• Title/Summary/Keyword: Tripping

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Experimental Study on the Flow around a Circular Cylinder with Tripping Wires (트리핑 와이어가 설치된 원형실린더 주위의 유동현상 연구)

  • 류병남;부정숙;조민기
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.3
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    • pp.413-422
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    • 2004
  • The flow characteristic in the wake around a circular cylinder with tripping wires, which was set in constant distance, was experimentally investigated in the uniform flow, Re=2.92$\times10^4$. The measurement of velocity vector and pressure distribution are carried out various angles of tripping wires in the range of $50^(\circ)$ to $80^(\circ)$ with $10^(\circ)$ interval. The results show that velocity profiles and pressure distributions are different with angles of tripping wires. The drag of the circular cylinder was decreased about 60% maximum when tripping wires' angle was $50^(\circ)$. The lowest reduction of the velocity and wake width was occurred by coanda effect when the angle was $60^(\circ)$, and the vortex shedding periodicity become rare at the same time.

A Study on Heat Transfer Enhancement from Flat Plate Using Multiple Tripping Wires (복수 트리핑 와이어를 사용한 평판에서의 열전달 촉진에 관한 연구)

  • Yoo, Seong-Yeon;Cho, Woong-Sun;Ahn, Jong-Kyu
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.12
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    • pp.837-845
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    • 2012
  • The purpose of this research is to investigate the heat transfer enhancement by the multiple tripping wires installed on a flat plate. Naphthalene sublimation technique is used to measure the local mass transfer coefficients, and then heat transfer coefficients are calculated using heat/mass transfer analogy. Experiments are performed for the developed and developing flow conditions. Local and average heat transfer coefficients from the flat plate with three tripping wires are compared with those of no and one tripping wire. Remarkable heat transfer enhancements are found resulting from the boundary layer separation by the tripping wires, especially in the laminar boundary layer.

Experimental Study on Local Mass Transfer Characteristics of Flat Plate Using Tripping Wire (트리핑 와이어를 사용한 평판에서의 국소물질전달 특성에 관한 실험적 연구)

  • Yoo, Seong-Yeon;Cho, Woong-Sun;Jo, Woo-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.3
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    • pp.285-292
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    • 2013
  • The purpose of this research is to investigate how the boundary layer separation caused by a tripping wire installed in front of the flat plate affects the transition from laminar to turbulent flow, and consequently mass transfer. A naphthalene sublimation technique is used to measure the local mass transfer coefficients on the flat plate, and two boundary conditions for the developed and developing flow are considered to evaluate the effects of the flow boundary. The local mass transfer data for a flat plate with a tripping wire are compared with the data for a flat plate without a tripping wire. The variation trends of the local heat transfer coefficients for the plates with and without the tripping wire are similar to each other in the case of the developing flow, but are quite different for the developed flow. The average Sherwood number for the flat plate with a tripping wire is much higher than that without a tripping wire because of the boundary layer separation.

Effects of Tripping Wire on Entrance Regions of a Duct (Part 2: Experimental Study) (관의 입구구간에 있어서 Tripping Wire의 효과 (제 2 보, 실험적 연구))

  • 박승덕;문명국
    • Journal of the KSME
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    • v.16 no.3
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    • pp.277-283
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    • 1976
  • An analytical study on the effects of initial turbulence intensities and Reynolds Number on the transition flow of a circular tube is conducted in Part I;Analysis of Transition Flow. In this second report, however, the effects of tripping wire on the developing regions of a horizontal pipe are studied experimentally and the results of analytical and experimental studies are compared. The agreements between the two results are relatively good. The diameter of the apparatus tube in the experimental works is 76.25mm. and the length is about 7m. The tripping wire diameters used in the experiments are 1.0,1.5,2.0,2.5mm., etc. From the experimental works, the relations between tripping wire size; o.e., diameter and Reynolds Number are proposed for the given thbe diameter.

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A Novel SIME Configuration Scheme Correlating Generator Tripping for Transient Stability Assessment

  • Oh, Seung-Chan;Lee, Hwan-Ik;Lee, Yun-Hwan;Lee, Byong-Jun
    • Journal of Electrical Engineering and Technology
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    • v.13 no.5
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    • pp.1798-1806
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    • 2018
  • When a contingency occurs in a large transmission route in a power system, it can generate various instabilities that may lead to a power system blackout. In particular, transient instability in a power system needs to be immediately addressed, and preventive measures should be in place prior to fault occurrence. Measures to achieve transient stability include system reinforcement, power generation restriction, and generator tripping. Because the interpretation of transient stability is a time domain simulation, it is difficult to determine the efficacy of proposed countermeasures using only simple simulation results. Therefore, several methods to quantify transient stability have been introduced. Among them, the single machine equivalent (SIME) method based on the equal area criterion (EAC) can quantify the degree of instability by calculating the residual acceleration energy of a generator. However, method for generator tripping effect evaluation does not have been established. In this study, we propose a method to evaluate the effect of generator tripping on transient stability that is based on the SIME method. For this purpose, the measures that reflect generator tripping in the SIME calculation are reviewed. Simulation results obtained by applying the proposed method to the IEEE 39-bus system and KEPCO system are then presented.

