OMACON형 LM-MHD 시스템에서의 에너지전환특성 시뮬레이션

김창녕 한국시뮬레이션학회 1997 한국시뮬레이션학회 논문지 Vol.6 No.2

The characteristics of the flow and energy conversion in OMACON liquid-metal MHD system are investigated. Numerical simulation of two-phase flow in the OMACON system without magnetic field was carried out by the Phoenics code and the energy conversion characteristics are studied in association with the fact that the mechanical energy loss at the nozzle of the OMACON system are to be converted into electrical energy. In this system, working fluid (gas) is injected through the mixer located at the bottom of the riser, and is mixed with hot liquid metal. Therefore in the riser two-phase flow is developed under the influence of the gravity. In this study, the interaction between the gas and liquid is considered by the use of IPSA(InterPhase Slip Algorithm) where standard drag coefficient has been used. It has been assumed that in the flow regime the liquid is continuous and the gas is dispersed. For the liquid and gas, the continuity equations, momentum equations and energy equations are solved respectively in association with void fraction in the flow field. In order to calculate the energy conversion efficiency, firstly the ratio of the mechanical energy loss of liquid metal flow at the nozzle to the input thermal energy is considered. Secondly flow pattern of liquid metal in the generator has been analyzed, and the characteristics of the conversion of the mechanical energy into the electrical energy has been investigated. For an representative case where Hartmann number is 540 and magnetic field is 0.35 T, the present analysis shows that the energy conversion efficiency is 0.653. This result is considered to be reasonable in comparison with published experimental results.

Numerical examination of liquid metal magnetohydrodynamic flow in multiple channels in the plane perpendicular to the magnetic field

김창녕 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12

In the current study, investigated are steady-state, three-dimensional liquid metal (LM) magnetohydrodynamic (MHD) flows in a conduitsystem including three sub-channels with co-current flows under a uniform magnetic field. Though there have been numerous analytic,experimental and numerical studies on MHD duct flow, detailed flow characteristics of a LMMHD flow in a conduit system withmultiple channels have not been reported much. The current study predicts detailed behaviors of the flow velocity, pressure, current andelectric potential of LMMHD flows in multiple channels in the plane perpendicular to the magnetic field. Here, the characteristics of theMHD flow in a conduit system with multiple channels are elucidated. The mass flow rate in each of outer channel turns out to be higherthan that in the central channel. The mechanism governing the imbalance of mass flow rate in the sub-channels is discussed in detailbased on the interdependency of flow variables in LMMHD flow.

Czochralski 유동장에서 Boron의 거동에 관한 수치적 연구

김창녕 慶熙大學校 1993 論文集 Vol.22 No.-

The characteristics of flows, tremperatures, concentrations of the Boron are numerically studied when uniform axial magnetic fields are applied in the Czochralski crucible. The governing factors to the flow regimes are byuoyancy, thermocapillarity, centrifugal forces, magnetic forces, diffusion coefficient and segregation coefficient of the Boron. Since th concentration of the Boron is so low that the buoyancy effects are negligible, it cannot affect the flow and temperature fields. From the fact that the flow fields are rotationally symmetric, two velocity components in the meridional plane and the circumferential velocity are calculated together with the temperature in the steady state. Based on the known velocity and temperature distributions the unsteady concentration distributions of the Boron are calculated. As the strength of the magnetic is increased, the flow velocities are decreased. Circumferential velocities are large near the crucible side-wall and in the region below the rotating crystal. Steep temperature gradient near the edge of the rotating crystal causes the Marangoni convection. It has been found out that the convection characteristics affects the unsteady transport phenomena of the Boron.

자기장이 인가된 초크랄스키 실리콘 단결정 성장에서 산소의 거동특성

김창녕 慶熙大學校 1998 論文集 Vol.27 No.-

The characteristics of concentration of oxygen are numerically investigated for various magnetic fields in the Czochralski single crystal growth. Flow fields with uniform axial and cusp magnetic fields are studied for concentration of oxygen. The distributions of temperature and concentration of oxygen are strongly dependent on flow field. Uniform axial magnetic field suppresses the inward flow at the free surface so that the gradient of oxygen concentration is much large at the free surface and is very small at the growing surface of crystal. While in cusp magnetic field, the gradient of oxygen concentration on the growing surface decreases as the magnetic field increases.

경사진 자장의 영향을 받는 관안에서의 자기유체유동

김창녕 金烏工科大學校 1990 論文集 Vol.11 No.-

A numerical procedure ws devised to predict the characteristics of the flow field in a liquid metal magnetohydrodynamic(MHD) flow. By the use of the procedure, a steady-state, incompressible, viscous, three-dimensional MHD flow under the influence of a magnetic field applied obliquely at an angle of 45˚ to each side wall of a rectangular duct has been studied at an extremly low magnetix Reynolds number by means of a finite volume method. The use of the control volume approach enables the implementation of the corrective step based on the fluid flux across the face of the volume, which contributes to convergence and physical accuracy. Numerical results shows that the axial velocities are large on the diagonal region of the cross-section lying parallel to the magnetic field with the peak velocities located at the corners.

