bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuzzy Modeling of Imprecise Material Parameters in the Analysis of Metal Matrix Composite Structures
Authors: Wehrle Erich , Wedekind Max , Baier Horst
Published: August 2012

Engineering information is often uncertain, deviated, imperfect, erroneous, imprecise, etc. Fuzzy methods, based on possibility theory are well suited for describing epistemic uncertainty. Included in epistemic uncertainty are data sets where only few samples are available and are appropriately modeled with fuzzy methods. The resulting fuzzy parameters can then be used in structural analysis, allowing for nondeterministic consideration and, therefore, uncertainty assessment. In this study, different approaches to construct fuzzy membership functions are discussed and compared. Further, the influence of fuzzy modeling, or fuzzification, is evaluated within the framework of structural analysis and then in the safety factor assessment. The mechanical response was calculated using finite element analysis with uncertain material, evaluating stress and buckling load factor. Finally, the fuzzy safety factors were quantified for the different fuzzification methods, showing the importance of uncertainty consideration.
Influence of van der Waals Forces on Electrostatically Actuated MEMS/NEMS Circular Plates
Authors: Caruntu Dumitru I. , Alvarado Iris
Published: August 2012

This paper deals with electrostatically actuated micro and nano-electromechanical (MEMS/NEMS) circular plates. The system under investigation consists of two bodies, a deformable and conductive circular plate placed above a fixed, rigid and conductive ground plate. The deformable circular plate is electrostatically actuated by applying an AC voltage between the two plates. Nonlinear parametric resonance and pull-in occur at certain frequencies and relatively large AC voltage, respectively. Such phenomena are useful for applications such as sensors, actuators, switches, micro-pumps, micro-tweezers, chemical and mass sensing, and micro-mirrors. A mathematical model of clamped circular MEMS/NEMS electrostatically actuated plates has been developed. Since the model is in the micro- and nano-scale, surface forces, van der Waals and/or Casimir, acting on the plate are included. A perturbation method, the Method of Multiple Scales (MMS), is used for investigating the case of weakly nonlinear MEMS/NEMS circular plates. Two time scales, fast and slow, are considered in this work. The amplitude-frequency and phase-frequency response of the plate in the case of primary resonance are obtained and discussed.
Numerical Characterization of a Novel Staged Combustion Concept Applied to Oxy-Fuel Carbon Capture Technology
Authors: Goanta Adrian , Bohn Jan-Peter , Blume Maximilian , Li Xinmeng , Spliethoff Hartmut
Published: August 2012

In oxy-combustion the fuel is burnt in a mixture of oxygen and recirculated flue gas to keep the temperature inside the furnace to levels similar to conventional combustion. This eliminates the atmospheric nitrogen from the process, leading to a flue gas consisting mainly of carbon dioxide and water vapor. Further on, the CO2 can be separated for storage purposes. A major drawback of the conventional oxy-fuel combustion technology consists in the high amount of flue gas that has to be recirculated in order to control the temperature level inside the furnace. A novel oxy-fuel firing concept based on a combination of pulverized coal burners operating under non-stoichiometric conditions is investigated as a solution for lowering the necessary flue gas recirculation rate, while keeping the temperature inside the furnace at feasible levels. This paper presents a numerical analysis of the most relevant aspects for this new firing concept, such as process specifics and limitations, burner design criteria, aerodynamic characterization of the near burner zone, flame ignition and temperature. First the process is defined via thermodynamic calculations which are necessary to establish the operating conditions and to generate sets of parameters for the design phase of the burners. Subsequently the parameters generated in the first phase are used as boundary conditions for the design of the burners via CFD simulations. The CFD code used in this study is updated for oxy-firing conditions with the recent developments in terms of gas phase reactions, char conversion modeling and radiative heat transfer in high temperature atmospheres with elevated CO2 concentration. Additionally, the most relevant aspects regarding the validation of the CFD code against in-flame experimental values are presented and discussed. The simulations show good agreement with the averaged experimental data collected along the flame centerline.
An Efficient Method for Simulation of 3D Multi-Body Dynamic Problems Using Maple and Simulink Packages
Authors: Shirazi Kourosh H. , Attaran Behrooz , Zaeri Reza
Published: August 2012

In this paper, an efficient method is proposed for modelling and simulation of multi-body dynamic problems. The method employs symbolic computational abilities of Maple as well as graphical environment of Matlab-Simulink to obtain and solve the equations of motion of a multi-body system accurately and rapidly. Considering a typical multi-body dynamical system the governing equations of system including second order equations of motion, first order nonholonomic and holonomic algebraic constraint equations are derived in Maple software. The state variables of the system are defined based on the systems degrees of freedom or generalized velocities. Converting the system’s equations to an algebraic form and combining them together by using a few Maple commands, the simplest form of the system’s equations of motion are obtained in the canonical standard state space form. This form is suitable when an explicit numerical method of integration is used. Then using a few toolboxes of Simulink, the equations are solved and can be studied. To procedural illustration of the method a lateral vehicle dynamic problem having thirty equations is considered. Beside the present method, Maple as well as Matlab is used to solve the problem. The results show the distinction of the method from the points of execution CPU time, accuracy and longer simulation. This method is suitable when investigation of long term behavior of multi-body dynamical systems is needed.
Vision Guided Motion Control of a Biomimetic Quadruped Robot: RoboCat
Authors: Carpenter Steven , Yu Xinming , Altun Melih , Graham James , Zhu J. Jim , Starzyk Janusz
Published: August 2012

