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Diagnostics for the Combustion Science Workbench

Description: As the cost of computers declines relative to outfitting andmaintaining laser spectroscopy laboratories, computers will account foran increasing proportion of the research conducted in fundamentalcombustion science. W.C. Gardiner foresaw that progress will be limitedby the ability to understand the implications of what has been computedand to draw inferences about the elementary components of the combustionmodels. Yet the diagnostics that are routinely applied to computerexperiments have changed little from the sensitivity analyses includedwith the original chemkin software distribution. This paper describessome diagnostics capabilities that may be found on the virtual combustionscience workbench of the future. These diagnostics are illustrated bysome new results concerning which of the hydrogen/oxygen chain branchingreactions actually occur in flames, the increased formation of NOx inwrinkled flames versus flat flames, and the adequacy oftheoreticalpredictions of the effects of stretch. Several areas are identified wherework is needed, including the areas of combustion chemistry and laserdiagnostics, to make the virtual laboratory a reality.
Date: February 21, 2007
Creator: Grcar, J.F.; Day, M.S. & Bell, J.B.
Partner: UNT Libraries Government Documents Department

Active Control for Statistically Stationary Turbulent PremixedFlame Simulations

Description: The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. Furthermore, the stabilization introduces additional fluid mechanical complexity into the overall combustion process that can complicate the analysis of fundamental flame properties. To circumvent these difficulties we introduce a feedback control algorithm that allows us to computationally stabilize a turbulent premixed flame in a simple geometric configuration. For the simulations, we specify turbulent inflow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm on methane flames at various equivalence ratios in two dimensions. The simulation data are used to study the local variation in the speed of propagation due to flame surface curvature.
Date: August 30, 2005
Creator: Bell, J.B.; Day, M.S.; Grcar, J.F. & Lijewski, M.J.
Partner: UNT Libraries Government Documents Department

Numerical simulation of a laboratory-scale turbulent V-flame

Description: We present a three-dimensional, time-dependent simulation of a laboratory-scale rod-stabilized premixed turbulent V-flame. The simulations are performed using an adaptive time-dependent low Mach number model with detailed chemical kinetics and a mixture model for differential species diffusion. The algorithm is based on a second-order projection formulation and does not require an explicit subgrid model for turbulence or turbulence chemistry interaction. Adaptive mesh refinement is used to dynamically resolve the flame and turbulent structures. Here, we briefly discuss the numerical procedure and present detailed comparisons with experimental measurements showing that the computation is able to accurately capture the basic flame morphology and associated mean velocity field. Finally, we discuss key issues that arise in performing these types of simulations and the implications of these issues for using computation to form a bridge between turbulent flame experiments and basic combustion chemistry.
Date: February 7, 2005
Creator: Bell, J.B.; Day, M.S.; Shepherd, I.G.; Johnson, M.; Cheng, R.K.; Grcar,J.F. et al.
Partner: UNT Libraries Government Documents Department

Scaling and efficiency of PRISM in adaptive simulations of turbulent premixed flames

Description: The dominant computational cost in modeling turbulent combustion phenomena numerically with high fidelity chemical mechanisms is the time required to solve the ordinary differential equations associated with chemical kinetics. One approach to reducing that computational cost is to develop an inexpensive surrogate model that accurately represents evolution of chemical kinetics. One such approach, PRISM, develops a polynomial representation of the chemistry evolution in a local region of chemical composition space. This representation is then stored for later use. As the computation proceeds, the chemistry evolution for other points within the same region are computed by evaluating these polynomials instead of calling an ordinary differential equation solver. If initial data for advancing the chemistry is encountered that is not in any region for which a polynomial is defined, the methodology dynamically samples that region and constructs a new representation for that region. The utility of this approach is determined by the size of the regions over which the representation provides a good approximation to the kinetics and the number of these regions that are necessary to model the subset of composition space that is active during a simulation. In this paper, we assess the PRISM methodology in the context of a turbulent premixed flame in two dimensions. We consider a range of turbulent intensities ranging from weak turbulence that has little effect on the flame to strong turbulence that tears pockets of burning fluid from the main flame. For each case, we explore a range of sizes for the local regions and determine the scaling behavior as a function of region size and turbulent intensity.
Date: December 1, 1999
Creator: Tonse, Shaheen R.; Bell, J.B.; Brown, N.J.; Day, M.S.; Frenklach, M.; Grcar, J.F. et al.
Partner: UNT Libraries Government Documents Department

Chemical kinetics models for semiconductor processing

Description: Chemical reactions in the gas-phase and on surfaces are important in the deposition and etching of materials for microelectronic applications. A general software framework for describing homogeneous and heterogeneous reaction kinetics utilizing the Chemkin suite of codes is presented. Experimental, theoretical and modeling approaches to developing chemical reaction mechanisms are discussed. A number of TCAD application modules for simulating the chemically reacting flow in deposition and etching reactors have been developed and are also described.
Date: December 31, 1997
Creator: Coltrin, M.E.; Creighton, J.R.; Meeks, E.; Grcar, J.F.; Houf, W.G. & Kee, R.J.
Partner: UNT Libraries Government Documents Department

