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Heat Transfer And Friction Augmentation In A Narrow Rectangular Duct With Symmetrical And Non-Symmetrical Wedge-Shaped Turbulators, Michelle Valentino 2011 University of Central Florida

Heat Transfer And Friction Augmentation In A Narrow Rectangular Duct With Symmetrical And Non-Symmetrical Wedge-Shaped Turbulators, Michelle Valentino

Electronic Theses and Dissertations

The need for cleaner and more fuel efficient means to produce electricity is growing steadily. Advancements in cooling technologies contribute to the improvements in turbine efficiency and are used for gas turbines and for power generation in automotive, aviation, as well as in naval applications, and many more. Studies introducing turbulators on walls of internal cooling channels, which can be applied to hot gas components and in recuperative heat exchangers, have been reviewed for their ability to promote heat transfer in the channel while observing pressure loss caused by adding the features. Several types of turbulators have been studied; ribs ...


Modeling Of Thermal Properties Of Fiber Glass Polyester Resin Composite Under Thermal Degradation Condition, Marvin S. Tsoi 2011 University of Central Florida

Modeling Of Thermal Properties Of Fiber Glass Polyester Resin Composite Under Thermal Degradation Condition, Marvin S. Tsoi

Electronic Theses and Dissertations

Composites, though used in a variety of applications from chairs and office supplies to structures of U.S. Navy ships and aircrafts, are not all designed to hold up to extreme heat flux and high temperature. Fiber-reinforced polymeric composites (FRPC) have been proven to provide the much needed physical and mechanical properties under fire exposure. FRPC notable features are its combination of high specific tensile strength, low weight, along with good corrosion and fatigue resistance. However FRPC are susceptible to thermal degradation and decomposition, which yields flammable gas, and are thus highly combustible. This property restricts polymeric material usage. This ...


Purge And Secondary Flow Interaction Control By Means Of Platform Circumferential Contouring, Melissa Harris 2011 University of Central Florida

Purge And Secondary Flow Interaction Control By Means Of Platform Circumferential Contouring, Melissa Harris

Electronic Theses and Dissertations

This study presents an attempt to reduce the losses produced by the purge flow in a turbine stage by incorporating circumferential platform contouring. Two contours are proposed and compared against a baseline at different levels of swirl. The computational simulations were performed using a RANS three-dimensional Computational Fluid Dynamics code with the Shear Stress Transport turbulence model. The results of steady simulations demonstrate that for the first contour, when the flow is swirled to 50% of the rim speed, the purge flow exits the cavity with less cross flow. This in turn reduces the strength of the passage vortex. However ...


On Feasibility Of Reducing Metal Fuel Content And Operating Temperatures In Chemical Oxygen Generators, Allen Garcia 2011 University of Texas at El Paso

On Feasibility Of Reducing Metal Fuel Content And Operating Temperatures In Chemical Oxygen Generators, Allen Garcia

Open Access Theses & Dissertations

Chemical oxygen generators are widely used in aircraft, submarines, spacecraft, and other applications, problems such as combustion instabilities and a risk of fire may be present. For example, due to malfunction of an oxygen generator, fire occurred onboard the Mir Space Station in 1997. It is thus important to improve the process stability and fire safety of chemical oxygen generators. Chemical compositions for oxygen generators include an oxygen source such as sodium chlorate (NaClO3), a transition metal oxide as a catalyst, and a metal fuel to provide energy for self-sustaining combustion. Eliminating or decreasing the metal fuel would decrease the ...


Experimental Study Of Thermoelectric Properties For Randomly Distributed Carbon Nanotubes And Silicon Carbide Nanoparticles, Onasis Garcia 2011 University of Texas at El Paso

Experimental Study Of Thermoelectric Properties For Randomly Distributed Carbon Nanotubes And Silicon Carbide Nanoparticles, Onasis Garcia

Open Access Theses & Dissertations

In this experimental study, the thermoelectric (TE) properties of carbon nanotubes (CNTs) and Silicon carbide (SiC) nanoparticles have been investigated. Nanoparticles were randomly disrtibuted on a non-conductive glass or quartz substrate. The carbon nanotubes used were single-walled and multi-walled type, consisting of approximately 60% semiconducting 40% metallic tubes. The experimental design is analogous to that of a thermocouple measurement, with the nanoparticle layers creating hot and cold joints with a dissimilar metal Alumel (Ni-Al). Voltage (mV), current (μA) and resistance (Ω) values were measured with respect to temperature (°C), and Seeback coefficient values were also calculated in parallel. Summarized results ...


