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Articles 511 - 540 of 914
Full-Text Articles in Chemical Engineering
Reduction Of Model Order Based On Proper Orthogonal Decomposition For Lithium-Ion Battery Simulations, Long Cai, Ralph E. White
Reduction Of Model Order Based On Proper Orthogonal Decomposition For Lithium-Ion Battery Simulations, Long Cai, Ralph E. White
Faculty Publications
A reduced-order model (ROM) is developed using proper orthogonal decomposition (POD) for a physics-based lithium-ion battery model. The methodology to obtain the proper orthogonal modes and to analyze their optimality is included. The POD-based ROM for a lithium-ion battery is used to simulate a charge/discharge process and the behavior of a battery pack. Compared to the physics-based model, the computational time to solve the ROM is significantly less, and the two models show excellent agreement.
Effect Of Water Transport On The Production Of Hydrogen And Sulfuric Acid In A Pem Electrolyzer, John A. Staser, John W. Weidner
Effect Of Water Transport On The Production Of Hydrogen And Sulfuric Acid In A Pem Electrolyzer, John A. Staser, John W. Weidner
Faculty Publications
The thermochemical cycle involving the interconversion between sulfur dioxide and sulfuric acid is a promising method for efficient, large-scale production of hydrogen. A key step in the process is the oxidation of sulfur dioxide to sulfuric acid in an electrolyzer. Gaseous SO2 fed to a proton exchange membrane (PEM) electrolyzer was previously investigated and was shown to be a promising system for the electrolysis step. A critical factor in the performance of this gas-fed electrolyzer is the management of water since it: (i) is needed as a reactant, (ii) determines the product sulfuric acid concentration, …
Electrochemical Removal Of Carbon Monoxide In Reformate Hydrogen For Fueling Proton Exchange Membrane Fuel Cells, Sivagaminathan Balasubramanian, Charles E. Holland, John W. Weidner
Electrochemical Removal Of Carbon Monoxide In Reformate Hydrogen For Fueling Proton Exchange Membrane Fuel Cells, Sivagaminathan Balasubramanian, Charles E. Holland, John W. Weidner
Faculty Publications
A twin-cell electrochemical filter is demonstrated to reduce the CO concentration in reformate hydrogen. In this design, the potential and gas flow are switched between the two filter cells so that alternative CO adsorption and oxidation occur in each cell while providing a continuous flow of H2 to a fuel cell. The effects of filter switching time and applied potential on the CO concentration of gas exiting the filter are presented here for a CO concentration of 1000 ppm in nitrogen flowing at 100 cm3/min. The parasitic loss of hydrogen from a corresponding reformate stream was estimated to be 1.5%.
An Infrared Imaging Method For High-Throughput Combinatorial Investigation Of Hydrogenation-Dehydrogenation And New Phase Formation Of Thin Films, H. Oguchi, Jason R. Hattrick-Simpers, I. Takeuchi, E. J. Heilweil, L. A. Bendersky
An Infrared Imaging Method For High-Throughput Combinatorial Investigation Of Hydrogenation-Dehydrogenation And New Phase Formation Of Thin Films, H. Oguchi, Jason R. Hattrick-Simpers, I. Takeuchi, E. J. Heilweil, L. A. Bendersky
Faculty Publications
We have developed an infrared imaging setup enabling in situ infrared images to be acquired, and expanded on capabilities of an infrared imaging as a high-throughput screening technique, determination of a critical thickness of a Pd capping layer which significantly blocks infrared emission from below, enhancement of sensitivity to hydrogenation and dehydrogenation by normalizing raw infrared intensity of a Mg thin film to an inert reference, rapid and systematic screening of hydrogenation and dehydrogenation properties of a Mg–Ni composition spread covered by a thickness gradient Pd capping layer, and detection of formation of a Mg2Si phase in a …
Inhomogeneous Degradation Of Polymer Electrolyte Membrane In Pem Fuel Cells, Xinyu Huang, Wonseok Yoon
Inhomogeneous Degradation Of Polymer Electrolyte Membrane In Pem Fuel Cells, Xinyu Huang, Wonseok Yoon
Faculty Publications
Membrane durability is one of the technical barriers for the commercialization of polymer electrolyte membrane (PEM) fuel cells. Membrane embrittlement (a form of mechanical weakening) can lead to the frequently observed “sudden death” behavior of PEM fuel cells. It is the objective of this study to explore the fundamental mechanisms of the mechanical weakening of perfluorosulfonic acid (PFSA) based electrolyte membranes during the accelerated degradation test.
