• Clean Technology
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• v.24 no.1
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• pp.63-69
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• 2018

The reduction reaction characteristics and physicochemical properties were studied for the selection of oxygen carrier, which is the core of the chemical looping combustion (CLC) technology. Fuel conversion and $CO_2$ selectivity of oxygen carrier according to the concentration of reducing gas and the reduction temperature using three kinds of oxygen carrier (SDN70, N018-R2, N016-R4) were measured and compared. In addition, Attrition Index (AI) and BET surface area were measured to analyze the attrition resistance and the surface characteristics of the oxygen carrier. As a result, it was confirmed that all three kinds of oxygen carrier were suitable for use in chemical roofing combustion system, and the best particle was determined to be N016-R4.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.63-71
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• 2017

Liquid methane ($CH_4$)/oxygen ($O_2$) bipropellants have been recently considered as a next-generation propellant due to eco-friendly and non-toxic properties, low cost and high performance. In this study, the combustion characteristics of gaseous $CH_4/O_2$ nonpremixed coflow flames in a model combustor with variation of internal pressure are investigated through measuring the combustion stability limits and visualizing flames. Results show that the combustion stability limits are extended and the reaction region is widened with increasing internal pressure of the combustion chamber for fuel-rich condition.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.70-70
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• 2003

액체 로켓 엔진에 있어 극저온 추진제인 액체 산소를 사용하는 경우에는 He을 가압제로 사용하는 것이 가장 바람직하지만, 기체인 헬륨은 발사 대기시, 선가압시, 비행중에 액체산소에 서서히 녹게 된다. 일정량 이상의 He이 용해되어 있는 LOX가 엔진에 공급되는 경우에는 터보펌프의 이상 작동 또는 연소 불안정을 야기하게 되므로, 추진기관이 작동하는 동안에 용해되어 있던 He이 액체 산소에서 분해되어 가스로 발생되는지 여부를 판단하고, 이는 엔진의 연소 시험을 통해서 검증되어야 한다. 본 연구에서는 가상의 작동 상태에 대해 최대로 용해될 수 있는 러e의 양을 계산하고, 현재 사용되는 발사체의 경우와 비교를 하여 추진시스템 운용 조건을 적절히 조절하는 방안을 제시하였다.

• Journal of Energy Engineering
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• v.20 no.3
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• pp.191-199
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• 2011

The char burn-out and NOx emissions from sub-bituminous coal were investigated in drop tube furnace under $O_2/N_2$ and $O_2/CO_2$ environments with different $O_2$ concentrations of 12, 21 and 31%. Results show that the char burn-out rate is faster as $O_2$ concentration increases higher and char burn-out rate under $O_2/CO_2$ decreases due to the lower oxygen diffusion into coal surface through the $CO_2$ rich boundary layer. NO concentration increases with increasing $O_2$ concentration, but declines at $O_2$ concentration of 31%. Meanwhile, NO emission indexes decreases monotonically with increasing $O_2$ concentration, which indicates that more NO reduction occurs with higher $O_2$ concentration probably due to greater HCN formation. For all conditions of $O_2$ concentration, the NO concentration under $O_2/N_2$ maintains higher than those of $O_2/CO_2$ due to presence of thermal NO.

• Journal of the Korean Magnetics Society
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• v.9 no.2
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• pp.78-84
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• 1999

$(Ni, Zn)Fe_2O_4$ powders were prepared through self-propagating high temperature synthesis reaction and the effects of initial zinc oxide powder size and oxygen pressure on the magnetic properties of the final combustion products were studied. The ferrite powders were combustion synthesized with iron, iron oxide, nickel oxide, and zinc oxide powders under various oxygen pressures of 0.5~10 atmosphere after blended in n-hexane solution for 5 minutes with a spex mill, followed by dried at 120 $^{\circ}C$ in vacuum for 24 hours. The maximum combustion temperature and propagating rate were about 1250 $^{\circ}C$ and 9.8 mm/sec under the tap density, which were decreased with decreasing ZnO size and oxygen pressure. The final product had porous microstructure with spinel peaks in X-ray spectra. As the ZnO particle size in the reactant powders and oxygen pressure during the combustion reaction increase, coercive force, maximum magnetization, residual magnetization, squareness ratio were changed from 1324 Oe, 43.88 emu/g, 1.27 emu/g, 0.00034 emu/gOe, 37.8$^{\circ}C$ to 11.83 Oe, 68.87 emu/g, 1.23 emu/g, 0.00280 emu/gOe, 43.9 $^{\circ}C$ and 7.99 Oe, 75.84 emu/g, 0.791 emu/g, 0.001937 emu/gOe, 53.8 $^{\circ}C$ respectively. Considering the apparent activation energy changes with oxygen pressure, the combustion reaction significantly depended on initial oxygen pressure and ZnO particle size.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.647-654
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• 2018

