• 한국자동차공학회논문집
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• 제10권6호
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• pp.11-18
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• 2002

Residual gas fraction in an engine cylinder affects engine performance, efficiency and emission characteristics. With high residual gas fractions, a flame speed and maximum combustion temperature are decreased and these are deeply related with combustion stability especially at idle and NOx emission at relatively high engine load. In this work, the residual gas fraction was calculated by an engine simulation code, which was validated by the experimental data (cylinder pressure and emissions) obtained from 4-cyliner spark ignition engine. A comparison between experimental and computational calculation results was made. The residual gas is generated mostly at low engine speed by the larger pressure difference between the intake and exhaust port. As the valve overlap duration was increased, the amount of residual gas in the cylinder, the amount of HC emission in the exhaust gas and the variation of power output increased.

• 대한기계학회논문집B
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• 제23권9호
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• pp.1178-1184
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• 1999

The in-cylinder flow field of gasoline engine comprises unsteady compressible turbulent flows caused by the intake port, combustion chamber geometry and the change of the spatial shape. Thus the quantitative analysis of the in-cylinder bulk flow plays an important role in the improvement of engine performances and the reduction of exhaust emission. The influences of tumble intensifying valve (TIV) and swirl intensifying valve (SIV), and various intake-flow conditions are compared with the tumble ratio obtained by the measured results of the in-cylinder gas flow. In order to obtain the quantitative analysis of the in-cylinder gas flows of gasoline engine this investigation applied the particle tracking method to the analysis of gas flow characteristics. Various intake conditions such as tumble and swirl intensifying valve, the deactivated condition of one valve among two intake valves, and the other factors of gas flow are considered.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.216-217
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• 2008

In recent years, scientific community has found renewed interest in hypersonic flight research. These hypersonic vehicles undergo severe aero-thermal environment during their flight regimes. During reentry and hypersonic flight of these vehicles through atmosphere real gas effects come into play. The analysis of such hypersonic flows is critical for proper aero-thermal design of these vehicles. The numerical simulation of hypersonic real gas flows is a very challenging task. The present work emphasizes numerical simulation of hypersonic flows with thermal non-equilibrium. Hyperbolic system of equations with stiff relaxation method are identified in recent literature as a novel method of predicting long time behaviour of systems such as gas at high temperature. In present work, Energy Relaxation Method (ERM) has been considered to simulate the real gas flows. Navier-Stokes equations A numerical scheme Advection Upstream Splitting Method (AUSM) has been selected. Navier-Stokes solver along with relaxation method has been used for the simulation of real flow over a circular cylinder. Pressure distribution and heat flux over the surface of cylinder has been compared with experiment results of Hannemann. Present heat flux results over the cylinder compared well with experiment. Thus, real gas effects in hypersonic flows can be modeled through energy relaxation method.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2008년도 추계학술논문발표회 논문집
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• pp.7-10
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• 2008

In our study, Monitoring RF System in real-time on leakage of gas cylinder is developed. The system is consisted of Pressure Transmitting part, Main Controller and Operating program. The pressure data of gas cylinder are transmitted to the modem of main controller part by RF module of Pressure Transmitting part and the data received through the modem are recorded in real-time and showed the situation of gas cylinder on the PC monitor. Through the test on the case of the artificial pressure-reduction, the detecting performance. of the developed system is conformed.

• 열처리공학회지
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• 제11권4호
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• pp.283-294
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• 1998

This paper presents an investigation why Mn-steel high pressure gas cylinders have been failed in service. The fractured cylinders have been collected to identify the reason of the failure using various methods. The undamaged, new cylinder has also been tested for the base data. We examined the chemical compositions and fracture facets as well as the mechanical properties of the vessels. The microstructural observations of the fractured regions of the cylinder did not indicate the noticeable defects which might cause the failure. The experiments of cylinders on the compositinal and mechanical tests showed that the cylinder was in good shape according the standards of gas pressure vessel. The morphological analysis of the fracture surfaces concluded that the origin of the failure was the local weak segments induced by the external impact to the cylinder, which result in a sudden, fast fracture.