실리콘 단결정 성장에서 용융물질의 회전효과

김창녕,이제희 慶熙大學校 材料科學技術硏究所 1996 材料科學技術硏究論集 Vol.9 No.-

For various angular velocities of crucible and crystal, the characteristics of melt flows, temperatures and concentrations of oxygen are numerically studied in the Czochralski furnace with a uniform axial magnetic field. With an assumption that two velocity components in the meridional plane and circumferential velocity, temperature, electric current intensity have reached the steady state, unsteady concentration field of oxygen has been analyzed with an initially uniform oxygen concentration. when the angular velocities of crucible and crystal are remarkable, oxygen cannot be easily transported to the area close to the bottom of crystal due to the noticeable centrifugal force. Therefore absorption rate of oxygen to the surface of crystal growth is small and is nearly uniform in the radial direction. On the contrary, when the angular velocities are small, the absorption rate of oxygen shows large gradient in the radial direction.

磁場의 영향을 받는 Czochralski 유동장에 관한 수치적 연구

김창녕 慶熙大學校 1992 論文集 Vol.21 No.-

均一한 磁場이 Czochralski 도가니에 가하여졌을 때의 溫度場과 流動場이 數値的으로 연구되었다. 여기에서 온도차이에 의한 浮力, 自由表面에서의 반경방향으로의 온도구배로 因한 thermocapillarity, 도가니와 結晶의 회전으로 인한 遠心力및 외부에서 걸러준 磁場에 의한 磁性力등이 Czochralski 유동장을 지배하고 있다. 회전방향으로의 對稱性으로부터 자오평면 (meridional plane) 에서의 속도성분과 회전방향의 속도성분이 구하여졌으며 온도, 압력, 電位등이 해석되었다. 磁場의 영향아래에서의 Czochralski 流動場에서는 회전방향의 속도성분이 電位의 구배를 惹起시키고 있는데 이러한 회전방향의 속도성분을 대류작용에 의하여 도가니벽에서부터 자유표면을 다라 결정표면의 아래까지 전달되어 현저하게 나타난다. 또 이러한 회전방향의 속도성분을 結晶표면의 아래에서 큰 반경방향으로의 압력구배를 만들어주고 있다. 磁場의 세기가 큰 경우에 모든 속도성분이 작아지고 있으며 결정표면 아래에서 압력구배가 작아진다. 이와 같이 磁場의 영향아래에서의 Czochralski 유동장의 이해하게 되면 受動性을 갖는 solute의 濃度에 관한 擧動을 把握할 수 있게 될 것이다.

장방형관에서의 자기유체유동

김창녕 金烏工科大學校 1991 論文集 Vol.12 No.-

In order to simulate flows in an MHD pump, a three-dimensional, steady-state, incompressible, liquid metal magnetohydrodynamic(MHD) flow has been investigated under the influence of applied magnetic and electric fields. Governing equations including the viscous and inertial effects are solved by means of the finite volume method. At an intermediate interaction parameter and Hartmann number, the distributions of axial velocity, pressure and electric current are obtained under, the assumption that magnetic Reynolds number is very small. In the vicinity of electrodes, the axial velocity distribution is generally flatted and the velocities near the electrodes become larger, yielding M shape profile. Here, the velocity gradients near the duct walls are very steep, forming side layers and Hartmann layers. As the fluid passes the electrodes, the pressure becomes lager and the peculiar pressure behavior near the edge of the electrodes is seen. The transverse electrical currents are concentrated in the Hartmann layers. This study has shown the intrinsic three-dimensional effect of the MHD flow which was not reported yet by one-.and two- dimensional approaches.

Misaligned된 비균일 자장이 인가된 초크랄스키 유동특성에 대한 수치적 해석

김창녕 慶熙大學校 材料科學技術硏究所 1999 材料科學技術硏究論集 Vol.12 No.-

Flow Characteristics have been analyzed numerically in the process of Czochralski single crystal growth of silicon under the influence of misaligned cusp magnetic fields. Since the silicon melt in a crucible for crystal growth is of high temperature and of highly electrical-conducting, experimentation method has difficulty in analyzing the behavior of the melt flow. A set of simultaneous nonlinear equations including Navier-Stokes and Maxwell equations has been used for the modelling of the melt flow which can be regarded as a liquid metal. Together with the melt flow which forms the Marangoni convection, a flow circulation is observed near the corner close both to the crucible wall and the free surface. The melt flow tends to follow the magnetic lines instead of traversing the lines. These flow characteristics helps the flow circulation exist.

두 전극이 있는 장방형관에서의 자기유체유동

김창녕 한국항공우주학회 1991 한국항공우주학회 학술발표회 논문집 Vol.- No.-