OPPDIF: A Fortran program for computing opposed-flow diffusion flames

Description: OPPDIF is a Fortran program that computes the diffusion flame between two opposing nozzles. A similarity transformation reduces the two-dimensional axisymmetric flow field to a one-dimensional problem. Assuming that the radial component of velocity is linear in radius, the dependent variables become functions of the axial direction only. OPPDIF solves for the temperature, species mass fractions, axial and radial velocity components, and radial pressure gradient, which is an eigenvalue in the problem. The TWOPNT software solves the two-point boundary value problem for the steady-state form of the discretized equations. The CHEMKIN package evaluates chemical reaction rates and thermodynamic and transport properties.
Date: May 1, 1997
Creator: Lutz, A.E.; Kee, R.J.; Grcar, J.F. & Rupley, F.M.
Partner: UNT Libraries Government Documents Department

Computer workstation speeds

Description: This report compares the performance of several computers. Some of the machines are discontinued, and some are anticipated, but most are currently installed at Sandia Laboratories. All the computers are personal workstations or departmental servers, except for comparison, one is a Cray C90 mainframe supercomputer (not owned by the Laboratories). A few of the computers have multiple processors, but parallelism is not tested. The time to run three programs is reported for every computer. Unlike many benchmarks, these are complete application programs. They were written and are used at Sandia Laboratories. Also SPECmarks are reported for many computers. These are industry standard performance ratings. They are in general agreement with the speeds of running the Sandia programs. This report concludes with some background material and notes about specific manufacturers.
Date: June 1, 1996
Creator: Grcar, J.F.
Partner: UNT Libraries Government Documents Department

AURORA: A FORTRAN program for modeling well stirred plasma and thermal reactors with gas and surface reactions

Description: The AURORA Software is a FORTRAN computer program that predicts the steady-state or time-averaged properties of a well mixed or perfectly stirred reactor for plasma or thermal chemistry systems. The software was based on the previously released software, SURFACE PSR which was written for application to thermal CVD reactor systems. AURORA allows modeling of non-thermal, plasma reactors with the determination of ion and electron concentrations and the electron temperature, in addition to the neutral radical species concentrations. Well stirred reactors are characterized by a reactor volume, residence time or mass flow rate, heat loss or gas temperature, surface area, surface temperature, the incoming temperature and mixture composition, as well as the power deposited into the plasma for non-thermal systems. The model described here accounts for finite-rate elementary chemical reactions both in the gas phase and on the surface. The governing equations are a system of nonlinear algebraic relations. The program solves these equations using a hybrid Newton/time-integration method embodied by the software package TWOPNT. The program runs in conjunction with the new CHEMKIN-III and SURFACE CHEMKIN-III packages, which handle the chemical reaction mechanisms for thermal and non-thermal systems. CHEMKIN-III allows for specification of electron-impact reactions, excitation losses, and elastic-collision losses for electrons.
Date: February 1, 1996
Creator: Meeks, E.; Grcar, J.F.; Kee, R.J. & Moffat, H.K.
Partner: UNT Libraries Government Documents Department

The change tool for changing programs and scripts. Version 2.03 of April 1993

Description: Change is a computer program that interactively changes other programs. It allows one source text to move among many computers without proliferating versions for different compilers, precisions and the like. Change also modifies makefiles, shell scripts and programs embedded in makefiles and shell scripts. This is a guide to the program`s use and a description of its operation.
Date: May 1, 1993
Creator: Grcar, J. F.
Partner: UNT Libraries Government Documents Department

SPIN (Version 3. 83): A Fortran program for modeling one-dimensional rotating-disk/stagnation-flow chemical vapor deposition reactors

Description: In rotating-disk reactor a heated substrate spins (at typical speeds of 1000 rpm or more) in an enclosure through which the reactants flow. The rotating disk geometry has the important property that in certain operating regimes{sup 1} the species and temperature gradients normal to the disk are equal everywhere on the disk. Thus, such a configuration has great potential for highly uniform chemical vapor deposition (CVD),{sup 2--5} and indeed commercial rotating-disk CVD reactors are now available. In certain operating regimes, the equations describing the complex three-dimensional spiral fluid motion can be solved by a separation-of-variables transformation{sup 5,6} that reduces the equations to a system of ordinary differential equations. Strictly speaking, the transformation is only valid for an unconfined infinite-radius disk and buoyancy-free flow. Furthermore, only some boundary conditions are consistent with the transformation (e.g., temperature, gas-phase composition, and approach velocity all specified to be independent of radius at some distances above the disk). Fortunately, however, the transformed equations will provide a very good practical approximation to the flow in a finite-radius reactor over a large fraction of the disk (up to {approximately}90% of the disk radius) when the reactor operating parameters are properly chosen, i.e, high rotation rates. In the limit of zero rotation rate, the rotating disk flow reduces to a stagnation-point flow, for which a similar separation-of-variables transformation is also available. Such flow configurations ( pedestal reactors'') also find use in CVD reactors. In this report we describe a model formulation and mathematical analysis of rotating-disk and stagnation-point CVD reactors. Then we apply the analysis to a compute code called SPIN and describe its implementation and use. 31 refs., 4 figs.
Date: August 1, 1991
Creator: Coltrin, M.E. (Sandia National Labs., Albuquerque, NM (United States)); Kee, R.J.; Evans, G.H.; Meeks, E.; Rupley, F.M. & Grcar, J.F. (Sandia National Labs., Livermore, CA (United States))
Partner: UNT Libraries Government Documents Department