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Professor Mohamad (Hameed) Metghalchi
Modeling
Combustion Using the Rate-Controlled Constrained-Equilibrium (RCCE) Method Modeling
of a non-equilibrium combustion process involves the solution of large systems
of differential equations with as many equations as species present during the
process. The process of chemical reaction and combustion is complicated since it
may be governed by hundreds, sometimes thousands of microscopic rate processes.
Integration of these equations simultaneously becomes more difficult with
the complexity of the combustible. In order to reduce the size of these systems
of equations, the Rate-Controlled Constrained-Equilibrium method (RCCE) is used
within our group to model non-equilibrium combustion processes. This method is
based on the Second Law of Thermodynamics, assuming that the evolution of a
complex system can be described by a small number of rate-controlling reactions
which impose slowly changing constraints on all allowed states of the system,
therefore a non-equilibrium system will relax to its final equilibrium state
through a sequence of rate controlled constrained equilibrium states.
Oxidation induction times and concentration of species during a
combustion process are found in a less complicated way with this method, as
equations for constraints rather than for species determine the composition and
evolution of the system. The time evolution of the system can be reduced since
the number of constraints is much smaller than the number of species present, so
the number of equations to solve. The
RCCE method has been successfully applied to the stoichiometric combustion of
mono-carbon fuels. Results of using 8, 9, 10 and 11 constraints compared very
well to those of the detailed calculations at all conditions for the cases of
formaldehyde (H2CO), methanol (CH3OH) and methane (CH4).
For these systems, ignition delay times and major species concentrations were
within 5% of the values given by detailed calculations, and computational saving
times up to 50% have been met. Currently
our group is working on the application of this technique to heavier
hydrocarbons, as well as to broaden the range of applications for the
mono-carbon combustion modeling.
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