Combined Model Predictive Control And Scheduling With Dominant Time Constant Compensation, 2017 Brigham Young University
Combined Model Predictive Control And Scheduling With Dominant Time Constant Compensation, Logan Beal, Junho Park, Damon Petersen, Sean C. Warnick, John Hedengren
All Faculty Publications
Linear model predictive control is extended to both control and optimize a product grade schedule. The proposed methods are time-scaling of the linear dynamics based on throughput rates and grade-based objectives for product scheduling based on a mathematical program with complementarity constraints. The linear model is adjusted with a residence time approximation to time-scale the dynamics based on throughput. Although nonlinear models directly account for changing dynamics, the model form is restricted to linear differential equations to enable fast online cycle times for large-scale and real-time systems. This method of extending a linear time-invariant model for scheduling is designed for ...
Likelihood And Bayesian Methods For Accurate Identification Of Measurement Biases In Pseudo Steady-State Processes, Sriram Devanathan, Stephen B. Vardeman, Derrick K. Rollins Sr.
Stephen B. Vardeman
Two new approaches are presented for improved identification of measurement biases in linear pseudo steady-state processes. Both are designed to detect a change in the mean of a measured variable leading to an inference regarding the presence of a biased measurement. The first method is based on a likelihood ratio test for the presence of a mean shift. The second is based on a Bayesian decision rule (relying on prior distributions for unknown parameters) for the detection of a mean shift. The performance of these two methods is compared with that of a method given by Devanathan et al. (2000 ...
A Fully Coupled Fluid-Particle Flow Solver Using Quadrature-Based Moment Method With High-Order Realizable Schemes On Unstructured Grids, Varun Vikas, Z. J. Wang, Alberto Passalacqua, Rodney O. Fox
Rodney O. Fox
Kinetic Equations containing terms for spatial transport, gravity, fluid drag and particle-particle collisions can be used to model dilute gas-particle flows. However, the enormity of independent variables makes direct numerical simulation of these equations almost impossible for practical problems. A viable alternative is to reformulate the problem in terms of moments of the velocity distribution function. A quadrature method of moments (QMOM) was derived by Desjardins et al.  for approximating solutions to the kinetic equation for arbitrary Knudsen number. Fox [2, 13] derived a third-order QMOMfor dilute particle flows, including the effect of the fluid drag on the particles ...
Numerical Simulation Of Turbulent Gas-Particle Flow In A Riser Using A Quadrature-Based Moment Method, 2017 Iowa State University
Numerical Simulation Of Turbulent Gas-Particle Flow In A Riser Using A Quadrature-Based Moment Method, Alberto Passalacqua, Rodney O. Fox
Rodney O. Fox
Gas-particle flows are used in many industrial applications in the energy, oil and gas fields, such as coal gasification, production of light hydrocarbons by fluid catalytic cracking, catalytic combustion and different treatments aiming to reduce or eliminate pollutants. The particle phase of a gas-particle flow is described by analogy to a granular gas, by finding an approximate solution of the kinetic equation in the velocity-based number density function. In the recent past, many studies have been published on the mathematical modeling of gas-particle flows using hydrodynamic models (e.g. Enwald et al. 1996), where Navier-Stokes-type equations are solved to describe ...
Numerical Simulations Of Turbulent Bluff-Body Flames Using Multi-Environment Presumed Pdf Method With Realistic Chemistry, 2017 Reaction Engineering International
Numerical Simulations Of Turbulent Bluff-Body Flames Using Multi-Environment Presumed Pdf Method With Realistic Chemistry, Qing Tang, Wei Zhao, Micahel Bockelie, Rodney O. Fox
Rodney O. Fox
A Computational Fluid Dynamics (CFD) tool for performing turbulent combustion simulations that require finite rate chemistry is developed and tested by modeling a series of bluff-body stabilized flames that exhibit different levels of finite-rate chemistry effects ranging from near equilibrium to near global extinction. The new modeling tool is based on the multi-environment probability density function (MEPDF) methodology and combines the following: the direct quadrature method of moments (DQMOM); the interaction-by-exchange-with-the-mean (IEM) mixing model; and realistic combustion chemistry. A pseudo time splitting scheme is adopted to solve the MEPDF equations; the reaction source terms are computed with a highly efficient ...
