• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.400-403
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• 2003

Etching characteristics of (Pb,Sr)$TiO_3$(PST) thin films were investigated using inductively coupled chlorine based plasma system as functions of gas mixing ratio, RF power and DC bias voltage. It was found that increasing of Ar content in gas mixture lead to sufficient increasing of etch rate and selectivity of PST to Pt. The maximum etch rate of PST film is $562\;{\AA}$/min and the selectivity of PST film to Pt is 0.8 at $Cl_2/(Cl_2+Ar)$ of 20 %. It was proposed that sputter etching is dominant etching mechanism while the contribution of chemical reaction is relatively low due to low volatility of etching products.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.19-25
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• 2006

Energy efficient and low pollution combustion systems the use gaseous fuels have been in great demand in recent year. Radiant burner in many different forms are emerging as very desirable combustion systems for same reason. Porous radiant burners are used in drying, preheating and curing, and in other type of materials processing and manufacturing processes. However, little knowledge is available about the operating characteristics and the structure of flames in porous ceramic fiber radiant burners. The objective of the present work is to investigate the global performance characteristics of the ceramic fiber burner. A detailed study which includes the spectral intensity, gas temperature, radiation efficiency and global pollutant emissions. Another objective is to study the flame structure of the ceramic fiber burner by measuring the local gas temperature. The results indicate that ceramic fiber burner do offer a 19-44% gain in radiant efficiency. The ceramic fiber burner exhibit significant spectral intensity peaks in the band at $2.0-2.5{\mu}m$. The local temperature distribution inside the mat and near the mat surface as a function of the equivalence ratio can be reasonably interpreted by the relation of the heat balance in the mat and movement of the reaction zone. Nox emission from ceramic fiber burner is less than 25ppm throughout the operating range.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.265-270
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• 1989

The present study considers the thermal structure variation in a porous medium caused by changing the most important radiative property of porous medium, absorption coefficient, as well as altering the physical dimension of porous medium and the equivalence ratio of premixed gas mixture. The radiation model was introduced as an unsteady differential form using the two-flux gray radiation model. The role of the conductive heat transfer through both gas phase and porous medium was found to be almost insignificant compared with that of the radiative heat transfer. The reaction zone shifted upstream and the flame thickness decreased as either the geometrical length of porous medium increased or the absorption coefficient decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1028-1039
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• 1996

This study was focused on the examination of the flame structure and the combustion characteristics of diffusion flame which was formed the turbulent shear flow of a double coaxial air jet system. The shear flow was formed by the difference velocity of surrounding air jet(U$\_$s/) and center air jet (U$\_$c/). So experimental condition was divided S-type flame (.lambda. > 1) and C-type flame (.lambda. < 1) by velocity ratio .lambda. (=U$\_$s//U$\_$c/). For examination of the flame structure and the combustion characteristics in diffusion flame, coherent structure was observed in flame by schlieren photograph method. We measured fluctuating temperature and ion current simultaneously and accomplished the statistical analysis of its. According to schlieren photograph, the flame was stabilized in the rim of the direction of lower velocity air jet, coherent eddy was produced and developed by higher velocity air jet. The statistical data of fluctuating temperature and ion current was indicated that reaction was dominated by higher velocity air jet. The mixing state of burnt gas and non-burnt gas was distributed the wide area at Z = 100 mm of C-type flame.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.466-471
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• 2004

In gas turbines, excess air for combustion is available and therefore lean premixed combustion is the most promising approach to the significant reduction of thermal NOx emissions. At lean conditions, however, flame stability is inherently worse and hence combustion tends to be incomplete. Efforts have been devoted toward extending the operating range of complete combustion at leaner conditions. One of them is the lean-lean two-stage combustion where lean to ultra-lean secondary mixtures are mixed with the hot burned gas from the primary stage. Conventional flame combustion or flameless reaction are initiated depending on the conditions of the secondary zone. In the first part of the present study, the effects of fuel injection on the emissions and flame stability were investigated for a single tubular flame, In the second part, the emissions and flame stability were studied for a two-stage combustor with secondary mixture injected through the tangential slots on a cylindrical combustor wall. The effects of the ratio of air flow rates to the primary and secondary zones on the emissions and combustion characteristics were investigate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.182-185
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• 2003

