• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.5
• /
• pp.481-488
• /
• 2013

Nitric oxide ($NO_x$) formation characteristics in non-premixed diffusion flames of methane fuels have been investigated experimentally and numerically by adding 10% ammonia to the fuel stream, according to the variation of the oxygen ratio in the oxidizer with oxygen/carbon dioxide and oxygen/nitrogen mixtures. In an experiment of coflow jet flames, in the case of an oxidizer with oxygen/carbon dioxide, the $NO_x$ emission increased slightly as the oxygen ratio increased. On the other hand, in case of an oxygen/nitrogen oxidizer, the $NO_x$ emission was the maximum at an oxygen ratio of 0.7, and it exhibited non-monotonic behavior according to the oxygen ratio. Consequently, the $NO_x$ emission in the condition of oxyfuel combustion was overestimated as compared to that in the condition of conventional air combustion. To elucidate the characteristics of $NO_x$ formation for various oxidizer compositions, 1D and 2D numerical simulations have been conducted by adopting one kinetic mechanism. The result of 2D simulation for an oxidizer with oxygen/nitrogen well predicted the trend of experimentally measured $NO_x$ emissions.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.7
• /
• pp.765-772
• /
• 2015

In this research, the characteristics of SOFC/GT (Solid Oxide Fuel Cell/Gas Turbine) system temperature, stack power and system efficiency for flow rates of air, CH4 and water supplied to SOFC stack have been investigated. The temperature of the gas supplied to cathode and anode of SOFC stack in the SOFC/GT system are maintained by utilizing exhaust gas without the addition of external heat source. As a result, within the scope of this study, temperatures of gas supplied to cathode and anode of SOFC stack were maintained at 1000 (K) by utilizing the exhaust gas of the SOFC/GT system without the addition of external heat source. The system efficiency is increased with increase of air flow rate supplied to the stack and with decrease of $CH_4$ flow rate supplied to the stack. In addition, it can be found that the flow rate of the exhaust gas supplied to the turbine had a significant effect on the system efficiency. And the efficiencies of SOFC stack and SOFC/GT system depending upon various operating conditions of the SOFC/GT system is 51~57% and 57~73%, respectively.

• Economic and Environmental Geology
• /
• v.38 no.3 s.172
• /
• pp.335-346
• /
• 2005

In this study, core sediments and pore water were analysed to identify the origin of organic matter and Bas in late Quaternary sediments from the northwestern Ulleung Basin of the East Sea. C/N and C/S ratios in the sediments show that the organic matter in the study area originated predominantly from marine algae. However, the results of Rock-Eval pyrolysis indicate that the organic matter has an origin of the land-plant (Type III), locating in the immature stage. These different results might be due to the heavy oxidizing of the organic matter during sinking down to the seafloor or after deposition in the sediments. Concentration of sulfate in the pore water decreases gradually with core depth, while concentration of $CH_4$ increases gradually with core depth. This indicates that sulfate reduction and methanogenesis occurred actively in the sediments. Also, it is likely that the compositions of $CH_4$ are characterized as a more biogenic origin, mostly caused by microbial activity, rather than a thermogenic one.