Turbulent Combustion Of Polydisperse Evaporating Sprays With Droplet Crossing: Eulerian Modeling And Validation In The Infinite Knudsen Limit, S. De Chaisemartin, L. Freret, D. Kah, F. Laurent, Rodney O. Fox, J. Reveillon, M. Massot
Rodney O. Fox
The accurate simulation of the dynamics of polydisperse evaporating sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. The difficulties encountered by the usual Lagrangian approaches make the use of Eulerian models attractive, aiming at a lower cost and an easier coupling with the carrier gaseous phase. Among these models, the multi-fluid model allows for a detailed description of the polydispersity and size-velocity correlations for droplets of various sizes. The purpose of the present study is twofold. First, we extend the multi-fluid model in ...
Conditional-Moment Closure With Differential Diffusion For Soot Evolution In Fire, 2017 Sandia National Laboratories
Conditional-Moment Closure With Differential Diffusion For Soot Evolution In Fire, J. C. Hewson, A. J. Ricks, S. R. Tieszen, A R. Kerstein, Rodney O. Fox
Rodney O. Fox
The conditional-moment closure (CMC) equation for the evolution of a large Lewis number scalar, soot, is derived starting from the joint probability density function (pdf) equation for the gas-phase mixture fraction, ξ g , and the soot mass fraction, Y s . Unlike previous approaches starting with the joint pdf, the residual terms that result from the typical closure models were retained. A new formulation of the one-dimensional turbulence (ODT) model suitable for spatially evolving flows with buoyant acceleration and radiative transport in participating media was employed to carry out simulations of a prototypical ethene fire. The resulting ODT evolution of ξ ...
Instantaneous Particle Acceleration Model For Gas-Solid Suspensions At Moderate Reynolds Numbers, 2017 Iowa State University
Instantaneous Particle Acceleration Model For Gas-Solid Suspensions At Moderate Reynolds Numbers, Sudheer Tenneti, Rodney O. Fox, Shankar Subramaniam
Rodney O. Fox
Gas-solid flows are encountered in many industrial applications such as fluidized beds and coal gasification. The design and scale-up of such industrial devices required a better understanding of the characteristics of gas-solid suspensions. Device-scale computational fluid dynamics (CFD) simulations that solve for average quantities such as solid volume fraction and phasic mean velocity fields are being extensively used in the industrial design process. The capability of the simulations to accurately predict the characteristics of gas-solid flow depends upon the accuracy of the models for unclosed terms that appear in the equations for mass, momentum and energy conservation. Hrenya and Sinclair ...
A Quadrature-Based Moment Closure For The Williams Spray Equation, 2017 Iowa State University
A Quadrature-Based Moment Closure For The Williams Spray Equation, O. Desjardins, Rodney O. Fox, P. Villedieu
Rodney O. Fox
Sprays and other dispersed-phase systems can be described by a kinetic equation containing terms for spatial transport, acceleration, and particle processes (such as evaporation or collisions). In principle, the kinetic description is valid from the dilute (non-collisional) to the dense limit. However, its numerical solution in multi-dimensional systems is intractable due to the large number of independent variables. As an alternative, Lagrangian methods "discretize" the density function into "parcels" that are simulated using Monte-Carlo methods. While quite accurate, as in any statistical approach, Lagrangian methods require a relatively large number of parcels to control statistical noise, and thus are computationally ...
