지하 복합발전 플랜트 내부의 가스 누출 및 확산 특성에 관한 수치해석 연구

방주원,이성혁 한국에너지학회 2017 한국에너지공학회 학술발표회 Vol.2017 No.4

지하 복합발전 플랜트 내부의 가스 누출 특성에 대한 수치해석 연구

방주원(Joo Won Bang),성건혁(Kun Hyuk Sung),유홍선(Hong Sun Ryou),이성혁(Seong Hyuk Lee) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.5

본 연구에서는 수치해석 기법을 활용하여 간략화한 지하 복합발전 플랜트 내 파공 위치에 따른 가스 확산 및 유동 특성을 고찰하였다. 특히 가스 누출 위치 주변의 장애물 배치가 밀폐 공간 내부의 가스 농도 분포에 미치는 영향을 분석하였 으며, 메탄가스의 가연 한계 값을 이용하여 누출 특성을 정량적으로 비교하였다. 수치해석 결과, 분사류 주변으로 수직 벽면 이 있을 경우, 장애물이 횡 방향 유동을 제한하여 종 방향 누출 거리가 장애물이 없을 경우에 비해 약 60% 가량 증가하였다. 하지만 Air filter가 가스 분사류 경로에 있을 경우, 횡 방향 누출 거리는 장애물이 없을 경우에 비해 최대 8배까지 증가하였다. 이러한 이유는 분사류가 수평 및 하부 방향으로 굴절되어 장애물 주변으로 재순환 유동이 형성되었기 때문이다. 따라서 밀폐 공간 내 사고 방지 시스템 설계 시 주요 설비 위치 및 공간 구조가 누출 분사류 경로에 미치는 영향을 고려할 필요가 있다. The present study numerically investigated the gas leakage characteristics in a simplified underground combined cycle power plant. The effect of obstacles near a crack location on the gas concentration in the confined space was analyzed by using the lower flammable limit (LFL) of methane gas. When the jet flow was close to the vertical walls, the longitudinal leakage distance increased by about 60% (when an obstacles was present) compared to the case without any obstacle, because these obstacles prevented transverse flows. In addition, when an air filter was installed near to the trajectory of the gas flow, the longitudinal leakage distance was similar to the distance between the crack and obstacle, whereas the transverse leakage distance increased up to 8 times compared to the case without any obstacle. As the jet flow impacts on the obstacle and changes its direction, the gas flows recirculate. Therefore, it is necessary to consider the effect of the structure and facility locations on the trajectory of the jet flow to propose an accident prevention system in confined spaces.

포스터 전시회 : 지하복합발전플랜트의 가스 누출 및 확산 거동에 관한 수치해석

방주원 ( Joo Won Bang ),박재용 ( Jae Yong Park ),이성혁 ( Seong Hyuk Lee ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-

It has been reported that the leakage accident frequently happens which can cause serious fire at the gas transportation at the power plant. Especially, a combined cycle power plant (CCPP) in underground might be exposed to substantial human injury and facility damage. The main objective of present study is to investigate the effect of crack sizes on transient evolution of temperature and concentration of leakage gas under various accident scenarios. The commercial code (ANSYS FLUENT V.16.1) was used to predict the three-dimensional thermo-fluid flows. To analysis the quantitative risk assessment (QRA) factor, such as flammable volume ratio, radius of damage, and transient numerical analysis were carried out for different scenarios, and LNG volume fraction in closed space were estimated in time. From the numerical results, the maximum propagation length of LNG gas concentration between 2.5% and 15% increased with the crack size. LNG gas is rapidly spread by convection in confined space because of the high release rate of LNG and the circulation flow was shown after generating the secondary flow at the upper wall. The study is expected to be used later as the basis for accident through the consequence risk analysis, we provide QRA results in the development of a fuel leakage.

지하 복합발전 플랜트 내에서의 가스 누출 및 확산 거동에 관한 수치해석 연구

방주원(Joo Won Bang),이성혁(Seong Hyuk Lee) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.4

