• Proceedings of the KSME Conference
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• 2001.06d
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• pp.25-30
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• 2001

The liquid fuel film on the cylinder liner is believed to be a major source of engine-out hydrocarbon emissions in SI engines, especially during cold start and warm-up period. Quantifying the liquid fuel film on the cylinder liner is essential to understand the engine-out hydrocarbon emissions formation in SI engines. In this research, two-dimensional visualization was carried out to quantify liquid fuel film on the quartz liner in an SI engine test rig. The visualization was based on laser-induced fluorescence and total reflection. Using a quartz liner and a special lens, only the liquid fuel on the liner was visualized. The calibration technique was developed to quantify the fluorescence signal with the thickness gage and the calibration device. The fluorescence intensity increases linearly with increase in the fuel film thickness on the quartz liner. Using this technique, the distribution of the fuel film thickness on the cylinder liner was measured quantitatively for different valve lifts and injected fuel mass in the test rig.

• Journal of Hydrogen and New Energy
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• v.13 no.4
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• pp.279-286
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• 2002

In this study, quantitative nitric oxide concentration distributions are investigated in the laminar non-premixed $H_2/N_2$ flames by laser-induced fluorescence (LIF). The measurements are taken in flames for different $N_2$ dilution ratios varying from 20~80%, and fuel flow rate is fixed as Islpm. The NO A-X (0,0) vibrational band around 226 nm is excited using a XeCl excimer-pumped dye laser. We applied same excitation line used in $CH_4$, premixed flame. Overall, NO concentration was rapidly decreased with Na addition and we could not measure the concentration any longer for $N_2$ dilution above 80%.

• 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.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.8-16
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• 1999

In this study, a new type of laser-induced ignition using a conical cavity has been developed to utilize all the available incident laser energy. In the method, it is possibile to ignite combustible methane/air mixtures by directing a laser beam of a constant small diameter into a small conical cavity, without focusing the laser beam. Shadow graphs for the early stage of combustion process show that a hot gas jet is ejected from the cavity, especially with lean mixture. After a very show time, the hot gas jet finishes issuing and the flame behavior is quite similar to flame propagation initiated by a conventional spark ignition. The combustion process using the new method exhibits more rapid pressure increase and a higher maximum pressure rise than that of the center ignition using laser-induced spark, with significant decrease in the combustion time. Also, the new ignition method is numerically modeled to simulate the flame kernel development and subsequent combustion process using the KIVA-IIcode. The calculated results show satisfactory agreement with experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.55-65
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• 2005

Mixing performance between fuel and oxidizer is a significant parameter of combustion efficiency and stability in an air-turbo ramjet combustor. Two types of petal mixer were experimented to research the mixing performance. Mixing performance and fuel distribution images were obtained for petal mixers. Planar laser-induced fluorescence(PLIF) was used to obtain 2-D fuel distribution. The obtained images were processed in order to make use of the image information to a quantitative level. The results of analyzing the fluorescence images could be useful to find better mixing performance between mixers.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.2
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• pp.141-148
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• 2014

In this work, effects of plasma on different hardness of welding steel using laser-induced breakdown spectroscopy were investigated. The ratios of ionic to atomic spectrum peaks were related to its material hardness. The major spectrum peak (Fe) and minor spectrum peak (Mn) were considered as monitoring elements. The stronger repulse plasma was generated, the harder material it was. The ratios of ionic to atomic spectrum peaks increased with respect to the material hardness as well. The correlation of minor spectrum peaks was stronger than that of major spectrum peaks. However, the major spectrum peaks indicated a similar trend, which could be used to estimate the hardness, too. Based on this result, the method could be used as a non-contact remote measurement of material properties.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.2
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• pp.53-59
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• 2019

LIBS plug, a simplified laser-induced breakdown spectroscopy(LIBS) device with the purpose of measuring the fuel distribution inside the combustion chamber, was developed and manufactured. The LIBS plug receives only two wavelengths (H:656.3 nm, O: 777 nm) that are closely related to the equivalence ratio in the overall spectrum. The calibration curve between the signal of the LIBS plug and the equivalence ratio was constructed, and the fuel distribution of gasoline-air and LPG-air mixtures was measured using the LIBS plug.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.1
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• pp.46-53
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• 2008

Ultrasonic C-scan technique is one of very popular techniques being used for detection of flaws in polymer matrix composite(PMC). However, the application of this technique is very limited for evaluation of defects in PMC fabricated by the automated fiber placement process. The purpose of this study is to develop a novel ultrasonic hybrid system based on nondestructive and non-contact ultrasonic techniques for evaluation of delamination in carbon/epoxy and carbon/PPS composite laminates. It was shown that the newly developed ultrasonic hybrid system based on dual air-coupled pitch-catch technique with ultrasonic scattering reflection concept could provide excellent image with higher resolution of delamination in PMC compared with the conventional pitch-catch method. It is expected that this ultrasonic hybrid technique can be applied for on-line inspection of flaws in PMC during the fabrication process.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.4
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• pp.346-353
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• 2012

The Laser-Induced Breakdown Spectroscopy (LIBS) has great advantages as an analytical technique, namely real-time analysis without sample preparation, ideal for mobile chemical sensor for space exploration. The LIBS plasma characteristics are strongly dependent on the surrounding pressure. In this study, seven types of target (C, Ti, Ni, Cu, Sn, Al, Zn) were investigated for their elemental lifetime. The target was located in vacuum chamber which has the pressure range of 760 to $10^{-5}$ torr. As the pressure is decreased, the elemental lifetimes of carbon and titanium declined, while all other targets showed increased lifetimes until reaching 1 torr and declined with continued pressure decrease. The boiling point and electronegativity amongst the physicochemical properties of the samples are used to explain this peculiarity.

• Journal of Hydrogen and New Energy
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• v.13 no.3
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• pp.169-180
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• 2002

Rayleigh scattering and laser induced predissociative fluorescence are used to obtain two-dimensional images of temperature and species concentration in a laminar non-premixed flame of a diluted hydrogen jet. Rayleigh scattering cross-sections are experimentally obtained at 248nm. Planar images of OH and $O_2$ with tunable KrF excimer laser which has a) $0.5cm^{-1}$ linewidth, b) 0.5nm tuning range, c) 150mJ pulse energy, and d) 20ns pulse width are obtained to determine spatial distributions of OH and $O_2$. The technique is based on planar laser induced predissociative fluorescence (PLIPF) in which collisional quenching is almost avoided because of the fast predissociation. Dispersed LIPF spectra of OH and $O_2$ are also measured in a flame in order to confirm the excitation of single vibronic state of OH and $O_2$. OH and $O_2$ are excited on the $P_2$(8) and $Q_1$(11) line of the $A^2{\Sigma}^{+}({\nu}^{'}=3)-X^{2}{\Pi}({\nu}^{''}=o)$ band and R(17) line of the Schumann-Runge band $B^{3}{\Sigma}_{u}{^-}(\nu^{'}=0)-X^{3}{\Sigma}_{g}{^-}({\nu}^{''}=6)$, respectively. Fluorescence spectra of OH and Hot $O_2$ are captured and two-dimensional images of the hydrogen flame field are successfully visualized.