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원자로배수탱크내 Sparger에 대한 유동특성 및 최적설계
김광추,박만홍,박경식,이종원,Kim, Kwang-Chu,Park, Man-Heung,Park, Kyoung-Suk,Lee, Jong-Won 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.11
A numerical analysis for ROT sparger of PWR(Pressurized Water Reactor) is carried out. Computation is performed to investigate the flow characteristics as the change of design factor. As the result of this study, RDT sparger's flow resistance coefficient is K=3.53 at the present design condition if engineering mar&in is considered with 20%, and flow ratio into branch pipe is $Q_s/Q_i=0.41$. Velocity distribution at exit is not uniform because of separation in branch pipe. In the change of inlet flow rate and section area ratio of branch pipe for main pipe, flow resistance coefficient is increased as $Q_s/Q_i$ decreasing, but in the change of branch angle and outlet nozzle diameter of main pipe, flow resistance coefficient is decreased as $Q_s/Q_i$ decreasing. As the change rate of $Q_s/Q_i$ is the larger, the change rate of flow resistance coefficient is the larger. The change rate of pressure loss is the largest change as section area ratio changing. The optimal design condition of sparger is estimated as the outlet nozzle diameter ratio of main pipe is $D_s/D_i=0.333$, the section area ratio is $A_s/A_i=0.2$ and the branch angle is ${\alpha}=55^{\circ}$.
CFD 해석을 통한 증기세척배관에 부착된 소음기로부터 방출되는 비산 입자들의 거동에 관한 고찰
김광추(Kwang Chu Kim),박만흥(Man Heung Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
A numerical analysis was performed to investigate on the motion of flying particles released from silencer connected to the steam blow-out pipe to air. Multiphase flow models were used for simulation by air, steam and particles. Used were mixture model and discrete phase model based on Euler-Lagrange method. Investigated was particle motion with the change of diameter/flow rate of particles and skirt length of cap. The results show that the shape of flying particles motion is not affected by the flow rate of particles, but that is affected by the particle diameter and the skirt length of cap. As the particle diameter is larger, the reflection and the maximum flying distance are increased. As the skirt length of cap is more extended, the maximum flying distance is decreased.
복합화력 탈질설비 성능향상을 위한 암모니아 주입 그리드의 최적설계 방안에 관한 연구
김광추(Kwang Chu Kim),박만흥(Man Heung Park),윤준규(Kyu-Yoon Jun),임종한(Jong-Han Lim) 대한설비공학회 2007 설비공학 논문집 Vol.19 No.12
A Study on the optimal design of the AIG(Ammonia Injection Grid) to improve the performance of DeNOx facilities in the HRSG(Heat Recovery Steam Generator) was performed using the CFD analysis. On the basis of the flow analysis results in the case that the AIG in the HRSG was not installed, the numerical analyses according to the positions of AIG, injection angles of nozzle and the control of ammonia injection quantity were carried out. The standard deviation according to factors was calculated for quantitative comparison. As the results, the AIG in the HRSG should be installed in the position that the uniform flow field shows through the exact flow analysis in the previous of the AIG design and installation. In the case the AIG has already been installed and non uniform flow distribution shows, it is recommended that flow correction device or KoNOx catalyst should be used. Otherwise, the control of ammonia injection angle or the ammonia injection quantity using the velocity profile analysis is demanded to accomplish the optimal performance.
김광추(Kwang Chu Kim),박만흥(Man Heung Park),염학기(Hag Ki Youm) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
A variety of schemes were sought for a mitigation of thermal stratification phenomenon in the branch piping of domestic nuclear power plant. Several mechanisms of thermal stratification occurrence were introduced in this paper. A number of factors were selected to find out the schemes for thermal stratification mitigation and the computational analysis were performed. The length of vertical branch piping, the diameter, the radius of curvature of the elbow, the direction of connection between main piping and branch piping, the slope of branch piping, the leakage flow rate, the installation of additional valve, the change of the 1<SUP>st</SUP> valve position and another branch piping connected with branch piping were mentioned as factors in this paper.
