• Asian Journal of Atmospheric Environment
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• v.8 no.4
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• pp.175-183
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• 2014

To visually and chemically verify the rainout of soot particles, a model experiment was carried out with the cylindrical chamber (0.2 m (D) and 4 m (H)) installing a cloud drop generator, a hydrotherometer, a particle counter, a drop collector, a diffusing drier, and an artificial soot particle distributer. The processes of the model experiment were as follows; generating artificial cloud droplets (major drop size : $12-14{\mu}m$) until supersaturation reach at 0.52%-nebulizing of soot particles (JIS Z 8901) with an average size of $0.5{\mu}m$-counting cloud condensation nuclei (CCN) particles and droplets by OPC and the fixation method (Ma et al., 2011; Carter and Hasegawa, 1975), respectively - collecting of individual cloud drops - observation of individual cloud drops by SEM - chemical identifying of residual particle in each individual droplet by SEM-EDX. After 10 minutes of the completion of soot particle inject, the number concentrations of PM of all sizes (> $0.3{\mu}m$) dramatically decreased. The time required to return to the initial conditions, i.e., the time needed to CCN activation for the fed soot particles was about 40 minutes for the PM sized from $0.3-2.0{\mu}m$. The EDX spectra of residual particles left at the center of individual droplet after evaporation suggest that the soot particles seeded into our experimental chamber obviously acted as CCN. The coexistence of soot and mineral particle in single droplet was probably due to the coalescence of droplets (i.e., two droplets embodying different particles (in here, soot and background mineral particles) were coalesced) or the particle capture by a droplet in our CCN chamber.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.209-212
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• 2012

This study was performed to analyze coal flames and measure tar and soot yields and structures of chars for two coals depending on the volatile content by the LFR(Laminar Flow Reactor) which can be applied to a variety of coal researches. The results show that volatile contents and oxygen concentration have significant influence on length and width of the soot cloud and it also indicate that the length and width of the cloud in condition of combustion decrease than those of pyrolysis atmosphere. Until the sampling height reach at 50 mm, the tar and soot yields of Berau (Sub-bituminous) coal contained relatively lots of volatile matters are less than those of Glencore A.P. (Bituminous) coal. On the other hand, tar and soot yields of Berau coal are higher than those of Glencore A.P. coal by reacted residual volatile matter. In addition, the images of samples obtained from the particle separation system of the sampling probe support for above results with the yields, and the pore development of char surface by devolatilization.

• International Journal of Automotive Technology
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• v.3 no.1
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• pp.17-26
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• 2002

The authors have reported significant reductions in particulate emissions of diesel engines by generating strong turbulence during the combustion process. This study aims to identify optimum conditions of turbulent mixing for effective soot reduction during combustion. The experiments were conducted with a constant volume combustion vessel equipped with abet-generating cell, in which a small amount of fuel is injected during the combustion of the main spray. The jet of burned gas from the cell impinges the main flame, causing changes In the mixing of fuel and air. Observation was made for a variety combinations of distances between spray nozzle and Jet orifice at different directions of impingement. It Is shown that compared with the case without Jet flame soot decreases when the jet impinges. When the jet is very close to the flame, it penetrates the soot cloud and causes little mixing. There were no apparent differences in the combustion duration when the direction of impingement was varied, although the mechanisms of soot reduction seemed different. An analysis of local turbulent flews with PIV (Particle image Velocimetry) showed the relationship between the scale of the turbulence and the size of the soot cloud.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.42-48
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• 2014

Soot and tar which were derived from combustion or pyrolysis processes in Puverized Coal(PC) furnace or boiler have been significantly dealing in a radiative heat transfer and an additional source of NOx. Furthermore, the increasing for the use of a coal with low caloric value gives rise to a lot of tar-soot yield and LOI in a recycled ash for using cement materials. So, the ash with higher tar-soot yield and LOI can not recycle due to decreased strength of concrete. In this study, tar-soot yields and flame structures were investigated using the LFR for a blending combustion with bituminous coal and sub-bituminous coal. Also, The investigation were conducted as each single coals and blending ratio. The coals are used in a doestic power plant. In the experimental results, sub-bituminous coal with high volatile contents shows longer soot cloud length than bituminous coal, but overall flame length was shorter than bituminous coal. Tar-soot yields of sub-bituminous coal is lower than those of bituminous coal. Combustion characteristics are different between single coal and blended coal. Therefore, finding an optimal coal blending ratio according to coal rank effects on tar-soot yields.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.66-70
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• 2002

