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Articles 1 - 23 of 23

Full-Text Articles in Mechanical Engineering

Effect Of Density Ratio On Velocity Fluctuations In Dispersed Multiphase Flow From Simulations Of Finite-Size Particles, Vahid Tavanashad, Alberto Passalacqua, Rodney O. Fox, Shankar Subramaniam Nov 2018

Effect Of Density Ratio On Velocity Fluctuations In Dispersed Multiphase Flow From Simulations Of Finite-Size Particles, Vahid Tavanashad, Alberto Passalacqua, Rodney O. Fox, Shankar Subramaniam

Chemical and Biological Engineering Publications

Velocity fluctuations in the carrier phase and dispersed phase of a dispersed multiphase flow are studied using particle-resolved direct numerical simulation. The simulations correspond to a statistically homogeneous problem with an imposed mean pressure gradient and are presented for Rem=20 and a wide range of dispersed phase volume fractions (0.1≤ϕ≤0.4) and density ratios of the dispersed phase to the carrier phase (0.001≤ρp/ρf≤1000) . The velocity fluctuations in the fluid and dispersed phase at the statistically stationary state are quantified by the turbulent kinetic energy (TKE) and granular temperature, respectively. It is found ...


A Delayed Detached Eddy Simulation Model With Low Reynolds Number Correction For Transitional Swirling Flow In A Multi-Inlet Vortex Nanoprecipitation Reactor, Zhenping Liu, James C. Hill, Rodney O. Fox, Alberto Passalacqua, Michael G. Olsen Aug 2018

A Delayed Detached Eddy Simulation Model With Low Reynolds Number Correction For Transitional Swirling Flow In A Multi-Inlet Vortex Nanoprecipitation Reactor, Zhenping Liu, James C. Hill, Rodney O. Fox, Alberto Passalacqua, Michael G. Olsen

Chemical and Biological Engineering Publications

The objective of the presented work is to verify a delayed detached eddy simulation (DDES) model for simulating transitional swirling flow in a micro-scale multi-inlet vortex reactor (MIVR). The DDES model is a k-w based turbulence model with a low Reynolds number correction applied to the standard k-w model such that the Reynolds-averaged Navier-Stokes (RANS) component of the DDES model is able to account for low Reynolds number flow. By limiting the dissipation rate in the k-equation, the large-eddy simulation (LES) part of the DDES model behaves similarly to a one-equation sub-grid model. The turbulent Reynolds number is redefined to ...


An Open-Source Quadrature-Based Population Balance Solver For Openfoam, Alberto Passalacqua, Frédérique Laurent, Ehsan Madadi-Kandjani, Jeffrey C. Heylmun, Rodney O. Fox Feb 2018

An Open-Source Quadrature-Based Population Balance Solver For Openfoam, Alberto Passalacqua, Frédérique Laurent, Ehsan Madadi-Kandjani, Jeffrey C. Heylmun, Rodney O. Fox

Chemical and Biological Engineering Publications

The extended quadrature method of moments (EQMOM) for the solution of population balance equations (PBE) is implemented in the open-source computational fluid dynamic (CFD) toolbox OpenFOAM as part of the OpenQBMM project. The moment inversion procedure was designed (Nguyen et al., 2016) to maximize the number of conserved moments in the transported moment set. The algorithm is implemented in a general structure to allow the addition of other kernel density functions defined on R+, and arbitrary kernels to describe physical phenomena involved in the evolution of the number density function. The implementation is verified with a set of zero-dimensional cases ...


