기-액 2상유동에 따른 원심펌프 성능변화에 대한 연구

이종철,김윤제,김철수,Lee, Jong C.,Kim, Youn J.,Kim, C.-S. 한국유체기계학회 2000 한국유체기계학회 논문집 Vol.3 No.3

In this study, experimental and numerical analyses are carried out to investigate the performance of centrifugal pump with various air admitting conditions. Experiments on the pump performance under air-water two-phase flow are accomplished using a centrifugal pump with semi-open type impeller having three, five and seven blades, respectively. Also, the numerical analysis of turbulent air-water two-phase flow using the finite volume method has been carried out to obtain the pressure, velocities and void fraction on the basis of a so-called bubbly flow model with the constant size and shape of cavity. The results obtained through this study show the reasonable agreements within the range of bubbly flow regime. There are promising developments concerning application of the present study for the flow in a centrifugal pump with two-phase flow conditions and efforts must be followed to improve the turbulence model and two-phase flow model for turbomachinery.

랑뮤어 탐침에 의해 변형된 열플라즈마 특성에 관한 해석적 연구

이종철,김윤제,Lee, J.C.,Kim, Y.J. 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.3

플라즈마 진단법 중 손쉽고 구동이 용이한 장점으로 인해 범용 플라즈마 진단 장치로 사용되는 랑뮤어 (Langmuir) 탐침법은 탐침이 직접 플라즈마 내에 삽입됨으로써 플라즈마를 간섭하기 때문에 플라즈마 고유의 특성을 변형시키는 약점이 있다. 본 연구에서는 대기압 아르곤 자유 연소 아크 (free-burning arc)에 삽입된 랑뮤어 탐침에 의한 교란 영향을 고찰하기 위하여 탐침 유무에 따른 열플라즈마 상태를 수치계산 하였고, 온도장과 속도장이 왜곡된 정도를 비교 분석하였다. 열플라즈마를 모델링하기 위하여 열유동장과 전자기장에 관한 두 종류의 지배방정식을 상용 CFD 프로그램과 자체 제작한 서브루틴을 이용하여 연계 계산하였다. 삽입된 탐침에 의해 열플라즈마 온도장은 탐침의 앞뒤에서 모두 플라즈마 축의 수직 방향으로 큰 변화를 나타내는 열적 교란이 발생되었다. 속도장에서는 탐침 선단의 정체 영역과 후단 후류 영역에서 유동 교란이 발생되었으며, 삽입 된 탐침의 영향이 국부적인 것이 아닌 플라즈마 유동장 대부분 영역에 영향을 미침을 확인할 수 있었다. 따라서 탐침법의 신뢰성을 높이기 위해서는 탐침 삽입에 의한 플라즈마의 열유체역학적 교란을 고려해야 한다. Measurements with a Langmuir probe, which are the most often used procedures of plasma diagnostics, can disturb plasma flows and change its characteristics quite a little because the probe should be inserted into thermal flowing plasmas. In this study, we calculated the characteristics of thermal plasmas with and without the probe into an atmospheric argon free-burning arc numerically, and investigated aerodynamic and thermal disturbances with temperature and axial velocity distributions. For the modelling of thermal plasmas, we have made two governing equations, which are on the thermal-flow and electromagnetic fields, coupled together with a commercial CFD package and user-coded subroutines. It was found that thermal disturbances happened to both sides of the probe, before and behind, seriously. Due to the aerodynamic disturbance, we could find that there were the stagnation point in front of the probe and the wake behind it. Therefore, aerodynamic and thermal disturbances caused by the probe insertion should be considered to increase the reliability of the probe diagnostics.

탄소나노튜브 가스센서의 SF₆ 분해생성물 검출 및 확산현상에 관한 연구

이종철,정세훈,백승현,Lee, J.C.,Jung, S.H.,Baik, S.H. 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.1

