• 대한조선학회논문집
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• 제58권6호
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• pp.400-406
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• 2021

The primary effect of the far-field underwater explosion (UNDEX) is the whipping of the ship hull girder. This paper aims to verify why inelastic effects should be considered in the whipping response estimations from the UNDEX simulations. A navy ship was modeled using Timoshenko beam elements over the ship length uniformly keeping the constant midship section modulus. The transient UNDEX pressure was produced using two types of the Geers-Hunter doubly-asymptotic models: compressible and incompressible fluids. Because the UNDEX model based on incompressible fluid assumption provided more increased fluid volume acceleration in the bubble phase, the incompressible fluid-based UNDEX model was adopted for the inelastic whipping response analyses. The non-linear hull girder bending moment-curvature curve was used to embed inelastic effects in the UNDEX analyses where the Smith method was applied to derive the non-linear stiffness. We assumed two stand-off distances to see more apparent inelastic effects: 40.5 m and 35.5 m. In the case of the 35.5 m stand-off distance, there was a statistically significant inelastic effect in terms of the average of peak moments and the average exceeding proportional limit moments. For the conservative design of a naval ship under UNDEX, it is recommended to use incompressible fluid. In the viewpoint of cost-effective naval ship design, the inelastic effects should be taken into account.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.33-34
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• 2005

The internal state of an automotive engine is very severe. A piston exposes burnt gas of over $2000^{\circ}$ nd is shocked by high pressure at the time of explosion. Furthermore strong friction is caused by high speed motion. A study on the cooling of the piston requires because the cooling and lubrication of the piston has an effect on the life and efficiency of engine directly. The previous system of oil jet cooled only the bottom of the piston. In order to improve the cooling efficiency, the oil gallery is made inside the piston, and oil flows into the oil gallery. The flow rate of oil at the entrance of oil gallery is important because of the cooling efficiency. The purpose of this study is the investigation of fluid flow characteristics of oil jet and flow rate into the oil gallery.

• 시큐리티연구
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• 제2호
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• pp.83-98
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• 1999

The LPG station's explosion at Bucheon city was a major accident which with rare frequency of occurrence but large damage effect. Therefore, to prevent similar accident in the future from LPG chargings stations which located at inner urban area, it needs to identify the damage effects of such facilities by comparing theoretically quantities risks-PHAST. The BLEVE effects from the accident showed similar level in case of heat flux, however, the over pressure level reflected at reduced distance. The structure damage to the nearby area showed comparatively large reduction of concrete strength and shape changes through by heat effect while the overpressure effect was small.

• 한국생산제조학회지
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• 제22권4호
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• pp.686-692
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• 2013

Today, environmental issues have become a matter of worldwide concern. In particular, automobile industries engage in considerable research and investment to develop high-efficiency and ecofriendly cars. Most ecofriendly cars use natural gas or hydrogen gas instead of fossil fuels. In this regard, low-weight and high-pressure vessels have gradually been developed to increase the driving distance of a car. However, most pressure vessels installed in cars develop many defects over time owing to shocks sustained when the car is being driven. Such defects can cause the explosion of the pressure vessel. Therefore it is important to prevent such explosions due to internal defects. The use of shearography for measuring the internal defects of objects afford many advantages. It is a non-contact and non-destructive method, and it is not limited by the object shape. In this study, the internal defect deformation and strain of an aluminum liner that is used in a CNG bus for the fuel storage tank is measured using shearography. It is important to measure the strain and deformation in order to detect defects and repair the pressure vessel. To verify the accuracy of the shearography measurement method, the measurement results of shearography, out-of-plane ESPI, and FEM are compared quantitatively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.275-277
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• 2005

In a lithium-ion battery which is being used in many portable electronic goods, electrolyte is disaggregated and then the gas is happened when electric charging volt is over the 4.5V. So, the pressure on the safety valve is increased and electrolyte is leaked out in the cell. It leads to the risk of explosion. On the other hand, in the case which the battery is discharged excessively, the negative pole is damaged and the performance of the battery is deteriorated. The protection module of a lithium-ion battery is used for preventing such risk and the inspection system is needed to check the performance of such protection module. In this research, a PC-based auto inspection system is developed for the inspection of a battery protection module using Dallas chipset. In the inspection system, AVRl28 chip is used as a controller and the communication protocol is developed for the data communication between the protection module and the AVR128 chip. And GPIB interface is used for the control of measuring devices. Also, MMI environment is developed using LabView for convenient monitoring by the tester.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.205-209
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• 2005

Now a days Automobiles are becoming more important in our life, the study on piston of engine is needed because, piston's cooling and lubrication of piston have an effect on the life and efficiency of engine directly. So, this study is about nozzle part of oil jet for cooling piston in the automotive engine. Piston exposes combustion gas of over $2000^{\circ}C$ and is shocked high pressure at the time of explosion shortly. Furthermore strong friction occurs by high speed rotation. The cooling system is considered from oil jet to piston. The previous system cooled the lower part of piston only. So, efficiency was low. To improve this system, make the oil gallery in the piston, and oil flows into the gallery. The value of oil flow rate into the gallery is important. Consequently, the point of this study is the research of investigation of flow characteristics for variable Re number. This study has been modelled by a commercial CFD code FLUENT, allowing to assess its validity

