• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.641-646
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• 2016

Soot particles generated by fossil fuel combustion normally have fractal morphology with aggregates consisting of small spherical particles. Thus, Rayleigh or Mie elastic light scattering theory is not feasible for determining the fractal properties of soot aggregates. This paper describes a detailed process for applying Rayleigh-Debye Gans (RDG) scattering theory to effectively extract the morphological properties of any nano-scale particles. The fractal geometry of soot aggregates produced from an isooctane diffusion flame was observed using ex situ transmission electron microscopy (TEM) after thermophoretic sampling. RDG scattering theory was then used to analyze their fractal morphology, and various properties were calculated, such as the diameter of individual soot particles, number density, and volume fraction. The results show indiscernible changes during the soot growth process, but a distinct decreasing trend was observed in the soot oxidation process. The fractal dimension of the soot aggregates was determined to be around 1.82, which is in good agreement with that produced for other types of fuel. Thus, it can be concluded that the value of the fractal dimension is independent of the fuel type.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1583-1594
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• 1992

A numerical calculation on the flame structure and soot particle distribution in a coannular laminar diffusion flame was performed. Flame analysis model utilized basically flame sheet concepts, Shvab-Zel'dovich assumption, and one step overall irreversible reaction. It was also considered the variation of thermodynamics and transport properties, and the stagnation enthalpy was used for solving temperature field. Radiation was taken into account, since it has been found to be important in determining the flame temperature in sooty flames. For soot particle analysis, we adopted the coagulation, suface condensation, and the oxidation model in addition to tesner's two-step formation model. Equations for primary soot particle excluding the agglomeration process were solved. Based on the results, the regions of soot generation, growth, and oxidation in the flame have been observed and radiation strongly influenced flame temperature and soot distribution.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.241-249
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• 1999

Soot particle temperatures in co-flow diffusion flames have been measured using a two-color pyrometry at the pressure of 0.2 MPa(2 atm). The measured soot particle temperatures along with the integrated soot volume fractions are analyzed to understand soot formation characteristics. At 0.2 MPa, the addition of small amount of air into ethylene do not change the soot particle temperature in soot formation regions. This result showed that the increase of soot formation with addition of air is mostly due to the chemical effect of the added air, such as the increased role of C3 chemistry during the early stage of soot inception process. The addition of sufficient air into ethylene, however, changes soot particle temperatures and the understanding of soot formation characteristics becomes complicated. Measured soot particle temperatures also showed that there is no significant temperature effect for the synergistic effect of ethylene/propane mixture on soot formation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1326-1338
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• 1997

Electrical characteristics of soot particles in a LPG diffusion flame were studied for the control of soot particle coagulation. When a DC voltage was applied between two electrodes installed parallel to gas flow, ionic wind effect caused soot deposition on the cathode, implying that most of the soot particles were positively charged. Soot deposit on the cathode linearly increased and was saturated with respect to the strength of the applied voltage. The possibility of applying an AC voltage to enhance the particle coagulation was then investigated and the efficiency of the size control was checked with transmission electron microscope photographs. For the amplitude of 2 kV AC field, primary (spherical) soot particle size decreased from 30 ~ 40 nm to around 20 nm when the frequency of the applied AC voltage was 60 Hz and higher. Collisions between the soot particles in such a selected AC condition could lead to the formation of much bigger agglomerates of roughly 1-5 .mu.m in size.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.8
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• pp.2626-2636
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• 1996

A study of soot deposition and reentrainment was carried out both theoretically and experimentally to understand behavior of soot formed by incomplete combustion in a diesel engine. Theoretically, soot deposition on engine cylinder wall and/or piston head was studied with a stagnation point flow approximation. Soot reentrainment occurred upon exhaust gas blowdown was also studied by assuming a long-normal shear velocity distribution. Experimentally, a LPG$O_2/N_2$ flame impinging on a disk, produced by a concentric tubular burner, was chosen as deposition configuration and a shear flow unit with compressed air was installed for the study of reentrainment. For selected flame configuration, soot deposition measurements were conducted and showed that the dominant deposition mechanism was thermophoresis. Distributions of gas temperature and soot number density were estimated by combining data obtained by a B-type thermocouple with a thermophoretic transport theory. Disk temperature distributions were directly measured using a K-type thermocouple. Soot size and morphology were estimated from a TEM photograph. Ratios of soot deposit to reentrained amount were measured for a wide range of shear flow velocities, which showed that the reentrainment model was reasonable.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.984-993
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• 2000

