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하지수(Ji Soo Ha),심성훈(Sung Hoon Shim) 한국가스학회 2014 한국가스학회지 Vol.18 No.2
MILD 연소는 고온의 배기가스를 연소로 내에 재유입 되는 양에 따라 질소산화물 저감 특성에 많은 영향을 받는다. 본 연구에서는 MILD 연소로에서 고온의 배기가스를 연소로 내에 재순환하기 위해 코안다 노즐을 사용하였는데. 코안다 노즐의 중심에 중심 축소관을 설치한 경우와 설치하지 않은 경우에 고압공기 유량, 배기가스 유입량 특성을 수치해석을 통해 살펴봄으로써 최적의 코안다 노즐 형상을 도출하는 것을 연구의 목적으로 하였다. 본 연구의 전산 해석의 결과는 혼합가스 출구의 압력이 대기압일 때는 중심축소관이 없을 때가 배기가스 유입량이 약 18% 크게 나타나고 혼합가스 출구 압력이 증가하면 중심축소관이 있을 때가 유입량이 더 큼일 알 수 있었다. 이에 대한 분석은 노즐 목에서의 압력, 유입가스 입구와 혼합가스 출구 압력 그리고 유동 단면적으로 구성한 유입구동력으로 해석 가능하였다. A MILD(Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used a coanda nozzle for the exhaust gas recirculation in a MILD combustor. A numerical analysis was accomplished to elucidate the effect of exhaust gas entrainment toward the furnace with or without a coaxial contractor. The result of the present CFD analysis showed that the entrainment mass flow rate without a coaxial contractor had 18% larger than that with a coaxial contractor when the mixed gas outlet pressure was ambient pressure. On the other hand, if the outlet pressure increased, the mass flow rate with a contractor was larger than that without a contractor. It could be analysed by the entrainment driving force composed with the nozzle throat pressure, inlet and outlet pressures and flow cross sectional area.
Dodaran, Asgar Ahadpour,Park, Sang-Kil,Mardashti, Asadollah,Noshadi, Masoud Korean Society of Ocean Engineers 2012 International journal of ocean system engineering Vol.2 No.2
Several methods have been proposed to control the sedimentation process. These include catchment management, flushing, sluicing, density current venting, and dredging. Flushing is used to erode previously deposited sediments. In pressurized flushing, the sediment in the vicinity of the outlet openings is scoured and a funnel shaped crater is created. In this study, the effect of localized vibrations in the sediment layers on the dimensions of the flushing cone was investigated experimentally. For this purpose, experiments were carried out with two bottom outlet diameters, five discharge releases for each desired water depth, and one water depth above the center of the bottom outlets. The results indicate that the volume and dimensions of the flushing cone are strongly affected by localized vibrations.
Asgar Ahadpour Dodaran,Sang Kil Park,Asadollah Mardashti,Mehrzad Noshadi,Mohammad Afsari 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.2
Most natural river reach are approximately balanced with respect to sediment inflow and outflow. Dam construction dramatically alters this balance, creating an impounded river reach characterized by extremely low flow velocities and efficient sediment trapping. The impounded reach will accumulate sediment and lose storage capacity until a balance is again achieved, which would normally occur after the impoundment has become “filled up” with sediment and can no longer provide water storage and other benefits. This paper aims to investigate the sediment removal process in dam reservoir using simultaneously pressure flushing operation and vibrator machine. The main objective of this study is to identify the effect of vibrator in flushing cone dimensions. To achieve the objectives of present study, laboratory test have conducted under different hydraulic conditions such as two bottom outlets with diameter equal to 2” and 3”, five discharges 0.23, 0.53, 1.21, 1.53 and 2.1 lit/s and only one water depth above the center of bottom outlets. Using the vibrator machine mounted into the reservoir and close to the bottom outlet, different frequency e.g. 20, 35 and 50 HZ, have been introduced to the deposited sediment at the vicinity of outlet. The results indicate that the volume and width of flushing cone are strongly affected by frequency of vibrations. The results indicate that the volume and width of flushing cone are strongly affected by frequency of vibrations.
공병진,박다인,변상호,이상호 한국기계기술학회 2023 한국기계기술학회지 Vol.25 No.6
Air blower has been widely used in many industrial fields such as wind tunnel and large ventilation systems. Its performance is affected by operating conditions and system geometry of inpeller and duct, and these design parameter optimization is essential for the effective development. CFD analysis is carried out to investigate the air flow field characteristics with outlet total pressure in a blower system. Intake air into the impeller blade through the inlet is compressed, and then gradually discharged from the outlet with ascending total pressure, and predicted results are compared with test data. Especially this overall pressure difference in the blower system severely depends on the flow rate. These results are expected to be used as applicable design data for blower performance improvement.
