• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.44-46
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• 2001

This paper describes the use of the PHOENICS CFD package for the simulation of the high-current period of the arcing process in a hybrid rotating arc/auto expansion by interrupter. The operating principle of this device depends on rapid arc rotation due to the magnetic field created by the fault current through a coil which is mounted on contacts and also relies on the principle of thermal expansion created by arc energy in extinguishing chamber and finally causes pressure rise in expansion volume. This paper is divided into three main sections. The first gives a brief overview of the interrupter. The second section gives a full description of the methods used in the calculation. The final section presents some sample results for the hybrid interrupter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.689-694
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• 2003

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported pipe conveying fluid subject to the moving mass. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass and the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The presence of crack results in higher deflections of pipe. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow and the crack severity are increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The time which produce the maximum dynamic deflection of the simply supported pipe is delayed according to the increment of the crack severity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.41-44
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• 2003

In spite of many researches made on the supersonic jets until now, detailed three-dimensional structures of supersonic jets are not well hewn. In the current study, the detailed structures of three-dimensional supersonic jets are numerically investigated using a CFD method. The total variation diminishing (TVD) scheme is used to solve the unsteady, three-dimensional, compressible Euler equations. Computational results are visualized to investigate the major features of supersonic jets. The three-dimensional computation results show that the structures of the supersonic jets are significantly different from those of the two-dimensional or axisymmetric supersonic jets.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.816-818
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• 2000

본 논문에서는 $SF_6$ 차단기 내의 대전류 아크에 대한 수치적인 해석을 모의하는 도구를 제시한다. 대전류의 차단을 위해서 해석을 통해 열적 파괴를 예측하는 것이 필수적이다. 본 논문에서 사용한 방법은 FVFLIC(finite volume fluid in cells)이며 지배방정식은 압축성 오일러 방정식으로 아크와 유동의 상호 작용을 해석한다. 아크는 기본적으로 에너지 보존식에서 열소스항으로 나타나며 주울열과 복사항으로 표현된다. 주울열은 플라즈마 영역내의 전계해석을 통해 계산되며 복사항은 방출과 흡수항의 합으로 나타내어지고 이것은 국소적인 온도와 압력의 함수이다. 본 논문에서는 수정된 방출과 흡수 모델로 복사 열전달을 계산하였다.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.171-176
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• 1999

In the present paper, three types of the flow solvers were used to investigate the influence on the airfoil shape optimization. The adopted equations, i.e., Euler , thin layer Navier- Stokes and full Navier-Stokes ones, are solved using implicit LU-ADI decomposition scheme. The feasible direction algorithm with the sinusoidal function was used as an optimization algorithm. The present numerical method was applied to the drag minimization problems under the initial shape of NACA0012 airfoils.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.30-32
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• 2001

There are many difficult problems in analyzing the flow characteristics in a high voltage circuit breaker such as shock wave and complex geometries, which may be either static or in relative motion. Although a variety of mesh generation techniques are now available, the generation of meshes around complicated, multi-component geometries like a gas circuit breaker is still a tedious and difficult task for the computational fluid dynamics. This paper presents the CFD program for analyzing the compressible flow fields in a high voltage gas circuit breaker using the Cartesian cut-cell method based on the CFD-CAD integration, which can achieve the accurate representation of the geometry designed by a CAD tools. This technique is frequently satisfied, and it will be almost universally so in the future, as the CFD-CAD traffic increase.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1032-1034
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• 2005

초고압 차단기 내부에는 여러 종류의 절연물들이 존재하며, 절연물들중 노즐은 차단현상에 큰 영향을 미치는 요소 중에 하나로 작용을 하고 있다. 노즐의 형상과 노즐 목의 길이, 노즐의 재질에 따라 전계강도의 차이와 유동의 흐름에 영향을 미치고 있으며 결국 차단기의 차단성능의 변화를 발생시킬수 있다. 따라서 본 논문에서는 서로 다른 형상의 노즐을 가지고 차단기 내부 접점의 이동에 따른 스트로크별 해석 데이타와 시험 데이타를 비교함으로써 절연성능의 변화를 연구하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.419-426
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• 2004

In this paper, studied about the effect of open crack and the moving mass on the dynamic behavior of simply supported pipe conveying fluid. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass, the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. Therefore, the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow is increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The position of the crack is located in the middle point of the pipe, the mid-span deflection of simply supported pipe presents maximum deflection.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.1012-1014
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• 2012

본 논문에서는 기존의 대형 모니터링 시스템의 틀에서 벗어나 정보의 신속, 정확성을 중점으로 시스템의 기능 및 특징으로는 선실들의 센서 값 을 실시간으로 표시하는 것으로 선박내의 어느 위치에서든지 한눈에 볼 수 있도록 휴대용기기로 실시간으로 모니터링 한다. 효율성으로는 선원이 모니터 실에서 모니터하지 않고 유동적으로 움직일 수 있으며 인가받은 선원도 선실을 바로 모니터링 할 수 있어 효율적인 사고 및 재난에 신속히 대응 할 수 있도록 하였다.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.757-762
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• 2018

LDV(laser Doppler velocimetry) measurements were conducted on the exit region of the impeller passage and the gap between the impeller and turbine blades under 0.8 speed ratio. The 0.8 speed ratio has an impeller speed of 2000rpm and a turbine speed of 1600rpm. A periodic variation of the mass flow rate is present in many of the measurements made. The frequency of this variation is the same as the frequency of the turbine blades passing the impeller passage exit. It is found that the instantaneous position of the turbine had effect on fluid flow inside the impeller passage and gap region. This study would aid in the construction of higher accuracy CFD models of this complex turbomachinery device.