본 연구에서는 상용코드인 Fluent(v.17.1)을 사용하여 수치해석을 진행하였으며, 지하복합발전 플랜트의 형상을 단순화하여 파공 크기 및 파공 위치에 따른 가스 누출에 관한 해석을 진행하였다. 누출 가스는 메탄으로 설정하였다. 파공 크기는 10 ㎜, 20 ㎜로 설정하였으며, 파공 위치는 파이프 엘보우 부근, 가스터빈 부근에서 가스가 누출될 경우로 가정하여, 총 4가지 Case에 대해 비교 및 분석을 진행하였다. 가스 누출을 분석하기 위해 연소 하한계의 개념을 바탕으로 누출 거리를 정의하여 종 방향, 횡 방향으로의 거리를 추정하여 정량적으로 분석하였다. 결과적으로 동일 위치에서 파공 크기에 따라 누출거리가 최대 52.3 %의 차이를 보이며 종 방향의 누출 거리가 달라지는 것을 알 수 있었다. 그리고 동일 파공 크기일 때, 파공 위치에 따라 최대 34.8 %의 차이를 보이며 가스의 확산 경향이 달라지게 된다. 공기보다 가벼워 부력의 영향으로 상승하던 가스가 장애물로 인해 수평방향으로 확산이 제한되어 장애물이 없는 경우보다 재순환이 빨라지게 된다. 따라서 종 방향누출거리와 횡 방향 누출거리가 파공 크기 및 파공 위치에 따라 다른 성장 거동을 보인다. 이와 같은 결과는 지하 복합발전 플랜트와 같은 밀폐공간에서 가스 센서의 위치 및 개수를 최적화 하는데 유용한 데이터가 될 것으로 보인다. In this study, a numerical simulation was performed using co㎜ercial code Fluent(v.17.1). The underground Combined Cycle Power Plant (CCPP) was simplified to analyze the methane gas leakage with the crack size and position. In addition, extensive numerical simulations were carried out for different crack sizes from 10 ㎜ to 20 ㎜. The crack position is the gas leakage, which is assumed to be near the pipe elbow and the gas turbine. A total of 4 cases were compared and analyzed. To analyze the gas leakage, the concept of the Lower Fla㎜able Limit (LFL) was applied. The leakage distance was defined in the longitudinal direction, and the transverse direction was estimated and quantitatively analyzed. As a result, the leakage distance in the longitudinal direction varies by 52.3 % depending on the crack size at the same crack position. Moreover, the maximum difference was 34.8 % according to the crack position when the crack sizes are identical. As jet flow impacts on the obstacle and changes its direction, the recirculation flows are formed. These results are expected to provide useful data to optimize the location and number of gas detections in confined spaces, such as underground CCPP.

밀폐공간에서 프로드 수가 가스 누출 확산 거동에 미치는 영향

방주원(Joo Won Bang),이성혁(Seong Hyuk Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.5

수침고목재(水浸古木材)의 화학조성

김윤수,방주원,김익주,최광남 한국목재공학회 1990 목재공학 Vol.18 No.2

The chemical Composition of Chinese red pine (Pinus massoniana) submerged in the Yellow Sea for more than 700 years has been exmined. When compared to the recent wood, the marked chemical changes in the waterlogged wood is the higher amount of lignin with lesser amount of holocellulose and abnormally high ash content. In the heavily degraded samples, the degradation of cellulose is more severe than that of hemcellulose. however, hemicellulose is much mere attacked than the cellulose at the initial stage of deterioration in the sea water. Chemical analysis suggests that the cellulolytic marine microorganisms, whether they are fungi or bacteria, can be regarded as the primary agents for the destruction of the archaeological woods submerged in the sea water.

Optogenetic and Chemogenetic Approaches for Studying Astrocytes and Gliotransmitters

이효상,방주원,김학영 한국뇌신경과학회 2016 Experimental Neurobiology Vol.25 No.5

The brain consists of heterogeneous populations of neuronal and non-neuronal cells. The revelation of their connections and interactions is fundamental to understanding normal brain functions as well as abnormal changes in pathological conditions. Optogenetics and chemogenetics have been developed to allow functional manipulations both in vitro and in vivo to examine causal relationships between cellular changes and functional outcomes. These techniques are based on genetically encoded effector molecules that respond exclusively to exogenous stimuli, such as a certain wavelength of light or a synthetic ligand. Activation of effector molecules provokes diverse intracellular changes, such as an influx or efflux of ions, depolarization or hyperpolarization of membranes, and activation of intracellular signaling cascades. Optogenetics and chemogenetics have been applied mainly to the study of neuronal circuits, but their use in studying non-neuronal cells has been gradually increasing. Here we introduce recent studies that have employed optogenetics and chemogenetics to reveal the function of astrocytes and gliotransmitters.