Coherent Structures of Turbulent Wake Past a Rotating Circular Cylinder with a Tripping Wire (Tripping wire가 부착된 회전원주에 의한 난류휴류의 응집구조)

  • 부정숙;이종춘
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1927-1939
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    • 1995
  • An experimental investigation is conducted to find out the large scale coherent structures in the intermediate wake past a rotating cylinder with a single tripping wire attached. Relation between the vortex shedding frequency and the spin rate of rotating cylinder and the effects of the tripping wire on the flow characteristics were studied by using spectral analysis and conditional phase average technique, respectively. It is found that the vortex shedding frequency is bound to a certain range and varies regularly as spin rate increases. The coherent structures are compared with those of the plain rotating cylinder in the case of spin rate of 1.0. Distance between the upper and lower center of vortices increase and the vortex shedding time is delayed, the velocity fluctuation energy decreases near the center line of vortices and it spreads out to the outer region. The Reynolds shear stress increases highly in the upper region and the turbulent wake width expands with strong entrainment process.

Effect of Harmonics on Residual Current Protective Devices (고조파가 누전차단기에 미치는 영향)

  • Jeon, Jeong-Chay;Lee, Sang-Ick;Yoo, Jae-Geun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.3
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    • pp.84-89
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    • 2006
  • Tripping of residual current protective devices(RCPDs) caused by harmonics has been continuously reported, but no literature is available on the behavior of RCPDs caused by harmonics. This paper, in order to find out the effects of harmonics on RCPDs, investigated the present condition on malfunction of RCPDs and measured harmonics at buildings where nuisance tripping of RCPDs was often occurred. Also, the operational characteristics of RCPDs were tested by the harmonics synthesizer that can generate distorted waveform. Results of experiment detected that there was minimum tripping current of RCPDs when third harmonic added to the fundamental frequency. And it was found that the leakage current to cause tripping of RCPDs increased with more higher order harmonics added to the fundamental frequency.

A Survey on the Actual Conditions of False-Tripping of MCCB ard ELB (배선용 및 누전차단기 오동작 실태조사)

  • Yoo, Jae-Geun;Lee, Sang-Ick;Jeon, Jeong-Chay;Jeong, Jong-Wook;Lim, Yong-Bae
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2004.11a
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    • pp.223-227
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    • 2004
  • False-tripping of MCCB(Molded Case Circuit Breaker) and ELB(Earth Leakage Circuit Breaker), using to protect overload and ground-fault accidents in power system raise direct and indirect losses like as information loss, facilities damage, slipup of goods production in industry place. Cause of false-tipping of MCCB and ELB is various and cause analysis of false-tripping is mostly made up by inference because trip is not reappeared. This paper investigated and analyzed causes and influences of false-tripping of MCCB and ELB by making up a question to safety managers of two hundred and eighteen electrical facilities for private use. Also, the necessity of experimental study on the effect of harmonics on false-tipping of MCCB and ELB was presented.

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The effects of tripping structure on the development of turbulent boundary layer subjected to adverse pressure gradient (역압력 구배가 존재하는 난류 경계층의 발달에 트리핑 구조물이 미치는 영향에 관한 연구)

  • 임태현;김대성;윤순현
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2001.11a
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    • pp.36-44
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    • 2001
  • The effects of various tripping structures on turbulent boundary layer subjected to adverse pressure gradient were examined. The profiles are compared to zero pressure gradient and adverse pressure gradient. The increases of tripping structures of height, k are affects almost flow parameter included velocity fluctuation, skin friction coefficient and turbulent boundary thickness.

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Ground fault circuit interrupter design (누전차단기의 설계와 제작)

  • 설승기
    • 전기의세계
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    • v.29 no.5
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    • pp.303-311
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    • 1980
  • The hazards of electrical shock are well known, but the conventional ground fault circuit breakers did not provide the statis factory safety for human body. Thus this paper considers the standards of performance that they must meet, and describes the new tripping mechanism the operations and the improvements. The experiment at new G.F.C.I. indicates maximum tripping time 25msec minimum sensitive leakage current 25mA and maximum nonaperation leakage current 15mA.

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