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Development of an Automatic Reduction Tool for Chemical Mechanisms and an Optimized Sparse Matrix Solver for Systems of Differential and Algebraic Equations

Arvidsson, Andreas LU (2010)
Abstract
Abstract

An N-Heptane mechanism and a Methane/Propane mechanism have been reduced by an Automatic Reduction Tool (ART) and simulated with two different solver combinations, which solve the set of ordinary differential equations governing the time evolution of the species simultaneously with solving algebraic equations for species that can be considered to be in quasi steady state. The most successful of the two solver combinations is an optimized combination of Newton solvers. The algebraic part of the solver is based on a Newton solver and is given a speed-up by using the fact that the sparseness pattern of the Jacobian is constant in time. This allows for automatically written source code and an optimization of the sparseness... (More)
Abstract

An N-Heptane mechanism and a Methane/Propane mechanism have been reduced by an Automatic Reduction Tool (ART) and simulated with two different solver combinations, which solve the set of ordinary differential equations governing the time evolution of the species simultaneously with solving algebraic equations for species that can be considered to be in quasi steady state. The most successful of the two solver combinations is an optimized combination of Newton solvers. The algebraic part of the solver is based on a Newton solver and is given a speed-up by using the fact that the sparseness pattern of the Jacobian is constant in time. This allows for automatically written source code and an optimization of the sparseness pattern in a preprocessing step. The optimization method is based on a simulated annealing procedure that minimizes the number of operations in the algebraic part of the solver. The speed-up of the Newton solver for the algebraic equations is one of the major developments presented in this thesis. The other one is the development of the ART and the reduction of the N-Heptane and the Methane/Propane mechanisms using the ART.

A reduction down to 37 out of 110 species and 23 out of 118 species is achieved for the N-Heptane and Methane/Propane mechanism respectively, while the accuracy of the solution is maintained and the CPU time is significantly lower than that of the detailed mechanism. Less, but still greatly reduced mechanisms are generated for larger ranges of physical conditions.

Also, the two solver combinations were implemented into a commercial Computational Fluid Dynamics (CFD) code. CFD simulations were then performed for a detailed and reduced mechanism. The implementation involving the optimized combination of Newton solvers resulted in a speed-up for the reduced mechanism compared to the detailed mechanism, while the accuracy of important species for the reduced mechanism was well within acceptable limits. (Less)
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author
supervisor
opponent
  • PhD Skevis, George, National Technical University of Athens, Greece
organization
publishing date
type
Thesis
publication status
published
subject
pages
415 pages
defense location
Lecture hall F, Department of Physics, Sölvegatan 14A, Lund University Faculty of Engineering
defense date
2010-01-27 10:00
ISSN
1102-8718
language
English
LU publication?
yes
id
071836c6-fcea-437f-a891-20beeeb03850 (old id 1748912)
date added to LUP
2010-12-22 15:36:56
date last changed
2016-09-19 08:45:00
@misc{071836c6-fcea-437f-a891-20beeeb03850,
  abstract     = {Abstract <br/><br>
An N-Heptane mechanism and a Methane/Propane mechanism have been reduced by an Automatic Reduction Tool (ART) and simulated with two different solver combinations, which solve the set of ordinary differential equations governing the time evolution of the species simultaneously with solving algebraic equations for species that can be considered to be in quasi steady state. The most successful of the two solver combinations is an optimized combination of Newton solvers. The algebraic part of the solver is based on a Newton solver and is given a speed-up by using the fact that the sparseness pattern of the Jacobian is constant in time. This allows for automatically written source code and an optimization of the sparseness pattern in a preprocessing step. The optimization method is based on a simulated annealing procedure that minimizes the number of operations in the algebraic part of the solver. The speed-up of the Newton solver for the algebraic equations is one of the major developments presented in this thesis. The other one is the development of the ART and the reduction of the N-Heptane and the Methane/Propane mechanisms using the ART.<br/><br>
A reduction down to 37 out of 110 species and 23 out of 118 species is achieved for the N-Heptane and Methane/Propane mechanism respectively, while the accuracy of the solution is maintained and the CPU time is significantly lower than that of the detailed mechanism. Less, but still greatly reduced mechanisms are generated for larger ranges of physical conditions.<br/><br>
Also, the two solver combinations were implemented into a commercial Computational Fluid Dynamics (CFD) code. CFD simulations were then performed for a detailed and reduced mechanism. The implementation involving the optimized combination of Newton solvers resulted in a speed-up for the reduced mechanism compared to the detailed mechanism, while the accuracy of important species for the reduced mechanism was well within acceptable limits.},
  author       = {Arvidsson, Andreas},
  issn         = {1102-8718},
  language     = {eng},
  pages        = {415},
  title        = {Development of an Automatic Reduction Tool for Chemical Mechanisms and an Optimized Sparse Matrix Solver for Systems of Differential and Algebraic Equations},
  year         = {2010},
}