CFD를 이용한 고압파이프 파단 시 초음속제트의 압축성유동 특성에 관한 수치해석
정종길(Jong-Kil Jung),김광추(Kwang-Chu Kim),윤준규(Jun-Kyu Yoon) 대한기계학회 2017 大韓機械學會論文集B Vol.41 No.10
고압의 파이프 파단 시 파이프 내에 있던 유체가 고속으로 대기로 분출될 때 압축성유동을 동반하는 초음속제트가 발생한다. 이러한 초음속제트는 일반적으로 복잡한 비정상거동을 보여줄 수 있다. 본 연구는 이러한 고압파이프에서 분출되는 초음속제트에 의해 생성되는 압축성유동을 고찰하기 위하여 전산유체역학 해석이 수행되었다. 분출기체의 종류 및 파이프직경 변화에 따른 비정상유동 특성을 해석하기 위해 SST k - ω 난류모델이 채택되었다. 전산해석 시 기본 경계조건은 파이프직경 10 cm, 제트 압력비 5, 기체온도 300 K로 가정하였다. 그 해석결과로 초음속제트로 인해 생성되는 충격파의 거동이 관찰되었고, 간접적인 영향으로 폭풍파도 발생됨을 알 수 있었다. 기체의 분자량이 가장 작은 H₂의 압력파 특성은 안전영역까지의 거리가 가장 짧았으며, 분자량이 비슷한 N₂, 공기 및 O₂는 큰 차이가 없었다. 또한 파이프직경이 커져 제트에 의한 영향범위도 더욱 증대됨을 알 수 있었다. A rupture in a high-pressure pipe causes the fluid in the pipe to be discharged in the atmosphere at a high speed resulting in a supersonic jet that generates the compressible flow. This supersonic jet may display complicated and unsteady behavior in general . In this study, Computational Fluid Dynamics (CFD) analysis was performed to investigate the compressible flow generated by a supersonic jet ejected from a high-pressure pipe. A Shear Stress Transport (SST) turbulence model was selected to analyze the unsteady nature of the flow, which depends upon the various gases as well as the diameter of the pipe. In the CFD analysis, the basic boundary conditions were assumed to be as follows: pipe of diameter 10 cm, jet pressure ratio of 5, and an inlet gas temperature of 300 K. During the analysis, the behavior of the shockwave generated by a supersonic jet was observed and it was found that the blast wave was generated indirectly. The pressure wave characteristics of hydrogen gas, which possesses the smallest molecular mass, showed the shortest distance to the safety zone. There were no significant difference observed for nitrogen gas, air, and oxygen gas, which have similar molecular mass. In addition, an increase in the diameter of the pipe resulted in the ejected impact caused by the increased flow rate to become larger and the zone of jet influence to extend further.
덕트누기시험기용 풍량측정 오리피스의 최적위치 선정에 관한 연구
이승철(Seung-Chul Lee),박만흥(Man-Heung Park),김광추(Kwang-Chu Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
In this study, five experiments were carried out, with an orifice located downstream of a fan in case I and upstream distance to the fan in the rest cases(case II V), so as to determine the optimal location of the orifice and reduce the size of airflow measurement device. The resulting flow rate-pressure drop correlations were found to satisfy the limitation of SMACNA standard, which specified an error of ±7.5% based on the real flow rate. The best outcome was achieved with the orifice located midway of the orifice duct 4 times its diameter long.
사각블록을 갖는 채널내의 유체운동에 관한 수치해석적 연구
정경진,김광추,이종원,김종현 慶熙大學校 레이저 工學硏究所 1994 레이저공학 Vol.5 No.-
A numerical study of fluid flow in the channel with rectangular blocks is performed by using finite volume method. SIMPLER algorithm and Power-law scheme are used for numerical scheme. Numerical computation is divided into the precomputation and the main computation. In the precomputation, driven square cavity and backward-facing step are studied, and the results are shown to agree with other numerical and experimental data. In the main computation, convergence become more slow as the Reynolds number is increased. For flow fields near blocks, the severe pressure gradient is formed near the upper-left corner, and recircular zones are formed in the front and rear of blocks and in the space of blocks. In addition, the size of the recircular zone become larger as the Reynolds number increases.