• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.4
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• pp.145-151
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• 2005

The synthetic breaking test method was developed to evaluate the breaking performance of ultra high-voltage circuit breaker and made up of two independent circuits; current source circuit and voltage source circuit. In application of this test method, it is necessary to extend the arc of the test breaker. So, the new re-ignition system using VTGS (Vacuum Triggered Gap-Switch) was constructed to improve the efficiency and reliability of this test. In this re-ignition system, VTGS operates in high vacuum state of $5{\time}10^{17}$torr and control system consists of the triggering device and the air M-G (Motor-Generator). This re-ignition system showed the operating characteristics, such as delay time ($t_d$) and jitter time ($t_j$ not exceeding 5us and 1us respectively, and had the operating voltage of $25\~150kVdc$ at the gap distance of 24mm.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1752-1758
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• 2018

In a low-voltage distribution system, the molded case circuit breaker (MCCB) is a widely used device to protect loads by interrupting over-current; however the hot gas generated from the arc discharge in the interrupting process depletes the dielectric recovery strength between electrodes and leads to re-ignition after current-zero. Even though the circuit breaker is ordinarily tripped and successfully interrupts the over-current, the re-ignition causes the over-current to flow to the load again, which carries over the failure interruption. Therefore, it is necessary to understand the dielectric recovery process and the dielectric recovery voltage of the MCCB. To determine these characteristics, a measuring system comprised of the experimental circuit and source is implemented to apply controllable recovery voltage and over-current. By changing the controllable recovery voltage, in this work, re-ignition is driven repeatedly to obtain the dielectric recovery voltage V-t curve, which is used to analyze the dielectric recovery strength of the MCCB. A measuring system and an evaluation technique for the dielectric recovery strength of the MCCB are described. By using this system and method, the measurement to find out the dielectric recovery characteristics after current-zero for ready-made products is done and it is confirmed that which internal structure of the MCCB affects the dielectric recovery characteristics.

• Fire Science and Engineering
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• v.19 no.4 s.60
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• pp.37-41
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• 2005

The present study describes the cooling performance of two kinds of water mist systems used in fire extinguishment. The cooling is necessary for the prevention of an auto re-ignition of the power transformer. A heat source for such the re-ignition is the accumulated thermal energy in the dielectric oil from the transformer core. Because of the weight of the real core, reduced-scale experiments are carried out. A similarity analysis Is also performed to determine the discharge time of the water mist systems from the experimental results. The discharge time to prevent the re-ignition in the real-scale transformer is estimated about 12 hour from the similarity analysis of the reduced-scale experiments.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.1
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• pp.71-76
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• 2002

Because the driving time is increased under the low speed by rapidly increasing of vehicles, this paper is presented a new ignition control system for improvement the fuel economy, which only some of cylinders are using under the idle status or low speed and preserving the engine rpm. is applicable to effective in fuel economy. An actual hardware was made to prove this new control system. The developed variable cylinder engine concentrated the heat neat the cylinders in idle status or low speed, so there was a problem in re-ignition. It was the reason of a lot of exhaust gas, high fuel consumption and instability of engine revolution. In this paper, in order to solve above problem to show the improvement fuel economy using the new ignition control system and valve opening period at idle status of low speed.

• Advances in aircraft and spacecraft science
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• v.7 no.5
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• pp.425-440
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• 2020

The work presented herein is a numerical investigation of the flow field inside a resonant igniter, with the aim of predicting the performances in terms of cavity temperature and noise spectrum. A resonance ignition system represens an attractive solution for the ignition of liquid rocket engines in space missions which require multiple engine re-ignitions, like for example debris removal. Furthermore, the current trend in avoiding toxic propellants leads to the adoption of green propellant which does not show hypergolic properties and so the presence of a reliable ignition system becomes fundamental. Resonant igniters are attractive for in-space thrusters due to the low weight and the absence of an electric power source. However, their performances are strongly influenced by several geometrical and environmental parameters. This motivates the study proposed in this work in which the flow field inside a resonant igniter is numerically investigated. The unsteady compressible Reynolds Averaged Navier-Stokes equations are solved by means of a finite volume scheme and the effects of several wall boundary conditions are investigated (adiabatic, isothermal, radiating). The results are compared with some available experimental data in terms of cavity temperature and noise spectrum.