Elucidating The Effect Of Desilication On Aluminum-Rich Zsm-5 Zeolite And Its Consequences On Biomass Catalytic Fast Pyrolysis, Thomas Hoff, David W. Gardner, Rajeeva Thilakaratne, Juan Proano-Aviles, Robert C. Brown, Jean-Philippe Tessonnier Jan 2017

Elucidating The Effect Of Desilication On Aluminum-Rich Zsm-5 Zeolite And Its Consequences On Biomass Catalytic Fast Pyrolysis, Thomas Hoff, David W. Gardner, Rajeeva Thilakaratne, Juan Proano-Aviles, Robert C. Brown, Jean-Philippe Tessonnier

Chemical and Biological Engineering Publications

Catalytic fast pyrolysis (CFP) offers a simple and robust route to convert raw lignocellulosic biomass to aromatic hydrocarbons. During CFP, cellulose, hemicellulose, and lignin are first thermally decomposed to bio-oil vapors that are further converted to aromatics in the presence of a ZSM-5 zeolite catalyst. The high temperatures required for CFP also favor coke formation, an undesired byproduct, through condensation of the oxygenated intermediates on ZSM-5′s outer surface and/or secondary reactions inside its micropores. Introducing mesopores through desilication represents a possible strategy to enhance mass transport and intracrystalline diffusion, and consequently favor aromatic production over undesired coke formation ...


Conversion Of Methoxy And Hydroxyl Functionalities Of Phenolic Monomers Over Zeolites, Rajeeva Thilakaratne, Jean-Philippe Tessonnier, Robert C. Brown Jan 2016

Conversion Of Methoxy And Hydroxyl Functionalities Of Phenolic Monomers Over Zeolites, Rajeeva Thilakaratne, Jean-Philippe Tessonnier, Robert C. Brown

Chemical and Biological Engineering Publications

This study investigates the mechanisms of gas phase anisole and phenol conversion over zeolite catalyst. These monomers contain methoxy and hydroxyl groups, the predominant functionalities of the phenolic products of lignin pyrolysis. The proposed reaction mechanisms for anisole and phenol are distinct, with significant differences in product distributions. The anisole mechanism involves methenium ions in the conversion of phenol and alkylating aromatics inside zeolite pores. Phenol converts primarily to benzene and naphthalene via a ring opening reaction promoted by hydroxyl radicals. The phenol mechanism sheds insights on how reactive bi-radicals generated from fragmented phenol aromatic rings (identified as dominant coke ...


Cellulose–Hemicellulose And Cellulose–Lignin Interactions During Fast Pyrolysis, Jing Zhang, Yong S. Choi, Chang G. Yoo, Tae H. Kim, Robert C. Brown, Brent H. Shanks Jan 2015

Cellulose–Hemicellulose And Cellulose–Lignin Interactions During Fast Pyrolysis, Jing Zhang, Yong S. Choi, Chang G. Yoo, Tae H. Kim, Robert C. Brown, Brent H. Shanks

Chemical and Biological Engineering Publications

Previously, the primary product distribution resulting from fast pyrolysis of cellulose, hemicellulose, and lignin was quantified. This study extends the analysis to the examinations of interactions between cellulose–hemicellulose and cellulose–lignin, which were determined by comparing the pyrolysis products from their native mixture, physical mixture, and superposition of individual components. Negligible interactions were found for both binary physical mixtures. For the native cellulose–hemicellulose mixture, no significant interaction was identified either. In the case of the native cellulose–lignin mixture, herbaceous biomass exhibited an apparent interaction, represented by diminished yield of levoglucosan and enhanced yield of low molecular weight ...


Measurement Of Stress Changes During Growth And Dissolution Of Anodic Oxide Films On Aluminum, Ömer Ö. Çapraz, Pranav Shrotriya, Kurt R. Hebert Jan 2014

Measurement Of Stress Changes During Growth And Dissolution Of Anodic Oxide Films On Aluminum, Ömer Ö. Çapraz, Pranav Shrotriya, Kurt R. Hebert

Chemical and Biological Engineering Publications

While stress is thought to play an important role in the development of self-organized porous films, mechanisms of stress generation during anodizing are not yet understood. In order to reveal depth distributions of stress in anodic films, phase-shifting curvature interferometry was used to monitor force transients (in-plane stress integrated through the sample thickness) during formation of anodic oxides on aluminum in phosphoric acid, aswell as subsequent open-circuit dissolution. Themeasurements were not influenced significantly by electrostatic stress, internal stress in the metal samples, thermal stress, or stress induced by open-circuit dissolution. At typical current densities, the force became more compressive during ...