This paper presents the vision system and visual processing for a biomimetic elastic cable-driven quadruped robot—RoboCat. The paper is geared towards selection of appropriate visual servoing techniques for RoboCat such as vision algorithms, high-level cognition algorithms, software architecture and hardware implementation. The system uses two video cameras for stereo vision data acquisition and a SUMIT-ism form factor embedded computer for vision data processing. The vision system employs a color based target recognition algorithm, a neural network based shape recognition algorithm and a Color and Zernike moment based face detection algorithm. The paper presents the vision algorithms, vision guidance and motion tracking algorithms, rule-based decision making algorithms and the open architecture of the autonomous vision tracking system. Experimental testing results (including video clips) are also presented.
Panther Peer: A Web-Based Tool for Peer and Self Evaluation
Authors: Venkataramanujam Venkatesh , Larochelle Pierre
Published: August 2012

Panther Peer is a novel web based tool for peer evaluation. It has been developed at the Florida Institute of Technology to enable students (specifically those involved in capstone design projects) to give one another anonymous feedback on their team performance. Panther Peer is simple to implement and completely automated. Panther Peer automates the process of peer evaluation and minimizes the workload for both instructors and students. With the benefits of automation students can gain feedback more quickly. Moreover, the reduction in workload for course instructors enables them to encourage peer evaluations. The primary advantage of this system is the feedback students receive from their peers which helps them identify their weaknesses and focus on their strengths. The automated process means that the collection and dissemination of information is highly efficient. From the peer evaluations by students, instructors can have a fair idea about the teams progress and intervene where deemed necessary.
Macro-System Model for Hydrogen Energy Systems Analysis in Transportation
Authors: Diakov Victor , Ruth Mark , Goldsby Michael E. , Sa Timothy J.
Published: August 2012

The introduction of hydrogen as an energy carrier for light-duty vehicles involves concomitant technological development of an array of infrastructure elements, such as production, delivery, and dispensing, all associated with energy consumption and emission levels. To analyze these at a system level, the suite of corresponding models developed by the United States Department of Energy and involving several national laboratories is combined in one macro-system model (MSM). The MSM uses a federated simulation framework for consistent data transfer between the component models. The framework is built to suit cross-model as well as cross-platform data exchange and involves features of “over-the-net” computation. While the MSM can address numerous hydrogen systems analysis aspects, of particular interest is the optimal deployment scenario. Depending on user-defined geographic location and hydrogen demand curve parameters, the cost-optimal succession of production/delivery/dispensing pathways undergo significant changes (the most important of these being the transition between distributed and central H2 production with delivery). Some ‘tipping’ (break-even) points are identified.
Continuing Towards the Optimization of a Pulsatile Three-Stream Coaxial Airblast Injector
Authors: Strasser Wayne
Published: August 2012

The performance of a rather large-scale self-exciting coaxial three-stream airblast injector was studied experimentally and computationally by Strasser (International Journal of Multiphase Flow, 2010). Changes in the relative flow of the inner gas stream produced measurable responses in transient behavior and spray pattern. Particularly, above an inner gas momentum ratio of about 0.2, a transition occurred from a repeatable bursting pattern to one that exhibited a wide range of bursting events. In addition, the spray pattern shifted from unimodal to polymodal. Frequency domain analyses revealed distinct changes in the inner and outer air stream pulsations as a function of air feed rates. Since that work, efforts have progressed in studying the effects of injector geometry on spray characteristics and pulsating flow field response. Geometric features considered included inner nozzle retraction, stream meeting angle, outer annulus gap, and nozzle diameters. Changes to retraction produced the most profound, but not always monotonic, responses in the energy content and nature of the spray pattern. A flushed design was shown to have the strongest pressure pulsations, as well as having the spray bursts moved the farthest downstream of the injector, but only when the angle was moderate. Increases in the other geometric values also moved the ligament formation downstream and reduced the pre-filming dominant frequencies. In general, the time-averaged spray profiles were trimodal in shape and were focused or diffused by geometric permutations. The frequency responses of ligament production and feed pressures did not necessarily coincide; however, all but the highest retraction case exhibited frequencies that were multiples of approximately 200 Hz.
Reliability Centered Maintenance as Applied to Wind Turbine Power Plants
Authors: Farrington Seth E. , Sillivant Daniel , Sautter Chris
Published: August 2012