Sulfur Dioxide Crossover During The Production Of Hydrogen And Sulfuric Acid In A Pem Electrolyzer, John A. Staser, John W. Weidner
Sulfur Dioxide Crossover During The Production Of Hydrogen And Sulfuric Acid In A Pem Electrolyzer, John A. Staser, John W. Weidner
Faculty Publications
A proton exchange membrane (PEM) electrolyzer has been investigated as a viable system for the electrolysis step in the thermochemical conversion of sulfur dioxide to sulfuric acid for the large-scale production of hydrogen. Unfortunately, during operation, sulfur dioxide can diffuse from the anode to the cathode. This has several negative effects, including reduction to sulfur that could potentially damage the electrode, consumption of current that would otherwise be used for the production of hydrogen, introduction of oxygen and SO2 to the hydrogen stream, and loss of sulfur to the cycle. However, proper water management can reduce or eliminate the …
The Effect Of Copt Crystallinity And Grain Texturing On Properties Of Exchange-Coupled Fe/Copt Systems, H. Oguchi, A. Zambano, M. Yu, Jason R. Hattrick-Simpers, D. Banerjee, Y. Liu, Z. L. Wang, J. P. Liu, S. E. Lofland, D. Josell, I. Takeuchi
The Effect Of Copt Crystallinity And Grain Texturing On Properties Of Exchange-Coupled Fe/Copt Systems, H. Oguchi, A. Zambano, M. Yu, Jason R. Hattrick-Simpers, D. Banerjee, Y. Liu, Z. L. Wang, J. P. Liu, S. E. Lofland, D. Josell, I. Takeuchi
Faculty Publications
The effect of the crystallinity and the grain texturing of CoPt hard layers on exchange coupled Fe/CoPt soft/hard magnetic systems was studied using gradient thickness multilayer thin films. We have studied the hard layer structures by transmission electron microscopy and x-ray diffraction, and characterized the exchange coupling interaction through magnetization loops obtained by the magneto-optical Kerr effect measurement. We found that exchange coupling strongly depends on the crystalline characteristics of the CoPt hard layer. There is correlation between the mixture of different grain orientations of the CoPt hard layer and coupling efficiency. In particular, interlayer coupling is enhanced when there …
Fingering Instabilities On Reaction Fronts In The Co Oxidation Reaction On Pt(100), D. Bilbao, Jochen A. Lauterbach
Fingering Instabilities On Reaction Fronts In The Co Oxidation Reaction On Pt(100), D. Bilbao, Jochen A. Lauterbach
Faculty Publications
Fingering instabilities arising from local perturbations to planar reaction fronts in the CO oxidation reaction on Pt(100) are presented. CO oxidation represents a heterogeneous nonlinear system with the necessary kinetic and diffusive transport properties to support the development of fingered wave fronts. External forcing was utilized to create CO wave fronts on an otherwise monostable, O-covered surface, which, upon destabilization, gave rise to fingers of adsorbed CO extending into the O adlayer ahead of the reaction front. Finger spreading and tip-splitting were observed as the finger pattern evolved towards an intrinsic wavelength, independent of the length of the reaction front, …
A-Priori Analysis Of Conditional Moment Closure Modeling Of A Temporal Ethylene Jet Flame With Soot Formation Using Direct Numerical Simulation, David O. Lignell, John C. Hewson, Jacqueline H. Chen
A-Priori Analysis Of Conditional Moment Closure Modeling Of A Temporal Ethylene Jet Flame With Soot Formation Using Direct Numerical Simulation, David O. Lignell, John C. Hewson, Jacqueline H. Chen
Faculty Publications