The Influence Of Alkali And Alkaline Earth Metals And The Role Of Acid Pretreatments In Production Of Sugars From Switchgrass Based On Solvent Liquefaction, Xianglan Bai, Robert C. Brown, Jie Fu, Brent H. Shanks, Matthew Kieffer Jan 2014

The Influence Of Alkali And Alkaline Earth Metals And The Role Of Acid Pretreatments In Production Of Sugars From Switchgrass Based On Solvent Liquefaction, Xianglan Bai, Robert C. Brown, Jie Fu, Brent H. Shanks, Matthew Kieffer

Chemical and Biological Engineering Publications

This study investigated the influence of alkali and alkaline earth metals (AAEM) and the role of acid pretreatments in the production of sugars during solvent liquefaction of lignocellulosic biomass using 1,4-dioxane and water as solvents. The present study found that removal of AAEM by acid washing/water rinsing did not enhance sugar production during solvent liquefaction of pretreated switchgrass nearly to the extent observed for fast pyrolysis nor did it inhibit lignin decomposition, suggesting that AAEM play less of a role in determining product yields in solvent liquefaction. On the other hand, acid infusion greatly enhanced the yields of ...


In Situ Stress Measurement During Aluminum Anodizing Using Phase-Shifting Curvature Interferometry, Ömer Özgür Çapraz, Kurt R. Hebert, Pranav Shrotriya Jan 2013

In Situ Stress Measurement During Aluminum Anodizing Using Phase-Shifting Curvature Interferometry, Ömer Özgür Çapraz, Kurt R. Hebert, Pranav Shrotriya

Chemical and Biological Engineering Publications

Stress measurements yield insight into technologically relevant deformation and failure mechanisms in electrodeposition, battery reactions, corrosion and anodic oxidation. Aluminum anodizing experiments were performed to demonstrate the effectiveness of phase-shifting curvature interferometry as a new technique for high-resolution in situ stress measurement. This method uses interferometry to monitor surface curvature changes, from which stress evolution is inferred. Phase-shifting of the reflected beams enhanced measurement sensitivity, and the separation of the optical path from the electrochemical cell in the present system provided increased stability. Curvature changes as small as 10−3 km−1 were detected, at least comparable to the resolution ...


A Hierarchy Of Eulerian Models For Trajectory Crossing In Particle-Laden Turbulent Flows Over A Wide Range Of Stokes Numbers, Frederique Laurent, Aymeric Vie, Christophe Chalons, Rodney O. Fox, Marc Massot Jan 2013

A Hierarchy Of Eulerian Models For Trajectory Crossing In Particle-Laden Turbulent Flows Over A Wide Range Of Stokes Numbers, Frederique Laurent, Aymeric Vie, Christophe Chalons, Rodney O. Fox, Marc Massot

Chemical and Biological Engineering Publications

With the large increase in available computational resources, large-eddy simulation (LES) of industrial configurations has become an efficient and tractable alternative to traditional multiphase turbulence models. Many applications involve a liquid or solid disperse phase carried by a gas phase (eg, fuel injection in automotive or aeronautical engines, fluidized beds, and alumina particles in rocket boosters).


A Quadrature-Based Kinetic Model For Dilute Non-Isothermal Granular Flows, Alberto Passalacqua, Janine E. Galvin, Prakash Vedula, Christine M. Hrenya, Rodney O. Fox Jul 2011

A Quadrature-Based Kinetic Model For Dilute Non-Isothermal Granular Flows, Alberto Passalacqua, Janine E. Galvin, Prakash Vedula, Christine M. Hrenya, Rodney O. Fox

Chemical and Biological Engineering Publications

A moment method with closures based on Gaussian quadrature formulas is proposed to solve the Boltzmann kinetic equation with a hard-sphere collision kernel for mono-dispersed particles. Different orders of accuracy in terms of the moments of the velocity distribution function are considered, accounting for moments up to seventh order. Quadrature-based closures for four different models for inelastic collisionthe Bhatnagar-Gross-Krook, ES-BGK, the Maxwell model for hard-sphere collisions, and the full Boltzmann hard-sphere collision integral-are derived and compared. The approach is validated studying a dilute non-isothermal granular flow of inelastic particles between two stationary Maxwellian walls. Results obtained from the kinetic models ...