Treatment Of Fast Chemistry In Fdf/Les: In Situ Adaptive Tabulation, 2017 Iowa State University
Treatment Of Fast Chemistry In Fdf/Les: In Situ Adaptive Tabulation, Van Vliet E., Rodney O. Fox, J. J. Derksen, S. B. Pope
Rodney O. Fox
The feasibility to implement fast-chemistry reactions in a three-dimensional large eddy simulation (LES) of a turbulent reacting flow using a filtered density function (PDF) technique is studied. Low-density polyethylene (LDPE) is used as an representative reaction due to the stiff nature of the ordinary differential equation (ODE's) describing the kinetics. In FDF/LES, the chemistry needs to be evaluated many times for a large number of fictitious particles that are tracked in the flow, and therefore a constraint is put to the CPU time needed to solve the kinetics. Pope (1997) developed an in situ adaptive tabulation (ISAT) to ...
Numerical Description Of Dilute Particle-Laden Flows By A Quadrature-Based Moment Method, 2017 Office National d'Etudes et de Recherches Aerospatiales, France
Numerical Description Of Dilute Particle-Laden Flows By A Quadrature-Based Moment Method, N. Le Lostec, Rodney O. Fox, O. Simonin, P. Villedieu
Rodney O. Fox
The numerical simulation of gas-particle flows is divided into two families of methods. In Euler-Lagrange methods individual particle trajectories are computed, whereas in Euler-Euler methods particles are characterized by statistical descriptors. Lagrangian methods are very precise but their computational cost increases with instationarity and particle volume fraction. In Eulerian methods (also called moment methods) the particle-phase computational cost is comparable to that of the fluid phase but requires strong simplificaions. Existing Eulerian models consider unimodal or close-to-equilibrium particle velocity distributions and then fail when the actual distribution is far from equilibrium. Quadrature-based Eulerian methods introduce a new reconstruction of the ...
Development Of High-Order Realizable Finite-Volume Schemes For Quadrature-Based Moment Method, 2017 Iowa State University
Development Of High-Order Realizable Finite-Volume Schemes For Quadrature-Based Moment Method, Varun Vikas, Z. J. Wang, Alberto Passalacqua, Rodney O. Fox
Rodney O. Fox
Kinetic equations containing terms for spatial transport, gravity, fluid drag and particle-particle collisions can be used to model dilute gas-particle flows. However, the enormity of independent variables makes direct numerical simulation of these equations almost impossible for practical problems. A viable alternative is to reformulate the problem in terms of moments of velocity distribution. Recently, a quadrature-based moment method was derived by Fox for approximating solutions to kinetic equation for arbitrary Knudsen number. Fox also described 1st- and 2nd-order finite-volume schemes for solving the equations. The success of the new method is based on a moment-inversion algorithm that is used ...
Modeling Fluidization In Biomass Gasification Processes, 2017 Iowa State University
Modeling Fluidization In Biomass Gasification Processes, Emmanuela Gavi, Theodore J. Heindel, Rodney O. Fox
Rodney O. Fox
Extensive validation of computational fluid dynamics (CFD) models is required when modeling biomass fluidization, because several required model inputs are not know or not easily measured experimentally for biomass. In the present work, CFD fluidization modeling of a biomass bed is validated by comparison with X-ray computed tomography experimental data. A parametric study was carried out by employing ground walnut shell or ground corncob as model biomass bed materials, and fluidization was performed at a gas velocity twice the minimum fluidization velocity. An important result is the use of an "effective density" for biomass in the CFD model, the use ...
Consistent Hybrid Les-Fdf Formulation For The Simulation Of Turbulent Combustion, 2017 Iowa State University
Consistent Hybrid Les-Fdf Formulation For The Simulation Of Turbulent Combustion, Venkatramanan Raman, H. Pitsch, Rodney O. Fox
Rodney O. Fox
The numerical simulation of turbulent reactive flows is a complex and challenging problem with widespread practical use. Recent breakthroughs in algorithmic techniques and the drastic increase in computing power have provided us with the tools to understand the complex interaction between turbulence and chemical reactions. In the past decade, the use of the large-eddy simulation (LES) technique has made it possible to make accurate predictions of turbulent flows even for complex configurations.