A Combined X-Fem And Level Set Approach For Modeling Composite Material's Micro Structure, Himanshu Kumar 2011 University of Texas at El Paso

A Combined X-Fem And Level Set Approach For Modeling Composite Material's Micro Structure, Himanshu Kumar

Open Access Theses & Dissertations

Composite materials are usually made of fibers and binding matrix. It's always a challenge to model composite materials' microstructure through the traditional finite element method because construction of an approximation space which is discontinuous across a given line or surface will place strict restrictions on the FE mesh. The interfacing of fibers in composites' microstructure through the standard finite element method is irksome and tedious because the presence of fiber presents a discontinuity in the binding material. In this present work, the composite's microstructure is modeled through the combined approach of Level Set and Extended Finite Element Method ...


Synthesis, Microstructure And Thermal Analysis Of Gd2o3 - Hfo2 Coatings, Chandan Kumar Roy 2011 University of Texas at El Paso

Synthesis, Microstructure And Thermal Analysis Of Gd2o3 - Hfo2 Coatings, Chandan Kumar Roy

Open Access Theses & Dissertations

Thermal barrier coatings (TBCs) are critical for future gas turbines of advanced coal based power generation systems. The TBCs are protective layers of low thermal conductivity ceramic materials, which prevent the damage of components that are exposed to very high temperature of the hot gases. Due to increasing demand to improve the efficiency, it is necessary to find alternate TBC materials which can withstand higher temperature for longer period than state-of-art TBCs. The present study focuses on the Gd2O3 stabilized HfO2 (GSH) as a potential candidate for TBC. GSH materials were synthesized in bulk and coatings form. The Gd2O3 content ...


Experimental And Numerical Investigation Of The Effect Of Fuel Composition On Flame Stability On A Gas Turbine Combustor, Gilberto Corona 2011 University of Texas at El Paso

Experimental And Numerical Investigation Of The Effect Of Fuel Composition On Flame Stability On A Gas Turbine Combustor, Gilberto Corona

Open Access Theses & Dissertations

Gas turbines are used for power generation and aviation all over the world. Fossil fuels remain the main source of energy for the operation of gas turbines but the recent increase in environmental awareness has influenced government agencies to impose stringent limits on pollutant emissions from power generation plants. Pollutant emissions control is one of the major challenges for gas turbine designers. In this study, experimental methods and computational fluid dynamics (CFD) technologies are used to study the problems that arise when coal derived fuels are used in Gas Turbine Combustors.

Gas turbine designers need both experimental data and combustion ...


Heat Transfer In A Coupled Impingement-Effusion Cooling System, Mark W. Miller 2011 University of Central Florida

Heat Transfer In A Coupled Impingement-Effusion Cooling System, Mark W. Miller

Electronic Theses and Dissertations

Gas turbine engines are prevalent in the today’s aviation and power generation industries. The majority of commercial aircraft use a turbofan gas turbine engines. Gas turbines used for power generation can achieve thermodynamic efficiencies as high as 60% when coupled with a steam turbine as part of a combined cycle. The success of gas turbines is a direct result of a half century’s development of the technology necessary to create such efficient, powerful, and reliable machines. One key area of technical advancement is the turbine cooling system. In short, increasing the turbine inlet temperature leads to a rise ...


A Turbulence-Based Model For The Primary Breakup Of Pressure Atomized Liquid Jets, Christopher D. Schmitz 2011 Iowa State University

A Turbulence-Based Model For The Primary Breakup Of Pressure Atomized Liquid Jets, Christopher D. Schmitz

Graduate Theses and Dissertations

The primary objective of this study was to investigate and validate a predictive, turbulence based primary breakup model. The ESE model is based on a modeled evolution of the turbulent energy spectrum, and is sufficiently general that it may be applied to a broad range of pressure-atomized spray processes, such as those found in agricultural irrigation, industrial coating, automotive fuel injection, and others. In this study, the governing equations are derived and applied to diesel sprays to address a lack of predictive primary breakup models in literature. Tests are performed to demonstrate that the ESE model is numerically converged and ...


