scholarly journals Assessing relative contributions of PAHs to soot mass by reversible heterogeneous nucleation and condensation

2021 ◽  
Author(s):  
Nick A. Eaves ◽  
Seth B. Dworkin ◽  
Murray J. Thomson
Keyword(s):  
Soot Particle ◽  
Particle Number ◽  
Particle Number Density ◽  
Condensation Process ◽  
Nucleation Process ◽  
Soot Particles ◽  
Land Vehicles ◽  
Soot Mass ◽  
Size Groups ◽  
Tracking Model

Given the recent EURO 6 regulations, which include limits on particle number density (and hence size) for soot emissions from land vehicles, soot models must be capable of accurately predicting soot particle sizes. Previous modeling work has demonstrated the importance of the relative strengths of nucleation and condensation in predicting soot primary particle size. Due to this importance, a fundamental reversible model for nucleation and condensation, called the reversible PAH clustering (RPC) model, was developed in previous work through the use of statistical mechanics and the results from several recent works. In the present work, the RPC model is enhanced to include multiple nucleation (or dimerization) events from 6 different PAH size groups, resulting in 21 unique dimer pairs. In addition, a soot PAH tracking model is developed to track the amount of each PAH size group within soot particles. The addition of this model resulted in reduced computation times and the ability to investigate PAH-PAH reactions within soot particles. The results of the enhanced RPC model demonstrate that smaller PAHs are most important for the nucleation process, while small and large PAHs are important for the condensation process. These results are shown to be due to the relatively lower reversibility of condensation versus the nucleation process. These findings are discussed in light of recent experimental results in the literature and are shown to be well supported. Keywords: reversibility, PAH nucleation, PAH condensation, laminar diffusion flame, soot model

scholarly journals Assessing relative contributions of PAHs to soot mass by reversible heterogeneous nucleation and condensation

2021 ◽  
Author(s):  
Nick A. Eaves ◽  
Seth B. Dworkin ◽  
Murray J. Thomson
Keyword(s):  
Soot Particle ◽  
Particle Number ◽  
Particle Number Density ◽  
Condensation Process ◽  
Nucleation Process ◽  
Soot Particles ◽  
Land Vehicles ◽  
Soot Mass ◽  
Size Groups ◽  
Tracking Model

Given the recent EURO 6 regulations, which include limits on particle number density (and hence size) for soot emissions from land vehicles, soot models must be capable of accurately predicting soot particle sizes. Previous modeling work has demonstrated the importance of the relative strengths of nucleation and condensation in predicting soot primary particle size. Due to this importance, a fundamental reversible model for nucleation and condensation, called the reversible PAH clustering (RPC) model, was developed in previous work through the use of statistical mechanics and the results from several recent works. In the present work, the RPC model is enhanced to include multiple nucleation (or dimerization) events from 6 different PAH size groups, resulting in 21 unique dimer pairs. In addition, a soot PAH tracking model is developed to track the amount of each PAH size group within soot particles. The addition of this model resulted in reduced computation times and the ability to investigate PAH-PAH reactions within soot particles. The results of the enhanced RPC model demonstrate that smaller PAHs are most important for the nucleation process, while small and large PAHs are important for the condensation process. These results are shown to be due to the relatively lower reversibility of condensation versus the nucleation process. These findings are discussed in light of recent experimental results in the literature and are shown to be well supported. Keywords: reversibility, PAH nucleation, PAH condensation, laminar diffusion flame, soot model

scholarly journals An Exploratory Study of Soot Sample Integrity and Probe Perturbation in a Swirl-Stabilized Combustor

1981 ◽  
Vol 103 (4) ◽  
pp. 759-771 ◽  
Author(s):  
R. L. Hack ◽  
G. S. Samuelsen ◽  
C. C. Poon ◽  
W. D. Bachalo
Keyword(s):  
Soot Particle ◽  
Particle Number ◽  
Particle Morphology ◽  
Fold Increase ◽  
Particle Number Density ◽  
Operating Conditions ◽  
Optical Data ◽  
Reacting Flow ◽  
Optical Sampling ◽  
Sampling Volume

In-flame measurements of soot particulate using conventional extractive and nonintrusive optical probes are compared for a swirl-stabilized combustor. Except for large (∼5μm) particulate present in the extracted samples, the soot particle size compares favorably with optically measured values, and the soot particle morphology reflects that formed in gas turbine combustors. Two, nonflame sources for the large particulate are suggested by the optical data: particles formed or elongated during transport subsequent to extraction, and particles attrited from upstream carbon deposits on a solid surface. The extractive probe produces a change in the local particle number density which varies from little change to a 70-fold suppression in reacting flow and a 200-fold increase in cold seeded flow depending on the location within the combustor of the optical sampling volume, the location of the extractive probe relative to the optical sampling volume, and the combustor operating conditions.