The objective of this paper is to present the methodology for the application of Reliability Centered Maintenance to wind turbines. The reliability and maintenance of wind turbines is a growing area of interest. The inherent variation in the loading experienced by wind turbines presents unique problems that differ from current practice within the power generation sector. The core of these issues center on the inherent variability of the wind and the resulting loads transferred to the equipment. Reliability Centered Maintenance (RCM) is a useful tool that provides the means to overcome some of these difficulties. RCM is implemented through either Condition Based Maintenance (CBM) or Time-Directed Maintenance (TDM). CBM is implemented through the use of condition monitoring based on defined condition indicators established through field experience, or laboratory testing. TDM is implemented through the use of reliability failure analysis to characterize a time directed maintenance interval. This failure analysis is performed on either laboratory test specimens, or failed field components. This paper presents the methodology for applying CBM or TDM to a wind turbine as well as suggestions for scaled laboratory testing.
DC Flow Investigations in Thermoacoustic Prime Mover
Authors: Paridaens Richard , Kouidri Smaine , Jebali Jerbi Fathi
Published: August 2012

In thermoacoustic device, the nonlinear phenomena are the source of secondary flows superimposed on the oscillating flow. To date, the acoustic streaming have been only characterized for progressive and standing waves in current systems. A method to characterize theoretically the secondary flows in thermoacoustic systems with more complex geometries is developed in this paper. This method is applied in the case of an annular thermoacoustic prime mover. The streaming fields are then provided. As the determination of the streaming fields requires the knowledge of the first order acoustic parameters, a linear model is used. The theoretical results of the acoustic pressure are compared to the experimental data. A relative error less than 10% is obtained, allowing the validation of the linear model.
Non-Steady Planing and Advection Delay Effects on the Dynamics and Control of Supercavitating Vehicles
Authors: Nguyen Vincent , Hassouneh Munther A. , Balachandran Balakumar , Abed Eyad H.
Published: August 2012

Cavity-vehicle interactions play a significant role in the dynamics of supercavitating underwater vehicles. To date, in the vast majority of planing force models for supercavitating vehicle dynamics, a steady planing assumption is utilized, wherein the vehicle-cavity interaction is only dependent on the vehicle’s position relative to the cavity. In this work, a framework to properly account for the vehicle radial motions into and out of the fluid is presented. This effectively introduces damping or velocity related dependence into the planing force formulation. The planing force is applied to cavity sections that are described by a previous (or delayed) position and orientation of the cavitator. The physical basis for the advection delay and the expressions used to determine the vehicle immersion and immersion rate are presented. Analysis and simulations for the time-delayed, non-steady planing system are carried out, and the delay effect in this system is shown to be stabilizing for certain values of the cavitation number that is contrary to previous results that have assumed steady planing force models.
Energetic and Economic Performance of a Compressed Air Energy Storage Facility in Texas as a Function of Technical and Cost Parameters
Authors: Townsend Aaron K. , Webber Michael E.
Published: August 2012

In this research an optimization model was used to determine the sensitivity of the revenue, net cash flow (defined as revenue less amortized capital costs, fixed and variable operating costs, and return on investment), and operational characteristics of a compressed air energy storage (CAES) facility to certain technical factors in the Electric Reliability Council of Texas (ERCOT) zonal market. The technical factors considered were compressor capacity and storage capacity relative to turbine capacity, non-spinning reserve market participation, minimum allowable runtime of the compressor and turbine systems, and costs associated with startup of the compressor and turbine systems. Additionally, the work showed that the nine-year optimization problem could be decomposed into nine single-year optimization problems with decreased computation time and minimal divergence from the nine-year solution. Previous work had determined the optimal compressor and storage capacities for a given expander capacity; the current work expanded on the previous work to show that the economics of CAES are reasonably insensitive (defined as within 5% of the maximum net cash flow) to compressor capacity within a range of 0.45 to 0.8 MW per MW of turbine capacity in the West zone of ERCOT and 0.25 to 0.5 MW per MW of turbine capacity in the non-West zones in ERCOT. Similarly, the economics of CAES are reasonably insensitive to storage capacity within a range of 20 to 60 MWh per MW of turbine capacity in the West zone of ERCOT and 12 to 35 MWh per MW of turbine capacity in the non-West zones. Previous work had determined that participation of the turbine-generator system in the non-spinning reserve market increased the revenues and net cash flow and reduced the amount of electricity bought and sold in the balancing energy market. This work confirmed the previous finding and also determined that the participation of the motor-compressor as dispatchable load in the non-spinning reserve market increased the revenues and net cash flow and increased the amount of electricity bought and sold. The increase in electricity sales due to the motor-compressor participation in the non-spinning reserve market only partially offset the decrease in the amount of electricity sold due to the turbine-generator participation. The net effect of both systems participating in the non-spinning reserve market was an increase in revenue of 29% to 37% and net cash flow of 130% to 250% and a decrease in the amount of electricity bought and sold by about 10%. This work also found that a CAES facility is sensitive to minimum runtime constraints and startup costs. Minimum runtime constraints reduce the net cash flow by 11% to 13% and increase the amount of electricity bought and sold by 1% to 3%, for a minimum runtime of 4 hours. The effect of startup costs is to reduce both the net cash flow by 5% to 6% and the amount of electricity bought and sold by 4% to 5% for startup costs of $2/MW-start.
The Electrode-Electrolyte Interface in Acidic and Alkaline Fuel Cells
Authors: Sprague Isaac B. , Dutta Prashanta
Published: August 2012

