• Korean Journal of Metals and Materials
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• v.49 no.7
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• pp.535-540
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• 2011

The tensile and creep behaviors of Alloy 263, which is a wrought Ni-base superalloy used for gas turbine combustion systems, was studied. Anomalous increase of yield strength and abrupt decrease of elongation with increasing temperature were observed after tensile testing at an intermediate temperature. Elongation of the superalloy decreased as the temperature increased to and above 540$^{\circ}C$, and it reached a minimum value at 760$^{\circ}C$. It was found that creep strain was also very low at the same temperature. Inhomogeneous deformation with intensive slip bands was observed in the specimens tested at low temperature. A thermally-assisted dislocation climb process was regularly conducted at high temperature. Twinning was found to be an important mechanism of both tensile and creep deformations of the superalloy at an intermediate temperature where ductility minimum was observed.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.411-417
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• 1996

Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.163-170
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• 2002

The main objective of this study is to investigate the correlation of chemical structure and cetane number of reformed diesel fuels by ultrasonic irradiation. In order to analyze the effect of the chemical structure and the cetane number of reformed diesel fuels by ultrasonic irradiation, $^1H-NMR$ was used. From the study, following conclusive remarks can be made. 1) BI(=Branch Index), aromatics percentages, and $H_{\alpha}(={\alpha}-methyl$ functional group) of the reformed diesel fuels by ultrasonic irradiation decreased more than those of the conventional diesel fuel. 2) All the cetane numbers which were calculated from carbon type structure and hydrogen type distribution of the reformed diesel fuels increased more than those of the conventional diesel fuel. 3) Using predicated equation of cetane number caculated from carbon type structure is more reasonable than that caculated from hydrogen type distribution 4) BI, aromatics percentages, and $H_{\alpha}$ on both of conventional fuel and reformed diesel fuels by ultrasonic irradiation are inversely proportional to cetane number on these fuels.

• Journal of the Korean Society of Combustion
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• v.15 no.4
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• pp.58-64
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• 2010

Spontaneous ignition tests of five different coals with non-iso-thermal and iso-thermal test method based on the standard test procedure of NF T20-036 were carried. These five coals included the 2 low rank coals and 3 bituminous coals. Test results showed that the ignition temperatures of all coals at the iso-thermal conditions were higher than that of non-isothermal condition, and those of low rank SM and BR coal in both nonisothermal and isothermal conditions were lower than bituminous AN and CN coals. The chemical species of coals such as oxygen and hematite also plays an important role in enhancing the ignition rate that the ignition temperature of SM coal was lowered. The heat accumulation tendency of five coals inside outdoor stack pile was monitored with emphasis on the change in the temperature of the coal depth in stack pile. In case of low rank BR coal, its temperature inside coal stack pile due to the rate of high heat accumulation and oxidation was $59^{\circ}C$ compared to $51^{\circ}C$ for other SW bituminous coal. And the heat accumulation rate inside coal stack piles was increased with increased the Cp value which it was defined as the specific heat of coal at constant pressure, whereas other factors such as thermal diffusivity and conductivity of coal relatively had less effect on heat accumulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.5
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• pp.90-98
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• 2016

A high temperature heater is required to supply high temperature air to the hypersonic propulsion system in order to simulate high velocity flying condition during the ground test. Various high temperature heaters were reviewed, categorized, and analyzed in this paper. Heaters were categorized in 4 groups; in-stream combustion heater, electric arc heater, storage heater, and heat exchange heater. Each group has its own advantages and disadvantages, so the heater should be selected considering its purpose.