• 한국석유지질학회:학술대회논문집
• /
• 2005.09a
• /
• pp.94-100
• /
• 2005

동해 울릉분지 북서부해역에서 채취한 코어퇴적물을 이용하여 울릉분지의 제4기 후기 층서와 퇴적환경을 연구하였다. 이를 위하여 테프라층서, 탄소연대측정, 퇴적상, 퇴적물의 암질, 퇴적물과 공극수의 원소성분 등을 분석하였다. 퇴적상을 기준으로 코어퇴적물은 Unit 1, Unit II 및 Unit III으로 나누어지며, Unit의 경계부근에서는 주로 화산력으로 구성된 2매의 향암질 또는 조면암질 테프라층과 주로 화산재로 구성된 1매의 유문암질 테프라층이 협재되어 나타난다. 이들 테프라층에는 울릉도에서 기원한 울릉-오키층(Unit I/II 경계, 약 8.1 cal. kyr BC)과 울릉-야마토층(약 30.7 cal. kyr BC), 일본에서 기원한 아이라-탄자와층(Unit I/II경계, 약 22.8 cal. kyr BC)이 있다. Unit II의 중간부근에서 발견되는 DLM(Dark Laminated Mud) 층에는 망간보다는 철이 상대적으로 풍부하고, 철은 주로 구상집적체의 황화철로 발견되는데, 이들 광물은 정체환경 동안 물의 순환이 약화된 시기에 무산소환경에서 형성되었다. 퇴적물 내 유기물은 해양성 기원으로, 열적 성숙단계가 대부분 미성숙단계에 놓여 있다. Termination I 전에 급격하게 총유기탄소 (TOC)의 함량이 증가함을 보여주는데, 이는 빙기에서 간빙기로 변하는 시기에 해수면 변동과 관련이 있는 것으로 보인다. 공극수와 공기층 가스의 분석에 의하면, 황산염($SO_4^{2-}$) 농도는 매몰심도와 함께 증가하고, 반대로 공기층 가스의 주성분인 메탄($CH_4$)의 농도는 감소한다. 이는 미생물학적인 활동과 관련된 황산염 환원작용이 코어 상부에서 일어났으며, 점차 메탄생성단계 (methanogenesis)로 전이가 일어났음을 의미한다.측해본 결과 침몰선체의 강도는 초기강도에 비해 약 2/5정도 감소하였음을 알 수 있었다.할 수 있었다. 이 연구 사례를 통하여 3차원 GPR 탐사 또한 국부적인 이상대의 규명뿐만 아니라 광역적인 고고학 조사에도 다른 물리탐사와 마찬가지로 쉽게 활용될 수 있다는 결론을 얻을 수 있었다. 3차원 GPR 탐사가 향후 국내의 문화재 조사에 표준화된 탐사과정 중의 하나로써 적극 활용되길 기대한다.larity가 높은 oil에서는 약 $70 {\~} 90\%$의 phenoxyethanol이 유상에 존재하였다. 또한, 미생물에 대한 항균력도 phenoxyethanol이 수상에 많이 존재할수록 증가하는 경향을 나타내었다. 따라서, 제형 내 oil tomposition을 변화시킴으로써 phenoxyethanol의 사용량을 줄일 수 있을 뿐만 아니라, 피부 투과를 감소시켜 보다 피부 자극이 적은 저자극 방부시스템 개발이 가능하리라 보여 진다. 첨가하여 제조한 curd yoghurt는 저장성과 관능적인 면에서 우수한 상품적 가치가 인정되는 새로운 기능성 신제품의 개발에 기여할 수 있을 것으로 사료되었다. 여자의 경우 0.8이상이 되어서 심혈관계 질환의 위험 범위에 속하는 수준이었다. 삼두근의 두겹 두께는 남녀 각각 $20.2\pm8.58cm,\;22.2\pm4.40mm$으로 남녀간에 유의한 차이는 없었다. 조사대상자의 식습관 상태는 전체 대상자의 $84.4\%$가 대부분이 하루 세끼 식사를 규칙적으로 하고 있었으며 식사속도는 허겁지겁 빨리 섭취하는 경우가 남자는 $31.0\%$, 여자는 $21.4\%$로 나타났고 이들을 제외한 나머지 사람들은 보통 속도 혹은 충분한 시간을 가지고 식사를 하였다. 평소 식사량은 조금 적게

• Korean Journal of Agricultural Science
• /
• v.22 no.2
• /
• pp.143-150
• /
• 1995

In order to find a way to utilize paper mill sludge, its composting was conducted with anaerobic waste of kraft paper sludge, raw kraft paper sludge, and CMC sludge(CMC : Sodium Carboxymethylcellulose) under aerobic condition at $50^{\circ}C$. It took 3 days for initial fermentation with anaerobic waste and CMC sludge, and six days with raw kraft paper sludge. Each compost was applied to radish(Rhaphanus Stativus L.), and absorption rate of staple nutrients increased 6.7~9.3 times higher in N, 17~21 times in P and 2~3 times in K than control at the harvesting stage. Also, organic matter contents were increased 1.5~2.3 times 4.5~5.3 times in CEC compared to control soil.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.23 no.4
• /
• pp.40-51
• /
• 2015

This study is to estimate the viability of aerobic stabilization technology for reducing greenhouse gas (GHG) emissions from landfills in Korea. In this study, methane emissions were estimated by applying Landfill gas estimation model (LandGEM) to Y landfill in Korea. By comparison of an anaerobic condition (baseline) and an aerobic condition, the amount of $CO_2eq$ savings was calculated. The $CO_2eq$ savings take place inside the landfilled waste during aeration due to the conversion of previously anaerobic biodegradation to aerobic processes, releasing mainly $CO_2$. It was demonstrated that 86.6% of the total GHG emissions occurring under anaerobic conditions could be reduced by aerobic stabilization technology. This means the aerobic stabilization technology could reduce environmental contamination through early stabilization and GHG emissions considerably at the same time. Therefore, the aerobic stabilization technology is one of the optimal technologies that could be employed to domestic landfill sites to achieve sustainable landfill.