Hemorrhage Correlation With Total Energy And Surface Power Near Opossum Skull Exposed To Pulsed Ultrasound, Viksit Kumar 2011 Iowa State University

Hemorrhage Correlation With Total Energy And Surface Power Near Opossum Skull Exposed To Pulsed Ultrasound, Viksit Kumar

Graduate Theses and Dissertations

High intensity focused ultrasound (HIFU) has been used noninvasively for therapeutic applications. Previous studies have shown that HIFU when targeted on fetal rat and mice bones resulted in hemorrhage. Hemorrhage occurrence and area were found to correlate with total equivalent energy (i.e. product of energy density, number of pulses and volume of the focal region) and surface power (i.e. product of pulse average intensity, number of pulses and beam area). Continuation of the trend was observed in Opossum pups. Opossum pups (7- 8 post natal days) were exposed to 1.1 MHZ f/1 spherically focused transducer (6 ...


Solid Oxide Fuel Cell Reliability And Performance Modeling And Fabrication By Spray Pyrolysis, Lin Liu 2011 Iowa State University

Solid Oxide Fuel Cell Reliability And Performance Modeling And Fabrication By Spray Pyrolysis, Lin Liu

Graduate Theses and Dissertations

SOFCs have the potential to meet the critical energy needs of our modern civilization and minimize the adverse environmental impacts from excessive energy consumption. They are highly efficient, clean and can run on a variety of fuel gases. However, wide adoption of SOFCs is currently hindered by cell durability, manufacturing cost, and lack of fundamental understanding on electrochemical performance of the cell. In order to evaluate the durability of SOFCs, a mathematical thermo-mechanical model was developed to provide the distribution of thermal stresses during thermal cycling, and predict the lifetime of a cell. In addition, an ultrasonic spray pyrolysis prototype ...


A Study On Static Pressure Reset And Instability In Variable Air Volume Hvac Systems, Brian Wayne Housholder 2011 Iowa State University

A Study On Static Pressure Reset And Instability In Variable Air Volume Hvac Systems, Brian Wayne Housholder

Graduate Theses and Dissertations

This project began with testing five different versions of supply duct static pressure reset strategies that fall into two general categories: Proportional plus Integral control loops, and Trim and Respond control strategies. The testing took place from July 2009 through January 2011 at the Energy Resource Station in Ankeny. During this time, these five experimental control strategies were modified and altered in order to achieve substantial energy savings without unwanted instability. In the end, only one strategy, tiered Trim and Respond, was able to perform as desired by saving energy without displaying unstable behavior or significantly impacting maintenance costs.

The ...


Fabrication Of Metal Matrix Composite By Semi-Solid Powder Processing, Yufeng Wu 2011 Iowa State University

Fabrication Of Metal Matrix Composite By Semi-Solid Powder Processing, Yufeng Wu

Graduate Theses and Dissertations

Various metal matrix composites (MMCs) are widely used in the automotive, aerospace and electrical industries due to their capability and flexibility in improving the mechanical, thermal and electrical properties of a component. However, current manufacturing technologies may suffer from insufficient process stability and reliability and inadequate economic efficiency and may not be able to satisfy the increasing demands placed on MMCs. Semi-solid powder processing (SPP), a technology that combines traditional powder metallurgy and semi-solid forming methods, has potential to produce MMCs with low cost and high efficiency. In this work, the analytical study and experimental investigation of SPP on the ...


A Numerical And Experimental Study Of In-Situ No Formation In Laminar Nh3-Seeded Syngas Diffusion Flames, Miao Li 2011 Iowa State University

A Numerical And Experimental Study Of In-Situ No Formation In Laminar Nh3-Seeded Syngas Diffusion Flames, Miao Li

Graduate Theses and Dissertations

Oxides of nitrogen formed during combustion are significant threats to our environment. They result in the formation of "acid rain", smog, and depletion of the ozone layer. These combustion systems often include diffusion flames of hydrocarbon and air, where the NO can be formed at high levels (100's to 1000's of parts per million). In fuels produced from biomass or waste streams, small amounts of ammonia (NH3) can significantly enhance the production of NO. However, the chemical kinetic mechanisms for NO formation in the presence of NH3 are not well understood or validated. In the current work, a ...


