• International Journal of Advanced Culture Technology
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• 제10권3호
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• pp.295-306
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• 2022

The NOx removal performance of the SCR process depends on various factors such as catalytic factors (catalyst composition, shape, space velocity, etc.), temperature and flow rate distribution of the exhaust gas. Among them, the uniformity of the flow flowing into the catalyst bed plays the most important role. In this study, the flow characteristics in the SCR reactor in the design stage were simulated using a three-dimensional numerical analysis technique to confirm the uniformity of the airflow. Due to the limitation of the installation space, the shape of the inlet duct was compared with the two types of inlet duct shape because there were many curved sections of the inlet duct and the duct size margin was not large. The effect of inlet duct shape, guide vane or mixer installation, and venturi shape change on SCR reactor internal flow, airflow uniformity, and space utilization rate of ammonia concentration were studied. It was found that the uniformity of the airflow reaching the catalyst layer was greatly improved when an inlet duct with a shape that could suppress drift was applied and guide vanes were installed in the curved part of the inlet duct to properly distribute the process gas. In addition, the space utilization rate was greatly improved when the duct at the rear of the nozzle was applied as a venturi type rather than a mixer for uniform distribution of ammonia gas.

• 한국가스학회지
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• 제21권5호
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• pp.45-55
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• 2017

대부분의 가연성가스의 누출 및 화재/폭발 등의 실험은 큰 위험성이 있으며 실험을 진행할 수 있는 부지 선정에 큰 어려움이 있어 가급적 전산유동해석(CFD) 등의 간접적 방법을 많이 활용하였다. 그러나 2016년 10일 강원도 영월군에 에너지안전실증연구센터가 개소함에 따라 대규모/고압/초저온 등의 실험 뿐아니라 소규모 가연성 가스의 누출 및 검지 실험이 가능하게 되어 본 실험을 계획하였다. 본 실험에서는 가스센서를 교정하고 가스가 누출될 공간에 배치 후 LP가스를 누출시켜 가스센서에 검지된 값을 Contour map으로 가시화하였다. 또한 동일 조건으로 해석한 전산유동해석 결과값과 비교하여 LEL 25% 값의 실제 누출(28s, 최대 3.7m)의 차이점에 대해 분석하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권2호
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• pp.284-291
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• 2008

This study presents an aerodynamic design and numerical analysis of a centrifugal compressor in gas turbines for SOFC-gas turbine hybrid system application. Total-to-total pressure ratio of the compressor is 3.6:1 that could be used widely for small and large SOFC-gas turbine systems. The compressor consists of a centrifugal impeller and a wedge diffuser. Conceptual design and aerodynamic design with mean line analysis and quasi-3D analysis are performed, and aerodynamic parameters as well as design variables are discussed from the design results. A numerical analysis based on the Reynolds-averaged Navier-Stokes equation was performed for the flow analysis of the compressor. The results show that the centrifugal compressor designed meets the design target, and the aerodynamic parameters and results of the compressor can be used for the aerodynamic design of centrifugal compressors and the feasibility study of SOFC-gas turbine system design.

• 한국가스학회지
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• 제25권5호
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• pp.19-29
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• 2021

기후변화에 대응하기 위해 세계적으로 이산화탄소 및 대기오염 물질 배출 규제가 점차 강화됨에 따라 내연 기관 자동차를 친환경 자동차로 전환하려는 추세이다. 이는 정부의 수소 에너지 활성화 정책에 따른 충전 인프라 구축, 충전 설비 핵심 부품의 국산화 지원으로 가속화되고 있다. 본 연구에서는 유한 요소 해석을 통해 수소 연료 전지 자동차 용기 밸브의 과류 방지 장치를 설계하고, 시험을 통해 성능을 평가하였다. 주요 시험 항목인 정수압, 연속 작동, 압력 임펄스, 누설, 작동 시험을 ISO 12619-2, ISO 12619-11의 시험 방법에 따라 수행한 결과 요구 조건을 만족함을 확인하였다.

