• Title, Summary, Keyword: E-I-S Flow

Search Result 320, Processing Time 0.035 seconds

Flow field Analysis In Puffer Type Interrupters of GIS/GCB (파퍼형 GIS/GCB의 유동특성 해석)

  • Song, K.D.;Shin, Y.J.;Park, K.Y.;Choi, Y.G.;Song, W.P.;Kang, J.H.
    • Proceedings of the KIEE Conference
    • /
    • /
    • pp.1512-1516
    • /
    • 1994
  • FLIC(Fluid in cell) method has been used for analyzing a cold gas flow field in an interrupter of a circuit treater since 1970s. In this paper FLIC method is applied to calculation of a cold gas flow and then combined with the simple are analysis method in order to investigate the flow field characteristics in a puffer type interrupter rated at 145kV 40kA. The results for a cold gas flow agree with the experimental measurement well. The other results such as pressure rise, arc temperature, post-arc current and so forth am also reasonable and show the possibility that the combined program can be applied to the design of UHV interrupters.

  • PDF

Network analysis by signal-flow graph (Signal-flow graph에 의한 회로분석)

  • Hyung Kap Kim
    • 전기의세계
    • /
    • v.17 no.2
    • /
    • pp.11-15
    • /
    • 1968
  • One of the most important methods used in the modern analysis of linear networks and systems is the signal flow graph technique, first introduced by S.J. Mason in 1953. In essence, the signal-flow graph technique is a graphical method of solving a set of simultaneous. It can, therefore, be regarded as an alternative to the substitution method or the conventional matrix method. Since a flow-graph is the pictorial representation of a set of equations, it has an obvious advantage, i.e., it describes the flow of signals from one point of a system to another. Thus it provides cause-and-effect relationship between signals. And it often significantly reduces the work involved, and also yields an easy, systematic manipulation of variables of interest. Mason's formula is very powerful, but it is applicable only when the desired quantity is the transmission gain between the source node and sink node. In this paper, author summarizes the signal-flow graph technique, and stipulates three rules for conversion of an arbitrary nonsource node into a source node. Then heuses the conversion rules to obtain various quantities, i.e., networks gains, functions and parameters, through simple graphical manipulations.

  • PDF

A Study on Flow Characteristics of Branch Type Sparger in Drain Tank for Depressurization (감압용 배수탱크내의 분기형 증기분사기의 유동특성에 관한 연구)

  • 김광추;박만흥;박경석
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.13 no.5
    • /
    • pp.356-367
    • /
    • 2001
  • A numerical analysis on branch type sparger in drain tank for depressurization is performed to investigate the flow characteristics due to the change of design factor. As the result of this study, sparger\\`s flow resistance coefficient(K) is 3.53 at the present design condition when engineering margin for surface roughness is considered as 20%, and flow ratio into branch pipe ($Q_s/Q_i$) is 0.41. The correlation for calculating flow resistance coefficients as design factor is presented. Flow resistance coefficient is increased as section area ratio of branch pipe for main pipe and outlet nozzle diameter of main pipe decreasing, but the effects of branch angle and inlet flow rate of main pipe are small. As the change rate of ($Q_s/Q_i$)becomes larger, the change rate of flow resistance coefficient increases. The rate of pressure loss has the largest change as section area ratio changing. The condition of maximum flow resistance in sparger is when the outlet nozzle diameter ratio of main pipe ($D_e/D_i$) is 0.167, the section area ratio ($A_s/A_i$) is 0.1 and the branch angle ($\alpha$) is 55^{\circ}$.

  • PDF

Study of Dynamic Characteristics of an UPFC Switching-Level Model (UPFC의 스위칭레벨 상세 모의 및 동적 특성 고찰)

  • Won, D.J.;Kim, S.H.;Han, H.G.;Lee, S.K.;Moon, S.I.
    • Proceedings of the KIEE Conference
    • /
    • /
    • pp.1287-1289
    • /
    • 1999
  • The UPFC(Unified Power Flow Controller) controls the magnitude and phase of the series injected voltage to exchange the real and reactive power with transmission line. The UPFC consists of two inverters connected together through the DC link capacitor. This paper describes the detailed UPFC switching-level model. PWM (Pulse Width Modulation) method is chosen to operate the inverters. Automatic voltage control mode and automatic power flow control mode is selected to control the UPFC. EMTP simulation is offered to obtain the basic operation characteristics of the UPFC and the dynamic characteristics of the UPFC is studied in detail.

  • PDF

The Framework for the Choice of E-commerce Strategy in Manufacturing Firms (제조 기업이 선택하는 전자상거래 유형 구분의 틀: 공급업체와의 전자상거래를 중심으로)

  • Choe, Jong-Min
    • The Journal of Information Systems
    • /
    • v.23 no.2
    • /
    • pp.25-47
    • /
    • 2014
  • Based on the levels of inter-organizational information flow and the degrees of suppliers' power, this study aims to develop a framework useful for classifying four types of the buyer's e-commerce strategies in manufacturing firms: e-marketplace, e-partnership, e-procurement and supplier's e-marketplace (e-distribution). We adopted a multi-methodological approach by mixing both qualitative and quantitative methods. After developing a framework, through the cases of Cisco, JAL, Toyota Motor, KIST, AMP, and 3M, this paper aims to confirm the actual existence of the four forms of e-commerce. The results from the cases supported the four types of e-commerce strategies in manufacturing firms. With the empirical data, we also demonstrated the configuration of the framework and the four types of e-commerce strategies, and identified the characteristics (i.e., size, age, actual adoption rate of the each type of e-commerce, and supply-chain performance) of the organizations employing each strategy.

