• 대한기계학회논문집
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• 제19권6호
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• pp.1510-1517
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• 1995

A theoretical method is described to simulate the propagation of turbulent premixed flames in a closed vessel. The objective is to develop and test an efficient technique to predict the propagation speed of flame as well as the geometric structure of the flame surfaces. Flame is advected by the statistically generated turbulent flow field and propagates as a wave by solving twodimensional Hamilton-Jacobi equation. In the simulation of the unburned gas flow field, following turbulence properties were satisfied: mean velocity field, turbulence intensities, spatial and temporal correlations of velocity fluctuations. It is assumed that these properties are not affected by the expansion of the burned gas region. Predictions were compared with existing experimental data for flames propagating in a closed vessel charged with hydrogen/air mixture with various turbulence intensities and Reynolds numbers. Comparisons were made in flame radius growth rate, rms flame radius fluctuations, and average perimeter and fractal dimensions of the flame boundaries. Two dimensional time dependent simulation resulted in correct trends of the measured flame data. The reasonable behavior and high efficiency proves the usefulness of this method in difficult problems of flame propagation such as in internal combustion engines.

• 한국연소학회지
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• 제6권1호
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• pp.14-19
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• 2001

Interests and importance of down-scale combustor is increasing with the emerging need for miniaturized power source which is now a bottleneck of micro system development. But in down scaled combustor increased heat loss compared to thermal energy generation inhibits the usability and application of the device, so as a preliminary work of down scaled combustor fabrication. Modeling tool for the device should be established, in this study modeling approach of closed vessel combustion phenomena that can express heat loss effect and resulting quenching is proposed and the result is compared with experiment data. From this model heat loss effect following combustor scale down can be further understood, and further more design parameter and analysis tool can be obtained.

• 한국정보통신학회논문지
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• 제19권8호
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• pp.1853-1858
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• 2015

기존 선박 통신시스템은 위성통신을 이용한 음성, FAX, ISDN 등이 대부분으로 선박 해상관제 업무에 집중되고 있지만, 최근의 레저선박 통신시스템의 경우는 더 높은 품질의 스마트 통신 서비스 및 통신환경을 요구하고 있다. 기존 통신시스템을 활용하여 통신 환경을 실험한 결과, 선상에서는 위성통신이 가능하나, 밀폐된 선내에서는 위성통신을 중계한 음성통신만 가능하고 스마트 앱이나 이메일 사용은 불가하였다. 본 논문에서는 선상뿐 만아니라 선내에서도 음성, 문자, 이메일, 대규모 파일 전송, 해상관제 앱 실행이 가능한 통신시스템 구현을 제안한다. 본 연구를 통해 위성통신단말기와 스마트폰이 결합한 듀얼 복합 통신단말기와 선내에서도 대용량 이메일 및 스마트 앱 사용이 가능한 시스템을 구현하였다. 실험 결과 선박 어느 위치에서나 다양한 통신이 가능하였다.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1591-1602
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• 1996

In operating the underwater engines such as encountered in exploring submarines, the dumping of the exhaust gas out of the engine requires a large portion of the total power, frequently amounting to 25-30% of the power generated. This unfavorable circumstance can be cured by liquefying the exhaust gas and storing it. In the present study, two liquefaction systems were simulated to enhance the overall efficiency; one is a closed cycle diesel engine and the other is a closed cycle LNG engine. The liquefied natural gas (LNG) is chosen as a fuel, not only because its use is economical but also because its cold energy can be utilized within the liquefaction system. Since a mixture of oxygen and carbon dioxide is used as an oxidizer, liquefying carbon dioxide is of major concern in this study. For further improving this system, the intercooling of the compressor is devised. The necessary power consumed for the liquefying system is examined in terms of the related properties such as pressure and temperature of the carbon dioxide vessel as a function of the amount of the exhaust gas which enters the compressor. The present study was successful to show that much gain in the power and reduction of the vessel pressure could be achieved in the case of the closed cycle LNG engine. The compression power of exhaust gas were observed remarkably lower, typically only 6.3% for the closed cycle diesel engine and 3.4% for the closed cycle LNG engine respectively, out of net engine power. For practicality, a design -purpose map of the operating parameters of the liquefaction systems was also presented.