Numerical optimization of a diesel combustion system to reduce soot mass and particle number density

Fuel ◽  
2020 ◽  
Vol 266 ◽  
pp. 117015 ◽  
Author(s):  
Pavan Prakash Duvvuri ◽  
Rajesh Kumar Shrivastava ◽  
Sheshadri Sreedhara
Keyword(s):  
Numerical Optimization ◽  
Particle Number ◽  
Particle Number Density ◽  
Diesel Combustion ◽  
Combustion System ◽  
Number Density ◽  
Soot Mass

Experimentally determined particle number density statistics in an industrial-scale, pulverized-coal-fired boiler

1993 ◽  
Vol 7 (6) ◽  
pp. 842-851 ◽  
Author(s):  
M. Queiroz ◽  
M. P. Bonin ◽  
J. S. Shirolkar ◽  
R. W. Dawson
Keyword(s):  
Particle Number ◽  
Particle Number Density ◽  
Pulverized Coal ◽  
Industrial Scale ◽  
Number Density

The next step in precipitation polymerization of N-isopropylacrylamide: particle number density control by monochain globule surface charge modulation

2016 ◽  
Vol 7 (32) ◽  
pp. 5123-5131 ◽  
Author(s):  
O. L. J. Virtanen ◽  
M. Brugnoni ◽  
M. Kather ◽  
A. Pich ◽  
W. Richtering
Keyword(s):  
Particle Size ◽  
Robust Control ◽  
Surface Charge ◽  
Particle Number ◽  
Particle Number Density ◽  
Precipitation Polymerization ◽  
Number Density ◽  
Density Control ◽  
Charge Modulation

Many applications of poly(N-isopropylacrylamide) microgels necessitate robust control over particle size.

Effect of Particle Number Density on Wave Dispersion in a Two-Dimensional Yukawa System

2017 ◽  
Vol 34 (7) ◽  
pp. 075203
Author(s):  
Rang-Yue Zhang ◽  
Yan-Hong Liu ◽  
Feng Huang ◽  
Zhao-Yang Chen ◽  
Chun-Yan Li
Keyword(s):  
Particle Number ◽  
Wave Dispersion ◽  
Particle Number Density ◽  
Two Dimensional ◽  
Number Density

Numerical Study of Temperature and Incandescence Intensity of Nanosecond Pulsed-Laser Heated Soot Particles at High Pressures

2005 ◽  
Author(s):  
Fengshan Liu ◽  
David R. Snelling ◽  
Gregory J. Smallwood
Keyword(s):  
Soot Particle ◽  
High Pressures ◽  
Particle Diameter ◽  
Aggregate Size ◽  
Primary Particle Diameter ◽  
Time Resolved ◽  
Soot Particles ◽  
Nanosecond Pulsed Laser ◽  
Primary Particles ◽  
Laser Heated

Histories of temperature and incandescence intensity of nanosecond pulsed-laser heated soot particles of polydispersed primary particles and aggregate sizes were calculated using an aggregate-based heat transfer model at pressures from 1 atm up to 50 atm. The local gas temperature, distributions of soot primary particle diameter and aggregate size assumed in the calculations were similar to those found in an atmospheric laminar diffusion flame. Relatively low laser fluences were considered to keep the peak particle temperatures below about 3400 K to ensure negligible soot particle sublimation. The shielding effect on the heat conduction between aggregated soot particles and the surrounding gas was accounted for based on results of direct simulation Monte Carlo calculations. After the laser pulse, the temperature of soot particles with larger primary particles or larger aggregates cools down slower than those with smaller primary particles or smaller aggregates due to smaller surface area-to-volume ratios. The effective temperature of soot particles in the laser probe volume was calculated based on the ratio of thermal radiation intensities of the soot particle ensemble at 400 and 780 nm. Due to the reduced mean free path of molecules with increasing pressure, the heat conduction between soot particles and the surrounding gas shifts from the free-molecular to the transition regime. Consequently, the rate of conduction heat loss from the soot particles increases significantly with pressure. The lifetime of laser-induced incandescence (LII) signal is significantly reduced as the pressure increases. At high pressures, the time resolved soot particle temperature is very sensitive to both the primary particle diameter and the aggregate size distributions, implying the time-resolved LII particle sizing techniques developed at atmospheric pressure lose their effectiveness at high pressures.