가스절연개폐장치 (Gas-insulated switchgear, GIS)의 내부에는 절연에 관한 이상 여부를 감시하고 판단할 수 있는 시스템이 요구된다. 부분방전에 의해 발생되는 $SF_6$ 분해생성물에 관한 단일벽 탄소나노튜브 (Single-walled carbon nanotube, SWNT)가 지닌 우수한 검출기능 때문에 SWNT를 이용한 가스센서 개발이 활발히 진행되고 있다. 하지만 아직까지 부분방전에 의해 발생된 분해생성물의 확산현상에 관한 해석적 연구는 미흡한 실정이다. 본 논문에서는 실험 데이터 및 상용 CFD (Computational Fluid Dynamics) 프로그램을 이용하여 SWNT 가스센서에 포획되는 분해생성물의 코로나 방전에 의한 발생 과정과 챔버 내부에서의 확산과정을 모델링하여 부분방전 발생 시 챔버 내부의 온도, 압력, 그리고 분해생성물의 농도 등을 수치계산하였다. 분해생성물의 시간당 질량생성율과 발생온도는 각각 $5.04{\times}10^{-10}$ [g/s]와 773 K이라 가정하였다. 농도방정식을 계산함에 있어 미지의 확산계수를 임의의 값으로 가정하여 직접 부여하는 방법을 사용하지 않고, 확산계수를 정의하는데 사용되는 Schmidt수의 값을 지정하여 확산계수가 $SF_6$ 가스의 물성치인 점성계수와 밀도의 함수로 계산되도록 하였다. 수치결과로부터 분해생성물의 농도구배가 확산을 일으키는데 주요 구동포텐셜 (Drive potential)이 됨을 확인하였다. 센서 설치위치가 부분방전 발생영역에서 멀리 떨어질수록 분해생성물 농도가 낮음을 알 수 있었고, 부분방전이 지속될수록 분해생성물의 농도가 증가함을 확인하였다. 다수의 센서를 챔버 내부에 설치하면 각 센서의 응답시간을 확인하여 PD 발생위치를 판단할 수 있을 것이고, 이를 통해 GIS 진단 및 유지보수에 관한 유용한 정보로 사용될 수 있을 것이다. The detection methods are required to monitor and diagnose the abnormality on the insulation condition inside a gas-insulated switchgear (GIS). Due to a good sensitivity to the products decomposed by partial discharges (PDs) in $SF_6$ gas, the development of a SWNT gas sensor is actively in progress. However, a few numerical studies on the diffusion mechanism of the $SF_6$ decomposition products by PD have been reported. In this study, we modeled $SF_6$ decomposition process in a chamber by calculating temperature, pressure and concentration of the decomposition products by using a commercial CFD program in conjunction with experimental data. It was assumed that the mass production rate and the generation temperature of the decomposition products were $5.04{\times}10^{-10}$ [g/s] and over 773 K respectively. To calculate the concentration equation, the Schmidt number was specified to get the diffusion coefficient functioned by viscosity and density of $SF_6$ gas instead rather than setting it directly. The results showed that the drive potential is governed mainly by the gradient of the decomposition concentration. A lower concentration of the decomposition products was observed as the sensors were placed more away from the discharge region. Also, the concentration increased by increasing the discharge time. By installing multiple sensors the location of PD is expected to be identified by monitoring the response time of the sensors, and the information should be very useful for the diagnosis and maintenance of GIS.

전류용량 변화에 따른 초고압 진공차단부 온도상승에 관한 실험적 연구

이종철(J. -C. Lee),김우영(W. Y. Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Nowadays, it is emphasized that the rated-current and the thermal performance should be improved together in order to satisfy the market demands on scale-down, safe function and reliability in the development of large-scale electric equipments as well as small-scale electronic devices. Due to the high complexity of heat generation and loss mechanism, it is not easy to predict the temperature-rise of switchgears under various load conditions. In this paper, we made experiments on the temperature-rise of an ultrahigh-voltage (UHV) vacuum interrupter (VI), which is the main component of vacuum switchgear, with the various rated-currents. It was found that the maximum limit of the rated-current of VI is investigated with the international standard (IEC-60943) and correlates with the electrical contact resistance between electrodes inside the vacuum bottle.

고온 아크 플라즈마에 의한 PTFE 용삭 모델링

이종철(J. -C. Lee),김태윤(T. Y. Kim),김홍규(H. K. Kim),김윤제(Y. -J. Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

The high-voltage circuit breaker plays an important role in the electrical system because there has been a need for suitable switching devices capable of initiating and interrupting the flow of the electric current. It continues as the contacts recede from each other and as the newly created gap is bridged by a plasma. The arc plasma happens inside the insulation nozzle of SF6 self-blast interrupter which is newly developed as the next-generation switching principle. The ablation of PTFE nozzle is caused by this high temperature medium, the PTFE vapor generated flows toward the outlets and the pressure chamber. This PTFE vapor makes the pressure inside the compression chamber increase. Because the rate of ablation depends on the magnitude of applied current, it decreases when the current goes to zero. The compressed gas inside the chamber flows reversely toward the arc plasma during this moment. According to this principle, the arc can be cooled down and the fault current can be interrupted successfully. In this study, we investigate numerically the relationship between the rate of ablation on the surface of PTFE nozzle and the pressure-rise inside the chamber. From the results near current zero such as the temperature of arc plasma and the characteristics of thermal-flow, we might predict the success or not of switching performance of the interrupter.

전력용 개폐장치의 열플라즈마 유동에 관한 수치해석

이종철(J. -C. Lee),김우영(W. Y. Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5

In this study, we calculated thermal plasmas happened in two types of switchgears for understanding the complex physics and the probability of thermal breakdown. The first part concerns modeling of switching arc itself with an auto-expansion chamber as an example. The second part focuses on simulation of the PTFE nozzle ablation effect by high-temperature switching arc with an puffer-assisted self-blast switchgear. The present method is expected to be useful for setting guideline of switchgear design and predicting the interruption capacity of arcing chambers.

대기압 아르곤 자유연소아크에 관한 수치해석적 연구

이종철(J. -C. Lee),이원호(W. -H. Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

폴리우레탄 양 아이오노머의 기본 구조 물성

이종철(J . C . Lee),김병규(B . K . Kim) 한국고분자학회 1993 폴리머 Vol.17 No.6

테스트가 용이한 CMOS 순서 PLA의 설계

이종철(J. C. Lee),임재윤(J. Y. Lim),한석붕(S. B. Han),홍인식(I. S. Hong),임인칠(I. C. Lim) 대한전기학회 1987 대한전기학회 학술대회 논문집 Vol.1987 No.7

CMOS PLA의 Stuck-open 故障에 대한 테스트 生成

李種哲(J.C.Lee),申容澈(Y.C.Shin),趙相福(S.B.Cho),林寅七(I.C.Lim) 대한전자공학회 1985 대한전자공학회 학술대회 Vol.1985 No.6