• Journal of Chest Surgery
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• 제24권2호
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• pp.206-211
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• 1991

Interruption of the aortic arch may be defined as discontinuity of the aortic arch in which either an aortic vessel or a patent ductus arteriosus supplies the descending aorta. This anomaly is a rare congenital malformation that usually occurs with severe associated intracardiac congenital anomalies, such as ventricular septal defect, patent foramen ovale and abnormal arrangement of the brachiocephalic arteries. Rarely, transposition of the great vessel, truncus arteriosus are coexistent. We experienced a case of the interrupted aortic arch [Type A] associated with VSD, PDA and patent foramen ovale in a 16 years old female. One stage total correction was done under profound hypothermia with total circulatory arrest. Aortic continuity was established using patent ductus arteriosus with anterior wall of main pulmonary artery, which was anastomosed obliquely to anteromedial side of the ascending aorta. Ventricular septal defect was closed using Dacron patch and patent foramen ovale was closed directly. Postoperative course was uneventful, except mild hoarseness.

• 한국안전학회지
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• 제14권3호
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• pp.40-47
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• 1999

A numerical study on gaseous explosion was carried out to predict the transient pressure behavior with the partial rupture in confined vessels. Equations, assumptions and solutions for central ignition of premixed gases in closed spherical vessels are proposed with various equivalence ratios of gas fuel, as $CH_4$ and $C_3H_8$, vent areas and vent opening pressures. Given vent opening pressure in a vessel, the magnitude of second peak pressure results from the vent areas and burning velocity, varied by equivalence ratio of gas fuel. In a living room of an apartment, the higher second peak pressure than the vent pressure is not appeared due to its large window areas. As vent opening pressure is higher, the larger damage by gaseous explosion is expected and the larger vent area is necessary for relieving the damage. In the same concentration, the gaseous explosion by propane rather than methane shows the larger damage due to its higher adiabatic flame temperature and equivalence ratio.

• 연구논문집
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• 통권32호
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• pp.45-53
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• 2002

Hydraulic breaker attached excavator generally used for the destroying and disassembling of buildings, crashing road pavement, breaking rocks at quarry and etc. The developed breaker are determined their own destructive force and number of impact by the input hydraulic flow rate and pressure than the operating conditions, In this study, the characteristics of pressure variation in closed vessel is invested for testing the impact energy of hydraulic breaker. To test the impact energy, the test system is designed as a mechanism consisted with a hydraulic cylinder, main base, pressure sensor, LVDT, data acquisition system and etc.. The developed test system is applied to measure the impact energy for hydraulic breaker. The proposed testing method could be applied for conventional impact test and the control system evaluation for hydraulic breakers.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.451-455
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• 2017

ZPP와 THPP 화약의 압력 카트리지가 밀폐용기에 장착되어 연소될 때의 현상을 반응성 오일러리안-라그랑지안 이상 유동 해석 코드를 통해 모사 하였다. ZPP와 THPP는 압력 카트리지 내에서 boron nitride 판으로 격리되어있고, ZPP만 열선에 의해 직접 점화되기 때문에 THPP의 연소지연효과가 발생할 가능성이 높다. 실험을 통한 THPP의 점화지연 측정은 힘들기 때문에 기존의 연구를 통해 검증된 수치해석 코드를 통해 점화지연에 대한 케이스 스터디를 수행하고 현상학적 분석을 수행하였다. 해석 결과 THPP의 점화지연 정도에 따라 초기 충격파의 강도가 변하여 압력선도의 초기 피크특성 뿐만 아니라 주파수에도 영향을 미친다는 것을 알 수 있었다.

• 한국정밀공학회지
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• 제22권3호
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• pp.154-161
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• 2005

In this study, the leaflet motion of a mechanical heart valve and the characteristics of two-dimensional transient blood flow in an elastic blood vessel have been numerically investigated by using fluid-structure interaction method. Here, blood has been assumed as a Newtonian, incompressible fluid. Pressure profiles have been used as boundary conditions at the ventricle and the aorta. As a result, closing motion of the leaflet is faster than opening one. While opening angles of leaflet grow up, vortex is detected at the sinus and backward of the leaflets. When the leaflet is fully closed, vortex is detected at the ventricle and at that moment maximum displacement of the elastic blood vessel is observed in the vicinity of the sinus region. Maximum displacement is caused in association with the blood flow that is oriented toward the elastic blood vessel.

• 소성∙가공
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• 제17권4호
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• pp.292-301
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• 2008

Type 2 compressed natural gas(CNG) storage vessels for automobiles are becoming widely used. They are not only supplied to automakers in Korea, such as Hyundai Motors, but increasingly, they are being exported overseas. Autofrettage is a process that produces beneficial residual stresses in a vessel by subjecting it to excessive internal pressure. This strengthens the vessel and improves its fatigue resistance. This paper presents research investigating the autoftettage process and residual stresses it produces in type 2 CNG storage vessels. A finite element analysis technique and a closed form equation are used. Then, fatigue resistance is analyzed through a fatigue evaluation performed according to ASME section VIII.