The transient soot distributions within the region bounded by the droplet surface and the flame were measured using a full-filed light extinction technique and subsequent tomographic inversion using Abel transforms. The soot volume fraction results for n-heptane droplets represent the first quantitative assessment of the degree of sooting for isolated droplets burning under microgravity condition. The absence of buoyancy(which produces longer residence times) and the effects of thermophoresis produce a situation in which a significant concentration of soot is produced and accumulated into a soot-cloud. Results indicate that indeed the soot concentration within the microgravity droplet flames(with maximum soot volume fractions as high as ~60ppm) are significantly higher than corresponding values that are reports for normal-gravity flames. This increase in likely due to longer residence times and thermophoretic effects that manifested under microgravity conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1222-1233
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• 1990

The formation and oxidation processes of soot particles in a diesel flame were investigated with a rapid compression machine. A cloud of soot particles was successfully visualized by means of the instantaneous laser shadow photographs technique and the equivalence ratio of the soot formation zone was estimated from a measured fuel concentration distribution in a nonevaporating spray. The temporal and spatial variation of soot concentration in the flame was also correlated with the rate of heat release. Soot particles appears first in a region near the flame tip when diffusion combustion period starts, and its concentration is a maximum at about the end of injection, then decreases due to oxidation. The reason for soot being formed in a fuel lean region near the flame tip is the evaporated fuel requires time to be pyrolized as it travels through the burning fuel rich zone towards the flame tip.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1034-1042
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• 2012

This study was performed by using an LFR (laminar flow reactor), which can be used to carry out different types of research on coal. In this study, an LFR was used to analyze coal flames, tar and soot yields, and structures of chars for two coals depending on their volatile content. The results show that the volatile content and oxygen concentration have a significant effect on the length and width of the soot cloud and that the length and width of the cloud under combustion conditions are less than those under a pyrolysis atmosphere. At sampling heights until 50 mm, the tar and soot yields of Berau (sub-bituminous) coal, which contains a large amount of volatile matter, are less than those of Glencore A.P. (bituminous) coal because tar is oxidized by the intrinsic oxygen component of coal and by radicals such as OH-. On the other hand, at sampling heights above 50 mm, the tar and soot yields of Berau coal are higher than those of Glencore A.P. coal by reacted residual volatile matter, tar and light gas in char and flame. With above results, it is confirmed that the volatile matter content and the intrinsic oxygen component in a coal are significant parameters for length and width of the soot cloud and yields of the soot. In addition, the B.E.T. results and the images of samples (SEM) obtained from the particle separation system of the sampling probe support the above results pertaining to the yields; the results also confirm the pore development on the char surface caused by devolatilization.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.51-54
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• 2003

We analyzed radiative properties of aerosols, $CO^{2}$ and clouds using Optical Properties of Aerosols and Clouds(OPAC) and the Column Radiation Model (CRM). From OPAC, if the soot component is disregarded, dust-like components depict the highest extinction values in the solar spectral range and the lowest. single scattering albedoes, which are attributable to the presence of large particles. In the dust aerosol, the high absorptivity in the infrared may induce a warming of the lower atmospheric layer in the nighttime. The radiative properties of aerosols, clouds and double $CO^{2}$ using the CRM model at Seoul (37N, 127.4 E) on 3 April 2003 were calculated. The solar zenith angle is 65˚ and the surface albedo is 0.1836 during the clear day. The aerosol optical depth change 0.14 to 1.7, which is derived during Asian dust days in Korea. At this time, abedo by aerosols is considered as 0.3. In cloudy condition, the short wave cloud forcing on both the TOA and the surface is -193.89 $Wm^{-2}$ and -195.03 $Wm^{-2}$, respectively, and the long wave cloud forcing is 19.58 $Wm^{-2}$ and 62.08 $Wm^{-2}$, respectively. As a result, the net radiative cloud forcing is -174.31 $Wm^{-2}$ and -132.95 $Wm^{-2}$, respectively. We calculate also radiative heating rates by double $CO^{2}$ during the clear day. The $CO^{2}$ volumn mixing ratio is 3.55E-4.