• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.291-293
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• 2015

The experimental study on flow characteristic in various laminar coflow diffusion flame has been conducted with a particular focus on the buoyancy force exerted from gaseous hydrocarbon fuels. Methane ($CH_4$), Ethylene ($C_2H_4$) and n-Butane ($C_4H_{10}$) were used as fuels. Coflow burner and Schlieren technique were used to observe the fuel flow field near nozzle exit and flow characteristics in flames. The result showed that the vortices in n-Butane with density heavier than air were appeared near the nozzle exit with the strong negative buoyancy on the fuel stream. As Reynolds number increases by the control of velocity, the vortices were greater and the vortices tips were moved up from the nozzle exit. In addition, it can be found that the heated nozzle can affect to the flow fields of fuel stream near the nozzle exit.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2009년도 춘계학술논문발표회 논문집
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• pp.358-364
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• 2009

본 연구에서는 우리나라 주요 침엽수종인 소나무(Pinus densiflora)와 활엽수종인 굴참나무(Quercus variabilis)의 낙엽에 대해 FTIR(Fourier Transform Infrared) 분광계를 이용하여 배출 연소가스 종류 및 농도를 측정하였다. 실험결과 소나무와 굴참나무 낙엽에서 Carbon monoxide, Carbon dioxide, Acetic acid, Butyl acetate, Ethylene, Methane, Methanol, Nitrogen dioxide, Ammonia, Hydrogen Fluoride, Sulfur dioxide, Hydrogen bromide 등 13개 연소가스가 검출되었고 굴참나무 낙엽에서는 Nitrogen monoxide가 추가로 검출되었다. 방출된 연소가스의 전체 농도는 소나무 낙엽이 굴참나무 낙엽에 비해 4.5배 많이 검출되었다. 특히, 시간가중평균가스농도(TWA : Time-weighted average, ppm) 기준을 초과하는 연소가스는 Carbon monoxide, Carbon dioxide, Butyl acetate가 검출되었고 단시간노출기준(STEL : Short Term Exposure Limit, ppm) 기준을 초과하는 연소가스는 Carbon monoxide, Carbon dioxide로 소나무 및 굴참나무 모두에서 나타났다. 이에 산불에서의 낙엽층 지표화 연소시 전체 가스 방출량의 99% 이상을 차지하고 있는 Carbon monoxide, Carbon dioxide의 건강 위험성이 높은 것으로 나타났다. 하지만, 검출된 다른 건강 위험성 가스의 경우에도 연소물질의 양이 증가할수록 연소가스의 농도가 높아져 건강안정성에 해가 있을 것으로 판단되며 또한 검출된 연소가스 중 나무의 주요구성 원소가 아닌 Bromide, Fluoride 화합물에 대해서는 토양으로부터의 오염 또는 분석과정에서의 노이즈로 인한 검출 등에 대한 보다 면밀한 검토가 필요할 것으로 판단된다.

• 한국해양공학회지
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• 제35권6호
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• pp.393-402
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• 2021

As greenhouse gas emissions from maritime transport are increasing, the International Maritime Organization is continuously working to strengthen emission regulations. Liquefied natural gas (LNG) fuel is less advantageous as a point of CO₂ reduction due to the methane leakage that occurs during the bunkering and operation of marine engines. In this study, greenhouse gas emissions from an LNG-fueled ship were analyzed from the perspective of the life cycle. The amount ofmethane emission during the bunkering and operation procedures with various boil-off gas (BOG) treatment methods and gas engine specifications was analyzed by dynamic simulation. The results were also compared with those of other liquid fuel engines. As a result, small LNG-fueled ships without a BOG treatment facility emitted 32% more greenhouse gas than ships utilizing marine gas oil or heavy fuel oil. To achieve a greenhouse gas reduction via a BOG treatment method, a gas combustion unit or re-liquefaction system must be mounted, which results in a greenhouse gas reduction effect of about 25% and 30%. As a result of comparing the amount of greenhouse gas generated according to the BOG treatment method used with each tank size from the perspective of the operating cycle with the amounts from using existing marine fuels, the BOG treatment method showed superior effects of greenhouse gas reduction.