Characteristics of carbon soot particles generated in diffusion flames were studied. Non-sooting and sooting normal diffusion flames using propane or ethylene as fuel were selected. In the flames, soot volume fraction was measured by a thermocouple, and primary particle diameter and cluster size were analyzed by TEM photographs. The characteristics of soot particles depended on flame(non-sooting or sooting) and fuel(propane or ethylene) type. Unlike the sooting diffusion flames, particle growth and oxidation processes were clearly observed in the non-sooting diffusion flames. In the sooting diffusion flames, soot particle size was slightly changed at the flame tip.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1359-1365
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• 2011

The purpose of this study is to investigate the effect of ethanol content on the emission of nanosized particles from a diesel-ethanol blended fuel engine. The engine combustion and exhaust emission characteristics of a singlecylinder diesel engine were analyzed using an emission analyzer and an SMPS(scanning mobility particle sizer). The analysis revealed that soot emission increased with the ignition delay. When the ignition delay was fixed, an increase in the ethanol content caused a decrease in the soot emission. With an increase in the ethanol blending ratio, the number concentration and mass distribution of nanosized particles generally decreased. However, for 30% ethanol blending, large particles were observed because of the agglomeration of soot particles, and consequently, the particle mass increased.

• Journal of the Korean Society of Combustion
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• v.8 no.1
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• pp.9-16
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• 2003

Carbon soot emission from combustion processes, especially from diesel engines, is a subject of growing concern since soot is known to seriously affect human health. Efforts have been made to oxidize soot particles utilizing Non-Thermal Plasma(NTP) techniques. When oxygen is carried into a plasma device, electrons generated by the plasma dissociate the oxygen, resulting in the formation of oxygen atoms. These highly activated atoms, called O radicals, are known as strong oxidizing agent. This paper presents concentration variations of CO and $CO_2$ at the exit of the plasma device, resulting from the soot oxidation by O radicals, with variations of inlet oxygen concentration, gas temperature, and gas flow rate. Based on the data, Arrehenious rate constants of reactions between C(s)+O and C(s)+O+O were proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.204-210
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• 2016

This paper presents an experimental analysis of the growth and oxidation processes of soot particles generated in an isooctane diffusive laminar flame due to incomplete combustion. The effects of iron-based diagnostics were employed to measure the elastic scattering light from soot particles in a flame at different flame heights, and the differential scattering coefficients were calculated through a calibration process. The growth and oxidation of soot particles in flame was investigated by comparing differential scattering coefficients, and the soot volume fraction was seen to decrease in the soot oxidation process. In the same manner, the differential scattering coefficients were calculated for iron-based fuel-additive seeded flame, and these coefficients were revealed to be smaller than those obtained in the fuel-additive unseeded flame. In addition, transmission through the radial direction of the flame was measured, and transmission in the soot oxidation regime was approximately 5% higher for the seeded flame. The propensity of the data coincided well with the differential scattering coefficients, and it can be concluded that the iron component of the fuel additive plays a crucial role as a catalyst, which eventually enhanced soot particle oxidation.

• Fire Science and Engineering
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• v.33 no.5
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• pp.13-18
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• 2019

In this study, the soot formation characteristics of Jet-A1 liquid fuel droplet flames were investigated by measuring the soot concentration under atmospheric conditions similar to the working environment of the Korea Space Launch Vehicle (KSLV) To obtain the desired atmospheric conditions, the oxygen concentration in the combustion chamber was maintained at 30% and the pressure was varied between 0.1 and 0.06 MPa. The full-field light extinction technique was used to measure the concentration of soot particles generated by applying the identical to 2-mm-diameter Jet-A1 fuel droplets. The soot concentration of the Jet-A1 droplet flames was the highest in the nitrogen-substituted atmosphere and the lowest in the carbon dioxide-substituted atmosphere, despite the pressure. the pressure was decreased the measured soot concentrations reduced as a function of Pⁿ.