This numerical study presents the role of diffuse region of the electric double layer in both acidic and alkaline fuel cells. The numerical model is based on the Poisson-Nernst-Planck (PNP) and generalized-Frumkin-Butler-Volmer (gFBV) equations. The Laminar Flow Fuel Cell (LFFC) is used as the model fuel cell architecture to allow for the appropriate and equivalent comparison of acidic and alkaline cells. In particular, we focus on how each device behaves to changing reactant supply at the electrodes, including the overall cell performance and individual electrode polarizations. It is found that the working ion concentration at the reaction plane contributes to differing performance behaviors in acidic and alkaline fuel cells, including activation losses and reactant transport overpotentials. This is due to the working ion, and the electrode where it’s consumed, being opposite for acidic and alkaline fuel cells.
Modeling of Internal Combustion Engine Ignition Coil via MATLAB® Simulink® and Ansoft Maxwell® Software
Authors: Nordstrom Robert S. , Kumpaty Subha K.
Published: August 2012

Electrical ignition (spark ignition) is the mechanism that ignites the air-fuel mixture provided by the induction system of an internal combustion engine. SAE J973 NOV1999 is a test method that was designed and established by the Society of Automotive Engineers (SAE). This specification provides a test sequence along with the equipment that ensures the proper test for a spark delivery device. To have a mathematical model of the ignition coil to function per this SAE specification would be beneficial to the design engineer. This paper will discuss the operation and simulation of an ignition coil using MATLAB® Simulink® and Ansoft Maxwell® finite element analysis software. The aforementioned numerical packages are used to evaluate a coil design and how it would correlate to the SAE J973 prescribed by the SAE Ignition Systems Standards Committee. The coil that is simulated is of inductive type ignition. The simulation results show that accuracy within 10% to 15% from tested values is obtainable with lumped parameter elements using this modeling technique.
Experimental Study of Subcooled Pool Boiling Heat Transfer on Metal Foam
Authors: Shi Juan , Jacobi Anthony M. , Chen Zhenqian
Published: August 2012

The present experimental study is focused on subcooled pool boiling heat transfer on aluminum metal foam at atmospheric pressure. Experiments are conducted with open-cell metal foam of different porosity and different thickness, using water as the working fluid. The surface superheat ranges up to 15 °C, with maximum heat flux of about 30 W/cm2. The thermal performance of pool boiling on metal foams is compared to that on a roughened copper surface of the same dimensions. The thickness and the geometry of metal foams significantly influence the pool boiling heat transfer coefficient. The effect of orientation on the thermal performance in metal foam is also studied. The surface temperature excursion at boiling incipience and small hysteresis is observed in the experiments. When the metal foam thickness is reduced, hysteresis becomes more significant.
Design and Development of a Portable Off-Grid Water Chlorination System
Authors: LePage Will S. , Hampton Kyle B. , Johnson Bradford H. , Mayer Kevin J. , Henshaw John M. , Purser Gordon H.
Published: August 2012

The design and fabrication of a portable water chlorination system is described. The backbone of the system is a custom-designed, efficient, and easily operated chlorine electrolysis cell. The cell produces concentrated hypochlorous acid (HOCl), a form of chlorine that readily kills harmful pathogens in untreated water. The cell is fabricated from durable yet inexpensive materials and requires only two inputs: (1) 12 volts of direct current, which can be supplied with standard car batteries that are commonplace worldwide, and (2) 800 milliliters of 0.43 molar sodium chloride solution, which can be substituted with seawater. The system was first tested in the laboratory under controlled conditions. The cell was powered for 70 minutes and samples of the solution were taken in 10-minute intervals. The hypochlorite ion (OCl−) concentration was measured with a UV-visible light spectrophotometer. The results show that the cell produces enough hypochlorite in one hour to disinfect up to 1500 liters of clear surface water or 750 liters of turbid water. Successful laboratory test results led to field tests utilizing a solar photovoltaic power supply. Preliminary results of these tests are presented.
Fabrication of a MEMS-Based Solar Thermal Collector for Energy Sustainability
Authors: Ogbonnaya E. , Gunasekaran A. , Weiss L.
Published: August 2012

