in charge transfer from NO2 …
A Collaborative Computational Framework For Multidisciplinary And Reliability-Based Analysis And Optimization Using Sorcer, Karkada Nagesha Aithala
A Collaborative Computational Framework For Multidisciplinary And Reliability-Based Analysis And Optimization Using Sorcer, Karkada Nagesha Aithala
Browse all Theses and Dissertations
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 …
Effect Of Fullerene Nano-Spheres On Evaporation Kinetics Of Fluids, Wenhu Wang
Effect Of Fullerene Nano-Spheres On Evaporation Kinetics Of Fluids, Wenhu Wang
Browse all Theses and Dissertations
As the interest in fluid evaporation kinetics keeps increasing, it's inevitably noticed that fullerene nanospheres play an important role on it. In this study, we investigate the C60 nanospheres' effect on the evaporation kinetics and thermal transitions of different solvents (water, chlorobenzene) over the entire range of solubility. According to distinct polarity of different solvent, fullerene solution would behave differently, the trend of increasing in evaporation rate as the concentration increased was observed in aromatic solvents while the rate kept decreasing in water. The result of differential scanning calorimetry (DSC) and Raman spectroscopy provided an evidence about structuring in water …