An aerosol model to predict size and structure of soot particles

Park, S. H.; Rogak, Steven N.; Bushe, W. Kendal; Wen, John Z.; Thomson, Murray J.

doi:10.1080/13647830500195005

Cited by 67 publications

(51 citation statements)

References 25 publications

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“…As compared with the earlier but widely used ABF PAH mechanism [10], the predictions of pyrene concentrations showed improved agreement with the experimental data. In most recent developments of detailed soot models [23][24][25][26], the primary particle is formed through the dimerization of pyrene (C 16 H 10 or A4). As an attempt to enhance the soot nucleation rates, some of these studies made an unrealistic assumption that every collision leads to a successful creation of a soot nucleus.…”

Section: Introductionmentioning

confidence: 99%

A computational study of ethylene–air sooting flames: Effects of large polycyclic aromatic hydrocarbons

Selvaraj

Arias

Lee

et al. 2016

Combustion and Flame

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An updated reduced gas-phase kinetic mechanism was developed and integrated with aerosol models to predict soot formation characteristics in ethylene nonpremixed and premixed flames. A primary objective is to investigate the sensitivity of the soot formation to various chemical pathways for large polycyclic aromatic hydrocarbons (PAH). The gas-phase chemical mechanism adopted the KAUST-Aramco PAH Mech 1.0, which utilized the AramcoMech 1.3 for gas-phase reactions validated for up to C2 fuels. In addition, PAH species up to coronene (C 24 H 12 or A7) were included to describe the detailed formation pathways of soot precursors. In this study, the detailed chemical mechanism was reduced from 397 to 99 species using directed relation graph with expert knowledge (DRG-X) and sensitivity analysis. The method of moments with interpolative closure (MOMIC) was employed for the soot aerosol model. Counterflow nonpremixed flames at low strain rate sooting conditions were considered, for which the sensitivity of soot formation characteristics to different nucleation pathways were investigated. Premixed flame experiment data at different equivalence ratios were also used for validation. The findings show that higher PAH concentrations result in a higher soot nucleation rate, and that the total soot volume and average size of the particles are predicted in good agreement with experimental results. Subsequently, the effects of different pathways, with respect to pyrene-or coronene-based nucleation models, on the net soot formation rate were analyzed. It was found that the nucleation processes (i.e., soot inception) are sensitive to the choice of PAH precursors, and consideration of higher PAH species beyond pyrene is critical for accurate prediction of the overall soot formation.

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Section: Introductionmentioning

confidence: 99%

A computational study of ethylene–air sooting flames: Effects of large polycyclic aromatic hydrocarbons

Selvaraj

Arias

Lee

et al. 2016

Combustion and Flame

View full text Add to dashboard Cite

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“…For all operating conditions, the standard deviations of the primary particle size distributions are approximately 35% of the average primary particle diameter. Primary particle diameter is affected by different parameters including local EQR, temperature, and residence time of the particles in the combustion region (Glassman 1989;Park et al 2005). The reduction observed in primary particle diameter when load increased from low to high levels may attribute to faster carbonization and higher oxidation rates due to higher temperature.…”

Section: Particulate Matter From a Cidi Natural-gas Enginementioning

confidence: 99%

Characterization of Particulate Matter Morphology and Volatility from a Compression-Ignition Natural-Gas Direct-Injection Engine

Graves

Olfert

Patychuk³

et al. 2015

Aerosol Science and Technology

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The particulate matter (PM) emitted from a single-cylinder compression-ignition, natural-gas engine fitted with a HighPressure Direct-Injection (HPDI) system distinctly different from a duel fuel engine was investigated, and characterized by size distribution, morphology, mass-mobility exponent, effective density, volatility, mixing state, and primary particle size using transmission electron microscopy (TEM), and tandem measurements from differential mobility analyzers (DMA) and a centrifugal particle mass analyzer (CPMA). Six engine conditions were selected with varying load, speed, exhaust gas recirculation (EGR) fraction, and fuel delivery strategy. An increase in engine load increased both the number concentration and the geometric mean diameter of the particulate. The fraction of the number of purely volatile particles to total number of particles (number volatile fraction, NVF) was found to decrease as load increased, although at the lower speed, partially premixed mode, the lowest NVF. All size distributions were also found to be unimodal. The size-segregated ratio of the mass of internally mixed volatile material to total particle mass (mass volatile fraction, MVF) decreased with load and with particle mobility-equivalent diameter. A roughly constant amount of volatile material is likely produced at each engine mode, and the decrease in MVF is due to the increase in PM number with load. Effective density and massmobility exponent of the non-volatile soot at the different engine loads were the same or slightly higher than soot from traditional diesel engines. Denuded effective density trends were observed to collapse to approximately the same line, although engine modes with higher MVFs had slightly higher effective densities suggesting that the soot structures have collapsed into more dense shapes-a suspicion that is confirmed with TEM images. TEM results also indicated that primary particle size first decreases from low to medium load, then increases from medium to high load. An increase in EGR was also seen to increase primary particle size. Coefficients were determined for a relation that gives primary particle diameter as a function of projected area equivalent diameter. A decrease in load or speed results in a stronger correlation.

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“…In most engineered combustion systems, soot particles are typically formed in turbulent conditions with large variation in local stoichiometry (M€ uhlbauer et al 2013) and time spent in conditions affecting soot formation, growth, and oxidation (Park and Rogak 2003;Park et al 2005). Dastanpour and Rogak (2014) have recently shown that the average diameter of the primary particles changes with the aggregate size in many combustion sources.…”

Section: Introductionmentioning

confidence: 99%

Improved sizing of soot primary particles using mass-mobility measurements

Dastanpour

Rogak

Graves

et al. 2015

Aerosol Science and Technology

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The properties and impacts of aggregated aerosol particles (i.e., soot, metal oxide fumes) depend on their morphology, as characterized by fractal dimension, prefactor, and primary particle diameter. The morphology may be measured directly by time-consuming ex situ microscopy or rapid but indirect in situ methods. Previously, it was found that particle mass and mobility measurements could be used for the estimation of the primary particle diameter of zirconia aggregates, using plausible assumptions related to the fractal structure (specifically, prefactor k a and exponent D a ). Since the formation and growth of zirconia aggregates are different from carbon soot, here we compare primary particle diameters measured directly from transmission electron microscopy analysis of soot particles with the diameters estimated from mass-mobility measurements. Performing extensive measurements on soot emissions from two reciprocating engines over a range of operating conditions, we found that there are no universal values of k a and D a that can be used for all conditions. However, new optimized values of k a and D a are estimated here for soot particles. The variation of the primary particle diameter with particle size is also taken into consideration and is shown to be essential to obtain physically realistic results. Using optimized values of k a and D a , the average primary particle sizing error is reduced for all soot types. This suggests that with some calibration, in situ sizing of the primary particle diameter, using mass and mobility measurements, can provide useful accuracy.

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An aerosol model to predict size and structure of soot particles

Cited by 67 publications

References 25 publications

A computational study of ethylene–air sooting flames: Effects of large polycyclic aromatic hydrocarbons

A computational study of ethylene–air sooting flames: Effects of large polycyclic aromatic hydrocarbons

Characterization of Particulate Matter Morphology and Volatility from a Compression-Ignition Natural-Gas Direct-Injection Engine

Improved sizing of soot primary particles using mass-mobility measurements

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