A micro solar thermal collector has been fabricated by chemical electrodeposition technique. The coating is made of black nickel-tin selective absorber deposited on a copper substrate. The fabrication technique is presented. The electrodeposition was performed using processes that are less hazardous than many common approaches at a near-neutral pH. The procedure was also performed at room temperature. The environmentally friendly plating procedure makes it a potential replacement for black chromium. The final coating has a dendrite crystal structure of about 100 nm in diameter. The use of this selective coating significantly improved the ability of the fabricated solar collector to convert incident radiation to thermal energy. The performance of the collector plate in a simulated solar environment was examined. An increase in the stagnation temperature of the collector of 10 °C was observed when the selective coating was applied to the base collector plate.
HEM as an Environmental Friendly Alternative to Produce UFC
Authors: Arteaga-Arcos J. C. , Trujillo-Reyes J. , Delgado-Herna´ndez D. J. , Santamari´a-Ortega A. , Chimal-Valencia O. A. , Yee-Madeira H. T.
Published: August 2012

High fineness is one of the most important characteristics of the Ultrafine Cements (UFC) with maximum particle size below 20 μm. Usually, UFC is obtained once the Ordinary Portland Cement (OPC) is grinded in common grinding devices e.g. drum mills; however this is a time consuming process, as it becomes complicated to reduce such a size once the particles have reached ultrafine powder dimensions. Some modern grinding devices as High Energy-Ball Mills (HEM) and shaker mills, have been used for ultrafine grinding-processes, especially at the advanced materials processing research field, but not in the cement industry. The most suitable combination of parameters (time, ball/powder (B/P) ratio and milling speed) was determined after the characterization of processed cement powder, in order to obtain UFC at laboratory level. The optimal combination of parameters produced an UFC having a maximum particle size below 15 μm. The HEM horizontal-rotary-ball-mill device used herein is not only intended for laboratory purposes, but also has one of the advantages of a direct-scaling-up, as it could be used for industrial purposes by means of more capacity mills. Furthermore, it is more efficient than both a shaker mill and a traditional ball milling device. As a result, if this kind of device is used instead of the traditional ball mill, the environmental impact due to the UFC production process could be minimized. This represents an environmental friendly alternative process for obtaining UFC from OPC.
Proper Orthogonal Decomposition Analysis of JaVA Flows for Cross-Flow Conditions
Authors: Cadirci Sertac , Gunes Hasan
Published: August 2012

Jet and Vortex Actuator (JaVA) is a zero-net-mass flux device for active flow control of boundary layers and transition. JaVA produces various jets which can be used to delay flow separation or to “steer” the boundary layer velocity profile. In this study, numerical simulations of JaVA-boundary layer interactions are analyzed using Proper Orthogonal Decomposition (POD). JaVA-induced flow regimes are governed by the plate width (b), the amplitude (a) and the operating frequency (f). In this study the frequency is changed between 2/3 Hz and 8/3 Hz keeping the plate width and the amplitude constant. A commercial finite-volume-based unsteady, laminar, incompressible Navier-Stokes solver has been used to study the flow fields generated by JaVA. Then, POD is applied to time dependent snapshots of velocity fields at each operating frequency. The POD modes revealed the behavior of the flat plate boundary layer under the effect of active flow control. Traveling modes can be captured in the successive modes for high frequencies.
Renewable Energy Load Matching for Continental U.S.
Authors: Short Walter , Diakov Victor
Published: August 2012

The variability of wind and solar energy technologies is perceived as a major obstacle to employing otherwise abundant renewable energy resources. Based on the available geographically dispersed data for the continental U.S. (excluding Alaska), we analyze to what extent the geographic diversity of these resources can offset their variability. We determine the best match to loads that can be achieved with wind power and photovoltaics with no transmission limitations. Without storage, wind and PV can meet up to 50% of loads in Western US. It is beneficial to build more wind than PV mostly because the wind contributes at night. When storage is available, the optimal mix has almost 75% as much nominal PV capacity as wind, with the PV energy contribution being 32% of the electricity produced from wind. With only 40 GW of storage (twice the pumped hydro storage capacity that already exists in the continental US), up to 82% of the load can be matched with wind and PV, while at the same time curtailing less than 10% of the renewable energy throughout the year.
Orthogonal Electrode Micropump Design Using DC and AC Electroosmosis
Authors: Islam Nazmul , Sayed Saief
Published: August 2012

This paper investigates the micropumping action using orthogonal electrode pattern. It is reported in literature that the high microflows velocity can be achieved using orthogonal electrode pattern when excited by AC signals. Here in this paper we will investigate the effect of both AC and DC signal on orthogonal electrode pattern. We will also investigate the flow in an orthogonal electroosmotic micropump, where the combination of both DC and AC voltages were applied to optimize the fluid flow rate. The design of an orthogonal electrode pair, improves the non-uniformity in electric field, as a result producing stronger net flows at lower voltages. The capacitive electrode polarization and faradaic polarization are proposed to explain the different flow patterns. The fluid flow is explained by impedance analysis and velocity measurement. This investigation of microflow can improve the understanding of electrokinetics and hence effectively manipulate fluids.
Optimal Parametric Model for Vortex Tube Using DOE
Authors: Alsayyed Basel , Hamdan Mohammad O. , Elnajjar Emad
Published: August 2012