Tilt variation and wake turbulence in the otter board of a bottom trawl during fishing operations

  • KIM, Yong-Hae
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.53 no.4
    • /
    • pp.337-348
    • /
    • 2017
  • The tension of warp from trawler and sea-floor contact can generate tilt and wake turbulence around otter boards. Preliminary measurements of otter board tilt and 3-D flow velocity during bottom trawl operations were taken using a vector instrument to investigate the effects of wake turbulence at the trailing edge of the otter board. Tilt data (i.e., yaw, pitch, and roll) at 1 Hz and flow data (velocities in the towing, lateral, and vertical directions) at 16 Hz were analyzed to determine their periods and amplitudes using global wavelet and peak event analyses. The mean period (${\pm}standard$ deviation) of the tilt from the peak event analysis ($5{\pm}2s$) was longer or double than that of flow velocity ($3{\pm}2s$). The two periods also had a significant linear relationship. The turbulence rate of flow was 30-50% at the trailing edge and was closely related to roll deviation. The frequency of phase difference ratios (i.e., peak time differences between tilts and flow periods) was significantly different from random occurrence in two trials, possibly due to side tidal effects. However, in the other trials, flow peaks were random, as shown by the even peak times between tilts and flows. Future studies should focus on reducing tilt variation, wake turbulence, and bottom contact to stabilize otter board motion.

Study on the Load Frequency Control of Power System Using Neural Networks (신경회로망을 이용한 전력계통의 부하주파수제어에 관한 연구)

  • Joo, S.W.;Yoon, J.T.;Kim, S.H.;Chong, H.H.;Lee, D.C.
    • Proceedings of the KIEE Conference
    • /
    • /
    • pp.600-602
    • /
    • 1995
  • The paper presents neural network control techniques for load frequency control of two area power system. Using learning algorithm of error back propagation after learning accept input on the optimal control $e_{i}$, $\dot{e}_{i}$, and $u_{i}$ frequency characteristic and tie-line load flow characteristic investigated dynamic. From result simulation, frequency deviation and tie-line load flow deviation have reduction remarkable.

  • PDF

Approximate Solutions for Laminar Film Condensation on a Flat Plate (평판에서 층류 막응축의 근사해)

  • Lee, S.H.;Kweon, J.Y.;Lee, E.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.3 no.4
    • /
    • pp.215-221
    • /
    • 1991
  • Laminar film condensation of a saturated vapor in forced flow over a flat plate is analyzed by using integral method. Laminar condensate film is so thin that the inertia and thermal convection terms in liquid flow can be neglected. Approximate solutions for water are presented and well agreed with the similarity solutions over the wide range of physical parameter, Cp1(Ts-Tw)/Pr.hfg. For the strong condensation case, it is found that magnitude of the interfacial shear stress at the liquid-vapor interphase boundary is approximately equal to the momentum transferred by condensation, i.e., ${\tau}_i{\simeq}\dot{m}(U_O-U_i)$.

  • PDF

The effects of drag reducing polymers on flow stability : Insights from the Taylor-Couette problem

  • Dutcher, Cari S.;Muller, Susan J.
    • Korea-Australia Rheology Journal
    • /
    • v.21 no.4
    • /
    • pp.213-223
    • /
    • 2009
  • Taylor-Couette flow (i.e., flow between concentric, rotating cylinders) has long served as a paradigm for studies of hydrodynamic stability. For Newtonian fluids, the rich cascade of transitions from laminar, Couette flow to turbulent flow occurs through a set of well-characterized flow states (Taylor Vortex Flow, wavy Taylor vortices, modulated wavy vortices, etc.) that depend on the Reynolds numbers of both the inner and outer cylinders ($Re_i$ and $Re_o$). While extensive work has been done on (a) the effects of weak viscoelasticity on the first few transitions for $Re_o=0$ and (b) the effects of strong viscoelasticity in the limit of vanishing inertia ($Re_i$ and $Re_o$ both vanishing), the viscoelastic Taylor-Couette problem presents an enormous parameter space, much of which remains completely unexplored. Here we describe our recent experimental efforts to examine the effects of drag reducing polymers on the complete range of flow states observed in the Taylor-Couette problem. Of particular importance in the present work is 1) the rheological characterization of the test solutions via both shear and extensional (CaBER) rheometry, 2) the wide range of parameters examined, including $Re_i$, $Re_o$ and Elasticity number E1, and 3) the use of a consistent, conservative protocol for accessing flow states. We hope that by examining the stability changes for each flow state, we may gain insights into the importance of particular coherent structures in drag reduction, identify simple ways of screening new drag reducing additives, and improve our understanding of the mechanism of drag reduction.