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기액 이상류를 전파하는 약한 충격파에 관한 이론해석적 연구
전구식(Gu-Sik Jun),백승철(Seung-Cheol Baek),김희동(Heuy-Dong Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
Two-phase flow of liquid and gas through pipe lines are frequently encountered in nuclear power plant or industrial facility. Pressure waves which can be generated by a valve operation or any other cause in pipe lines propagate through the two-phase flow, often leading to severe noise and vibration problems or fatigue failure of pipe line system. It is of practical importance to predict the propagation characteristics of the pressure waves for the safety design for the pipe line. In the present study, a theoretical analysis is performed to understand the propagation characteristics of a weak shock wave in a bubbly flow. A wave equation is developed using a small perturbation method to analyze the weak shock wave through a bubbly flow with comparably low void fractions. It is known that the elasticity of pipe and void fraction significantly affect the propagation speed of shock wave, but the frequency of relaxation oscillation which is generated behind the shock wave is not strongly influenced by the elasticity of pipe. The present analytical results are in close agreement with existing experimental data.
전구식(Gu-Sik Jun),백승철(Seung-Cheol Baek),김희동(Heuy-Dong Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Two-phase flow of liquid and gas through pipelines are frequently encountered in nuclear power plant or industrial facility. Pressure waves which can be generated by a valve operation or any other cause in pipe lines propagate into the two-phase flow, often leading to severe noise and vibration problems or fatigue failure of pipeline system. It is of practical importance to predict the propagation characteristics of the pressure waves for the safety design for the pipeline. In the present study, the experiment is performed to investigate the effect of void fraction on the propagation characteristics of weak pressure waves in a bubbly flow. The operating pressure of the shock tube and void fraction is changed. The pressure measurements are conducted by pressure transducers attached on the pipe, and the phenomena are analyzed in frequency domain. The measured results show that the propagation characteristics of weak pressure waves in bubbly flow are affected by the void fraction.
볼밸브를 통하는 압축성유동의 특성에 관한 수치해석적 연구
전구식(Gu-Sik Jun),백승철(Seung-Cheol Baek),김희동(Heuy-Dong Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
A ball valve is one of the flow devices most frequently employed in a pipeline system, but the gas flow passing through it is hardly known since the flow is subjected to extremely complicated, unsteady and 3- dimensional phenomena. Under a certain condition, the flow is choked at the minimum area section of the valve and strong flow oscillations occur inside the valve. For the safe operation and lower maintenance cost of a pipeline system, the flow characteristics around the ball valve should be fully understood. In the present study, a computational work has been made to investigate the flow characteristics passing through a ball valve. The 3-dimensional compressible Navier-Stokes equations have been solved using a fully implicit finite volume scheme. It is found that the oscillations are associated with the rotational flow motions which occur in the passage between the valve and valve seat. The present results show that this oscillation strongly depends on both mass flow rate and valve opening.
증기밸브 주위를 지나는 유동특성에 관한 수치해석적 연구
전구식(Gu-Sik Jun),이권희(Kwon-Hee Lee),김희동(Heuy-Dong Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
A control valve is one of the flow devices most frequently employed in pipeline system, but the gas flow passing through it is hardly known since the flow is subject to extremely complicated, unsteady, and 3- dimensional phenomena. Under a certain condition, the flow is choked at a minimum area of valve and strong flow oscillation occurs inside the valve. For the safe operation and lower maintenance cost of pipeline system, the flow characteristics around control valve should be fully understood. In the present study, a computational work has been made to investigate the flow characteristics passing through a system control valve. The 3- dimensional compressible Navier-Stokes equations have been solved using a fully implicit finite volume scheme. It is found that the oscillation is associated with the rotational flow motions which occur the passage between the valve and valve seat. The present results shows that this oscillation strongly depends on mass flow rate and valve opening.
전구식(Gu-Sik Jun),백승철(Seung-Cheol Baek),김희동(Heuy-Dong Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Two-phase flow of liquid and gas through pipelines are frequently encountered in nuclear power plant or industrial facility. Pressure waves which can be generated by a valve operation or any other cause in pipe lines propagate into the two-phase flow, often leading to severe noise and vibration problems or fatigue failure of pipeline system. It is of practical importance to predict the propagation characteristics of the pressure waves for the safety design for the pipeline. In the present study, the experiment is performed to investigate the effect of void fraction on the propagation characteristics of weak shock waves in a bubbly flow. The operating pressure of the shock tube and void fraction is changed. The pressure measurements are conducted by pressure transducers attached on the pipe. The measured results show that the propagation characteristics of weak shock waves in bubbly flow are affected by the void fraction.
Octamethylcyclotetrasiloxane를 이용한 광섬유 클래드 프리폼 형성
최진석,이태균,박성규,이가형,전구식,안성진,Choi, Jinseok,Lee, Tae Kyun,Park, Seong Gyu,Lee, Ga Hyoung,Jun, Gu Sik,An, Sung Jin 한국재료학회 2018 한국재료학회지 Vol.28 No.1
There are various manufacturing processes for pure $SiO_2$ that is used as abrasives, chemicals, filters, and glasses, and in metallurgy and optical industries. In the optical fiber industry, to produce $SiO_2$ preform, $SiCl_4$ is utilized as a raw material. However, the combustion reaction of $SiCl_4$ has caused critical environmental issues, such as ozone deficiency by chlorine compounds, the greenhouse effect by carbon dioxide and corrosive gas such as hydrochloric acid. Thus, finding an alternative source that does not have those environmental issues is important for the future. Octamethylcyclotetrasiloxane (OMCTS or D4) as a chlorine free source is recently promising candidate for the $SiO_2$ preform formation. In this study, we first conducted a vaporizer design to vaporize the OMCTS. The vaporizer for the OMCTS vaporization was produced on the basis of the results of the vaporizer design. The size of the primary particle of the $SiO_2$ formed by OMCTS was less than 100 nm. X-ray diffraction patterns of the $SiO_2$ indicated an amorphous phase. Fourier-transform infrared spectroscopy analysis revealed the Si-O-Si bond without the -OH group.
Scintillation properties of the Gd3Al2Ga3O12 : Ce crystal
김혜림,김홍주,장은정,이원근,기문광,Heun-Duk Kim,전구식,Vladimir Kochurikhin 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.1
We investigated luminescence and scintillation properties of the Gd3Al2Ga3O12 : Ce (GAGG) crystal grown in TPS(Total Polishing Solution) Co.. The GAGG crystal has the highest light yield among oxide crystal at room temperature and fast decay time for the detection of radioactivity and in nuclear and particle physics experiments and medical imaging. The scintillation properties of the GAGG crystal were studied by comparing the GAGG crystals grown by two companies. We measured an X-ray induced emission spectra, an energy resolution, an absolute light yield and a decay time. A pulse shape discrimination capability for a and g-ray was also demonstrated.