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GENERATION OF SOOT BASAL STRUCTURE UNITS WITH REAXFF
13/03/2016
PhD: Michel KellerIFPEN Supervisor: Theodorus de BruinAcademic Supervisor: André Nicolle
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S U S T A I N A B L E M O B I L I T Y
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Objective:Model the chemical composition of soot particle structures in differentoperating conditions (fuel composition, thermochemical surrounding).
Use these results to investigate the chemical kinetics at the gas‐phase boundary layer and the surface sites of soot particles.
MOTIVATION
Structure Kinetics
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S U S T A I N A B L E M O B I L I T Y
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METHODOLOGYObjective:Generation of a library of turbostratic soot structures spanning a wide range of fuels and engine operating conditions by molecular dynamics simulationsApproach:
We generated a gas phase precursor mixture using Chemkin.
Tested conditions:• Equivalence ratio• Temperature• Different fuels
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S U S T A I N A B L E M O B I L I T Y
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METHODOLOGYObjective:Generation of a library of turbostratic soot structures spanning a wide range of fuels and engine operating conditions by molecular dynamics simulationsApproach:
We generated a gas phase precursor mixture using Chemkin.
Tested conditions:• Equivalence ratio• Temperature• Different fuels
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S U S T A I N A B L E M O B I L I T Y
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Objective:Generation of a library of soot turbostratic structures spanning a wide range of fuels and engine operating conditions by an ReaxFF molecular dynamics simulations
METHODOLOGY
Criteria for BSUs:• aggregation of >3 molecules• distance <5.27 Å between
the centers of mass• lifetime >10ps
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Reactive Forcefield Approach* :
• Parametrization with QM calculations
Multi‐scale Approach
*as described by Chennoweth et al. (2008)
QM(6-311G**/B3LYP) and ReaxFF reaction profile for the 4 + 2 cycloaddition of O2 with butadiene, benzene, or cyclopentadiene(Cp).Published in: Kimberly Chenoweth; Adri C. T. van Duin; William A. Goddard; J. Phys. Chem. A 2008, 112, 1040-1053.
QM (6-311G**/B3LYP) and ReaxFF bond dissociation energies for C−O single, double, and triple bonds.Published in: Kimberly Chenoweth; Adri C. T. van Duin; William A. Goddard; J. Phys. Chem. A 2008, 112, 1040-1053
Motivation Multi‐scale Approach First Results
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Motivation
• CFD models correctly reproduce the Particle Size Distribution and Particle numbers, but they do not account for structural differences
• The influence of the structural differences and the functionalization of precursor molecules on the particle kinetics are not well understoodAim : Understand the influence of structural difference on the reactivityand selectivity of oxidation
Soot oxidation-induced fragmentation: Part 1: The relationship between soot nanostructure and oxidation-induced fragmentationPublished in: Hossein Ghiassi, Pal Toth, Isabel C. Jaramillo, JoAnn S. Lighty; Combustion and Flame, Volume 163, 2016, 179–187
Motivation Multi‐scale Approach First Results