• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.11a
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• pp.27-41
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• 1996

In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

• 전기의세계
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• v.22 no.5
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• pp.19-32
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• 1973

This paper treats with some of plasma jet behaviors under magnetic field for the purpose of controlling important characteristics of plasma jet in the practices of material manufacturings. Under the existence and non-existence of magnetic field, the pressure distribution, flame length, stability and noise of plasma jet are comparatively evaluated in respect of such parameters as are current, gap of electrode, quantity of argon flow, magnetic flux density, diameter and length of nozzle. The results are as follows: 1) the pressure, the length and the noise of plasma jet rise gradually with the increase of are current, and have high values under identical arc current as the diameter of nozzle increases, but reverse phenomenon tends to appear in the noise. 2) The pressure, the flame length and the noise increase with the increased quantity of argon flow, and the rising slope of noise is particularly steep. Under magnetic field, the quantity of argon flow in respect of flame length has the critical value of 80(cfh). 3) The pressure and length of flame decrease with small gradient value as the length of gap increases, but the noise tends to grow according to the increase of nozzle diameter. 4) The pressure and the length of jet flame decrease inversly with the increase of magnetic flux density, which have one critical value in the 100 amps of arc current and two values in 50 amps. The pressure of jet flame can be below atomospher pressure in strong magnetic field. 5) "The constriction length of nozzle has respectively the critical value of 6(mm) for pressure and 23(mm) for the length of flame. 6) Fluctuations in the wave form of voltage become greater with the increase of argon flow and magnetic flux density, but tends to decrease as arc current increases, having the frequency range of 3-8KHz. The wave form of noise changes almost in parallel with that of voltage and its changing value increases with argon flow, arc current and magnetic flux density, having the freuqency range of 6-8KHz. The fluctuation of jet presurre is reduced with the increase of argon flow and magnetic flux density and grows with arc current.rent.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.961-965
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• 1992

It is well-known that shock waves frequently occur inside the nozzle of the interrupter, and that they play important roles in the arc interruption. A model interrupter with two-dimensional dual-airflow nozzles was used for this experiment. The arc was ignited with 1.4 mil copper wire stretched between the electrodes which were spaced out 56 mm. The arc current of 60 to 230 A was achieved by adjusting the external resistance from 5.5 to 1.6 ohms. The arc tests have been conducted for investigating the air arc characteristics, and the effects of shock waves and nozzle pressure ratios on the arc voltage, the arc resistance, the arc power, and average electric field. The results of these tests have been analyzed to provide insights into the arc characteristics for gas circuit breakers. The average electric field is represented by the function of the arc current to show the negative E-I characteristic explicitly. The effects of shock waves and nozzle pressure ratios are shown to be significant for a circuit breaker performance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.9
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• pp.395-399
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• 2003

In this paper, physical phenomena which are related to the high temperature and high pressure arc plasma generated during the fault current interruption by SF6 gas circuit breakers are reviewed. In particular, in order to analyze nozzle ablation induced by the heats transferred to the surface of the poly-tetrafluoroethylene(PTFE) nozzle through arc radiation, a governing equation for the calculation of PTFE concentration is added to the governing equations for SF6 arc Plasma analysis. The proposed method is applied to the steady state analysis of $SF_6$ arc plasma generated by direct current taking account of the nozzle ablation and the results are presented.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.11
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• pp.555-563
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• 2006

This paper presents the measured radiation intensity of high-pressure and large-current arc with the current. In order to measure the radiation intensity of large-current arc, a model circuit breaker was specially designed and manufactured and the method using an astronomical telescope was utilized after various measuring methods were investigated. A trigger system was designed and fabricated to coincide the time of desired current with the exposure time of 1ms of the spectroscope. A high-speed camera was used to investigate the shape and behavior of the arc and the captured results have been used to calculate the radiation energy. The calculated arc temperature with Boltzmann plot method using the measured radiation intensity have $18,000{\sim}27,000K$ to the current $4kA{\sim}15kA$. And also, using the calculated arc temperature and the captured arc shape the radiation energy of the current $5kA{\sim}15kA$ were calculated with $8{\times}10^5{\sim}4.0{\times}10^6W/m$ respectively.

• Tribology and Lubricants
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• v.25 no.3
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• pp.157-162
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• 2009

In this paper, the hydrodynamic pressure and minimum oil film thickness of a pin bush bearing for a connecting rod have been analyzed as functions of the number of oil grooves and an arc length of oil grooves. The lubrication characteristic of a pin bush is governed by oil groove design factors, which are considered in this study. The most influential design parameter is a number of oil grooves, which is three oil grooves with an arc length of oil groove, 1/6($60^{\circ}$). This means that oil groove with a long arc length of a pin bush does not contribute to the hydrodynamic pressure development. Thus the optimal design of a pin bush is necessary with an increased number of oil grooves and a reduced arc length.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.124-130
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• 2008

The effect of nitrogen gas pressure in arc ion plating on surface properties of the TiN-coated high speed steel(SKH51) is presented in this paper. The surface roughness, micro-particle, micro-hardness, coated thickness, atomic distribution of TiN, and adhesion strength are measured fur various nitrogen gas pressures. It has been shown that the nitrogen gas pressure has a considerable effect on the surface roughness, adhesion strength, atomic distribution of TiN, and surface deposition of TiN of the high speed steels but that it has little influence on the micro-hardness and coated thickness.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.9
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• pp.655-659
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• 1987

This study presents a model of the electrical characteristics of the high-pressure mercury vapour arc discharge. Energy balance equation per unit volume of the arc tube is converted into the one per unit length by assuming the parabolic radial temperature distribution and integrating over the cross-section of the tube. Using this energy balance equation, together with the circuit equation and Ohm's law, the arc voltage and current variation for 1 cycle is numerically calculated and a good result is obtained. A simple method to calculate the axis temperature of the arc tube and the radiation output is also presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.255.2-255.2
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• 2014

Electrode erosion is indispensable for atmospheric plasma systems, as well as for switching devices, due to the high heat flux transferred from arc plasmas to contacts, but experimental and theoretical works have not identified the characteristic phenomena because of the complex physical processes. Our investigation is concerned with argon free-burning arcs with anode erosion at atmospheric pressure by computational fluid dynamics (CFD) analysis. We are also interested in the energy flux and temperature transferring to the anode with a simplified unified model of arcs and their electrodes. In order to determine two thermodynamic quantities such as temperature and pressure and flow characteristics we have modified Navier-Stokes equations to take into account radiation transport, electrical power input and the electromagnetic driving forces with the relevant Maxwell equations. From the simplified self-consistent solution the energy flux to the anode can be derived.

• International Journal of Fluid Machinery and Systems
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• v.10 no.1
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• pp.63-75
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• 2017

Many axial fans have circular arc blades with constant thickness. It is still a challenging task to calculate their performance, i.e. to predict how large their pressure rise and pressure losses are. For this task a need for cascade data exists. Therefore, the designer needs a method which works quickly for design purposes. In the present contribution a design method for such cascades consisting of circular arc blades with constant thickness is described. It is based on a singularity method which is combined with a CFD-data-based flow loss model. The flow loss model uses CFD-data to predict the total pressure losses. An interpolation method for the CFD-data are applied and described in detail. Data of measurements are used to validate the CFD-data and parameter variations are conducted. The parameter variations include the variation of the camber angle, pitch chord ratio and the Reynolds number. Additionally, flow patterns of two dimensional cascades consisting of circular arc blades with constant thickness are shown.