• Korean Journal of Acupuncture
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• v.30 no.3
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• pp.178-184
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• 2013

Objectives : The warm needling technique is the method combining the effects of acupuncture needle with those of moxibustion. We need to standardize the characteristics of the warm needling technique, in order to get more systematic and objective results in operation and effects and then get more clinical abilities in these fields. Methods : In this study, using labview system on the warm needling technique, we measured and compared partial temperature changes according to the kind of needle. We studied relations of moxa cones of various sizes with the peak combustion temperature. Results and Conclusions: When we measured the warm needling's partial temperature, temperature measured at 1 and 2 cm below the head, according to the kind of needle, gold needle got the higher result on the peak than SS304 stainless steel needle. In the case of combustion of the moxa cones, cones weighing 0.4 g and 0.8 g, respectively, and the apex ignition method with gold needle showed the higher result than the apex ignition method with stainless steel needle, when we measured the effective stimulus time at 2 cm below the head and the mean temperature during the effective stimulus time. Although more research to standardize the characteristics of the warm needling technique will be needed, we suggest, according to these results, that warm needling of gold needle combined with moxa cone of 0.4 or 0.8 g is effective.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1366-1377
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• 2005

Experimental study was carried out in an atmospheric pressure, laboratory-scale dump combustor showing features of combustion instabilities. Flame structure and heat release rates were obtained from OH emission spectroscopy. Qualitative comparisons were made between line-integrated OH chemiluminescence image and Abel-transformed one. Local Rayleigh index distributions were also examined. Mean temperature, normalized standard deviation and temperature fluctuations were measured by coherent anti-Stokes Raman spectroscopy (CARS). To see the periodic behavior of oscillating flames, phase-resolved measurements were performed with respect to the pressure wave in the combustor. Results on system damping and driving characteristics were provided as a function of equivalence ratio. It also could be observed that phase resolved temperatures have been changed in a well-defined manner, while its difference between maximum and minimum reached up to 280K. These results would be expected to play an important role in better understanding of driving mechanisms and thermo-acoustic interactions.

• Journal of the Korean Chemical Society
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• v.39 no.7
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• pp.513-523
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• 1995

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are the most concerned toxic organic pollutants to human. Because of their extremely high toxicity and uncertain genotoxic potential, their determination in environmental and biological samples is of great interest. Municipal solid waste incinerator facilities have been reported as the major contributors of dioxins and furans to the environment, and their formation from combustion is a universal phenomenon, everywhere. In this study dioxins and furans were analyzed from the bottom ash produced during combustion in an municipal waste incinerator located in Seoul. The EPA method was modified for sample pretreatment: the soxhlet method was used for extraction and clean-up procedures were performed by using silica and basic alumina, excluding active-carbon. The extract was then analyzed by HRGC/HRMS. A general trend of increase in the amounts of 6∼7 chlorine-substituted dioxins and furans was observed. Total dioxins, furans and 2,3,7,8-TCDD were determined as 8.05 ng/g, 4.75 ng/g, and 6.93 pg/g, respectively.

• Journal of Energy Engineering
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• v.18 no.1
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• pp.9-16
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• 2009

The experimental work has been carried out for the study of pyrolysis and char-air reaction of five coals used in Y power station in Korea. For five coals, the characteristics of pyrolyis and char reaction have been investigated with TGA, and their kinetic parameters were obtained and compared each other. The order of pyrolysis rate for five coals were as follows : Peabody, Flame, MIP, Indominco, Elk valley. The behavior of char - air reaction for five coal chars have been successfully described by the grain model. The rate of char-air reaction gave the maximum value for Flame coal char, on the while Elk valley coal char had the minimum value. For the reaction temperature over 1,000K, Flame coal char - air reaction was very fast compared with other coal chars.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.38-46
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• 2008

An object of this study is to understand the correlation between the characteristics of an engine performance and combustion characteristics, applying BD20 fuel reformed by ultrasonic energy irradiation to diesel engines. Before conducting the main experiment, an experiment was performed to determine the optimum injection timimg of reformed BD20 by ultrasonic energy irradiation. To control the duration of the ultrasonic energy irradiation, the capacity of an ultrasonic energy fuel supply system was tested with 550cc and 1100cc chambers. As the result of the analysis of the regular BD20 and reformed BD20 by ultrasonic energy irradiation, the BSFC and the Power of the reformed BD20 was improved 3% and 6%, respectively compared to those of non-irradiated BD20. When the fuel injection timing was delayed by $5^{\circ}$, the engine power was improved by 3%, and the BSFC was improved by 2%. The maximum cylinder pressure of reformed BD20 was improved by a maximum of 6% in comparison to that of regular BD20, and demonstrated a synergistic effect of 3% by delaying the injection timing $5^{\circ}$.