• Journal of Advanced Marine Engineering and Technology
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• v.38 no.5
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• pp.581-588
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• 2014

Extensive researches toward pool boiling characteristics have been widely investigated. However, the correct understanding of its boiling crisis by Critical Heat Flux (CHF) phenomenon during steady and transient heat transfer as a fundamental database for designing heat generation systems is still need to be clarified. The pool boiling CHFs were investigated to clarify the generalized phenomena of transition to film boiling at transient condition. The CHFs were measured on 1.0 mm diameter horizontal cylinder of platinum for exponential heat generation rates with various periods for saturated liquids at atmospheric pressure. The incipience of boiling processes was completely different depending on pre-pressurization. Also, the dependence of pre-pressure in transient CHFs changed due to the wettability of boiling liquids. The trend of typical CHFs were clearly divided into the first, second and third groups for long, short and intermediate periods, respectively. By the effect of pre-pressurization, the boiling incipience mechanism was replaced from that by active cavities entraining vapor to that by the HSN in originally flooded cavies.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.306-311
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• 2007

The transient fields generated during switching operations in a Gas Insulated Substation (GIS) are associated with high frequency components in the order of few tens of MHz. These transient fields leak into the external environment of the gas-insulated equipment and can interfere with the nearby electronics. Measurements of the transient fields are thus required to characterise the interference caused by switching phenomena in such substations. In view of the above, E-field emission measurement during a switching operation has been carried out for a 245 kV GIS model, using a resonant dipole antenna and D-dot sensor. The characteristics of the E-fields i.e., frequency spectra and their levels have been analysed and are reported in the paper. Suitability of the measurements has been confirmed by comparing frequency spectra of the measured and computed transient fields.

• Fire Science and Engineering
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• v.23 no.2
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• pp.55-61
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• 2009

This study has been carried on the transient phenomenon protection system to become fire alarm system control unit of high reliance which can be protected from transient phenomena for surge or transient overvoltage, and constructed engineering base that can develop transient phenomenon protection system by proving performance of protection system in a experimental. This study developed 1 step and 2 step protection system that can be protected from transient phenomenon with process thesis and theory for development of transient phenomenon protection system. It established engineering data construction and a source technology that can develop transient phenomenon protection system as gets satisfied result and test with all performance condition that present in fire protection law and connection regulation.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.100-112
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• 2003

This paper presents the transient response analysis of a rotating blade in resonant frequency range. It is shown that the modeling is considered in elastic foundation and friction damping effect. The equations of motion are derived and transformed into a dimensionless form to investigate general phenomena. Numerical results show that the magnitude of friction damping to reduce maximum transient response in near the critical angular speed. The method can be applied to a number of examples of the practical rotating blade system to minimize transient response in resonant frequency range.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.490-491
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• 2011

This paper describes the EMTP/ATP Draw modeling HVDC submarine cable. HVDC submarine cables consist of conductor, lead sheath and amore. It is different from general cable which is composed with just conductor and aluminium sheath. Therefore, the transient characteristics are totally different between HVDC submarin cable and general cable. However, the study on HVDC cable modeling and Transient are insufficient. In this paper, characteristic and effectiveness of HVDC Submarine Cable through Transient analysis. Therefore it is evaluated that the application of HVDC Submarine cable at the field should be considered cautiously when more detailed transient analysis, another electrical testes and economic evaluations are implemented.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.446-448
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• 2000

This paper discribes the modeling and transient analysis of cable in combined transmission line under high impedance fault(HIF). And also, transient characterstic analyzed on cable covering protection unit(CCPU) is presented. Modeling of the combined transmission line is established in PSCAD/EMTDC V3. The required data to analyze the transient phenomena is given from the actual system. The results show the HIF modeling in cable, fault current according to the value of fault resistance. And also when the value and method of grounding resistance is changed in CCPU, simulation results are presented.

• Nuclear Engineering and Technology
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• v.41 no.9
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• pp.1205-1214
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• 2009

The critical heat flux (CHF) levels that occurred due to exponential heat inputs for varying periods to a 1.0-mm diameter horizontal cylinder immersed in various liquids were measured to develop an extended database on the effect of high subcoolings for quasi-steady-state and transient maximum heat fluxes. Two main mechanisms of CHF were found. One mechanism is due to the time lag of the hydrodynamic instability (HI) which starts at steady-state CHF upon fully developed nucleate boiling, and the other mechanism is due to the explosive process of heterogeneous spontaneous nucleation (HSN) which occurs at a certain HSN superheat in originally flooded cavities on the cylinder surface. Steady-state CHFs were divided into three regions for lower, intermediate and higher subcooling at pressures resulting from HI, transition and HSN, respectively. HSN consistently occurred in the transient boiling CHF conditions that correspond to a short period. It was also found that the transient boiling CHFs gradually increased, then rapidly decreased and finally increased again as the period became shorter.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.308-318
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• 1988

The liquid disintegration and characteristics of atomization through the swirl nozzle is affected by injection pressure and injection time when the liquid is injected intermittently. These transient phenomena are investigated by electronic controlled-fuel injection nozzle. The effect of injection conditions on disintegration of liquid injected through nozzle is observed photographically by using delay circuit. Droplet size of the element of the sample is measured by the liquid immersion sampling technique. SMD of droplets is varied with time and is decreased as the injection pressure increases. As the injection pressure increases, the maximum diameter of droplet and diameter of droplet which has the maximum droplet number decrease. Spray angle is not affected on injection pressure and change of spray angle with time is associated with needle movement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1132-1140
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• 1998

The disintegration process of initial spray from high-pressure swirl injector was investigated at different injection pressures. The transient breakup phenomena that were difficult to observe at high injection pressure were easily observed at the low injection pressure of 0.4MPa. The effect of fuel remained inside a nozzle hole volume on the penetration of initial spray was also investigated. The disintegration process of initial spray could be classified four regions: the formation of mushroom shape, the first collision, the second collision, and the development of spray, The liquid film of cup shape was particularly found in the second collision region, and the growth ratio of its length and width at low and high injection pressures were compared.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.3
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• pp.151-158
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• 2013

Large generator of power plant is very important. In order to protect large generator from faults, digital protective relay or IED is required. However, all protective relays for generators of the domestic power plant are operated by foreign products. And now, for technological independence from foreign and improvement of import substitution effect, IEDs using domestic technology are being developed. To evaluate performance of developing next-generation power devices, the study of the dynamic characteristics of the power plant, generator system modeling, fault simulation and analysis, should be considered. Specially, To obtain IEEE Standards COMTRADE format for relay operation test, generator system modeling and fault simulation using PSCAD/EMTDC tools must be preceded. Until now, a complete modeling of generator internal windings and fault simulation techniques dose not exist. In this paper, for evaluation performance of relay elements of developing IED, the generator system modeling and various faults simulation using PSCAD/EMTDC tools were performed. And then, the various transient phenomena through obtained relaying signal of developed modeling were analyzed.