• 한국추진공학회지
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• 제25권5호
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• pp.53-64
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• 2021

SpaceX사는 Falcon 9으로 발사체 비용을 혁신적으로 낮추었으며 로켓의 1단 재사용을 실용화하였다. 현재는 완전 재사용이 가능하고 탑재량이 가장 큰 Starship 시스템을 개발 중이며 이로 인해 더욱 저렴한 비용의 발사와 임무의 다양화가 가능하다. 이를 위해 최초로 메탄 연료를 사용하는 전유동 다단 연소 싸이클을 사용하는 Raptor 엔진을 완성하였다. 그리고 완전 재사용을 위해 스테인리스강 탱크, 하강 중 배면낙하 및 역추진과 같은 거의 사용되지 않는 기술들을 함께 적용하여 다수의 시제기를 제작 및 시험하고 있다. 여기서는 Starship 시스템의 제원, 임무, 설계 특징에 대해 알아보았다. 또한 Raptor 엔진과 매우 빠르게 제작된 초기 13 기의 Starship 시제기 개발 과정에 대해서도 알아보았다.

• 한국수소및신에너지학회논문집
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• 제34권3호
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• pp.267-273
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• 2023

As the impacts of global climate change become increasingly apparent, the reduction of carbon emissions has emerged as a critical subject of discussion. Nuclear power has garnered attention as a potential carbon-free energy source; however, the rapidity of load following in nuclear power generation poses challenges in comparison to fossil-fueled methods. Consequently, power-to-gas systems, which integrate nuclear power and hydrogen, have attracted growing interest. This study presents a preliminary design of a very high temperature reactor (VHTR) integrated blue hydrogen production process utilizing DWSIM, an open-source process simulator. The blue hydrogen production process is estimated to supply the necessary calorific value for carbon capture through tail gas combustion heat. Moreover, a thermodynamic assessment of the main recuperator is performed as a function of the helium flow rate from the VHTR system to the blue hydrogen production system.

• 대한기계학회논문집B
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• 제35권2호
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• pp.179-188
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• 2011

본 연구에서는 합성가스-공기 화염의 셀 불안정성에 있어서 탄화수소 연료의 첨가효과를 알아보기 위하여 상온, 고압, 정적상태의 연소실에서 실험을 수행하였다. 층류화염전파속도는 상세반응기구와 전달물성치를 사용하여 계산하였고 이를 실험으로 측정된 값과 비교하였다. 탄화수소 연료가 첨가된 합성가스-공기 화염의 셀 불안정성은 수력학적 불안정성과 확산-열 불안정성의 관점에서 평가되며 희박예혼합 화염에 대해 실험으로부터 측정된 셀불안정성을 유발하는 임계 Peclet 수는 이론적으로 얻어진 값과 비교하였다. 실험결과는 반응혼합물에 탄화수소 계 연료의 첨가량이 증가할수록 화염전파속도는 감소함을 보였다. 합성가스-공기화염에 프로판과 부탄을 첨가하였을 경우 수력학적 불안정성과 확산-열 불안정성이 감소하여 셀 형성은 현저하게 감소하였다. 반면 메탄을 첨가하였을 경우 셀 불안정성이 완화되는 효과는 없었다.

• 한국가스학회지
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• 제14권1호
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• pp.15-20
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• 2010

최근 들어 유럽 및 미국을 중심으로 각광받고 있는 가스화 열병합 설비는 석탄이나 바이오매스, 폐기물로부터 지역의 전기 및 냉난방 에너지를 공급하는 중소형 규모의 에너지 시스템으로서 시장적 측면이나 기술적 측면에서 그 활용 가능성이 매우 밝은 것으로 예견되고 있다. 가스화로부터 얻어지는 합성가스는 일반적으로 가스엔진, 스털링 엔진, 마이크로 가스터빈 및 중소형 가스터빈 등이 원동기 연료로 사용될 수 있다. 그러나 가스화를 통한 합성가스는 일반적으로 LPG, CNG와 같은 고발열량 가스연료에 비해 발열량이 낮고, 반응성 및 화염속도도 매우 큰 차이를 보인다. 본 연구는 저발열량의 합성가스연료를 이용한 고효율 전소엔진 개발의 전 단계로서 60kW급 디젤혼소엔진을 개발하였다. 저발열량의 합성가스를 모사하기 위해 CNG에 질소를 희석한 연료를 사용하였으며, 디젤 연료 분사를 제어하기 위한 인젝터 드라이버 및 ECU를 적용하였다.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.386-401
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• 2011

