scholarly journals Analysis of the Influence of the Conduction Sub-Model Formulation on the Modeling of Laser-Induced Incandescence of Diesel Soot Aggregates

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 21
Author(s):  
Sébastien Menanteau ◽  
Romain Lemaire
Keyword(s):  
Thermionic Emission ◽  
Simulated Data ◽  
Diagnostic Technique ◽  
Aggregate Size ◽  
Accommodation Coefficient ◽  
Shielding Effect ◽  
Thermal Accommodation ◽  
Fitting Procedure ◽  
Laser Induced Incandescence ◽  
Thermal Accommodation Coefficient

Laser-induced incandescence (LII) is a powerful diagnostic technique allowing quantifying soot emissions in flames and at the exhaust of combustion systems. It can be advantageously coupled with modeling approaches to infer information on the physical properties of combustion-generated particles (including their size), which implies formulating and solving balance equations accounting for laser-excited soot heating and cooling processes. Properly estimating soot diameter by time-resolved LII (TiRe-LII), nevertheless, requires correctly evaluating the thermal accommodation coefficient α T driving the energy transferred by heat conduction between soot aggregates and their surroundings. To analyze such an aspect, an extensive set of LII signals has been acquired in a Diesel spray flame before being simulated using a refined model built upon expressions accounting for soot heating by absorption, annealing, and oxidation as well as cooling by radiation, sublimation, conduction, and thermionic emission. Within this framework, different conduction sub-models have been tested while a corrective factor allowing the particle aggregate properties to be taken into account has also been considered to simulate the so-called shielding effect. Using a fitting procedure coupling design of experiments and a genetic algorithm-based solver, the implemented model has been parameterized so as to obtain simulated data merging on a single curve with experimentally monitored ones. Eventually, values of the thermal accommodation coefficient have been estimated with each tested conduction sub-model while the influence of the aggregate size on the so-inferred α T has been analyzed.

scholarly journals Measurement of Thermal Accommodation Coefficients Using Laser-Induced Incandescence

2007 ◽  
Author(s):  
K. J. Daun ◽  
P. H. Mercier ◽  
G. J. Smallwood ◽  
F. Liu ◽  
Y. Le Page
Keyword(s):  
Deformation Rate ◽  
Surface Deformation ◽  
Accommodation Coefficient ◽  
Polyatomic Gases ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Translational Mode ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient ◽  
Gas Molecules

Laser-induced incandescence (LII) is used to measure the thermal accommodation coefficient between soot sampled from a well-characterized flame and various monatomic and polyatomic gases. These measurements show that the thermal accommodation coefficient between soot and monatomic gases increases with molecular mass due to the decreasing speed of incident gas molecules and corresponding decrease in surface deformation rate, and that energy is transferred preferentially from the surface to the translational mode of the polyatomic gas molecules over internal energy modes.

Thermal Accommodation Coefficients for Time-Resolved Laser-Induced Incandescence Sizing of Metal Nanoparticles in Monotomic Gases

2012 ◽  
Author(s):  
T. A. Sipkens ◽  
K. J. Daun ◽  
J. T. Titantah ◽  
M. Karttunen
Keyword(s):  
Metal Nanoparticles ◽  
Accommodation Coefficient ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Fundamental Relationship ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient ◽  
Molybdenum Nanoparticles ◽  
First Time

There is recent interest in adapting time-resolved laser-induced incandescence (TiRE-LII) to measure aerosolized metal nanoparticles, which requires knowledge of the thermal accommodation coefficient between the gas and the laser-energized particle. This paper presents accommodation coefficients for various metal particles in monatomic gases derived using molecular dynamics (MD). A comparative analysis of different gas/metal systems reveals a fundamental relationship between the thermal accommodation coefficient and the potential well depth. Finally, MD derived accommodation coefficients are used, for the first time, to recover particle sizes from TiRe-LII measurements made on molybdenum nanoparticles in helium and argon atmospheres.

Molecular Dynamics Simulation of Thermal Accommodation Coefficients for Laser-Induced Incandescence Sizing of Nickel Nanoparticles

2011 ◽  
Author(s):  
K. J. Daun ◽  
M. Karttunen ◽  
J. T. Titantah
Keyword(s):  
Molecular Dynamics ◽  
Nickel Nanoparticles ◽  
Accommodation Coefficient ◽  
Dynamics Simulation ◽  
Nickel Surface ◽  
Carbonaceous Particles ◽  
Thermal Accommodation ◽  
Gas Molecule ◽  
Laser Induced Incandescence ◽  
Thermal Accommodation Coefficient

While time-resolved laser-induced incandescence is most often used to characterize the size and concentration of aerosolized carbonaceous particles, it has recently been applied to aerosols containing metal nanoparticles. This calculation requires the thermal accommodation coefficient, however, which is often difficult to determine experimentally. This paper presents a molecular dynamics investigation of the thermal accommodation coefficient between laser-energized nickel nanoparticles immersed in argon, and the underlying the gas-surface scattering physics. The predicted interaction between gas molecules and the laser-energized surface depends strongly on the potential between the gas molecule and a surface atom: a Lennard-Jones 6–12 potential derived using the Lorentz-Berthelot combination rules overestimates the potential well due to a bond-order effect in the nickel, resulting in strong trapping-desorption and near-perfect thermal accommodation. A Morse potential with parameters obtained directly from ab initio free energies predicts a relatively brief interaction between the gas molecule and nickel surface, on the other hand, and a lower thermal accommodation coefficient similar to experimentally-derived values for laser-energized iron nanoparticles in argon reported in the literature.