• Tribology and Lubricants
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• 제18권1호
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• pp.24-33
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• 2002

The basic equations are derived for the analysis of a staggered labyrinth gas seal which are generally used in high performance compressors and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the staggered labyrinth gas seal. Theoretical results of leakage and rotordynamic characteristics for the staggered labyrinth gas seal are compared with those of the plain seal and see-through labyrinth seal.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.164-166
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• 1998

This paper presents the results of the measured pressure-rise and the analyzed results of the cold gas flow-field in a 72.5kV 20kA gas circuit breaker for the electrical railway system. The analysis of cold gas flow field and the calculation of electric field strength have been performed in 3 types of interrupters and the low current interruption capability has been estimated for each of the gas circuit breaker considering the opening speed, the nozzle shape and the stroke length.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2817-2822
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• 2007

The purpose of this paper is to study the influence of operating condition and ejector geometries on the hydrodynamics and on the mass transfer characteristic of ejector. The CFD results were validated with available experimental data. Flow field analyses and predictions of ejector performance were also carried out. Variation on the operating conditions was made by varying the gas-liquid flow rate ratio in the range of 0.2 to 1.2. The ejector configuration was also varied on the length to diameter ratio of mixing tube ($L_M/D_M$) in the range of 4 to 10. CFD studies show that at $L_M/D_M$ 5.5, the volumetric mass transfer coefficient increases with respect to gas flow rates. Meanwhile, at $L_M/D_M$ 4, the plot of volumetric mass transfer coefficient to gas-liquid flow rates ratio reach maximum at gas-liquid flow rates ratio of 0.6. This study also shows that volumetric mass transfer coefficient decrease with respect to the increase of mixing tube length.

• 반도체디스플레이기술학회지
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• 제22권2호
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• pp.35-39
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• 2023

Silicon oxide thin films have been deposited by plasma-enhanced chemical vapor deposition in SiH4 and N2O plasma along the variation of the gas flow ratio. Optical emission spectroscopy was employed to monitor the plasma and ellipsometry was employed to obtain refractive index of the deposited thin film. The atomic ratio of Si, O, and N in the film was obtained using XPS depth profiling. Fourier Transform Infrared Spectroscopy was used to analyze structures of the films. RI decreased with the increase in N2O/SiH4 gas flow ratio. We noticed the increase in the Si-O-Si bond angles as the N2O/SiH4 gas flow ratio increased, according to the analysis of the Si-O-Si stretching peak between 950 and 1,150 cm-1 in the wavenumber. We observed a correlation between the optical emission intensity ratio of (ISi+ISiH)/IO. The OES intensity ratio is also related with the measured refractive index and chemical composition ratio of the deposited thin film. Therefore, we report the added value of OES data analysis from the plasma related to the thin film characteristics in the PECVD process.

• 한국결정성장학회지
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• 제13권3호
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• pp.145-151
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• 2003

전산유체역학을 이용하여 전형적인 구조를 갖는 사이클론 분리기 시스템 내에서의 주입 가스 유동 및 입자 거 동해석을 통해 가스 주입 유속에 따른 입자 거동 양상을 3차원적으로 해석하였다. 해석 결과는 Navier-stokes 방정식을 이용한 유체 유동 현상과 Lagrangian 접근법을 이용한 입자 거동 경로 추적을 결합시켜 도출되었다. 주입 유속이 증가함에 따라 내부 압력 손실이 증가하였고 이런 내부 압력 변화는 분리기 내의 유체의 유동 양상에 영향을 미쳤다. 입자의 거동은 유체의 유동에 의해 결정되었으며 일정 유속에 대해서는 입자의 크기에 크게 의존하였다. 그리고 주입 유속의 증가는 입자의 경로를 증가시키면서 분리기의 하부 영역으로 이동시켰다. 이로 인해 분리기내에 존재하는 입자의 최소 크기가 작아지며 일정 크기의 입자의 경우 분리율이 증가하였다. 결론적으로 가스 유입 유속의 변화는 내부의 유체 유동 변화와 입자 거동 양상에 중요한 요인이 된다.

• 한국토양환경학회지
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• 제5권3호
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• pp.35-54
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• 2001

가스와 물이 공존하는 쓰레기 매립지에 개설된 여러개의 포집정으로부터 매립가스와 침출수의 추출량을 정확히 예측한다는 것은 매우 어렵다. 그러나 매립지 공극에 포함된 침출수와 가스의 상대적인 투과능력을 파악할 수 있다면 추출량을 어느정도 예측할 수 있다. 즉, 현장과 유사한 실험환경에서 침출수와 가스의 상대유체투과도를 측정하여 이 값을 다공질 매질을 통과하는 다상 유체유동방정식의 입력자료로 사용함으로써 포집정으로부터 각상의 추출량을 얻을수 있다.