Mathematical models for various steps in coal gasification reactions were developed and applied to investigate the effects of operation parameters on dynamic behavior of gasification process. Chemical reactions considered in these models were pyrolysis, volatile combustion, water shift reaction, steam-methane reformation, and char gasification. Kinetics of heterogeneous reactions between char and gaseous agents was based on Random pore model. Momentum balance and Stokes' law were used to estimate the residence time of solid particles (char) in an up-flow reactor. The effects of operation parameters on syngas composition, reaction temperature, carbon conversion were verified. Parameters considered here for this purpose were $O_2$-to-coal mass ratio, pressure of reactor, composition of coal, diameter of char particle. On the basis of these parametric studies some quantitative parameter-response relationships were established from both dynamic and steady-state point of view. Without depending on steady state approximation, the present model can describe both transient and long-time limit behavior of the gasification system and accordingly serve as a proto-type dynamic simulator of coal gasification process. Incorporation of heat transfer through heterogenous boundaries, slag formation and steam generation is under progress and additional refinement of mathematical models to reflect the actual design of commercial gasifiers will be made in the near futureK.

• 한국물환경학회지
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• 제34권1호
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• pp.121-131
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• 2018

Domestic sewage treatment plants (STPs) consume about 0.5 % of total electric energy produced annually, which is equivalent to 207.7 billion Korean won per year. To minimize the energy consumption and as a way of mitigating the depletion of energy sources, the sewage treatment strategy should be improved to the level of "energy positive". The core processes for the energy positive sewage treatment include A-stage for energy recovery and B-stage for energy-efficient nitrogen removal. The integrated process is known as the A/B-process. In A-stage, chemically enhanced primary treatment (CEPT) or high rate activated sludge (HRAS) processes can be utilized by modifying the primary settling in the first stage of sewage treatment. CEPT utilizes chemical coagulation and flocculation, while HRAS applies returned activated sludge for the efficient recovery of organic contents. The two processes showed organic recovery efficiencies ranging from 60 to 70 %. At a given recovery efficiency of 80 %, 17.3 % of energy potential ($1,398kJ/m^3$) is recovered through the anaerobic digestion and combustion of methane. Besides, anaerobic membrane bioreactor (AnMBR) can recover 85% of organic contents and generate $1,580kJ/m^3$ from the sewage. The recovered energy is equal to the amount of energy consumption by sewage treatment equipped with anaerobic ammonium oxidation (ANAMMOX)-based B-stage, $810{\sim}1,620kJ/m^3$. Therefore, it is possible to upgrade STPs as efficient as energy neutral. However, additional novel technologies, such as, fuel cell and co-digestion, should be applied to achieve "energy positive" sewage treatment.

• 대한기계학회논문집B
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• 제29권9호
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• pp.997-1005
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• 2005

The extinction characteristics of low strain rate normal gravity (1-g) nonpremixed methane-air flames were studied numerically and experimentally. A time-dependent axisymmetric two-dimensional (2D) model considering buoyancy effects and radiative heat transfer was developed to capture the structure and extinction limits of 1-g flames. One-dimensional (1D) computations were also conducted to provide information on 0-g flames. A 3-step global reaction mechanism was used in both the 1D and 2D computations to predict the measured extinction limit and flame temperature. A specific maximum heat release rate was introduced to quantify the local flame strength and to elucidate the extinction mechanism. Overall fractional contribution by each term in the energy equation to the heat release was evaluated to investigate the multi-dimensional structure and radiative extinction of 1-g flames. Images of flames were taken for comparison with the model calculation undergoing extinction. The two-dimensional numerical model was validated by comparing flame temperature profiles and extinction limits with experiments and ID computation results. The 2D computations yielded insight into the extinction mode and flame structure of 1-g flames. Two combustion regimes depending on the extinction mode were identified. Lateral heat loss effects and multi-dimensional flame structure were also found. At low strain rates of 1-g flame ('Regime A'), the flame is extinguished from the weak outer flame edge, which is attributed to multi-dimensional flame structure and flow field. At high strain rates, ('Regime B'), the flame extinction initiates near the flame centerline due to an increased diluent concentration in reaction zone, which is the same as the extinction mode of 1D flame. These two extinction modes could be clearly explained with the specific maximum heat release rate.