In order to solve the global warming and reduce greenhouse gas emissions, it has been developed the $CO_2$ capture technology by oxy-fuel combustion. But there is a problem that the economic efficiency is low because the oxygen production cost is high. ASU (Air Separation Unit) is known to be most suitable method for producing large capacity of oxygen (>2,000 tpd). But most of them are optimized for high purity (>99.5%) oxygen production. If the ASU process is optimized for low purity(90~97%) oxygen producing, it is possible to reduce the production cost of oxygen by improving the process efficiency. In this study, the process analysis and comparative evaluation was conducted for developing large capacity ASU for oxy-fuel combustion. The process efficiency was evaluated by calculating the recovery rate and power consumption according to the oxygen purity using the AspenHysys. As a result, it confirmed that the optimal purity of oxygen for oxyfuel combustion is 95%, and the power consumption can be reduced by process optimization to 12~18%.

• Journal of Korean Society of Forest Science
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• v.78 no.4
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• pp.396-400
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• 1989

The oxygen index test was carried out to obtain the relative flammability of wood-based materials (plywood, MDF, particleboard) and their oxygen indices. The oxygen index is the minimum concentration of oxygen, expressed as volume percent, in a mixture of oxygen and nitrogen that will just support flaming combustion of a material under the specified laboratory conditions. In this study the oxygen indices were calculated by using the Dixon and Massey's Up and Down method("N" Large method). The obtained results were as follows : 1. The oxygen indices calculated with Up and Down method were 27.9% for plywood, 26.9% for MDF, and 26.2% for particleboard, indicative of plywood being more difficult to burn than MDF and particleboard Lender the same surrounding conditions. 2. The oxygen indices were not affected by the total gas flow rate.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.61-68
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• 2015

Reactive sprays of two propellant combinations(GOx/kerosene and $GN_2O$/ethanol) were observed and compared with each other as a basic research of visualizing supercritical combustion. A shadowgraph imaging method was used to visualize the reactive sprays, and shadowgraph images were converted to density gradient magnitude images to analyse the structure of reactive sprays. The gas-liquid interface of GOx/kerosene spray showed rougher boundary and steeper density gradient near the injector face than the $N_2O$/ethanol at similar combustion chamber pressure. Spray core length was calculated from averaged density gradient magnitude images and it was revealed that spray core length of GOx/kerosene was shorter than that of $GN_2O$/ethanol, although momentum flux ratio of GOx/kerosene propellant combination was lower.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.58-68
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• 2000

In this paper, a mathematical model of describing oxygen density in multi-band type reheating furnaces was presented. Model designed in this paper was composed of majorly two parts. One is a model regarding 'variation of existing gas'. The other is a model of showing 'variation of oxygen content'. Each model is designed by considering four factors related to variation of oxygen density based on chemical reaction, fluid dynamics and fuzzy theory. Four factors to be considered are combustion reaction in burner, fluid transfer between adjacent combustion bands, fluid transfer from furnace's inner space to external space, and input of external air via gates. According to simulation results, it was shown that varying pattern of oxygen density in each combustion band is similar to generally expected operation data in reheating furnace.

• Journal of the Korean Chemical Society
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• v.59 no.4
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• pp.296-307
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• 2015

The purposes of this study were to develop the experiment for gas concentration measure during combustion of a candle and to investigate the application effect of the experiment. For this study, 15 elementary school teachers were selected by considering their gender, career, 6th grade science teaching experience, and 6th grade science teaching experience according to 2007 revised s cience curriculum. The experiment using MBL is designed to confirm gas concentrations visually during the combustion of a candle which burns in an acrylic container. The experiment method is as follows. 1) Make two sets of holes in the container and then insert oxygen sensors and carbon dioxide sensors in the holes. 2) Burn a candle in the container and observe the changes in the burning of the candle. The experiment has checked oxygen concentration and carbon dioxide concentration in real-time and displays gas concentration changes by graphs. The results of the application effect of the experiment are as follows. Most elementary school teachers who had not had scientific concepts on combustion got acquainted with scientific concepts about ‘the reason why a candle is blown out when it is covered with a bottle’, and ‘the concentrations of oxygen and carbon dioxide before and after combustion’. In addition, about half of elementary school teachers got acquainted with scientific concepts about ‘the definition of combustion’, and ‘distribution of carbon dioxide during combustion’. Thus, the experiment to measure gas concentrations during combustion is helpful to improve elementary school teachers’ concepts on combustion.