• 대한기계학회논문집B
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• 제30권10호
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• pp.973-981
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• 2006

Recently there is an increasing interest in particulate matter emission because of new emission regulations, health awareness and environmental problems. It requires to improve particulate measurement techniques as well as to reduce soot emissions from combustion systems. As mentioned above, it is demanded that reduction techniques together with measurement techniques of exhausted particulate matters in combustion systems such as vehicles. However, measurement techniques of particulate matters should be prior to reduction techniques of that because it is able to know an increase and a decrease of exhausted particulate matters when measured particulate matters. Therefore, in this study, we report the measurement of soot primary-particle size using time-resolved laser induced incandescence (TIRE-LII) technique in laminar ethylene diffusion flame. As an optical method, laser induced incandescence is one of well known methods to get information for spatial and temporal soot volume fraction and soot primary particle size. Furthermore, TIRE-LII is able to measure soot primary particle size that is decided to solve the decay ate of signal S $(t_1)$ and S $(t_2)$ at two detection time. In laminar ethylene diffusion flame, visual flame height is 40 mm from burner tip and measurement points are height of 15, 20, 27.5, 30 mm above burner tip along radial direction. As increasing the height of the flame from burne. tip, primary particle size was increased to HAB(Height Above Burner tip)=20mm, and then decreased from HAB=27.5 mm to 30 mm. This results show the growth and oxidation processes for soot particles formed by combustion.

• 대한기계학회논문집B
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• 제31권7호
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• pp.596-603
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• 2007

As increasing interest for soot emission. etc in combustion systems, various studies are being carried out for the reduction and measurement techniques of soot. Especially, laser induced incandescence is the useful measurement technique which has distinguished spatial and temporal resolution for primary particle size, volume fraction and aggregated particle size etc. Time resolved laser induced incandescence is the technique for measuring primary particle size that is decided to solve the signal decay rate which is related to the cooling behavior of heated particle by pulsed laser. The cooling behavior of heated particle is able to represent the heat and mass transfer model which are involved constants of soot property for surround gas temperature on the our previous work. In this study, it is applied to the time-dependence thermodynamic properties for soot temperature instead of constants of soot property for surround gas temperature and compared two different model results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1140-1145
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• 2004

Laser-induced incandescence (LII) is introduced as a valuable tool for the characterization of nanoparticles in flame environments. This technique is based on the heating of the particles by a short laser pulse and the subsequent detection of the thermal radiation. It has been applied successfully for the investigation of soot in different fields of application. The evaluation of the temporal decay of the laser-induced incandescence (LII) signal from soot particles is introduced as a technique to obtain two-dimensional distributions of particle sizes and is applied to a laminar diffusion flame. This novel approach to soot sizing exhibits several theoretical and technical advantages compared with the established combination of elastic scattering and LII, especially as it yields absolute sizes of primary particles without requiring calibration. With this technique a spatially resolved 2-D measurement of soot primary particle sizes is feasible in a combination process form the ratio of emission signals obtained at two delay times after a laser pulse, as the cooling behavior is characteristic of particle size.

• 대한기계학회논문집B
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• 제29권9호
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• pp.1022-1031
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• 2005

Temporal behavior of the laser induced incandescence (LII) signal is often used for soot particle sizing, which is possible because the cooling behavior of a laser heated particle is dependent on the particle size. In present study, LII signals of soot particles are modeled using two non-linear coupled differential equations deduced from the energy- and mass-balance of the process. The objective of this study is to obtain an appropriate calibration curve for determining primary particle size by comparing the gated signal ratio and double-exponential curve fitting methods. Not only the effects of laser fluence and gas temperature on the cooling behavior but also heat transfer mechanisms of heated soot particle have been investigated. The second-order exponential curve fitting showed better agreements with the LII signals than the gated signal ratio method which was based on the lust-order exponential curve fit. And the temporal decay rate of the LII signal and primary particle size showed nearly linear relationship, which was little dependent on the laser fluence. And it also could be reconfirmed that vaporization was dominant process of heat loss during first loons after laser pulse, then heat conduction played most important role while thermal radiation had little influence all the time.

• 대한기계학회논문집B
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• 제21권10호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1152-1157
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• 2004

Temporal behavior of the laser induced incandescence (LII) signal is often used for soot particle sizing, which is possible because the cooling behavior of a laser heated particle is dependent on the particle size. In present study, LII signals of soot particles are modeled using two non-linear coupled differential equations deduced from the energy- and mass-balance of the process. The objective of this study is to see the effects of particle size, laser fluence on soot temperature characteristics and cooling behavior. Together with this, we focus on validating our simulation code by comparing with other previous results. Results of normalized LII signals obtained from various laser fluence conditions showed a good agreement with that of Dalzell and Sarofim's. It could be found that small particles cool faster at a constant laser fluence. And it also could be observed that vaporization is dominant process of heat loss during first 100ns after laser pulse, then heat conduction played most important role while thermal radiation had little influence all the time.

• 대한기계학회논문집B
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• 제24권7호
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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.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.78-85
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• 2007

Recently, diesel vehicles have been increased and their emission standards have been getting strict. The emission of diesel vehicles contains numerous dangerous compounds, especially particulate matters cause a serious environmental pollutant and affect to human health seriously. Thousands of studies have already reported that particulate matters are associated with respiratory and cardiovascular diseases, and death. Due to these, it is necessary to measure the soot concentration and soot particle size in laboratory flames or practical engines to recognize the soot formation, and develop the control strategies for soot emission. In this study, the characteristics of exhausted soot particle size and volume fraction from 2.0L CRDI diesel engine have been investigated as varying engine speed and load. Laser induced incandescence has been used to measure soot concentration. Time-resolved laser induced incandescence has been used to determine soot particle size in the engine. The soot volume fraction is increased as increasing engine load but soot volume fraction is decreased as increasing engine speed. The primary particle size is distributed about $35nm{\sim}60nm$ at each experimental conditions.

• 대한기계학회논문집B
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• 제25권4호
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• pp.496-506
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• 2001

The effect of corona discharge on soot emission was experimentally investigated. Size and number concentrations of soot aggregates were measured and compared for various voltages. Regardless of the polarity of the applied voltage, the flame length decreased and the tip of flame spreaded with increasing voltage. For the experimental conditions selected, the flame was blown off toward the ground electrode by corona ionic wind. When the negative applied voltage was greater than 3kV(for electrode spacing = 3.5cm), soot particles in inception or growth region were affected by the corona discharge, resulting in the reduction of number concentration. The results show that the ionic wind favored soot oxidation and increased flame temperature. Number concentration and primary particle size greatly increased, when the corona electrodes were located the region of soot nucleation or growth(close to burner mouth).

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.261-264
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• 2015

Soot particles of diesel and bunker-A with different sulfur contents were generated by pyrolysis with varying conditions of fuel flow rate and residence time in the ceramic tube at $1300^{\circ}C$. TEM and particle size analyzer were used for analysing the primary and the secondary particle size distributions. The results showed that the sulfur content in fuel influences soot inception while the fuel concentration and residence time affects the growth of incepted soot particles.