Simulation of Multi-Phase Glass-Melt Flows in a Glass Melter

2001 ◽  
Author(s):  
S. L. Chang ◽  
C. Q. Zhou ◽  
B. Golchert ◽  
M. Petrick
Keyword(s):  
Heat Transfer ◽  
Molten Glass ◽  
Transfer Rate ◽  
Liquid Glass ◽  
Particle Number ◽  
Particle Number Density ◽  
Number Density ◽  
Melt Flow ◽  
Glass Melter ◽  
Multi Phase

Abstract A typical glass furnace consists of a combustion space and a melter. The intense heat, generated from the combustion of fuel and air/oxygen in the combustion space, is transferred mainly by radiation to the melter where the melt sand and cullet (scrap glass) are melted, creating molten glass. The melter flow is a complex multi-phase flow including solid batches of sand/cullet and molten glass. Proper modeling of the flow patterns of the solid batch and liquid glass is a key to determining the glass quality and furnace efficiency. A multi-phase CFD code has been developed to simulate glass melter flow. It uses an Eulerian approach for both the solid batch and the liquid glass-melt flows. The mass, momentum, and energy conservation equations of the batch flow are used to solve for local batch particle number density, velocity, and temperature. In a similar manner, the conservation equations of mass, momentum, and energy of the glass-melt flow are used to solve for local liquid molten glass pressure, velocity, and temperature. The solid batch is melted on the top by the heat from the combustion space and from below by heat from the glass-melt flow. The heat transfer rate from the combustion space is calculated from a radiation model calculation while the heat transfer rate from the glass-melt flow to the solid batch is calculated from a model based on local particle number density and glass-melt temperature. Energy and mass are balanced between the batch and the glass-melt. Batch coverage is determined from local particle number density and velocity. A commercial-scale glass melter has been simulated at different operating/design conditions.

Enhanced soot particle ice nucleation ability induced by aggregate compaction

2021 ◽  
Author(s):  
Kunfeng Gao ◽  
Chong-Wen Zhou ◽  
Zamin Kanji
Keyword(s):  
Pore Size ◽  
Soot Particle ◽  
Preliminary Evidence ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Cirrus Cloud ◽  
Dynamic Vapor Sorption ◽  
Soot Particles ◽  
Formation Pathway ◽  
Soot Aggregate

<p>Cirrus clouds have an important influence on the climate since the ice crystal size, concentration and distribution of the clouds determine their radiation properties and effects in the atmosphere. Aviation activities in the high troposphere impact cirrus cloud formation indirectly and significantly, due to aviation contrail evolution and aviation soot particles acting as potential ice nucleating particles (INPs). Soot particles have varying ice nucleation (IN) abilities. In cirrus cloud formation conditions, pore condensation and freezing (PCF) is an important ice formation pathway for soot particles, which requires the particle to have appropriate morphology properties and mesoporous structures. In this study, the morphology and pore size of two kinds of soot were changed by a physical agitation method without any chemical modification. The IN activities of both fresh and agitated soot particles with aggregate sizes, 60, 100, 200 and 400 nm, were tested by the Horizontal Ice Nucleation Chamber (HINC) under mixed phase and cirrus cloud conditions.</p><p>In general, the IN results show clear size dependence for particles with the same agitation degree both tested soot samples at all tested temperatures (<em>T</em>) from 218 K to 243 K with a step of 5 K. In addition, all soot particles do not form ice at <em>T </em>> 235 K (homogeneous nucleation temperature, HNT) but ice nucleation was observed well below homogeneous freezing relative humidity (<em>RH</em>) for <em>T</em> < HNT, suggesting PCF as the dominating mechanism rather than deposition nucleation. Furthermore, there are significant differences between agitated and fresh soot particles for both soot samples studied. We observed that all agitated soot particles reach a higher particle activation fraction (<em>AF</em>) value at the same <em>T</em> and <em>RH</em> condition, compared to the same size fresh soot particles. Moreover, 200 and 400 nm agitated soot particles require much lower ice saturation values to reach <em>AF</em> = 0.001 than their fresh counterparts. The enhanced IN abilities of agitated soot particles are attributed to soot aggregate structure compaction thus increasing mesopore occurrence probability induced by physical agitation. Preliminary evidence obtained from the mass measurements of the single aggregates show that agitated soot particles are more dense than fresh soot particles of the same size. Furthermore, soot aggregate morphology comparisons from HR-TEM (high resolution transmission electron microscopy) images, soot-water interaction ability results from DVS (dynamic vapor sorption) tests and micro-pore size distribution results from argon desorption tests will be used to explain the soot particle IN ability promotion induced by compaction.</p>

scholarly journals Diffusion of Particles, Heat and Magnetic Fields in Compressible Turbulent Media

1991 ◽  
Vol 130 ◽  
pp. 71-74
Author(s):  
A.Z. Dolginov ◽  
N.A. Silant’ev
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Vector Fields ◽  
Particle Number ◽  
Particle Number Density ◽  
Turbulent Diffusivity ◽  
Number Density ◽  
Scalar And Vector Fields ◽  
Kinetic Coefficients ◽  
The Magnetic Field

AbstractA new method for the calculation of kinetic coefficients is presented. This method allows us to obtain the distribution of scalar and vector fields (such as the temperature, the admixture particle number density and the magnetic field) in turbulent cosmic media with any value of S = u0т0/R0. The explicit expression for the “turbulent” diffusivity DT is obtained. In some cases DT becomes negative, implying the clustering of the admixture particles in patches (a local increase of the temperature and magnetic fields). The magnetic α-effect is considered for the case S ~ 1.

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