• Title/Summary/Keyword: Partial Field

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Application of the Flame Hole Dynamics to a Diffusion Flame in Channel Flow

  • Lee, Su-Ryong;Yang Na;Kim, Jong-Soo
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1775-1783
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    • 2003
  • The method of flame hole dynamics is demonstrated as a mean to simulate turbulent flame extinction. The core of the flame hole dynamics involves derivation of a random walk mapping for the flame holes, created by local quenching, between burning and quenched states provided that the dynamic characteristics of flame edges is known. Then, the random walk mapping is projected to a background turbulent field. The numerical simulations are carried out with further simplifications of flame string and unconditioned scalar dissipation rate. The simulation results show how the chance of partial quenching is influenced by the crossover scalar dissipation rate. Finally, a list of improvements, necessary to achieve more realistic turbulent flame quenching simulation, are discussed.

The Characteristics of Frequency Spectrum of Radiated Electromagnetic Waves with AC Discharge Progress in Liquid Nitrogen (액체 질소중 교류방전 진전에 따른 방사전자파의 주파수 스펙트럼 특성)

  • 박광서;윤대희;이상훈;이현동;김충년;최병주;김기채;이광식
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.52 no.3
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    • pp.123-129
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    • 2003
  • In this paper, a relationship between AC discharge progress and the radiated electromagnetic waves was investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The frequency spectrum of the radiated electromagnetic waves were measured at the atmospheric pressure in liquid nitrogen($LN_2$) during partial discharges progressed by AC high voltage in nonuniform electric field. Front the results of this study, a new method was introduced for measurement and analysis of the radiated electromagnetic waves with discharge progress in $LN_2$ Besides. according to the consideration of the mutual relation between frequency spectrum of the radiated electromagnetic waves and discharge progress, it was confirmed that detecting partial discharge and estimating discharge progress could be possible. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of electric insulations about superconducting and cryogenic power equipments.

The Structural and Electrical Properties of Vanadium Oxide Thin Films as $O_2/(Ar+O_{2})$ ratio ($O_2/(Ar+O_{2})$비에 따른 바나듐 산화막의 구조적, 전기적 특성)

  • 최용남;최복길;최창규;김성진
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.729-732
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    • 2001
  • In this study, the effect of oxygen partial pressure on the electrical properties of vanadium oxide(VO$_{x}$) thin films were investigated. The thin films were prepared by r.f. magnetron sputtering from V$_2$O$_{5}$ target in a gas mixture of argon and oxygen. The oxygen partial pressure ratio is changed from 0% to 8%. I-V characteristics were distinguished between linear and nonlinear region. In the low field region the conduction is due to Schottky emission, while at high fields it changes to Fowler-Nordheim tunneling type conduction. The conductivity measurements have shown an Arrhenius dependence of the conductivity on the temperature.ure.

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Analysis of Partial Discharge Signal Propagation Characteristics in GIS using FEM (FEM을 이용한 GIS내 부분방전 신호의 전파특성 해석)

  • Kim Jae-Chul;Lee Do-Hoon;Song Seung-Yeop;Kim Kwang-Whoa
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.53 no.11
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    • pp.624-629
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    • 2004
  • The UHF electromagnetic waves excited by PD pulses propagate along the GIS busbar not only TEM mode, but also TE and TM mode. Generally the waves detected by the UHF sensors are those of high order modes and such waves can only propagate higher than cut-off frequency. In this paper, the cut-off frequency of 362[kV] GIS for each modes is computed and the electromagnetic field of each propagation modes is simulated by FEM(Finite Element Method) program. Frequency band of each TEmn/TMmn modes was determinated by simulation results and was discussed optimal position of UHF sensor from this results.

A Study on the Transmission-tribology Design Based on Existing Problem of the Gear Drive and Tribology

  • Lyu, Sung-Ki;Lu, Long;Wei, Yun-Long
    • International Journal of Precision Engineering and Manufacturing
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    • v.7 no.2
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    • pp.3-7
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    • 2006
  • We propose a new concept of transmission-tribology design based on the investigation of development and existing problems of the gear drive and tribology. The content of transmission-tribology and transmission-tribology design is probed. Some effective methods of transmission-tribology design is probed. Some effective methods of transmission-tribology design are put forward. Partial achievements in this research are introduced tersely. Mechanical transmission, which is represented by the gear drive, and tribology are two main branches of mechanical engineering. They have their own definite research field. In recent years, we have been doing our utmost to suggest combining mechanical transmission-tribology and transmission-tribology design. Partial achievements in this research area are obtained.