• 오토저널
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• 제8권1호
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• pp.62-74
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• 1986

The simulation of power cycle and unsteady gas exchange processes in the inlet and exhaust systems of the single-cylinder 2-stroke cycle compression ignition engine was studied in this paper. In power cycle process, the single-zone model proposed by Whitehouse and Way was used, and the convective and radiative heat transfer from cylinder contents to surroundings was considered. To solve the equations for gas exchange process, the generalized method of characteristics including area change, friction, heat transfer and entropy gradients was used. Also with the path line calculation, the entropy change along the path line and the variation of specific heat due to the change of temperature and the composition of cylinder gas were considered. As a result of the simulation, the change of pressure and temperature in the cylinder against the crank angle, the rate of net heat release, and the change of properties at each point in the inlet and exhaust pipe against the crank angle were obtained. The engine performances under various operating conditions were also calculated.

• 오토저널
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• 제5권4호
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• pp.47-61
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• 1983

In this paper the simulation of a thermodynamic power cycle for a 4-stroke, single-cylinder, spark-ignition engine was studied. In this simulation the cylinder volume was restricted to two zones, a burnt and an unburnt zone, and the convective heat transfer from cylinder contents to surroundings was considered. The chemical species in burnt gas considered was 12 species including H$_{2}$O, H$_{2}$, OH, H, N$_{2}$, NO, N, CO$_{2}$, CO, $O_{2}$, O and Ar. Using this model, computer program for compression, ignition and expansion processes was composed and pressure, temperature and composition of cylinder gas at each crank angle were computed. The composition of CO$_{2}$, CO, $O_{2}$ in the burnt gas when exhaust valve opens, the maximum temperature, the maximum flame speed and the combustion duration were also computed as a function of equivalence ratio. The relation between burnt mass fraction and burnt volume fraction was also computed.

• 한국가스학회지
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• 제19권1호
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• pp.18-22
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• 2015

본 연구는 LPG 강재용기에서 상단반구와 하단반구의 코너반경이 응력강도 안전성에 미치는 영향을 FEM으로 해석한 것이다. FEM 해석결과에 의하면, 응력강도 안전성에 큰 영향을 미치는 요소는 용기의 두께보다 상단반구 및 하단반구의 코너반경이다. 그러나 강재용기의 두께는 경량화에 직결되기 때문에 간과해서는 안 되는 중요한 설계요소이다. LPG 강재용기의 강도안전성 검사에서 최고시험압력이 3.04MPa임을 감안할 때, 20kg용 LPG 강재용기의 두께는 2.3~2.6mm, 상단반구와 하단반구의 코너반경은 157mm 이상으로 최적화 설계하는 것이 바람직함을 알 수 있다.

• 한국안전학회지
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• 제21권1호
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• pp.48-52
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• 2006

This study is a research of safety valve development for LP gas cylinder which use sintering metal. Re-searcher wishes to apply technology of sintering metal for safety valve development and do gas flow control. The basis of this study is most suitable fluid examination that to reduce gas accident. This research concluded following results. 1. When press pin length is 42mm to 45mm powder quantity is 0.25g, in case of press pin length 36mm to 42mm powder quantity is 0.2g, displayed fluid optimization. 2. When press pin length is 39mm and powder quantity is 0.25g, press pressure displayed fluid optimization at all interests from $1.2\;tons/cm^{2}\;to\;2\;tons/cm^{2}$. 3. When apparent density is about $5.0g/cm^{3}\;to\;4.5g/cm^{3}$, fluid optimization becomes.

• 대한안전경영과학회지
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• 제16권4호
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• pp.175-183
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• 2014

This study examined the effective system, which manages LPG Gas Cylinder by inserting an electronic tag or module to store a production year, material specification, charging data, management data, and warehousing data. Therefore, the user can effectively monitor the checking date, reexamining the gas cylinder (or not), and manufacture and expiration date. Moreover, through this study, the user can simply monitor a production date, warehousing data, and charging frequency by connecting a mobile app and a gas cylinder in which has an electronic tag or module at any time.