In this study, a vortex tube geometric parametric model will be developed and the parameters will be considered as factors that affect the performance of a vortex tube. SolidWorks is used to generate parametric models; Minitab is used for Design Of Experiments (DOE) combination setups. A 3D printer is used to produce a physical model of the vortex tube to fit each of the DOE combinations. The study reports the effect of different geometric parameters on the cooling/heating load and the outlet temperature. The geometric parameters are investigated by measuring temperatures, pressures and mass flow rates for the inlet and hot/cold outlet flow. Two key factors were considered, namely mass fraction and angle of nozzle. Response factors analyzed are the maximum hot temperature (THMax) and the minimum cold temperature (TCMin).
Numerical and Experimental Study of Swirl Atomizers for Liquid Propellant Rocket Engines
Authors: Vasques Brunno B. , de Mendonc¸a Marcio Teixeira , Dourado Wladimyr Mattos da Costa
Published: August 2012

This work attempts to establish the vision for Computational Fluid Dynamics as a rocket injector design tool. Simulations of a 5-kN thrust liquid rocket engine swirl atomizer, under cold flow conditions, using an open source CFD code is the immediate goal of this research. The governing equations are solved based on the laminar volume of fluid (VOF) interface capturing method. The oxidizer and fuel injector elements were analyzed for discharge coefficient, spray-cone angle, liquid film thickness as well as other design related parameters. Results from cold flow experiments and particle image velocimetry (PIV) are compared to the predictions of the swirl models and the numerical results. The VOF model was able to predict the spray angle with reasonable confidence, however, a deviation of 25% was observed in the mass flow rate and discharge coefficient. Although the laminar model has proven inadequate, it constitutes a good starting point in the procedure needed to assess swirl injector performance. Work is currently in progress to evaluate Reynolds Averaged (RANS) and Large Eddy (LES) turbulent numerical models.
Nonlinear Model Tracking in Application to Failed Nondestructive Evaluations
Authors: Doughty Timothy A. , Higgins Natalie S. , Etzel Nicholas G.
Published: August 2012

The nondestructive health monitoring method of Nonlinear Model Tracking (NMT) is introduced and tested under various conditions. The study involves the fatigue and failure of a slender cantilevered beam subject to harmonic nonstationary base excitation around the beam’s second natural frequency. A nonlinear differential equation model for the system is assumed and parameters for the model are estimated using Continuous Time System Identification populated with healthy system stimulus and response data. Updated with real time data sets from the system in operation, the method tracks changes in parameter estimates. The NMT method indicates with repeatability the onset of plasticity, crack initiation and growth well in advance of system failure. Additionally, the NMT method is shown to not give false alarms when system behavior varies in a way that is associated with nonlinear phenomena. Linear methods based on tracking the system’s natural frequency are shown to misidentify the onset of failure for fully healthy systems.
Development and Characterization of a Loop Heat Pipe With a Planar Evaporator and Condenser
Authors: Kariya H. Arthur , Hanks Daniel F. , Peters Teresa B. , Brisson John G. , Wang Evelyn N.
Published: August 2012

We present the development and characterization of an air-cooled loop heat pipe with a planar evaporator and condenser. The condenser is mounted vertically above the evaporator, and impellers are integrated both sides of the condenser with tight clearance. The planar geometry allows for effective convective cooling by increasing the surface area and the convective heat transfer coefficient. To ensure condensation across the area of the condenser, a wicking structure is integrated in the condenser. The evaporator incorporates a multi-layer wicking structure to maintain a thermal gradient between the vapor and liquid regions, which is used to sustain the vapor and liquid pressures necessary for operation. The loop heat pipe was demonstrated to remove 140 W of heat at a temperature difference between the evaporator base and inlet air of 50 °C. This work is the first step towards the development of an air-cooled, multiple-condenser loop heat pipe.
Thermal Analysis of Encapsulated Phase Change Materials for Energy Storage
Authors: Zhao Weihuan , Oztekin Alparslan , Neti Sudhakar , Tuzla Kemal , Misiolek Wojciech M. , Chen John C.
Published: August 2012

Concentrating solar power technology is recognized as an attractive option for solar power. A major limitation however is that solar power is available for only about 2,000 hours a year in many places. Therefore it is critical to find ways to store solar thermal energy for the off hours and it is better to store the energy at high temperatures. The present work deals with certain aspects of storing solar thermal energy at high temperatures with phase change materials (PCM) in the range of 275°C to 425°C. NaNO3 is selected as a phase change material encapsulated by stainless steel. The objective is the storage of hundreds mega-watt-hours equivalent of solar energy in systems using encapsulated phase change materials (EPCM). Numerical predictions of conduction and phase change processes are reported here in the form of transient temperature profiles in the PCM and encapsulation materials of EPCM capsules for convective boundary conditions outside EPCM. The time for heating and melting during charging (storage of thermal energy into encapsulated phase change material) and the time for cooling and solidification during discharging (discharge/retrieval of thermal energy) are predicted for NaNO3 PCM in encapsulation. For a temperature range of about 125°C around melting/freezing temperature of the PCM the time it takes to melt/freeze the PCM during storage/retrieval is much longer than the time it takes for diffusion (sensible heat) storage alone. Depending on the properties of the PCM, the energy associated with the latent heat of melting can be a significant leading to smaller thermal energy storage systems and lower costs. As can be expected, the time for heat transfer is much shorter for liquid heat transfer fluids compared to those for gaseous heat transfer fluids that transport the energy to the EPCM.
Implementation of a New Freshman Year Interdisciplinary Course Sequence
Authors: Joo Sung-Hwan , Pung Chris
Published: August 2012