Confocal Imaging Of Laminar And Turbulent Mixing In A Microscale Multi-Inlet Vortex Nanoprecipitation Reactor, Yanxiang Shi, Rodney O. Fox, Michael G. Olsen Jan 2011

Confocal Imaging Of Laminar And Turbulent Mixing In A Microscale Multi-Inlet Vortex Nanoprecipitation Reactor, Yanxiang Shi, Rodney O. Fox, Michael G. Olsen

Chemical and Biological Engineering Publications

Mass production of functional nanoparticles may be realized through flash nanoprecipiation in microscale reactors such as the multi-inlet vortex reactor (MIVR). A comprehensive understanding of mixing in the MIVR is required for process control and reactor design. Mixing in the MIVR is studied using a technique coupling laser induced fluorescence with confocal laser scanning microscopy. It is shown to provide meaningful qualitative and statistical data of the scalar field for analysis and comparison with numerical simulations. Data were collected for four flow rates, showing that mixing is incomplete even at the highest flow rate.


Hybrid Thermochemical Processing: Fermentation Of Pyrolysis-Derived Bio-Oil, Laura R. Jarboe, Zhiyou Wen, Dong Won Choi, Robert C. Brown Jan 2011

Hybrid Thermochemical Processing: Fermentation Of Pyrolysis-Derived Bio-Oil, Laura R. Jarboe, Zhiyou Wen, Dong Won Choi, Robert C. Brown

Chemical and Biological Engineering Publications

Thermochemical processing of biomass by fast pyrolysis provides a nonenzymatic route for depolymerization of biomass into sugars that can be used for the biological production of fuels and chemicals. Fermentative utilization of this bio-oil faces two formidable challenges. First is the fact that most bio-oil-associated sugars are present in the anhydrous form. Metabolic engineering has enabled utilization of the main anhydrosugar, levoglucosan, in workhorse biocatalysts. The second challenge is the fact that bio-oil is rich in microbial inhibitors. Collection of bio-oil in distinct fractions, detoxification of bio-oil prior to fermentation, and increased robustness of the biocatalyst have all proven effective ...


Steam Reforming Of Bio-Oil Fractions: Effect Of Composition And Stability, Pedro J, Ortiz-Toral, Justinus A. Satrio, Robert C. Brown, Brent H. Shanks Jan 2011

Steam Reforming Of Bio-Oil Fractions: Effect Of Composition And Stability, Pedro J, Ortiz-Toral, Justinus A. Satrio, Robert C. Brown, Brent H. Shanks

Chemical and Biological Engineering Publications

The efficacy of steam reforming of the aqueous species in bio-oils produced from the fast pyrolysis of biomass is examined. A fractionating condenser system was used to collect a set of fractions of fast pyrolysis liquids with different chemical characteristics. The water-soluble components from the different fractions were steam-reformed using a nickel-based commercial catalyst in a fixed-bed reactor system. When reforming at 500 °C, an overall positive effect in hydrogen yields was observed for the fractions with higher concentrations of lower molecular-weight oxygenates, such as acetic acid and acetol, while the heavier compounds, such as the carbohydrates, showed an ...


Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 3. Reaction Rate Constant Calculations, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox Jan 2010

Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 3. Reaction Rate Constant Calculations, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox

Chemical and Biological Engineering Publications

The rate constants for the gas-phase reactions in the silicon carbide chemical vapor deposition of methyltrichlorosilane (Ge, Y. B.; Gordon, M. S.; Battaglia, F.; Fox, R. O. J. Phys. Chem. A 2007, 111, 1462.) were calculated. Transition state theory was applied to the reactions with a well-defined transition state; canonical variational transition state theory was applied to the barrierless reactions by finding the generalized transition state with the maximum Gibbs free energy along the reaction path. Geometry optimizations were carried out with second-order perturbation theory (MP2) and the cc-pVDZ basis set. The partition functions were calculated within the harmonic oscillator ...