Aerodynamic Shape Optimization of the Impulse Turbine using Numerical Analysis (수치해석을 이용한 충동형 터빈의 공력형상 최적화)

  • Lee E. S.;Seol W. S.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.191-196
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    • 2005
  • For the improvement of aerodynamic performance of the turbine blade in a turbopump for the liquid rocket engine, the optimization of turbine profile shape has been studied. The turbine in a turbopump in this study is a partial admission of impulse type, which has twelve nozzles and supersonic inflow. Due to the separated nozzles and supersonic expansion, the flow field becomes complicates and shows oblique shocks and flow separation. To increase the blade power, redesign of the blade shape using CFD and optimization method was attempted. The turbine cascade shape was represented by four design parameters. For optimization, genetic algorithm based upon non-gradient search has been selected as a optimizer. As a result, the final blade has about 4 percent more blade power than the initial shape.

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AERODYNAMIC SHAPE OPTIMIZATION OF THE SUPERSONIC IMPULSE TURBINE USING CFD AND GENETIC ALGORITHM (CFD와 유전알고리즘을 이용한 초음속 충동형 터빈의 공력형상 최적화)

  • Lee E.S.
    • Journal of computational fluids engineering
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    • v.10 no.2
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    • pp.54-59
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    • 2005
  • For the improvement of aerodynamic performance of the turbine blade in a turbopump for the liquid rocket engine, the optimization of turbine profile shape has been studied. The turbine in a turbopump in this study is a partial admission of impulse type, which has twelve nozzles and supersonic inflow. Due to the separated nozzles and supersonic expansion, the flow field becomes complicate and shows oblique shocks and flow separation. To increase the blade power, redesign ol the blade shape using CFD and optimization methods was attempted. The turbine cascade shape was represented by four design parameters. For optimization, a genetic algorithm based upon non-gradient search hue been selected as an optimizer. As a result, the final blade has about 4 percent more blade power than the initial shape.

Conductivity measurements at low oxygen partial pressure of the stabilized $ZrO_{2}$ ceramics prepared by SHS

  • Soh, Dea-Wha;Korobova, Natalya
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.451-454
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    • 2001
  • The ionic conductivity of cubic solid solutions in the system $Y_{2}O_{3}-ZrO_{2}$ prepared by SHS was examined. Conductivity-temperature data obtained at $1000^{\circ}C$ in atmosphere of low oxygen partial pressure ($10^{-40}$ atm) for $Y_{2}O_{3}-ZrO_{2}$ cubic solid solutions indicated that these materials could be reduced, the degree of reduction being related to the measuring electric field. At low impressed fields no reduction was observed. Thus, these conductivity data give a transference number for the oxygen ion in $Y_{2}O_{3}-ZrO_{2}$ cubic solid solutions greater than 0.99.

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HPF Application Test for PD Detection of XLPE Power Cable (XLPE 전력케이블의 부분방전 검출을 위한 HPF 적용 시험)

  • Kim, Jung-Yoon;Yang, Jong-Kyung;Park, Noh-Joon;Choi, Yong-Sung;Park, Dae-Hee;Lee, Yong-Sung
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.4
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    • pp.161-165
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    • 2006
  • In this paper, we developed HPF (high pass filter) consists of lumped LC components to decrease the noises that are detected in PD (partial discharge) measuring test, and adapted it to field test. We tested it under laboratory circumstances like the fields, and measured the phase change properties of detected signal in UHF sensor with Lemke Probe and oscilloscope (TDS-3054, Tektronix). As a result, we obtained available data showing the decrease of noises in the experiments with the developed HPF from the joint box of 22.9kV distribution line. The result can be adapted to prevent the degeneration of the XLPE power cable, and to observe and diagnosis the underground power transmission cable at the ultra-high voltage.

The Study on a PD On-line Monitoring System Used for Large Turbine Generators (대용량 터빈 발전기에 사용되는 온라인 부분방전 관측 시스템에 관한 연구)

  • O, Gwang-Yeong;Gang, Dae-Yong;Park, Dae-Hui
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.1
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    • pp.45-50
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    • 1999
  • This paper describes a partial discharge (PD) on-line monitoring system used for large turbine generators. The system consists of a broadband current transducer, a computer-aid PD measurement system. By using a programmable fabricate band pass filter and an adaptive digital filter, the system can suppress the noise and extract PD signal from the intense noise surroundings successfully. Two simulated PD sources, which often exist in the large generators, were simulated and detected. At the end of this paper, some field test results, obtained from a 200MW generating set, were presented and discussed.

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