• 한국가시화정보학회:학술대회논문집
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• 2004.04a
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• pp.29-36
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• 2004

A numerical study is carried out on the detonation wave propagation through a T-shaped flame tube, which represents a crucial part of the combustion wave ignition (CWI) system aimed for simultaneous ignition of multiple combustion chambers by delivering detonation waves. The formulation includes the Euler equations and an induction-parameter model. The reaction rate is treated based on a chemical kinetics database obtained from a detailed chemistry mechanism. A second-order implicit time integration and a third-order TVD algorithm are Implemented to solve the theoretical model numerically. A total of more than two-million grid points are used to provide direct insight into the dynamics of the detonation wave. Several important phenomena including detonation wave propagation, degeneration, and re-initiation are carefully examined. Information obtained can be effectively used to facilitate the design and optimization of the flame tubes of CWI systems.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.83-88
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• 2014

LTC(Low Temperature Combustion) technology has been studied to see feasibility of the combustion technology applied to heavy-duty engines on the laboratory scale. This study succeeded to develop a demo engine including realized low temperature combustion under partial load conditions. To find the best feasible LTC strategy, various LTC combustion methods such as PPCI, MK and highly diluted mixing controlled LTC were conducted on 6.0L heavy duty diesel engine. Air management system was re-designed to make these combustion scheme stable and the re-designed air system helped expand LTC operating range. This study finally revealed plausible LTC concept to maximize benefit of the alternative combustion technology while overcoming handicaps of the LTC strategy.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1513-1525
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• 2024

An improved mitigation system for thermally-induced steam generator tube rupture accidents was introduced to prevent direct environmental release of fission products bypassing the containment in the OPR1000. This involves injecting bypassed steam into the containment, cooling, and decontaminating it using a water coolant tank. To evaluate its performance, a severe accident analysis was performed using the MELCOR 2.2 code for OPR1000. Simulation results show that the proposed system sufficiently prevented the release of radioactive nuclides (RNs) into the environment via containment injection. The pool scrubbing system effectively decontaminated the injected RN and consequently reduced the aerosol mass in the containment atmosphere. However, the decay heat of the collected RNs causes re-vaporization. To restrict the re-vaporization, an external water source was considered, where the decontamination performance was significantly improved, and the RNs were effectively isolated. However, due to the continuous evaporation of the feed water caused by decay heat, a substantial amount of steam is released into the containment. Despite the slight pressurization inside the containment by the injected and evaporated steam, the steam decreased the hydrogen mole fraction, thereby reducing the possibility of ignition.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.119-126
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• 2019

For rockets using cryogenic liquid hydrogen or liquid oxygen, chilling is required to avoid cavitation and surge problems. Chilling is categorized by the initial chilling/filling stage and the low-temperature maintenance stage. In addition, to improve satellite insertion capability, a multi-ignition capability is required and accordingly chilling to prepare for the next ignition during low-gravity coasting is also required. This paper describes the overall aspects of filling and low temperature maintain marinating for the booster and the upper stage engine including chilling for multi-ignition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.49-54
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• 2015

Molded Circucit Breaker(MCCB) is a most widely used device to protect loads from the over-current in low power level distribution system. When the MCCB interrupts the over-current, the arc discharge occurred between fixed contact and moving contact to create hot gas. By the Lorentz force due to arc current, the occurred arc is bent to the grids. The grids extend and cool and divide it for arc extinguish. In the majority cases, the MCCB protects loads by interrupting the over-current successfully but in some cases the re-ignition is occurred by hot-gas created during process of interruption. The re-ignition arises when the recovery voltage(RV) is more higher than the recovery strength between contacts and it leads to interruption fault. Therefore to find out the dielectric recovery characteristics of protecting device has a great importance for preventing interruption fault. In this paper, we studies measurement method of the dielectric recovery characteristics considering inherent attribute of the MCCB. To measure the dielectric recovery characteristic of MCCB, we makes an experiment circuit for applying the over-current and the randomly recovery voltage. The measurement methode to find out the dielectric recovery voltage of the MCCB was established and the result was based on experiment results.