Modeling soot formation in turbulent nonpremixed combustion is a difficult problem. Unlike most gaseous combustion species, soot lacks a strong state relationship with the mixture fraction due to unsteady formation rates which overlap transport timescales, and strong differential diffusion between gaseous species and soot. The conditional moment closure model (CMC) has recently been applied to the problem of turbulent soot formation. A challenge in CMC modeling is the treatment of differential diffusion. Three-dimensional direct numerical simulation (DNS) of a nonpremixed ethylene jet flame with soot formation has been performed using a 19 species reduced ethylene mechanism and a four-step, three-moment, …
Three-Dimensional Direct Numerical Simulation Of Soot Formation And Transport In A Temporally Evolving Nonpremixed Ethylene Jet Flame, David O. Lignell, Jacqueline H. Chen, Philip J. Smith
Three-Dimensional Direct Numerical Simulation Of Soot Formation And Transport In A Temporally Evolving Nonpremixed Ethylene Jet Flame, David O. Lignell, Jacqueline H. Chen, Philip J. Smith
Faculty Publications
Three-dimensional direct numerical simulation of soot formation with complex chemistry is presented. The simulation consists of a temporally evolving, planar, nonpremixed ethylene jet flame with a validated, 19-species reduced mechanism. A four-step, three-moment, semiempirical soot model is employed. Previous two-dimensional decaying turbulence simulations have shown the importance of multidimensional flame dynamical effects on soot concentration [D.O. Lignell, J.H. Chen, P.J. Smith, T. Lu, C.K. Law, Combust. Flame 151 (1–2) (2007) 2–28]. It was shown that flame curvature strongly impacts the diffusive motion of the flame relative to soot (which is essentially convected with the flow), resulting in soot being differentially …
Modeling Phase Transitions Of Nanoemulsion For Ultrasonic Gene Delivery, Ghaleb A. Husseini, William G. Pitt, Ram Singh
Modeling Phase Transitions Of Nanoemulsion For Ultrasonic Gene Delivery, Ghaleb A. Husseini, William G. Pitt, Ram Singh
Faculty Publications
A computer model was written that simulates the transformation of a nanoemulsion droplet to a gas bubble by the application of ultrasound. Experimentally such a technique could be used to enhance non-viral gene transfection beyond the boundary of the endothelial lining of the circulatory system, particularly in tumors exhibiting enhanced permeation and retention of nanoparticles.
Nano-Polymeric Carrier Influences Ultrasonic Drug Delivery To Tumors, Odgerel Badamjav, Ghaleb A. Husseini, Peter Jones, William G. Pitt, Beverly L. Roeder
Nano-Polymeric Carrier Influences Ultrasonic Drug Delivery To Tumors, Odgerel Badamjav, Ghaleb A. Husseini, Peter Jones, William G. Pitt, Beverly L. Roeder
Faculty Publications
Our overall research goal is to alleviate the severe side effects of chemotherapy while enhancing the effectiveness of the treatment by localizing the delivery of anti-cancer drugs to the cancer tissue only. To this end we are synthesizing ultrasonically-activated delivery systems that can control drug delivery in space and time. Ultrasound (US) is non-invasive (no surgery required) and can be focused on the specific tissue to be treated. Our past research has developed a nano-sized polymeric drug carrier that sequesters the therapeutic drug, such as Doxorubicin (Dox), within the carrier and releases the drug upon insonation by ultrasound. This drug-containing …
Mpsa Effects On Copper Electrodeposition Investigated By Molecular Dynamics Simulations, John N. Harb, Richard L. Rowley, Dean R. Wheeler, Clint G. Guymon
Mpsa Effects On Copper Electrodeposition Investigated By Molecular Dynamics Simulations, John N. Harb, Richard L. Rowley, Dean R. Wheeler, Clint G. Guymon
Faculty Publications
In superconformal filling of copper-chip interconnects, organic additives are used to fill high-aspect-ratio trenches or vias from the bottom up. In this study we report on the development of intermolecular potentials and use molecular dynamics simulation.
Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part I: Physical Characteristics, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Jeffrey P. Bons, Thomas H. Fletcher
Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part I: Physical Characteristics, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Jeffrey P. Bons, Thomas H. Fletcher
Faculty Publications
Turbine blade coupons with three different surface treatments were exposed to deposition conditions in an accelerated deposition facility. The facility simulates the flow conditions at the inlet to a first stage high-pressure turbine (T=1150 C, M=0.31). The combustor exit flow is seeded with dust particulate that would typically be ingested by a large utility power plant. The three coupon surface treatments included: (1) bare polished metal; (2) polished thermal barrier coating with bondcoat; and (3) unpolished oxidation resistant bondcoat. Each coupon was subjected to four successive 2 h deposition tests. The particulate loading was scaled to simulate 0.02 parts per …
Effects Of Temperature And Particle Size On Deposition In Land Based Turbines, Jared M. Crosby, Scott Lewis, Jeffrey P. Bons, Weiguo Ai, Thomas H. Fletcher
Effects Of Temperature And Particle Size On Deposition In Land Based Turbines, Jared M. Crosby, Scott Lewis, Jeffrey P. Bons, Weiguo Ai, Thomas H. Fletcher
Faculty Publications
Four series of tests were performed in an accelerated deposition test facility to study the independent effects of particle size, gas temperature, and metal temperature on ash deposits from two candidate power turbine synfuels (coal and petcoke). The facility matches the gas temperature and velocity of modern first stage high pressure turbine vanes while accelerating the deposition process. Particle size was found to have a significant effect on capture efficiency with larger particles causing significant thermal barrier coating (TBC) spallation during a 4 h accelerated test. In the second series of tests, particle deposition rate was found to decrease with …
Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part Ii: Convective Heat Transfer, Jeffrey P. Bons, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Thomas H. Fletcher
Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part Ii: Convective Heat Transfer, Jeffrey P. Bons, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Thomas H. Fletcher
Faculty Publications
A thermal barrier coating (TBC)-coated turbine blade coupon was exposed to successive deposition in an accelerated deposition facility simulating flow conditions at the inlet to a first stage high pressure turbine (T=1150 C, M=0.31). The combustor exit flow was seeded with dust particulate that would typically be ingested by a large utility power plant. The turbine coupon was subjected to four successive 2 h deposition tests. The particulate loading was scaled to simulate 0.02 parts per million weight (ppmw) of particulate over 3 months of continuous gas turbine operation for each 2 h laboratory simulation (for a cumulative 1 year …
Characteristics Of Black Liquor Sprays From Gas-Assisted Atomizers In Hightemperature Environments, Andrew J. Mackrory, Dale Tree, Larry L. Baxter
Characteristics Of Black Liquor Sprays From Gas-Assisted Atomizers In Hightemperature Environments, Andrew J. Mackrory, Dale Tree, Larry L. Baxter
Faculty Publications
Black liquor droplets in an entrained-flow gasifier that are too large or too small can cause problems in the chemical recovery process. It is therefore important in gasifier design to understand the nature of the atomized-gas spray. We used high-speed imaging to study black liquor sprays in cold and hot environments. Significant conclusions are that: 1. the droplet size distribution width is linked to the mean droplet size as for other sprays in the literature, necessitating a gasifier design that is tolerant of the distribution width associated with the target droplet size; 2. the shape of black liquor droplets is …
Combinatorial Investigation Of Magnetostriction In Fe-Fa And Fe-Ga-Al, Jason R. Hattrick-Simpers, Dwight Hunter, Corneliu M. Craciunescu, Kyu Sung Jang, Makoto Murakami, James Cullen, Manfred Wuttig, Ichiro Takeuchi, Samuel E. Lofland, Leonid Bendersky, Noble Woo, Robert Bruce Vandover, Toshiya Takahashi, Yasubumi Furuya
Combinatorial Investigation Of Magnetostriction In Fe-Fa And Fe-Ga-Al, Jason R. Hattrick-Simpers, Dwight Hunter, Corneliu M. Craciunescu, Kyu Sung Jang, Makoto Murakami, James Cullen, Manfred Wuttig, Ichiro Takeuchi, Samuel E. Lofland, Leonid Bendersky, Noble Woo, Robert Bruce Vandover, Toshiya Takahashi, Yasubumi Furuya
Faculty Publications
A high-throughput high-sensitivity optical technique for measuringmagnetostriction of thin-film composition-spread samples has been developed. It determines the magnetostriction by measuring the induced deflection of micromachined cantilever unimorph samples. Magnetostrictionmeasurements have been performed on as-deposited Fe–Ga and Fe–Ga–Al thin-film composition spreads. The thin-film Fe–Ga spreads display a similar compositional variation of magnetostriction as bulk. A previously undiscovered peak in magnetostriction at low Ga content was also observed and attributed to a maximum in the magnetocrystalline anisotropy. Magnetostrictive mapping of the Fe–Ga–Al ternary system reveals the possibility of substituting up to 8at.%Al in Fe70Ga30 without significant degradation of magnetostriction.