Quantifying the Thermal Accommodation Coefficient for Iron Surfaces Using Molecular Dynamics Simulations

2015 ◽  
Author(s):  
T. A. Sipkens ◽  
K. J. Daun ◽  
J. T. Titantah ◽  
M. Karttunen
Keyword(s):  
Molecular Dynamics ◽  
Accommodation Coefficient ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Contemporary Science ◽  
Depth Analysis ◽  
Laser Induced Incandescence ◽  
Important Field ◽  
Thermal Accommodation Coefficient ◽  
Dynamics Simulations

With nanotechnology becoming an increasingly important field in contemporary science, there is a growing demand for a better understanding of energy exchange on the nanoscale. Techniques, such as time-resolved laser-induced incandescence, for example, require accurate models of gas-surface interaction to correctly predict nanoparticle characteristics. The present work uses molecular dynamics to define the thermal accommodation coefficient of various gases on iron surfaces. A more in depth analysis examines the scattering distributions from the surfaces and examines how well existing scattering kernels and classical theories can represent these distributions. The molecular dynamics-derived values are also compared to recent experimental time-resolved laser-induced incandescence studies aimed at evaluating the thermal accommodation coefficient across a range of surface-gas combinations.

Sizing of Molybdenum Nanoparticles Using Time-Resolved Laser-Induced Incandescence

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
T. Sipkens ◽  
G. Joshi ◽  
K. J. Daun ◽  
Y. Murakami
Keyword(s):  
Metal Nanoparticles ◽  
Materials Science ◽  
Accommodation Coefficient ◽  
Time Resolved ◽  
Distribution Width ◽  
Size Dependent ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Thermal Accommodation Coefficient ◽  
Molybdenum Nanoparticles

Aerosolized metal nanoparticles have numerous existing and emerging applications in materials science, but their functionality in these roles is strongly size-dependent. Very recently, time-resolved laser-induced incandescence (TiRe-LII) has been investigated as a candidate for sizing aerosolized metal nanoparticles, which requires an accurate model of the heat transfer through which the laser-energized particles re-equilibrate with the bath gas. This paper presents such a model for molybdenum nanoparticles, which is then used to analyze experimental TiRe-LII data made on aerosols of molybdenum nanoparticles in helium, argon, nitrogen, and carbon dioxide. While it is possible to estimate the particle size distribution width, recovering particles sizes requires independent knowledge of the thermal accommodation coefficient, which is presently unknown.

Investigation of Thermal Accommodation Coefficients in Time-Resolved Laser-Induced Incandescence

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
K. J. Daun ◽  
G. J. Smallwood ◽  
F. Liu
Keyword(s):  
Particle Size ◽  
A Priori ◽  
Accommodation Coefficient ◽  
Particle Sizing ◽  
Time Resolved ◽  
Polyatomic Gases ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient

Accurate particle sizing through time-resolved laser-induced incandescence (TR-LII) requires knowledge of the thermal accommodation coefficient, but the underlying physics of this parameter is poorly understood. If the particle size is known a priori, however, TR-LII data can instead be used to infer the thermal accommodation coefficient. Thermal accommodation coefficients measured between soot and different monatomic and polyatomic gases show that the accommodation coefficient increases with molecular mass for monatomic gases and is lower for polyatomic gases. This latter result indicates that surface energy is accommodated preferentially into translational modes over internal modes for these gases.

Thermal Accommodation Coefficients Between Nitrogen and Soot in Laser-Induced Incandescence Experiments

2008 ◽  
Author(s):  
K. J. Daun
Keyword(s):  
Md Simulation ◽  
Accommodation Coefficient ◽  
Monte Carlo Integration ◽  
Detailed Knowledge ◽  
Gas Temperature ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient

Time-resolved laser-induced incandescence demands detailed knowledge of the thermal accommodation coefficient, but to date little is understood about the gas/surface scattering physics underlying this parameter. We present a molecular dynamics (MD) simulation that models nitrogen molecules as rigid rotors and soot as crystalline graphite at 3000 K. A Monte Carlo integration over incident gas molecular speeds and surface atomic vibrational phases yields a simulated thermal accommodation coefficient that matches the experimentally-measured value. The MD simulation is then extended to assess how α changes with gas temperature, and finally to define a Cercingnani-Lampis-Lord scattering kernel.

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