• Title/Summary/Keyword: separation distance

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CFD Study on Aerodynamic Power Output of 6 MW Offshore Wind Farm According to the Wind Turbine Separation Distance (CFD를 활용한 6 MW 해상풍력발전단지의 풍력터빈 이격거리에 따른 공기역학적 출력 변화연구)

  • Choi, Nak-Joon;Nam, Sang-Hyun;Jeong, Jong-Hyun;Kim, Kyung-Chun
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.8
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    • pp.1063-1069
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    • 2011
  • This paper presents aerodynamic power outputs of wind turbine of 6 MW wind farm composed of 3 sets of 2 MW wind turbine according to the separation distance by using CFD. Layout design including offshore wind farm and onshore wind farm is key factor for the initial investment cost, annual energy production and maintenance cost. For each wind turbine rotor, not actuator disc model with momentum source but full 3-dimensional model is used for CFD and it has a great technical meaning. The results of this study can be applied to the offshore wind farm layout design effectively.

An Experimental Study About Interaction of Droplet Array Combustion (액적배열연소의 상호간섭에 관한 실험적 연구)

  • Kim, Heung-Sik;Baek, Seung-Wook;Park, Jun-Sung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.10
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    • pp.1355-1363
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    • 2002
  • An experimental study was conducted to investigate the interaction phenomena of droplet array combustion in ambient environment. The droplet with 1 mm in diameter was supported from an optical fiber and ignited with a hot wire. Combustion lifetimes and burning rate constants were measured for fuel of nheptane according to parameters, which were junction and suspender spacings, and array configuration. Results show that the burning process considerably depends on the initial away configuration. The d$^2$-law is found to be correct when applied to both of the droplets in away and the single droplet. For separation distance of about 5mm, there exists a critical state. So the transition from a merged flame to separated flames occurs and burning velocity is much faster than before. Combustion lifetime of the lower droplet is shorter than that of the upper droplet in the two-dimensional arrays combustion. Burning rate constants of the droplets in arrays are smaller than that of the single droplet, while they become higher as separation distance increases. Combustion lifetimes of the droplets in arrays are longer than that of the single droplet and decrease as separation distance increase. It is concluded that the array configuration and the mergedness of the flame are the most important factors governing multi-droplet combustion.

Fire Extinguishing Capability of an Automatic Spreading Fire Extinguisher in Accordance with Horizontal Distance from a Fire Source (자동확산소화장치의 이격거리에 따른 소화성능평가연구)

  • Kwark, Ji-Hyun;Kim, Dong-Suk;Ku, Jae-Hyun
    • Fire Science and Engineering
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    • v.27 no.5
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    • pp.38-43
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    • 2013
  • An automatic spreading fire extinguisher usually installed in a closed area like a boiler room, a laundry store or a restaurant's kitchen room is one of the fire protection equipments. This extinguisher automatically discharges dry powder, extinguishing fire. As this extinguisher has the extinguishing capability applicable to the nominal protection area, objects outside the area cannot be properly extinguished. However only its number is being requested according to the floor area in the related laws, and the extinguishing capability depends on the distance from a fire source. In this study we tried to investigate the extinguishing capability of the automatic spreading fire extinguisher in accordance with horizontal separation distance from a fire source. It appeared that the maximum horizontal separation distance was about 30 cm for both class A and B fire to be certainly extinguished.

A study on interference analysis between FHSS atd DSSS short range radio devices (FHSS 및 DSSS 방식 소출력 무선기기간 간섭분석에 관한 연구)

  • Choi, Jae-Hyuck;Koo, Sung-Wan;Chung, Kyou-Il;Kim, Jin-Young
    • 한국정보통신설비학회:학술대회논문집
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    • 2009.08a
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    • pp.242-247
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    • 2009
  • In this paper, we investigate interference between short-range radiocommunication devices (SRDs) with frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) methods when they are in the same frequency bands. In order to analyze interference from unwanted emission of SRD with DSSS to that of FHSS, Monte-Carlo (MC) simulation method is employed and interference probabilities are calculated. We simulate interference scenarios in accordance with several duty cycles and bandwidths. It is also assumed that the propagation model is free space The effect of distance between interfering transmitter and victim receiver is analyzed and bit error rate (BER) is simulated. From the interference analysis results, it is shown that duty cycle affects compatibility more than bandwidth does. Also, we can make sure of the separation distance which satisfies BER criterion when there are only one interfering transmitter and multiple interfering transmitters.

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A Study on the Separation Distance to Protection of Buried Pipeline from Arc Strikes Caused by Power Line Ground Fault Current (지락사고시 지중금속배관에 대한 아크이격거리에 관한 연구)

  • Ha, Tae-Hyun;Bae, Jeong-Hyo;Lee, Hyun-Goo;Kim, Dae-Kyeong;Kim, Suk-Won
    • Proceedings of the KIEE Conference
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    • 2002.07a
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    • pp.154-155
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    • 2002
  • The demand of the power and gas energy have been rapidly increasing with the industralization, therefore, the area where buried pipelines run parallel with the adjacent power lines and cross them increases in Seoul as well as other cities. These situation cause AC interference from the power lines. However, there aren't any standards to preserve the pipelines from AC interference in Korea. This study introduces the separation distance to protection of buried pipeline from arc strikes caused by power line ground fault current. And this study examines and compares the arc distance through case study.