Cho Ihn-Sung,Oh Seok-Hyung,Song Kyu-Keun,Jung Jae-Youn The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10
The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke's chart, which is an improvement over Johnson's chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.
Ihn-Sung Cho,Seok-Hyung Oh,Kyu-Keun Song,Jae-Youn Jung 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10
The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke’s chart, which is an improvement over Johnson’s chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 ㎫ greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.
대향류 매니폴드 입-출구 면적비에 따른 열교환기의 성능특성에 관한 수치적 연구
김상조(Sangjo Kim),최병익(Byoung-ik Chio),김귀순(Kuisoon Kim),손창민(Changmin Son),하만영(Man Young Ha),정지환(Ji Hwan Jeong),고정상(Jeong Sang Go) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.11
본 논문에서는 대향류 매니폴드의 면적비에 따른 튜브형 열교환기에서의 압력강하와 유량 균일도를 분석하기위해 전산해석을 수행하였다. 유동 분배와 압력손실 특성은 입-출구 면적비에 따라 영향을 받는다. 본 연구에서, 최적의 입-출구 면적비를 선택함으로서 튜브형 열교환기의 유동 불균일도 최소와 향상된 압력손실 특성을 얻을 수 있었다. In present paper focused on the influence of the inlet-outlet area ratio of counter flow manifold on the flow distribution and pressure drop characteristics of a tubular heat exchanger. The characteristics of flow distribution and pressure loss can be obtained depending on the inlet-outlet area ratio. In this paper, a tubular heat exchanger can be designed with minimum flow mal-distribution and better characteristic of pressure loss by choosing the optimum inlet-outlet area ratio.
고층 주거건물 급수·급탕설비의 운용실태에 따른 압력 및 유량 변화 특성에 관한 연구
석호태,여명석,조경재,김장한,차민철 대한건축학회 2005 대한건축학회논문집 Vol.21 No.6
As the structure, material and construction of building develop continuously, so the recent residential buildings are being large, high-rise and group. High-rise residential buildings consume a lot of energy on supplying cold and hot water. As well, high-rise residential buildings bring on discomfortable use and unexpected conditions on account of faucet outlet pressure rise and the difference of water supply pressure between top floor and bottom floor. Thus, the purpose of this study is to research on using conditions of cold and hot water supply system through field measurement in high-rise residential buildings and to analyze problems.
Seung Su Kim,Soon Ho Cheong,Won Jin Lee,Dong Hwa Jun,Myoung Jin Ko,Kwang Rae Cho,Sang Eun Lee,Young Hwan Kim,Se Hun Lim,Jeong Han Lee,Kun Moo Lee,Young Kyun Choe,Young Jae Kim 대한마취과학회 2010 Korean Journal of Anesthesiology Vol.58 No.1
Thoracic outlet syndrome has neurologic symptoms caused by compression of brachial plexus, blood vessel symptoms are caused by compression of the artery or vein. The authors report a case of sudden decrease in blood pressure of the left arm after turning the patient from supine position to prone position. They confirmed that the patient had thoracic outlet syndrome after performing computed tomography. (Korean J Anesthesiol 2010; 58: 91~94)
Combined operation of outlet streams swing with partial-feed in a simulated moving bed
Chang-Ha Lee,Kyung Min Kim,Ji-Yeon Song 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.3
The operational strategy of outlet streams swing (OSS) operation combined with partial-feed (PF) operation, OSS-PF, was studied under the constraint of maximum allowable pressure and flow-rate. Its separation performance and dynamic behavior were compared with those of OSS operation and conventional simulated moving bed (SMB) chromatography. During OSS-PF operation, the switching period consisted of two steps; raffinate was produced during the closed condition of extract node and feed node in the first step, while extracts were produced and feeds were injected during the closed condition of raffinate node in the second step. As a result, OSS-PF operation could be performed under the allowable maximum flow-rate in the corresponding conventional SMB without generating an additional pressure drop at the adsorbent bed, which was different from OSS operation. OSS-PF operation successfully improved the separation performance of the conventional SMB with regard to extract purity, raffinate recovery and raffinate productivity with equivalent eluent consumption. The step ratio during a switching period worked as one of important operating variables in separation performance. The dynamic behavior of OSS-PF operation was analyzed and compared with that of OSS and conventional SMB using simulated concentration profiles in the fluid phase.