Turbulence In A Microscale Planar Confined Impinging-Jets Reactor, Ying Liu, Michael G. Olsen, Rodney O. Fox Jan 2009

Turbulence In A Microscale Planar Confined Impinging-Jets Reactor, Ying Liu, Michael G. Olsen, Rodney O. Fox

Chemical and Biological Engineering Publications

Confined impinging-jets reactors (CIJR) offer many advantages for rapid chemical processing at the microscale in applications such as precipitation and the production of organic nanoparticles. It has been demonstrated that computational fluid dynamics (CFD) is a promising tool for ‘‘experiment-free’’ design and scale-up of such reactors. However, validation of the CFD model used for the microscale turbulence applications requires detailed experimental data on the unsteady flow, the availability of which has until now been very limited. In this work, microscopic particle-image velocimetry (microPIV) techniques were employed to measure the instantaneous velocity field for various Reynolds numbers in a planar CIJR ...


A Microscale Multi-Inlet Vortex Nanoprecipitation Reactor: Turbulence Measurement And Simulation, Janine C. Cheng, Michael G. Olsen, Rodney O. Fox Jan 2009

A Microscale Multi-Inlet Vortex Nanoprecipitation Reactor: Turbulence Measurement And Simulation, Janine C. Cheng, Michael G. Olsen, Rodney O. Fox

Chemical and Biological Engineering Publications

Microscale reactors capable of generating turbulent flow are used in Flash NanoPrecipitation, an approach to produce functional nanoparticles with unique optical, mechanical and chemical properties. Microreactor design and optimization could be greatly enhanced by developing reliable computational models of the nanoprecipitation process. A microscale multi-inlet vortex nanoprecipitation reactor was investigated using microscopic particle image velocimetry and computational fluid dynamics. Velocity data such as the mean velocity and turbulent kinetic energy displayed good agreement between experiment and simulation over flow conditions ranging from fully laminar to turbulent, demonstrating the accuracy of the simulation model over the entire turbulent transition range.


Effect Of Electrolytes On Co-Water Mass Transfer, Haiyang Zhu, Brent H. Shanks, Theodore J. Heindel Jan 2009

Effect Of Electrolytes On Co-Water Mass Transfer, Haiyang Zhu, Brent H. Shanks, Theodore J. Heindel

Chemical and Biological Engineering Publications

The influence of various electrolytes such as sulfate, nitrate, and chloride on CO-water mass transfer was investigated in this study. The results indicate that the enhancement in the CO-water volumetric masstransfer coefficient ranged from 1.5 to 4.7 times that of a baseline system without electrolytes, depending on electrolyte type and concentration. For those electrolytes with the same anions, copper-containing electrolytes provided stronger enhancement, whereas for those electrolytes with the same cations, sulfate-containing electrolytes showed stronger enhancement. By measuring both the CO-water volumetric mass-transfer coefficient (kLa) and the mass-transfer coefficient (kL), it was found that the electrolytes inhibit gas ...


Conditional Statistics Of Passive-Scalar Mixing In A Confined Wake Flow, Hua Feng, Michael G. Olsen, Rodney O. Fox, James C. Hill Jan 2008

Conditional Statistics Of Passive-Scalar Mixing In A Confined Wake Flow, Hua Feng, Michael G. Olsen, Rodney O. Fox, James C. Hill

Chemical and Biological Engineering Publications

Experimental results for conditional statistics in a confined turbulent wake were compared to the linear model and the transported probability density function (PDF) model for predicting the velocity conditioned on scalar mixture fraction and to a linear model for predicting the scalar mixture fraction conditioned on velocity. For velocity conditioned on scalar mixture fraction, the linear model was found to accurately predict the conditional transverse velocity, but for the conditional streamwise velocity, agreement between the experiments and the linear model was poor. The transverse conditional velocity was accurately predicted by the transported PDF model, but for the streamwise conditional velocity ...