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A Study on Separation Distance Calculation Model for Limitation of Earth Potential Rise Nearby Tower Footings (송전철탑 부근의 대지전위 억제를 위한 이격거리 산정모델 연구)

  • Choi, Jong-Kee;Cho, Hwan-Gu;Kim, Tai-Young;Lee, Dong-Il
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.2
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    • pp.179-183
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    • 2008
  • In case of a line-to-ground fault at transmission lines, a portion of fault current will flow into the earth through the footings of the faulted tower causing electrical potential rise nearby the faulted tower footings. In this situation, any buried pipelines or structures nearby the faulted tower can be exposed to the electrical stress by earth potential rise. Although many research works has been conducted on this phenomena, there has been no clear answer of the required separation distance between tower footings and neary buried pipeline because of its dependancy on the soil electrical charactersics of the concerned area and the faulted system. In this paper, an analytical formula to calculate the requried sepeartion distance from the faulted tower has been derived.

Acculturation Strategies and School Adjustment of Korean-Chinese and Chinese-Korean Children (중국 조선족 아동과 한국 화교 아동의 문화접변 유형 및 학교적응 비교연구)

  • Cho, Bokhee;Lee, Joo-Yeon
    • Korean Journal of Child Studies
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    • v.27 no.1
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    • pp.95-111
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    • 2006
  • In this study of acculturation strategies and adjustment in Korean-Chinese and Chinese-Korean children, 273 Korean-Chinese and 207 Chinese-Korean were asked about levels of assimilation to the mainstream language and culture, ethnic identity, emotional attitude toward their schools, teachers' support, peers' support, and social distance from the mainstream. Results revealed that separation was the most preferred strategy followed by integration, assimilation, and marginalization for both subject groups. Children categorized by separation strategies reported highest scores in school adjustment variables and lowest scores in social distance. There were some differences between Korean-Chinese and Chinese-Korean children in cultural assimilation, ethnic identity, emotional attitude toward school, and teacher's support. These findings were explained by their immigration history and the uniqueness of each mainstream society.

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Research on Assessment of Potential Interference between Individual Grounding Electrodes Using an Electrolytic Tank Modeling Method

  • Gil, Hyoung-Jun;Kim, Dong-Ook;Choi, Chung-Seog
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.22 no.3
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    • pp.27-33
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    • 2008
  • This paper deals with the assessment of potential interference between individual grounding electrodes using an Electrolytic Tank Modeling method. When a test current was passed through a grounding electrode, potential rise was measured and analyzed using an electrolytic tank in real time. In order to analyze the potential interference between grounding electrodes, a reduced scale modeling method was studied. Potential interference between isolated grounding electrodes was evaluated as a function of the separation distance between grounding electrodes and the configuration of grounding electrode to be induced. It was found that the separation distance between grounding electrodes was a major factor in reducing the potential interference.

A Study on Separation Distance Calculation Model for Limitation of Earth Potential Rise nearby Tower Footings (송전철탑 부근의 대지전위 억제를 위한 이적거리 산정모델 연구)

  • Choi, Jong-Kee;Lee, Dong-Il
    • Proceedings of the KIEE Conference
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    • 2007.11a
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    • pp.212-213
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    • 2007
  • In case of a line-to-ground fault at transmission lines, a portion of fault current will flow into the earth through the footings of the faulted tower causing electrical potential rise nearby the faulted tower footings. In this situation, any buried pipelines or structures nearby the faulted tower can be exposed to the electrical stress by earth potential rise. Although many research works has been conducted on this phenomena, there has been no clear answer of the required separation distance between tower footings and neary buried pipeline because of its dependancy on the soil electrical charactersics of the concerned area and the faulted system. In this paper, an analytical formula to calculate the requried sepeartion distance from the faulted tower has been derived.

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Dynamic Fracture Analysis at Strip with Composite Materials (복합재로 된 판재에서의 동적 파괴 해석)

  • Cho Jae-Ung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.7 no.3
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    • pp.265-270
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    • 2006
  • When the dynamic crack propagates along the boundary at the strip with composite materials and tears apart it, the equivalent stress and strain, and the traction stress are investigated near its boundary. There are the maximum equivalent stress and plastic strain at the very seperated part and the maximum displacement at the bent part of the end of strip. The traction stress becomes higher as the separation distance becomes more. Its maximum value becomes 75 MPa as this distance becomes 0.015 mm. As this distance becomes more than 0.015 mm, this stress becomes lower. As this distance becomes more than 0.13 mm, the value of this stress becomes 0 constantly. This study aims at doing the basic study to provide the data necessary for the precise analysis of fracture intensity, the safety design and the development of advanced materials.

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