High-Throughput Screening Of Shape Memory Alloy Thin-Film Spreads Using Nanoindentation, Arpit Dwivedi, Thomas J. Wyrobek, Oden L. Warren, Jason R. Hattrick-Simpers, Olubenga O. Famodu, Ichiro Takeuchi
High-Throughput Screening Of Shape Memory Alloy Thin-Film Spreads Using Nanoindentation, Arpit Dwivedi, Thomas J. Wyrobek, Oden L. Warren, Jason R. Hattrick-Simpers, Olubenga O. Famodu, Ichiro Takeuchi
Faculty Publications
We have demonstrated the utility of nanoindentation as a rapid characterization tool for mapping shape memoryalloy compositions in combinatorial thin-film libraries. Nanoindentation was performed on Ni–Mn–Al ternary composition spreads. The indentation hardness and the reduced elastic modulus were mapped across a large fraction of the ternary phase diagram. The large shape memoryalloy composition region, located around the Heusler composition (Ni2MnAl), was found to display significant departure in these mechanical properties from the rest of the composition spread. In particular, the modulus and the hardness values are lower for the martensite region than those of the rest of the …
Hydrogen Peroxide Formation Rates In A Pemfc Anode And Cathode: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Sathya Motupally, Lesia V. Protsailo
Hydrogen Peroxide Formation Rates In A Pemfc Anode And Cathode: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Sathya Motupally, Lesia V. Protsailo
Faculty Publications
Hydrogen peroxide (H2O2) formation rates in a proton exchange membrane fuel cell (PEMFC) anode and cathode were estimated as a function of humidity and temperature by studying the oxygen reduction reaction (ORR) on a rotating ring disk electrode. Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the disk and by varying the temperature, dissolved O2 concentration, and the acidity levels in hydrochloric acid (HClO4). The HClO4 acidity was correlated to ionomer water activity and hence fuel cell humidity. The H2O2 formation rates showed …
Durability Of Perfluorosulfonic Acid And Hydrocarbon Membranes: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Lesia V. Protsailo
Durability Of Perfluorosulfonic Acid And Hydrocarbon Membranes: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Lesia V. Protsailo
Faculty Publications
The effect of humidity on the chemical stability of two types of membranes [i.e., perfluorosulfonic acid type (PFSA, Nafion 112) and biphenyl sulfone hydrocarbon type, (BPSH-35)] was studied by subjecting the membrane electrode assemblies (MEAs) to open-circuit voltage (OCV) decay and potential cycling tests at elevated temperatures and low inlet-gas relative humidities. The BPSH-35 membranes showed poor chemical stability in ex situ Fenton tests compared to that of Nafion membranes. However, under fuel cell conditions, BPSH-35 MEAs outperformed Nafion 112 MEAs in both the OCV decay and potential cycling tests. For both membranes, (i) at a given temperature, …
Enhanced Dielectric Properties In Single Crystal-Like Bifeo3 Thin Films Grown By Flux-Mediated Epitaxy, S.-H. Lim, M. Murakami, J. H. Yang, S.-Y. Young, Jason R. Hattrick-Simpers, M. Wuttig, L. G. Salamanca-Riba, I. Takeuchi
Enhanced Dielectric Properties In Single Crystal-Like Bifeo3 Thin Films Grown By Flux-Mediated Epitaxy, S.-H. Lim, M. Murakami, J. H. Yang, S.-Y. Young, Jason R. Hattrick-Simpers, M. Wuttig, L. G. Salamanca-Riba, I. Takeuchi
Faculty Publications
We have fabricated single crystal-like BiFeO3 (BFO) thin films by flux-mediated epitaxy using pulsed laser deposition(PLD). The Bi–Cu–O flux composition and its thickness were optimized using composition spread, thickness gradient, and temperature gradient libraries. The optimized BFO thin films grown with this technique showed larger grain size of ∼2μm and higher dielectric constant in the range of 260–340 than those for standard PLD grown films. In addition, the leakage current density of the films was reduced by two orders of magnitude compared to that of standard PLD grown films.
