Effects of hydrodynamics and mixing on soot formation and growth in laminar coflow diffusion flames at elevated pressures

Abdelgadir, Ahmed; Rakha, Ihsan Allah; Steinmetz, Scott A.; Attili, Antonio; Bisetti, Fabrizio; Roberts, William L.

doi:10.1016/j.combustflame.2017.01.003

Cited by 33 publications

(9 citation statements)

References 53 publications

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“…Therefore, the differences in soot concentrations are only caused by variations in soot growth rates because the residence time and the flow rates of enthalpy and carbon mass remain constant across flames. 43 As described in our previous work, 3 particle number density close to the flame centerline is larger than that away from the centerline at the same height. Aggregate particles usually consist of a certain amount of primary particles.…”

Section: Effects Of Pressure Onsupporting

confidence: 51%

“…Liu et al pointed out that the axial velocity along the flame centerline remains essentially unchanged with the increase of pressure. Therefore, the differences in soot concentrations are only caused by variations in soot growth rates because the residence time and the flow rates of enthalpy and carbon mass remain constant across flames …”

Section: Results and Discussionmentioning

confidence: 99%

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Numerical Investigation of Soot Formation in a Methane Diffusion Flame Doped with n-Heptane at Elevated Pressure

et al. 2019

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Combustion characteristics are significantly affected by ambient pressure, which is usually much higher than the atmosphere in the engine cylinder. In this work, the effects of pressure on the flame structure and soot behavior in a methane diffusion flame doped with n-heptane were numerically investigated by a detailed chemical mechanism and a sectional soot model. The results show that the high-temperature region moves toward the wings of flame and the radius of the flame decreases as ambient pressure increases. Soot volume fraction increases significantly with its peak value scaled with p 2.25 for the pure methane flame and p 1.60 for the methane flame doped with n-heptane. In addition, the height at which the initial soot forms moves upstream, while the height at which soot particles are completely oxidized moves downstream, resulting in a larger sooting region. The increase of soot concentration is mainly due to the increase of the mixture density as pressure changes, and therefore, the collision frequency between gas species and particles increases, which in turn accelerates the inception rate and surface growth rate of particles. Primary number density also increases because of the increase in the inception rate. The aggregate characteristics, which are evaluated by the number of primary particles per aggregate, increase because of the increase in the particle number density that leads to an acceleration in particle coagulation. Soot mass addition, dominated by hydrogen-abstraction–carbon-addition reactions, increases because of the increase of absolute concentrations of C2H2 and H radicals, while soot mass consumption, dominated by OH oxidation, increases with a lower rate than that of soot addition because of the increase of the collision frequency and efficiency between the OH radicals and particles.

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Section: Effects Of Pressure Onsupporting

confidence: 51%

Section: Results and Discussionmentioning

confidence: 99%

Numerical Investigation of Soot Formation in a Methane Diffusion Flame Doped with n-Heptane at Elevated Pressure

et al. 2019

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“…The importance of hydrodynamics and scalar dissipation rate (mixing) in soot formation and growth at elevated pressures for coflow laminar diffusion flames is emphasized in. 49 And the high intermittency of soot in turbulent flames has been noted in both experimental (e.g., 50 ) and DNS (e.g., 51 ) studies of soot processes in turbulent flames. High soot intermittency is realized with the present PDF model through the combination of the EMST mixing model for gas-phase species and no mixing for soot.…”

Section: Reacting Cases: Sootmentioning

confidence: 96%

Soot and spectral radiation modeling for high-pressure turbulent spray flames

Fernandez

Paul

Sircar

et al. 2018

Combustion and Flame

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“…To understand the pressure effect on soot formation and evolution, many numerical studies on pressurized laminar flames have been conducted to show that the change of polycyclic aromatic hydrocarbons (PAH) concentration, scalar dissipation rate, and the different chemical pathways are the major issues for the increasing soot at higher pressures [7,8]. However, there lack studies on the soot formation and evolution in pressurized turbulent flames due to two reasons.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Study on Soot Formation and Evolution in Pressurized Turbulent Sooting Flames

Zhou

Vaage

Yang

et al. 2021

AIAA Scitech 2021 Forum

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Understandings on soot formation and evolution in pressurized flames are of significant interest due to the increasing operating pressures in different combustors and the accompanying increased soot emissions. In this study, a series of pressurized turbulent sooting flames at 1 bar, 3 bar and 5 bar, are simulated to study the pressure effect on the soot formation and evolution. The inflow conditions are chosen such that the Reynolds number at different pressures keeps constant. Via a Radiation Flamelet Progress Variable (RFPV) approach with a conditional soot sub-filter Probability Density Function (PDF) to consider the turbulence-chemistry-soot interaction, quantitatively good agreements (e.g., maximum discrepancy within one order of magnitude) are achieved for soot volume fraction predictions compared with the experimental data at different pressures. Soot volume fraction source terms are then discussed to show the pressure effect on nucleaion, condensation, surface growth and oxidation at different axial positions in these flames.

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Effects of hydrodynamics and mixing on soot formation and growth in laminar coflow diffusion flames at elevated pressures

Cited by 33 publications

References 53 publications

Numerical Investigation of Soot Formation in a Methane Diffusion Flame Doped with n-Heptane at Elevated Pressure

Numerical Investigation of Soot Formation in a Methane Diffusion Flame Doped with n-Heptane at Elevated Pressure

Soot and spectral radiation modeling for high-pressure turbulent spray flames

A Numerical Study on Soot Formation and Evolution in Pressurized Turbulent Sooting Flames

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