A Near Real-Time Framework For Extracting Tip-Sample Forces In Dynamic Atomic Force Microscopy, David Ray Busch 2011 Iowa State University

A Near Real-Time Framework For Extracting Tip-Sample Forces In Dynamic Atomic Force Microscopy, David Ray Busch

Graduate Theses and Dissertations

The atomic force microscope (AFM) is a versatile, high-resolution tool used to characterize

the topography and material properties of a large variety of specimens at nano-scale. The

interaction of the micro-cantilever tip with the specimen causes cantilever de

ections that are

measured by an optical sensing mechanism and subsequently utilized to construct the sample

topography. Recent years have seen increased interest in using the AFM to characterize soft

specimens like gels and live cells. This remains challenging due to the complex and competing

nature of tip-sample interaction forces (large tip-sample interaction force is necessary to achieve

favorable signal-to-noise ratios). However ...


A Remotely Operated Multi-Tracked Vehicle For Subterranean Exploration Of Gopher Tortoise Burrows, William Keese 2011 University of South Florida

A Remotely Operated Multi-Tracked Vehicle For Subterranean Exploration Of Gopher Tortoise Burrows, William Keese

Graduate Theses and Dissertations

The gopher tortoise is a land tortoise living in the southeastern United States. It is a species in decline and is listed as threatened or endangered in six different states. The gopher (as commonly referred) digs burrows that it uses for many reasons and spends most of its time underground. Problems occur when trying to estimate a population because a gopher tortoise digs more than one burrow. This thesis demonstrates an innovative way to survey and investigate a gopher tortoise burrow hole by using a multi-tracked remotely operated vehicle. The vehicle carried two cameras (fore and aft) and was equipped ...


Incorporating Uncertainty In Vehicle Miles Traveled Projections Of The National Energy Modeling System, David Michael Poetting 2011 Iowa State University

Incorporating Uncertainty In Vehicle Miles Traveled Projections Of The National Energy Modeling System, David Michael Poetting

Graduate Theses and Dissertations

The National Energy Modeling System (NEMS) is a computational model that forecasts the production, consumption, and prices of energy in the United States. Although NEMS is a complex and detailed model, it does not currently represent the multitude of uncertainties associated with the US energy system. These uncertainties need to be communicated to policy makers in order for them to develop better-informed decisions regarding energy policy. In this study, uncertainty is added to the vehicle miles traveled (VMT) equation of NEMS to demonstrate the importance and benefit of uncertainty in the model. The VMT model is derived and its uncertain ...


Stress Analysis Of Welded Gusseted Frames, Zamir Imtiyaz Syed 2011 Iowa State University

Stress Analysis Of Welded Gusseted Frames, Zamir Imtiyaz Syed

Graduate Theses and Dissertations

Welded gusseted frame design for fatigue loading is largely not addressed in modern machine design

texts. This research intends to uncover stress solutions for critical locations on welded gusseted frames

so that such a common engineering structure can have design basis. The problem was approached

using static equilibrium relations to populate coefficients of deliberately chosen line stress functions.

The results from that analysis were used in a subsequent fracture mechanics analysis to develop the

singular stress field at a weld toe. The current research resulted in solutions for the two most critical

stress states on welded gusseted frame structures.


3d Mesh Metamorphosis From Spherical Parameterization For Conceptual Design, Ruqin Zhang 2011 Iowa State University

3d Mesh Metamorphosis From Spherical Parameterization For Conceptual Design, Ruqin Zhang

Graduate Theses and Dissertations

Engineering product design is an information intensive decision-making

process that consists of several phases including design specification

definition, design concepts generation, detailed design and analysis,

and manufacturing. Usually, generating geometry models for

visualization is a big challenge for early stage conceptual design.

Complexity of existing computer aided design packages constrains

participation of people with various backgrounds in the design

process. In addition, many design processes do not take advantage of

the rich amount of legacy information available for new concepts

creation.

The research presented here explores the use of advanced graphical

techniques to quickly and efficiently merge legacy information with ...


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