• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 F
• /
• pp.1981-1983
• /
• 1998

The principle of the MHD generation is based on Faraday's law of induction that a eletromotive force(u ${\times}$ B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In MHD power generation system, enthalpy of the working gas is converted to electric power directly through expansion in generator channel. It means that electric power can be generated without moving mechanical linkage such as turbine blades. There are two types in the MHD generator; linear type Faraday and disk type hall generator. Disk type hall generator is the main target of this paper. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
• /
• 제24권1호
• /
• pp.11-18
• /
• 1996

A stability analysis in the geomagentotail is presented within MHD limit with a modified form ideal Ohm's law. Using the high ky approximation (ballooning limit), we derive the basic eigenmode equations which can be reduced to the ideal MHD limit. The incompressible limit is numerically solved for a number of model equilibria of tail by Kan [1973], and we have found no unstable Kan equilibrium. Also, an analytic theory is carried out for the case where Bkc is assumed to be constant along the field line, following the idea by Lee and Min [1996]. In that case, it is suggested that the tail stability to the incompressible antisymmetric mode is determined by the ideal MHD.

• 천문학회보
• /
• 제38권1호
• /
• pp.47.1-47.1
• /
• 2013

Supersonic turbulence is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this consensus of decaying magnetohydrodynamic (MHD) turbulence relies on local isothermal simulations, which are unable to investigate the role of global magnetic fields and structures. Utilizing three-dimensional MHD simulations including interstellar cooling and heating, we investigate decaying MHD turbulence within cold neutral medium sheets embedded in warm neutral medium. Early evolution is consistent with previous studies characterized rapid decay of turbulence with the decaying time shorter than a flow crossing time and power-law temporal decay of turbulent kinetic energy with slope of -1. If initial magnetic fields are strong and perpendicular to the sheet, however long term evolutions of kinetic energy shows that a significant amount of turbulent energy still remains even after ten flow crossing times, and decaying rate is reduced as field strengths increase. We analyse power spectra of remaining turbulence to show that incompressible, in-plane motions dominate.

• 대한전기학회논문지
• /
• 제38권9호
• /
• pp.733-739
• /
• 1989

유한요소법과 반복법을 적용하여 Grad-Shafranov식을 풀어 축대칭 토로이달 플라즈마의 고정경계 MHD평형을 해석하였다. 토로이달 전류항은 플라즈마 압력과 토로이달 자장함수로 표현하였고 해의 타당성 검증을 위하여 수치해석 결과를 해석적 평형과 비교하였다. 서울대의 SUNT-79장치에 적용하여 압력과 자장함수 변화에 따른 자기면 형상과 전류분포를 고찰하였고 안전인자와 ${\beta}$값도 함께 산출하였다.

• Journal of applied mathematics & informatics
• /
• 제41권5호
• /
• pp.1085-1102
• /
• 2023

In this study the magneto hydrodynamic (MHD) micro polar fluid flow of a viscous incompressible fluid past a porous medium in the presence of chemical reaction is considered. This work is devoted to investigate the Soret effect and Electromagnetic radiation effect and analyze analytically. In the energy equation the applied magnetic field strength and in the concentration equation the Soret effect are incorporated. The basic PDE (partial differential equations) are reduced to ODE (ordinary differential equations) using non dimensional variables. Then the analytical solution of the dimensionless equations are found using perturbation technique. The features of the fluid flow parameters are analyzed, discussed and explained graphically. The graphical solutions are found using MATLAB R2019b. Skin friction coefficient at the wall, Couple stress coefficient at the plate and the local surface heat flux are also thoroughly examined. Overall, this study sheds light on the complex interplay between physical parameters in the behavior of MHD micro-polar fluid past a porous medium in the presence of chemical reaction.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
• /
• pp.385-385
• /
• 2006

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 2002년도 춘계공동학술발표회요약집
• /
• pp.119-119
• /
• 2002

• 전기의세계
• /
• 제35권10호
• /
• pp.628-634
• /
• 1986

전력은 우리생활에서의 필수요소로서 그 수요가 지속적으로 증가되고 있는 반면에 기존화력 발전기술은 기술적으로 효율향상에 한계가 있기 때문에 고효율의 새로운 발전기술의 개발이 절실히 요구되고 있다. 여기서는 대체발전기술로서 선진국에서 적극 개발되고 있는 MHD발전기술에 대하여 살펴보았다. 국내에서의 본격적인 연구는 전무한 상태이나 기초연구를 통한 기술축적이 절실히 요구되는 분야이며 선진국에서의 기술개발 동향을 계속 추적분석할 필요가 있겠다.

• 천문학회보
• /
• 제40권1호
• /
• pp.65.2-65.2
• /
• 2015

We developed a three-dimensional magnetohydrodynamic (MHD) code to reproduce the structure of a solar wind, the properties of a coronal mass ejection (CME) and the interaction between them. This MHD code is based on the finite volume method incorporating total variation diminishing (TVD) scheme with an unstructured grid system. In particular, this grid system can avoid the singularity at the north and south poles and relax tight CFL conditions around the poles, both of which would arise in a spherical coordinate system (Tanaka 1994). In this model, we first apply an MHD tomographic method (Hayashi et al. 2003) to interplanetary scintillation (IPS) observational data and derive a solar wind from the physical values obtained at 50 solar radii away from the Sun. By comparing the properties of this solar wind to observational data obtained near the Earth orbit, we confirmed that our model captures the velocity, temperature and density profiles of a solar wind near the Earth orbit. We then insert a spheromak-type CME (Kataoka et al. 2009) into the solar wind to reproduce an actual CME event. This has been done by introducing a time-dependent boundary condition to the inner boundary of our simulation domain. On the basis of a comparison between a simulated CME and observations near the Earth, we discuss the physics involved in an ICME interacting with a solar wind.

• 전력전자학회논문지
• /
• 제4권5호
• /
• pp.405-412
• /
• 1999

메탈 할라이드 방전 램프는 연색성이 좋고 수명이 길며, 점광원이기 때문에 조명제어가 용이한 장점이 있으나, 고압 방전 할 때 방전관애의 음향 공명 현상을 감소하기 위하여 MHD 램프용 전자식 안정기의 주요부를 첫째, 구형파를 얻기 위한 타려식 하프브리지 인버터와 둘째, 저주파인 구형파에 고주파를 첨가하기 위한 플라이백 컨버터로 실현하였다. 이와 같이 설계 제작된 전자식 안정기로 70W의 MHD 램프를 점등한 결과 음향 공명 현상인 광속의 흔들림이 없는 매우 양호한 조명이 되었다.