Etching characteristics of (PB,Sr)$TiO_3$(PST) thin films Were investigated using inductively coupled chlorine based plasma system as functions of gas mixing ratio, RF power and DC bias voltage. It was found that increasing of Ar content in gas mixture' lead to sufficient increasing of etch rate and selectivity of PST to Pt. The maximum etch rate of PST film is 562 ${\AA}$/min and the selectivity of PST film to Pt is 0.8 at $Cl_2/(Cl_2+Ar)$ of 20 %. It was proposed that sputter etching is dominant etching mechanism while the contribution of chemical reaction is relatively low due to low volatility of etching products.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.11
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• pp.80-85
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• 2021

The gasification of coffee leaves, which are a type of biomass waste, was conducted on a pilot of a downdraft fixed gasification system to investigate the gasification characteristics. The experiment was performed using a coffee leaf pellet size and a batch-type gasification system consisting of a gasifier, cooling cyclone, scrubber, and bag filter. It was found that the air-to-fuel ratio was 2.32 Nm³/kg·h and the reaction temperature was 700 ℃-900 ℃. However, the air flow rate changed to 0.45 Nm³/min, which was lower than the initial starting value depending on the temperature change during the gasification process. It was concluded that coffee leaves can be converted from biomass waste into useful synthetic gas as an alternative energy source.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.3
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• pp.149-155
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• 2021

Most of the reformer experiments have been conducted only in high-temperature operation conditions above 700℃. However, to design high efficiency solid oxide fuel cell, it is necessary to test actual reaction performance in mid-temperature (550℃) operation areas. In order to study the operation characteristics and performance of commercial reforming catalysts, a reforming performance experiment was conducted on mid-temperature. The catalysts used in this study are Ni-based FCR-4 and Ru-based RuA, RuAL. Experiments were conducted with a Steam-to-carbon ratio of 2.0 to 3.0 under gas hourly space velocity (GHSV) 2,000 to 5,000 hr-1. As a result, RuA and RuAL catalysts showed similar gas composition to the equilibrium regardless of the reforming temperature. However, the FCR-4 catalyst showed a lower hydrogen yield compared to the equilibrium under high GHSV conditions.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.557-562
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• 1999

The reaction properties of Pd. Pd-Ce and Pd-La catalysts supported on ${\gamma}-Al_2O_3$ were investigated in the oxidation reaction of methane($CH_4$) exhausted from the compressed natural gas vehicle in a U-tube flow reactor with gas hourly space velocity of $72,000h^{-1}$. The catalysts were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), BET surface area and hydrogen chemisorption. Pd catalyst prepared by $Pd(NO_3)_2$ as a palladium precursor and calcined at $600^{\circ}C$ showed the highest activity for a methane oxidation. Catalytic activity of calcined $Pd/{\gamma}-Al_2O_3$ in which most of palladium was converted into palladium oxide species was higher than that of reduced $Pd/{\gamma}-Al_2O_3$ in which most of palladium existed in palladium metal by XRD. As increasing the number of reaction cycles in the wide range of redox, the catalytic activity of $Pd/{\gamma}-Al_2O_3$ was decreased and the highly active window became narrower. Lanthanum oxide promoted Pd catalyst, $Pd/La/{\gamma}-Al_2O_3$ showed enhanced thermal stability compared with $Pd/{\gamma}-Al_2O_3$ even after aging at $1000^{\circ}C$, which was ascribed to the role of La as a promoter to suppress the sintering of palladium metal and ${\gamma}-Al_2O_3$ support. Almost all of methane was removed by the reaction with NO at the redox ratio of 1.2 in case of oxygen excluded steam, but that activity was significantly decreased in the steam containing oxygen.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.629-633
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• 1998

The synthesis of 1,1-difluoroethane from acetylene as a function of HF/acetylene ratio, contact time and reaction temperature was studied on a fluorinated ${\gamma}-Al_2O_3$. The fluorination of ${\gamma}-Al_2O_3$ was treated with pure HF gas at high temperature. The crystallinity, the porosity, and the acid properties of the prepared samples were examined using XRD, the nitrogen adsorption, pyridine-IR and ammonia-TPD respectively. The activity was enhanced by further fluorination of alumina. The fraction of 1,1-difluoroethane was obtained above 90% at reaction temperature of about $200^{\circ}C$. The ratio of 1,1-difluoroethane to vinylfluoride over fluorinated ${\gamma}-Al_2O_3$ catalyst was increased with the mole ratio of HF/acetylene and contact time, and was found to be the highest ratio at reaction temperature of $200^{\circ}C$.