This paper presents the design and implementation of a two course freshman year sequence at a multi-disciplinary engineering school. The driver for this change was the interdisciplinary academic environment. The previous course sequence consisted of a CAD/CAM graphical communication course followed by a traditional C programming course. The CAD/CAM course consists of two hours of lecture and three hours of laboratory and covered graphical communication coupled with laboratory CAM activities as one semester (13 weeks) course. This particular course is named “EGR-101: Introduction to CAD/CAM” and this required course is the first engineering course that all freshmen identifying themselves as pre-engineering take. The C programming course was delivered using two hours of lecture and three hours of lab as a one semester (13 weeks) course. This particular course is named “EGR-261: Structured Programming in C” and this course is the second engineering course that all freshmen are required to take. The new combined sequence of courses includes similar topics with the addition of an introduction to basic electronics and microcontrollers. It was delivered using a two hour block and three hour block divided as needed between lecture and laboratory with mixed topics of CAD/CAM and C programming. A two semester open ended design and build project was used to combine the course elements. Final assessment result will be presented to evaluate the effect of the changes.
Progressive Damage Detection/Diagnosis on Composite Using Electromechanical Impedance Spectroscopy
Authors: Yu Lingyu , Gresil Matthieu , Pollock Patrick , Sutton Michael
Published: August 2012

Electromechanical impedance approach infers the structural dynamic characteristics at relatively high frequencies by using self-sensing piezoelectric wafer elements. Structural damage can be detected by comparing structural dynamic responses of damaged and undamaged structures. This paper presents an ongoing effort using piezoelectric wafer sensors to measure structural electromechanical impedance response under tensile loading and quantitatively correlate the measurements with damage progression. The purpose is not only to develop a better understanding of the damage progression in composite materials, but also to establish a relationship between electromechanical impedance measurements with local material damage progression. Multi-physics finite element codes are used to simulate the electromechanical resonance of a free piezoelectric wafer sensor to better understand the effect of electromechanical transduction. The effects on impedance measurement from bonding layer degradation and PWAS degradation are also studied. Our study confirms that the EMI changes are related to very small amount material or structural changes, indicating that electromechanical impedance spectroscopy offers a potential for detection of the progression of small damage at the material level.
Effects of Treatment for Cervical Disc Degenerative Disease in Military Populations
Authors: Cochran Joseph , Baisden Jamie L. , Yoganandan Narayan , Pintar Frank A.
Published: August 2012

Numerous clinical and biomechanical evaluations of cervical disc replacement and anterior cervical discectomy and fusion as treatment of cervical disc herniation have been performed. Military patients represent a unique patient population as they may be subject to large external forces in theatre. Military patients are more susceptible to degenerative disease of the cervical spine, and if treated with single-level bony fusion, the treated level may be subject to large forces postoperatively. Literature reviews were conducted to determine patient outcomes following cervical disc replacement compared to bony fusion surgery; compare cadaver studies that evaluated the two conditions; and finite element modeling studies. In the civilian population, patients treated with each type of surgery have clinical improvement that is at least equivalent in the 2- and 5-year follow-up periods. Based on the finite element and cadaver biomechanical studies, semiconstrained devices, ProDisc-C and Prestige, are less mobile and a larger load is placed on the core of the device in comparison to the more mobile and unconstrained Bryan disc.
Specific Treatments for Improving the Quality of Life in Rheumatologic Affections and Osteoporosis
Authors: Pop Petru A. , Lazar Liviu , Marcu Florin M.
Published: August 2012

The analysis and implementation of modern treatments for the patients diagnosed with osteoporosis, degenerative rheumatic affections and peripheral circulatory disorders have become a healthy priority for the society. These treatments have the goal to raise the bone mineral density of the skeleton, reducing joints pain and inflammation while improving and maintaining joints function. This paper presents a conservative treatment of patients from Recovery Clinical Hospital of Felix Spa, diagnosed with degenerative and rheumatoid affections. The treatment is complex and involves balneal-physical-kinetic recovery therapy that must be periodical repeated at every six months to perform. Ankylosing spondylitis was been evaluated by BASFI-BASDAI scores, while the gonarthrosis with Artroflex by SF-36 of quality life scale and Lequesne index. In addition, a vibration treatment combined with balneal-conservative treatment was been proposed to reduce the therapy time and improved the quality live of patients. The vibration system comprises a vibration bed with adjusting control of signal by a digital frequency convertor, and a command panel system for measuring and processing of data. Because the vibration trial is in incipient experiment stage, it was been applied first on Wistar rats, due to increase the calcium mass of bones. The results of all treatments were emphasized the efficiency of balneal cure in rheumatic affections.
Catalytic Ignition of Ethanol-Oxygen-Nitrogen Mixtures Over 90% Platinum - 10% Rhodium in Comparison With Pure Platinum
Authors: Mehaffey David , Steciak Judi , Budwig Ralph , Beyerlein Steve
Published: August 2012

