• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.725-732
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• 2000

Laser induced incandescence (LII) method is frequently used to measure soot volume fraction in flames. In this study, experiments were performed to measure soot volume fraction in coaxial diffusion flame using LII method and calibrated with laser scattering/extinction method. The effects of laser intensity (>$1{\times}10^8W/cm^2$), laser wavelength (532nm, 1064nm) and detection wavelength (400nm, 600nm) on the LII signal were investigated. On the range of $4{\times}10^8{\sim}8{\times}10^8W/cm^2$ there were no effects of laser intensity on LII signal. Except these ranges, LII signal was increased with laser intensity. For the long gate width, the LII signals of the higher laser intensity (>${\vartheta}(GW/cm^2)$) cases had better correlation with soot volume fraction which were measured by laser extinction method compared with lower laser intensity cases. The errors of 2-dimensional cases at the calibration height were approximately 50% regardless of laser wavelength.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.95-102
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• 2006

Recently particulate matter(PM) emission regulations are becoming more strict for diesel engines. There is increasing interest for measuring not only concentration but also size of the particles. Laser-induced incandescence (LII) has emerged as a promising technique for measuring particle volume fraction and size. In this study, the Simple Time Resolved-LII method was applied to exhaust of Ethylene diffusion flame and diesel engine exhaust for measuring soot and PM size. The particle size data from LII technique were calibrated using Field Emission Scanning Electron Microscope(FE-SEM) and Transmission Electron Microscope(TEM) photographs. In diesel engine experiments for particle size measurement, results from LII measurement are in a good agreement with those from TEM photograph, and difference between two measurements was less than 16%.

• Proceedings of the KSME Conference
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• 2004.11a
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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.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.108-111
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• 2004

Laser induced incandescence and laser induced fluorescence techniques have been investigated to measure the concentrations of soot and PAH, respectively. The Nd:YAG and dye lasers were used to form a sheet beam, and its wavelength were modulated to obtain a optimized signals of soot and PAH. Results showed that the relative size groups of soot and PAH can be measured by using our laser techniques.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.9 s.240
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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.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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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.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.1
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• pp.55-60
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• 2012

In order to investigate the effect of n-heptane mixing on PAH and soot formation, small amount of n-heptane has been mixed in counterflow ethylene diffusion flame. Laser-induced incandescene and laser-induced fluorescene techniques were employed to measure soot volume fraction and polycyclic aromatic hydrocarbon(PAH) concentration, respectively. Results showed that the mixing of n-heptane in ethylene diffusion flame produces more PAHs and soot than those of pure ethylene flame. However, signals of LIF for 20% n-heptane mixture flame were lower than that of pure ethylene flame. It can be considered that the enhancement of PAH and soot formation by the n-heptane mixing of ethylene can be explained by methyl($CH_3$) radical in the low temperature region. And it can be found that reaction rate of H radical for 10% n-heptane plays a crucial role for benzene formation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.6
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• pp.817-822
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• 2002

Sooting characteristics of counterflow ethylene/propane mixture flames have been experimentally studied to investigate the fuel structure effect on PHM and soot formation. Laser-induced incandescene and laser-induced fluorescene techniques were employed to measure soot volume fraction and polycyclic aromatic hydrocarbon (PAH) concentration, respectively. Importance of $C_{3-}$species on PAH growth as well as the H-abstraction-C$_2$ $H_2$addition (HACA) mechanism has been emphasized, considering that PAH growth rate is greater for with mixed fuel than fer pure fuel flames. It was also confirmed that HACA pathways are the dominant soot growth mechanism. A new PAH growth model including both $C_{2-}$ and $C_{3-}$growth mechanisms is proposed based on the experimental results.

• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.107-110
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• 2003

Characteristics of PAH and soot formation in coflow diffusion flames of methane, methane, propane, and ethylene have been experimentally studied to investigate the temperature and fuel structure effect on soot formation. PAH and soot images were acquired by applying PAH LIF and LII techniques, respectively and temperature was measured using R-type thermocouple. Direct photographs of soot particles have also been taken by transmission electron microscopy (TEM) through a thermophoretic sampling. Comparison of PAH and soot formation between the aliphatic fuels has shown the importance of fuel structure effect in diffusion flames.