• 한국전기전자재료학회논문지
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• 제32권3호
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• pp.256-261
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• 2019

The use of military lithium batteries in this field accelerates the generation of internal pressure because the active materials, lithium and the electrolyte, react to form sulfur dioxide gas. This also reduces the amount of electrolyte. In this condition, batteries can 'vent' or 'explode' especially when completely discharged. Such venting and explosion can be regarded as a safety accident, as toxic gases and shrapnel are ejected from the batteries which can harm the user. A DTaQ was carried out in 2017 as a quality problem solution project to solve this safety issue. A protection circuit was thereby developed, which included a micro controller unit (MCU) which can stop battery usage when in an over-discharging state by sensing its low-voltage condition. In 2018, this concept was expanded to lithium batteries for the remote controlled ammunition system. This paper reports results of the improved performance.

• 한국가스학회지
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• 제17권4호
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• pp.1-8
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• 2013

본 연구에서는 벌크 중합법을 이용한 폴리스티렌 중합공정의 폭주반응에 대한 열적 위험성을 가속속도열량계(ARC)와 소규모 반응열량계(MM)를 이용하여 평가하였다. 당해 중합공정은 반응온도 $120^{\circ}C{\sim}130^{\circ}C$로 운전되어져야 하며, $130^{\circ}C$ 이상의 반응온도에서는 반응 생성물의 급격한 점도 증가로 인하여 반응기의 온도제어 실패에 따른 폭주반응의 위험성이 존재하였다. 또한 당해 중합공정의 반응온도($120^{\circ}C{\sim}130^{\circ}C$)에서 공정운전 초기에 반응기의 냉각실패가 발생할 경우 폭주반응으로 인해 반응기의 온도와 압력이 각각 30 ~ 50분 이내에 약 $340^{\circ}C$, 5.3 bar 까지 급격히 상승하여 반응기의 파열판이 파열되거나 반응기가 폭발할 수 있는 열적 위험성이 높게 나타났다.

• 에너지공학
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• 제27권2호
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• pp.1-13
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• 2018

미세먼지 저감 및 에너지원 변환에 대한 정책 추진에 따라 천연가스를 연료로 하는 발전의 비중이 확대되고 있다. 복합화력발전 플랜트, 열병합발전 플랜트 등에서 천연가스 연료공급계통이 가스가 가열된 상태에서 고압으로 운용되고 있으므로, 누출사고를 예방하여 화재 및 폭발에 의해 사고를 방지하여야 한다. 본 연구에서는 API RP 581 RBI 코드를 기반으로 복합화력발전 플랜트의 천연가스 연료공급계통을 대상으로 위험도 평가를 수행하였다. API RBI 코드의 적용을 위해 평가 대상 계통의 라인 및 세그먼트를 구분하였다. 파손확률과 파손피해 산출을 위해 운전 데이터 및 입력 정보를 분석하였다. 설치 초기 시점 및 운전시간 경과에 따른 위험도 평가 결과 추이를 분석하였다. 코드 기반 평가 시 가스연료 공급계통은 두께 감육, 외부 손상, 기계적 피로 손상기구의 영향이 주로 반영되었다. 운전 시간이 경과함에 따라 단열재 하부 부식(CUI, Corrosion Under Insulation) 등에 의한 외부손상이 위험도를 상승시키는 원인으로 예상되었다.

• Nuclear Engineering and Technology
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• 제27권4호
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• pp.544-554
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• 1995

폴리머 수용액의 증기폭발 억제 효과에 대한 물리적 현상을 이해하기 위해 폴리에틸렌옥사이드 수용액에서의 풀비등 특성을 실험적으로 관찰하였다. 본 실험에서는 22.2mm와 9.5mm 직경의 두 구형 체를 가열하여 여러가지 농도의 3$0^{\circ}C$ 수용액에서 냉각시켰다. 그 결과, 순수한 물에서는 7$0^{\circ}C$ 이상인 최소막비등온도($\Delta$ $T_{MFB}$)가 300ppm농도의 폴리머 수용액에서 22.2mm구의 경우 15$0^{\circ}C$ 까지, 9.5mm구의 경우 35$0^{\circ}C$까지 낮아짐을 알 수 있었다. 이러한 폴리머 수용액에서 최소막비등온도가 크게 낮아지는 현상은 이 수용액에서 중기폭발이 억제되는 이유로 해석될 수 있다. 또한, 외부 압력파의 막비등에 대한 영향을 관찰한 결과, 수용액의 농도가 클수록 증기막의 안정도가 커짐을 알 수 있었다. 이러한 폴리머 수용액에서의 비등 특성과 증기폭발 억제에 대한 실험 결과들은 원자로 비상냉각수에 폴리에틸렌옥사이드와 같은 폴리머를 최소 300ppm 정도 소량 첨가하는 방법으로 중대사고시 폭발적 FCI 반응을 방지 또는 완화할 수 있음을 제시한다.다.