• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.551-554
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• 2006

Inhibition of propellant temperature rising in liquid propulsion rocket using cryogenic fluid as a propellant is very important. Especially propellant temperature rising during stand-by after filling and pre-pressurization can bring into cavitation in turbo-pump. One of the method preventing propellant temperature rising in cryogenic feeding system is recirculating propellant through the loop composed of propellant tank, feed pipe, and recirculation pipe. The circulation of propellant is promoted through gas-lift effect by gas injection to lower position of recirculation pipe. In this experiment liquid oxygen and gas helium is used as propellant and injection gas. Under atmospheric and pressurized tank ullage condition, helium injection flow-rate is varied to observe the variation of recirculating flow-rate and propellant temperature in the feed pipe. There is appropriate helium injection flow-rate for gas-lift recirculation system.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.205-212
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• 1999

Safety Depressurization System of the Korean Next Generation Reactor prevents the Reactor Coolant System from over-pressurization by discharging the coolant with high pressure and temperature into the In-containment Refueling Water Storage Tank(IRWST) during an accident. If temperature in the IRWST rises above the temperature limit of $200\;^{\circ}F$ due to the discharged coolant, an unstable steam condensation may occur and cause large load on the IRWST wall. To investigate whether this condition can be reached or not for the design basis accident, the flow and temperature distributions of water in the IRWST wire calculated by using CFX 4.2 computer code. The results show that the local water temperature does not exceeds the temperature limit within the transient time of 5 seconds.

• 동력기계공학회지
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• 제15권5호
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• pp.5-9
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• 2011

The hydraulic piston using a hydrostatic bearing has been used widely due to its satisfying performance at very high pressurized circumstance and relative higher power density in comparison to conventional one. For high pressurization, enhanced efficiency and long durability of the hydraulic piston, the design of hydrostatic bearing is at issue, which is installed between piston shoe and swash plate. The performance of the hydrostatic bearing is influenced significantly by the assembly of the piston shoe consisting of circular land and recess. In this study, to estimate the performance of the hydrostatic bearing, the characteristics for lubrication of the assembly of the piston shoe were investigated by measuring a leakage rate of hydraulic fluid under an experimental condition, where a rotating velocity of the piston, hydraulic pressure and temperature of the hydraulic fluid were changed systematically. In addition, a film thickness of the hydraulic fluid on the piston shoe was measured and compared to theoretical one.

• 항공우주기술
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• 제4권1호
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• pp.179-185
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• 2005

발사체의 추진 성능 및 효율성을 향상시키기 위한 로켓 구조물의 무게 절감은 발사체 개발에 있어 필수적인 사항이다. 특히 다수의 엔진 시스템을 클러스터링할 경우에는 엔진 지지부의 공간 축소가 추진기관 시스템의 고 효율성을 위해 필요하다. 본 논문에서는 클러스터링 엔진 시스템을 채택한 추진기관 시스템에 있어서 산화제 공급 배관의 분기 위치에 따른 추진기관 성능을 무게, 산화제 탱크 가압압력, 그리고 산화제 배관 내 2상 유동 발생 측면에서 비교, 검토하였다.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1174-1183
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• 2016

Hydrogen release during severe accidents poses a serious threat to containment integrity. Mitigating procedures are necessary to prevent global or local explosions, especially in large steel shell containments. The management of hydrogen safety and prevention of over-pressurization could be implemented through a hydrogen reduction system and spray system. During the course of the hypothetical large break loss-of-coolant accident in a nuclear power plant, hydrogen is generated by a reaction between steam and the fuel-cladding inside the reactor pressure vessel and also core concrete interaction after ejection of melt into the cavity. The MELCOR 1.8.6 was used to assess core degradation and containment behavior during the large break loss-of-coolant accident without the actuation of the safety injection system except for accumulators in Beznau nuclear power plant. Also, hydrogen distribution in containment and performance of hydrogen reduction system were investigated.

• Nuclear Engineering and Technology
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• 제56권4호
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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.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.85-91
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• 2018

최근 초고층 건축물에서 화재로 인해 많은 인명피해가 발생하고 있다. 특히, 화재 발생시 생성되는 유독성 가스 및 연기로 인해 많은 사망자가 발생하고 있다. 이러한 인명피해를 줄이기 위한 방안으로 제연시스템이 도입되어 있다. 제연시스템은 초고층 건축물에서 연기의 확산을 방지하고 재실자의 안전한 피난을 도와주는 장치이다. 또한, 엘리베이터를 이용한 피난은 초고층 건축물에서 필수적인 피난 방법으로 여겨진다. 하지만, 엘리베이터 구동시 생성되는 강력한 압력장 및 유동변화로 인해 제연시스템의 성능확보에 영향을 미친다. 따라서, 본 연구에서는 성능설계위주의 샌드위치 가압방식이 적용된 초고층 건축물에서 엘리베이터 구동에 따른 제연성능 확보에 미치는 영향을 실험 및 수치해석 연구로 수행하였다. 실제 초고층 건축물에서 발생되는 창문, 방화문 그리고 엘리베이터의 누설면적은 화재안전기준 및 면적비를 이용하여 산출하였다. 실제 엘리베이터 속도 7 m/s~17 m/s에 해당하는 20 m/s~100 m/s로 동역학적 상사를 통해 엘리베이터 속도를 변경하였다. 그 결과 엘리베이터 속도가 빠르면 빠를수록 부속실과 화재실 간 차압이 크게 발생하였으며 관계식은 ${\Delta}P=40{\cdot}{\exp}$(-Ves /-104.7)-23.735로 산출되었다. 본 연구 결과는 초고층 건축물에서 엘리베이터 구동을 고려한 제연시스템 설계 자료로 활용이 가능하다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.264-269
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• 2000

As a part of the ongoing effort towards commercial application of high-temperature fuel cell power generation systems, we have recently built a pilot-scale molten carbonate fuel cell power plant and tested it. The stack test system is composed of diverse peripheral units such as reformer, pre-heater, water purifier, electrical loader, gas supplier, and recycling systems. The stack itself was made of 40cells of $6000cm^2$ area each. The stack showed an output higher than 25kW power and a reliable performance at atmospheric operation. A pressurized performance was also tested, and it turned out the cell performance increased though a few cells have shown a symptom of gas crossover. The pressurized operation characteristics could be analyzed with numerical computation results of a stack model.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.597-604
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• 2013

Containment Filtered Vent Systems (CFVSs) have been mainly equipped in nuclear power plants in Europe and Canada for the controlled depressurization of the containment atmosphere under severe accident conditions. This is to keep the containment integrity against overpressure during the course of a severe accident, in which the radioactive gas-steam mixture from the containment is discharged into a system designed to remove the radionuclides. In Korea, a CFVS was first introduced in the Wolsong unit-1 nuclear power plant as a mitigation measure to deal with the threat of over pressurization, following post-Fukushima action items. In this paper, the overall features of a CFVS installation such as risk assessments, an evaluation of the performance requirements, and a determination of the optimal operating strategies are analyzed for the Wolsong unit 1 nuclear power plant using a severe accident analysis computer code, ISAAC.

• 항공우주기술
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• 제12권1호
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• pp.81-86
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• 2013

본 연구에서는 다양한 발사체 추진기관 공급계 배관 자재 중 STS 300 계열의 금속보다 강도가 높고 용접성이 우수할 것이라고 판단되는 21-6-9 합금소재를 이용하여 산화제 주배관의 시편을 제작 하였다. 제작된 시편은 내압 시험을 수행하여 요구되는 내압 강도를 유지할 수 있는지를 확인하였다.