화원 위치에 따른 지하 복합 발전 플랜트 내 열유동 특성 연구

성건혁(Kun Hyuk Sung),방주원(Joo Won Bang),이소영(Soyeong Lee),유홍선(Hong Sun Ryou),이성혁(Seong Hyuk Lee) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.5

본 연구에서는 Fire Dynamics Simulation (FDS)를 이용하여 화재 기류 전파 경로 상에 플랜트 설비 유무가 공간내 열유동 특성에 미치는 영향을 알아보기 위해 화원 위치에 따른 지하 복합 발전 플랜트 내 화재 해석을 수행하였다. 화원의 크기는 10 ㎿이며, 화원 상부의 장애물(설비)의 유무에 따라 화원 위치가 천장 및 화원 상부에서의 열 기류 선단의 전파특성을 미치는 영향을 정량적으로 비교분석하였다. 결과로서, 화원 상부에 장애물이 있을 경우, 화재 기류가 화원 상부 천장에 도달하는 시간이 장애물이 없을 때에 비해 약 5 배가량 증가하였다. 화원 상부 천장 벽면의 천장 기류 시작 지점으로부터 거리에 따른 각 지점에서 열 기류 선단의 전파 시간의 평균적으로 장애물이 없는 경우에 비해 약 70% 가량 증가하였으며, 특히 10 m 지점에서는 4 배 가까이 증가하였다. 이는 장애물이 화원으로부터 발생하는 수직 열기류의 흐름을 방해하고, 장애물 뒤 쪽에 불안정한 후류가 형성되었기 때문이다. 따라서 지하복합 발전 플랜트 내 피난 및 재난 관리의 초기 대응 목적의 화재 감지 설비 시스템 설계 시 화재 시나리오에 따른 열유동 분석이 중요할 것으로 판단된다. The present study numerically investigates the effect of obstacles located in the trajectory of fire plume flow on heat flow characteristics by using Fire Dynamics Simulation (FDS) software in an underground combined cycle power plant (CCPP). Fire size is taken as 10 ㎿ and two different locations of fire source are selected depending on the presence of an obstacle. As the results, when the obstacle is in the trajectory of fire plume, hot plume arrives at the ceiling about 5 times slower in the upper of the fire in comparison to the results without obstacle. In addition, the average propagation time of ceiling jet increases by about 70 % with the distance from the ceiling in the upper of the fire, and it increases mainly about 4 times at the distance of 10 m. Consequently, it is noted that the analysis of heat flow characteristics in the underground CCPP considering fire scenarios is essential to develop the fire detection system for initial response on evacuation and disaster management.

미생물에 의한 목질자원의 당화 및 사료화에 관한 연구 (Ⅰ) : alkaline peroxide 에 의한 현사시나무의 효소가수분해를 위한 탈리그닌화의 적정조건 Optimal Delignification condition with alkaline peroxide for enzymatic hydrolysis of poplar wood

김윤수,명규호,정기철,방주원,김윤식 한국목재공학회 1986 목재공학 Vol.14 No.3

Alakline peroxide pretreatment for the delignification of poplar wood was performed, sinceit is a simple and efficent method for enhancing the enzymatic digestibility of wood residues. Approximately one-half of their lignin and most of the hemicellulose present in poplar wood were removed when the wood sawdust was reacted at 25℃ for 100 hrs in an alkaline solution (pH 11.5) of 1% peroxide. The rate of decomposition as well as the saccharification efficiency were enhanced up to 550% and 266% respectively in comparision with Chase of the controll. This enhancement is comparable with that pretreated with 1% sodium hydroxide and 20% peractaic aicd successively. The advantages of alkaline peraxide, as delignifying agents against other chemicals were also discussed.

Numerical investigation of LNG gas dispersion in a confined space: An engineering model

Longnan Li,최진욱,방주원,이소영,이성혁,김대중 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.9

The present study has numerically investigated a dynamic methane leak and dispersion in a confined space. To establish a numerical prediction based engineering model of dynamic gas leak and dispersion in a confined space, numerical experiments are conducted for variation of a key parameter – leak hole size. Based on the numerical results data, an engineering model is developed. The parameters related to lower flammable limit of the methane were quantitatively analyzed to compare the potential risk due to a gas leak. To quantitatively investigate the flammable region, the longitudinal and transverse directional length is defined and studied. We found that the ratio between longitudinal and transverse directional length can be a bridge to model the flammable region. The aspect ratio of the flammable region is fitted by an exponential function to show the relation with time. Then, an oval-shape model is presented to predict flammable region. Oval-shape model is completed by the combination of aspect ratio relation and a function for transverse length. Finally, we compared the developed engineering model (oval-shape model) and numerical results. The engineering model can predict the flammable region quite well when it reaches steady state. It is expected that the established engineering model is valuable for the Quantitative risk assessment (QRA), initial emergency strategy preparation when a fuel gas leak accident happened in a Combined cycle power plant (CCPP). We hope it is also can be a kind of data base for power plant operation manual.