The Role Of Filler-Matrix Interaction On Viscoelastic Response Of Biomimetic Nanocomposite Hydrogels, Alireza S. Sarvestani, Xuezhong He, Esmaiel Jabbari
The Role Of Filler-Matrix Interaction On Viscoelastic Response Of Biomimetic Nanocomposite Hydrogels, Alireza S. Sarvestani, Xuezhong He, Esmaiel Jabbari
Faculty Publications
The effect of a glutamic acid (negatively charged) peptide (Glu6), which mimics the terminal region of the osteonectin glycoprotein of bone on the shear modulus of a synthetic hydorgel/apatite nanocomposite, was investigated. One end of the synthesized peptide was functionalized with an acrylate group (Ac-Glu6) to covalently attach the peptide to the hydrogel phase of the composite matrix. The addition of Ac-Glu6 to hydroxyapatite (HA) nanoparticles (50 nm in size) resulted in significant reinforcement of the shear modulus of the nanocomposite (~100% increase in elastic shear modulus). The reinforcement effect of the Glu6 peptide, a sequence in the terminal region …
Parameter Estimation And Life Modeling Of Lithium-Ion Cells, Shriram Santhanagopalan, Qi Zhang, Karthikeyan Kumaresan, Ralph E. White
Parameter Estimation And Life Modeling Of Lithium-Ion Cells, Shriram Santhanagopalan, Qi Zhang, Karthikeyan Kumaresan, Ralph E. White
Faculty Publications
Lithium-ion pouch cells were cycled at five different temperatures (5, 15, 25, 35, and 45°C ), and rate capability studies were performed after every hundred cycles. The data were used with a simple physics-based model to estimate parameters that capture the capacity fade in the cell, with cycling. The weight of active material within each electrode was estimated as a function of time, using rate capability data at the C/33 rate. The C-rate for these cells is 1.656 A. The capacity fade due to the loss of active material and that due to the loss of cyclable lithium …
Thermal Model For A Li-Ion Cell, Karthikeyan Kumaresan, Godfrey Sikha, Ralph E. White
Thermal Model For A Li-Ion Cell, Karthikeyan Kumaresan, Godfrey Sikha, Ralph E. White
Faculty Publications
A thermal model for a lithium-ion cell is presented and used to predict discharge performance at different operating temperatures. The results from the simulations are compared to experimental data obtained from lithium-ion pouch cells. The model includes a set of parameters (and their concentration and temperature dependencies) that has been obtained for a lithium-ion cell composed of a mesocarbon microbead anode, LiCoO2 cathode in 1 M LiPF6 salt, in a mixture of ethylene carbonate, propylene carbonate, ethyl-methyl carbonate, and diethyl carbonate electrolyte. The parameter set was obtained by comparing the model predictions to the experimental discharge profiles obtained …
Analytical Expression For The Impedance Response For A Lithium-Ion Cell, Godfrey Sikha, Ralph E. White
Analytical Expression For The Impedance Response For A Lithium-Ion Cell, Godfrey Sikha, Ralph E. White
Faculty Publications
An analytical expression to predict the impedance response of a dual insertion electrode cell (insertion electrodes separated by an ionically conducting membrane) is presented. The expression accounts for the reaction kinetics and double-layer adsorption processes at the electrode-electrolyte interface, transport of electroactive species in the electrolyte phase, and insertion of species in the solid phase of the insertion electrodes. The accuracy of the analytical expression is validated by comparing the impedance response predicted by the expression to the corresponding numerical solution. The analytical expression is used to predict the impedance response of a lithium-ion cell consisting of a porous LiCoO …
A Mathematical Model For A Lithium–Sulfur Cell, Karthikeyan Kumaresan, Yuriy Mikhaylik, Ralph E. White
A Mathematical Model For A Lithium–Sulfur Cell, Karthikeyan Kumaresan, Yuriy Mikhaylik, Ralph E. White
Faculty Publications
A mathematical model is presented for a complete lithium–sulfur cell. The model includes various electrochemical and chemical (precipitation) reactions, multicomponent transport phenomena in the electrolyte, and the charge transfer within and between solid and liquid phases. A change in the porosity of the porous cathode and separator due to precipitation reactions is also included in the model. The model is used to explain the physical reasons for the two-stage discharge profiles that are typically obtained for lithium–sulfur cells.