Conditional Statistics For Passive-Scalar Mixing In A Confined Rectangular Turbulent Jet, H. Feng, Michael G. Olsen, Rodney O. Fox, James C. Hill Jan 2007

Conditional Statistics For Passive-Scalar Mixing In A Confined Rectangular Turbulent Jet, H. Feng, Michael G. Olsen, Rodney O. Fox, James C. Hill

Chemical and Biological Engineering Publications

Experimental results for the conditional statistics, such as the velocity conditioned on a conserved scalar and the scalar conditioned on velocity, in a confined liquid-phase rectangular jet are presented and analyzed for a data set collected using simultaneous particle image velocimetry and planar laser-induced fluorescence. The joint velocity-scalar probability density function (PDF) is not joint Gaussian in this flow, as the PDF of the conserved scalar is accurately described by a beta-PDF. The conditional mean velocity is found to agree with a linear model when the scalar is close to its local mean value. A gradient PDF model is found ...


Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 1. Thermodynamics, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox Jan 2007

Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 1. Thermodynamics, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox

Chemical and Biological Engineering Publications

Structures and energies of the gas-phase species produced during and after the various unimolecular decomposition reactions of methyltrichlorosilane (MTS) with the presence of H2 carrier gas were determined using second-order perturbation theory (MP2). Single point energies were obtained using singles + doubles coupled cluster theory, augmented by perturbative triples, CCSD(T). Partition functions were obtained using the harmonic oscillator-rigid rotor approximation. A 114-reaction mechanism is proposed to account for the gas-phase chemistry of MTS decompositions. Reaction enthalpies, entropies, and Gibbs free energies for these reactions were obtained at 11 temperatures ranging from 0 to 2000 K including room temperature and typical ...


Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 2. Reaction Paths And Transition States, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox Jan 2007

Theoretical Study Of The Pyrolysis Of Methyltrichlorosilane In The Gas Phase. 2. Reaction Paths And Transition States, Yingbin Ge, Mark S. Gordon, Francine Battaglia, Rodney O. Fox

Chemical and Biological Engineering Publications

The kinetics for the previously proposed 114-reaction mechanism for the chemical vapor deposition (CVD) process that leads from methyltrichlorosilane (MTS) to silicon carbide (SiC) are examined. Among the 114 reactions, 41 are predicted to proceed with no intervening barrier. For the remaining 73 reactions, transition states and their corresponding barrier heights have been explored using second-order perturbation theory (MP2) with the aug-cc-pVDZ basis set. Final energies for the reaction barriers were obtained using both MP2 with the aug-cc-pVTZ basis set and coupled cluster theory (CCSD(T)) with the aug-cc-pVDZ basis set. CCSD(T)/aug-cc-pVTZ energies were estimated by assuming additivity ...


A Continuous-Time Nonlinear Dynamic Predictive Modeling Method For Hammerstein Processes, Derrick K. Rollins Sr., Nidhi Bhandari, Ashraf Maurice Bassily, Gerald M. Colver, Swee-Teng Chin Jan 2003

A Continuous-Time Nonlinear Dynamic Predictive Modeling Method For Hammerstein Processes, Derrick K. Rollins Sr., Nidhi Bhandari, Ashraf Maurice Bassily, Gerald M. Colver, Swee-Teng Chin

Chemical and Biological Engineering Publications

This paper extends the method introduced by Rollins et al. (ISA Trans. 1998, 36, 293) to multiple-input, multiple-output systems that give an exact closed-form solution to continuous-time Hammerstein processes written in terms of differential equations and nonlinear inputs. This ability is demonstrated on a theoretical nonlinear Hammerstein process of complex dynamics where perfect identification of the closed-form model is assumed. This paper then demonstrates the simplicity of the proposed identification procedure to obtain an accurate estimate of the exact model using a theoretical Hammerstein model. A powerful attribute of this methodology is the ability to make full use of the ...