Prior research of the catalytic ignition of renewable transportation fuels was conducted with pure platinum (Pt), an oxidation catalyst with mechanical properties that change at the temperatures expected in internal combustion engines. This study was undertaken to compare and contrast the ability of grain-hardened 90% platinum - 10% rhodium (Pt-Rh) to serve as an ignition catalyst. The temperature required to initiate surface reactions and the rate of heat generated from the reactions of ethanol-oxygen-nitrogen mixtures on Pt-Rh and Pt were obtained using a microcalorimeter. Catalyst wires were exposed to reacting flows in a plug-flow reactor and heated though electrical resistance until surface reactions occurred. The process was repeated for fixed fuel molar percentages of ethanol ranging from 1% to 3% and fuel-oxygen equivalence ratios (Φ) ranging from 0.2 to 1.0 at a constant total volumetric flow rate of 5 L/min, thus testing the effect of both the absolute and relative fuel content. Because of its lower coefficient of thermal resistance, Pt-Rh initiated surface reactions in fuel-oxygen mixtures at temperatures about 45 K higher than pure Pt; 3% ethanol mixtures ignited at an average ignition temperature of 512 K on Pt-Rh with very little variation with Φ while those on Pt ignited at temperatures ranging from a low of 450 K (Φ = 0.5) to a high of 473 K (Φ = 1.0), suggesting fuel-first coverage of the surface for these conditions. Also at 3% ethanol, reactions on Pt-Rh generated heat at an average rate of 5.5 W/cm2 while those on pure Pt generated 19.6 W/cm2. Pt-Rh did not exhibit significant seasoning at the conditions tested whereas Pt seasoned over time and became more reactive (initiating surface reactions at lower temperatures than an unseasoned surface), a phenomenon observed in prior research. This data will aid in the design and understanding of catalytic igniters used with alternative transportation fuels in internal combustion engines.
Assessing Team Conflict in Student Design Teams
Authors: Neumeyer Xaver , McKenna Ann F.
Published: August 2012

Our work is investigating the role of team conflict in the context of student design project work. We are interested in the types of conflicts that occur during the team’s development of their design solution, and how these conflicts may in fact contribute in a positive way to the overall design solution. We are using a mixed-method approach to data collection through student interviews, team observations, reflective memos, and surveys. This paper reports results from a study implemented in a required first-year engineering design course. Results from this study indicate that teams experience a range of conflicts, where some students perceive these conflicts as beneficial to team performance. In addition, our results describe several strategies teams use to manage and leverage these conflicts. Finally, methodologically we found that the team memos and team conflict surveys were better instruments for capturing team conflict, more so than self-report surveys.
Measuring Stress and Strain Fields in Connecting Rods Using Laser Interferometry (ESPI)
Authors: Vaz Bruno F. , e Silva Rafael A. L. , Junior Auteliano A. S.
Published: August 2012

The understanding of how mechanical stresses influence in the behavior of automotive components is of great interest to the automotive industry. The design of products must be performed considering these efforts, always aiming to ensure smooth operation and no failures. To learn more about these efforts, numerical simulation can be done. However, the results obtained from these simulations must be confirmed by carrying out physical experiments. Many methods are available to obtain the stress/strain fields of the object been tested, among which the best known and widespread is the use of strain-gauges. This technique requires a relatively long time of preparation as well as several measurement places to obtain the full stress/strain field. The laser interferometry technique, on the other hand, reduces considerably the testing time to obtain the full stress/strain field, and no intervention on the object is required. This work aims to present a methodology for measuring stress/strain fields in connecting rods using an Electronic Speckle Pattern Interferometry (ESPI) device. In this work we will focus on obtaining the stresses in a flat surface of the rod. The region corresponds to the inner portion of the rod body, excluding only the edges of it that are slightly higher. In this region it’s easier to obtain the stress and strain fields than in the whole rod, which has many non-planar regions with a relatively complex geometry, especially near the ends. To plan the experiments, an experimental design was developed, based mainly on the concepts of Design of Experiments — DOE, to eliminate or at least reduce the influence of the noise over the results. The tests were performed with a forged connecting rod from a local manufacturing, which was submitted to compressive efforts. Finally we present the results of the measurements of the stress and strain fields obtained by the ESPI technique.