• Clean Technology
• /
• v.26 no.1
• /
• pp.72-78
• /
• 2020

The use of fossil fuel and biogas production causes air pollution and climate change problems. Research endeavors continue to focus on converting methane and carbon dioxide, which are the major causes of climate change, into quality energy sources. In this study, a novel plasma-carbon converter was proposed to convert biogas into high quality gas, which is linked to photovoltaic and wind power and which poses a problem on generating electric power continuously. The characteristics of conversion and gas production were investigated to find a possibility for biogas conversion, involving parametric tests according to the change in the main influence variables, such as O₂/C ratio, total gas feed rate, and CO₂/CH₄ ratio. A higher O₂/C ratio gave higher conversions of methane and carbon dioxide. Total gas feed rate showed maximum conversion at a certain specified value. When CO₂/CH₄ feed ratio was decreased, both conversions increased. As a result, the production of solar fuel by plasma oxidation destruction-carbon material gasification conversion, which was newly suggested in this study, could be known as a possibly useful technology. When O₂/C ratio was 0.8 and CO₂/CH₄ was 0.67 while the total gas supply was at 40 L min^-1 (VHSV = 1.37), the maximum conversions of carbon dioxide and methane were achieved. The results gave the highest production for hydrogen and carbon dioxide which were high-quality fuel.

• Fire Science and Engineering
• /
• v.27 no.6
• /
• pp.64-69
• /
• 2013

The Numerical simulation was performed on the flow field around the two-dimensional rectangular bluff body in order to simulate an engine nacelle fire and to complement the previous experimental results of the bluff body stabilized flames. Fire Dynamic Simulator (FDS) based on the Direct Numerical Simulation (DNS) was employed to clarify the characteristics of reacting flow around bluff body. The overall reaction was considered and the constant for reaction was determined from flame extinction limits of experimental results. The air used atmosphere and the fuel used methane. For both fuel ejection configurations against an oxidizer stream, the flame stability and flame mode were affected mainly by vortex structure near bluff body. In the coflow configuration, air velocity at the flame extinction limit are increased with fuel velocity, which is comparable to the experiment results. Comparing with the isothermal flow field, the reacting flow produces a weak and small recirculation zone, which is result in the reductions of density and momentum due to temperature increase by reaction in the wake zone.

• Journal of the Korean Institute of Gas
• /
• v.1 no.1
• /
• pp.1-6
• /
• 1997

In case of using the electrical apparatus in the hazardous atmosphere which exist flammable gas mixtures, There is a dangerosity of gas explosion accident by the electrical spark. The most general method to prevent the explosion by the spark is to use the flame-proof type electrical apparatus to isolate the ignition source. from the flammable atmosphere. But actualy it is impossible to isolate the ignition sources from the atmosphere. So it was needed to find the safe gap which prevent ignition of flammable atmosphere by transmission of flame or heat when a flammable gas mixture exploded inside the apparatus. In this study we tried to find the maximum experimental safe gap(MESG) of $H_2$-air, and $CH_4$-air mixtures by using the 8 litre spherical vessel with 25mm flange. The experiment parameter were ignition position, concentration and initial pressure before explosion. From the experiment the ignition position was affected to the MESG. MESG value was minimum near the stoichiometric concentration of gas mixtures, and according to the increase of initial pressure MESG was decreased.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.7 no.4
• /
• pp.27-32
• /
• 2003

The Performance of micro combustor in various condition was exploited experimentally. Various geometric conditions of combustor were considered to figure out the performance of micro combustor. The micro combustor studied in this study was constant volume with cylindrical shape. Geometric parameters of combustor were defined to be combustor height and diameter. The effect of height was exploited parametrically with the size of 1mm, 2mm and 3mm. The effect of diameter was observed parameterized with 7.5mm and 15mm. Three different combustibles or Stoichiometric mixture of methane/air, hydrogen/air were used. Pressure transition during combustion process was recorded. The maximum pressure by combustion responded favorably with the change of height of combustor and the initial pressure. The flame propagation was visulized using Schlieren method. The flame propagation within combustor was observed when specific conditions such as combustor height and initial pressure over critical value was satisfied.