Book Review: Controlled And Living Polymerizations: From Mechanisms To Applications, 2017 Iowa State University
Book Review: Controlled And Living Polymerizations: From Mechanisms To Applications, Jennifer M. Heinen
Jennifer M. Heinen
Controlled/living polymerization makes it possible to synthesize polymers of low polydispersity with a predefined molecular weight and specified chain architecture. Such polymers are desirable for a broad range of applications, including coatings, adhesives, and lubricants. Although living polymerization was first discovered in anionic polymerizations in 1956, several decades passed prior to the development of living polymerization techniques for carbocationic polymerization (1984) and ring-opening metathesis polymerization (1986). During the 1990s, several techniques were developed for controlled/living free radical polymerizations. The development of these techniques led to a dramatic increase in the number of research publications dedicated to improving the ...
Tin Dioxide-Carbon Heterostructures Applied To Gas Sensing: Structure-Dependent Properties And General Sensing Mechanism, Catherine Marichy, Patricia A. Russo, Mariangela Latino, Jean-Philippe Tessonnier, Marc-Georg Wilinger, Nicola Donato, Giovanni Neri, Nicola Pinna
Carbon materials such as carbon nanotubes (CNTs), graphene, and reduced graphene oxide (RGO) exhibit unique electrical properties, which are also influenced by the surrounding atmosphere. They are therefore promising sensing materials. Despite the existence of studies reporting the gas-sensing properties of metal oxide (MOx) coated nanostructured carbon, an incomplete understanding of their sensing mechanism remains. Here we report a systematic study on the preparation, characterization, and sensing properties of CNT and RGO composites with SnO2 coating. Atomic layer deposition (ALD) was applied to the conformal coating of the inner and outer walls of CNTs with thin films of SnO2 of ...
Magnetic Stimulation On The Growth Of The Microalga Nannochloropsis Oculata, 2017 The University of Western Ontario
Magnetic Stimulation On The Growth Of The Microalga Nannochloropsis Oculata, Manuella Oliveira
Electronic Thesis and Dissertation Repository
Fossil fuels, our principal sources of energy supply, are non-renewable and research is needed on alternatives that are renewable and potentially more environmentally friendly. Microalgae have been investigated as a future feedstock alternative to petroleum but the technology is still expensive and improvements are needed. Reduction in costs might be achieved by increasing algal biomass and lipid productivity. The lipids can be used to produce biofuels such as biodiesel and biojet fuel. The marine microalga Nannochloropsis oculata grows well and can accumulate high lipid content. In this study, the effects of static magnetic field stimulation (SMF) of 0 (control), 5 ...
Acetone Production, 2017 Western Michigan University
Acetone Production, Ali Ibrahim Neamah
The Hilltop Review
Iraq struggles with a lack of acetone production. This overall deficiency impacts the economy of countries like Iraq. Inasmuch, acetone is a vital chemical component for many items imported into this country such as nail polish remover. Therefore, a process of acetone production is proposed in this study.
The ideal process of producing acetone with 90.0% isopropyl alcohol (IPA) decomposition method is proposed within this study. The feed of the process is 100000 ton/ day. This amount of feed is suggested due to the demographic need of acetone for the Iraqi population as well as the surrounding Middle Eastern ...
Cellulose–Hemicellulose And Cellulose–Lignin Interactions During Fast Pyrolysis, 2017 Iowa State University
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
Brent H Shanks
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 ...
Effect Of Electrolytes On Co−Water Mass Transfer, 2017 Iowa State University
Effect Of Electrolytes On Co−Water Mass Transfer, Haiyang Zhu, Brent H. Shanks, Theodore J. Heindel
Brent H Shanks
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 mass-transfer 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 ...