Transient Molecular Dynamics Simulations Of Viscosity For Simple Fluids, Richard L. Rowley, Jason C. Thomas
Transient Molecular Dynamics Simulations Of Viscosity For Simple Fluids, Richard L. Rowley, Jason C. Thomas
Faculty Publications
A transient molecular dynamics (TMD) method has been developed for simulation of fluid viscosity. In this method a sinusoidal velocity profile is instantaneously overlaid onto equilibrated molecular velocities, and the subsequent decay of that velocity profile is observed. The viscosity is obtained by matching in a least-squares sense the analytical solution of the corresponding momentum transport boundary-value problem to the simulated decay of the initial velocity profile. The method was benchmarked by comparing results obtained from the TMD method for a Lennard-Jones fluid with those previously obtained using equilibrium molecular dynamics (EMD) simulations. Two different constitutive models were used in …
The Effect Of Flame Structure On Soot Formation And Transport In Turbulent Nonpremixed Flames Using Direct Numerical Simulation, David O. Lignell, Jacqueline H. Chen, Philip J. Smith, Tianfeng Lu, Chung K. Law
The Effect Of Flame Structure On Soot Formation And Transport In Turbulent Nonpremixed Flames Using Direct Numerical Simulation, David O. Lignell, Jacqueline H. Chen, Philip J. Smith, Tianfeng Lu, Chung K. Law
Faculty Publications
Direct numerical simulations of a two-dimensional, nonpremixed, sooting ethylene flame are performed to examine the effects of soot–flame interactions and transport in an unsteady configuration. A 15-step, 19-species (with 10 quasi-steady species) chemical mechanism was used for gas chemistry, with a two-moment, four-step, semiempirical soot model. Flame curvature is shown to result in flames that move, relative to the fluid, either toward or away from rich soot formation regions, resulting in soot being essentially convected into or away from the flame. This relative motion of flame and soot results in a wide spread of soot in the mixture fraction coordinate. …
Comprehensive Study Of Biomass Fly Ash In Concrete: Strength, Microscopy, Kinetics And Durability, Shuangzhen Wang, Larry Baxter
Comprehensive Study Of Biomass Fly Ash In Concrete: Strength, Microscopy, Kinetics And Durability, Shuangzhen Wang, Larry Baxter
Faculty Publications
ASTM (American Standard Testing and Materials) C 618 prohibits use of biomass fly ash in concrete. This document systematically investigates the strength, microscopic study and durability (mitigation of Alkali Silica Reaction (ASR) expansion) of biomass fly ash concrete (cement partially replaced by fly ash) and kinetics of the mixture of biomass fly ash and calcium hydroxide. The biomass fly ash in the investigation comes from cofired (herbaceous with coal) fly ash, which includes different kinds of coal and biomass. All the results show that biomass fly ash with cofiring concentration within the interest to commercial coal–biomass cofiring operations at power …