• 한국기계가공학회지
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• 제9권1호
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• pp.14-18
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• 2010

Car muffler has the role to form the exhaust gas from high temperature- pressure to lower level and reduce the generated noise. Because of this role, its durability decrease as deformation by heat is occurred. This study is to analyze the flow of exhaust gas inside muffler and its coupled thermal deformation with 3-D modeling and ANSYS. There is the fastest flow at the exit of muffler with the maximum velocity of 54 m/s. And the maximum deformation or equivalent stress is shown at this model respectively as 0.00435 mm or 3414.4 MPa by the influence of heat and pressure at part of intersection with inlet and body of muffler.

• 항공우주시스템공학회지
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• 제15권3호
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• pp.79-86
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• 2021

추력조절이 가능한 가변유동형 덕티드 로켓(VFDR; Variable Flow Ducted Rocket)의 기초연구 목적으로 가스발생기와 유량조절장치를 개발하여 지상연소시험을 수행하였다. 연소시험을 통하여 본 개발에 대한 내열성, 연소시간, 압력 및 온도와 같은 성능 요구조건의 충족 여부를 확인하였으며 Boron/MgAl/AP 등을 혼합한 연료농후 고체추진제의 연소특성을 분석하였다. 유량조절장치는 Plunger 타입으로 개발하여 토출면적 조절로 유량 및 압력을 제어할 수 있음을 확인하였다. 그러나 토출 유로 내 연소 생성물 부착으로 인한 토출면적 감소에 따라 압력 안정화 구간 없이 연소압력이 증가하는 경향을 나타내었다. 토출면적 감소로 인한 압력증가의 연소특성 분석은 본 논문의 Part 2에서 다루어진다.

• 대한기계학회논문집B
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• 제26권12호
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• pp.1715-1721
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• 2002

Numerical analysis was conducted to characterize the gas flow field and particle deposition on a horizontal freestanding semiconductor wafer under the laminar flow field at vacuum environment. In order to calculate the properties of gas, the gas was assumed to obey the ideal gas law. The particle transport mechanisms considered were convection, Brownian diffusion and gravitational settling. The averaged particle deposition velocities and their radial distributions fnr the upper surface of the wafer were calculated from the particle concentration equation in an Eulerian frame of reference for system pressures of 1 mbar~1 atm and particle sizes of 2nm~10$^4$ nm(10 ${\mu}{\textrm}{m}$). It was observed that as the system pressure decreases, the boundary layer of gas flow becomes thicker and the deposition velocities are increased over the whole range of particle size. One thing to be noted here is that the deposition velocities are increased in the diffusion dominant particle size range with decreasing system pressure, whereas the thickness of the boundary layer is larger. This contradiction is attributed to the increase of particle mechanical mobility and the consequent increase of Brownian diffusion with decreasing the system pressure. The present numerical results showed good agreement with the results of the approximate model and the available experimental data.

• 대한기계학회논문집
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• 제19권3호
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• pp.763-770
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• 1995

Gas flow characteristics within the cylinder is important factors in impoving lean combustion stability. This paper shows the effects of various flow fields generated by a swirl control valve(SCV) on combustion process in a 4-valve spark ignition engine. An impulse swirl/tumble meter was used to elucidation the steady-state flow characteristics, and a rotating grating type LDV was developed to measure the mean velocity and tunbulence intensity in relation to the crank angle. These methodologies were applied to clarify the correlation between gas flow characteristics and combustion stability at a lean air fuel ratio. An analysis of the correlation revealed the gas flow conditions required to optimize a lean-burn system.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.85-88
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• 2002

In order to visually analyze the flow characteristics, gas was injected into the liquid bath through nozzle installed at the center of bottom of the bath. When gas was injected into the liquid bath, several flow patterns were observed bubble-liquid plumb, the spout flow that occurred at the free surface, liquid circulation flow by bubble's behavior, etc. Various bubbles, from small bubbles to Taylor bubbles, consisted of the bubble-liquid plumb. In the pure liquid region, the large and small several vortices were formed and irregularly circulated. These irregular repetition and circulation play a important role of mixing in the bath. The vortices were developed in the upper and the side wall regions and the movement of flow in the low region was very small. It is known as 'dead zone'.

• 대한기계학회논문집B
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• 제33권11호
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• pp.834-839
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• 2009

A three-dimensional computational fluid dynamics (CFD) analysis is performed to investigate flow characteristics in the anode channels and manifold of the internal reforming type molten carbonate fuel cell (MCFC). Considering the computational difficulties associated with the size and geometric complexity of the MCFC system, the polyhedral meshes that can reduce mesh connectivity problems at the intersection of the channel and the manifold are adopted and chemical reactions inside the MCFC system are not included. Through this study, the gas flow rate uniformity of the anode channels is mainly analyzed to provide basic insights into improved design parameters for anode flow channel design. Results indicate that the uniformity in flow-rate is in the range of ${\pm}$1% between the anode channels. Also, the mal-distributed inlet flow-rate conditions and the change in the size of the manifold depth have no significant effect on the flow-rate uniformity of the anode channels.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3120-3124
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• 2008

A three-dimensional computational fluid dynamics (CFD) analysis is performed to investigate flow characteristics in the anode channels and manifold of the internal reforming type molten carbonate fuel cell (MCFC). Considering the computational difficulties associated with the size and geometric complexity of the MCFC system, the polyhedral meshes that can reduce mesh connectivity problems at the intersection of the channel and the manifold are adopted and chemical reactions inside the MCFC system are not included. Through this study, the gas flow rate uniformity of the anode channels is mainly analyzed to provide basic insights into improved design parameters for anode flow channel design. Results indicate that the uniformity in flow-rate is in the range of ${\pm}1%$ between the anode channels. Also, the mal-distributed inlet flow-rate conditions and the change in the size of the manifold depth have no significant effect on the flow-rate uniformity of the anode channels.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1512-1516
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• 1994

FLIC(Fluid in cell) method has been used for analyzing a cold gas flow field in an interrupter of a circuit treater since 1970s. In this paper FLIC method is applied to calculation of a cold gas flow and then combined with the simple are analysis method in order to investigate the flow field characteristics in a puffer type interrupter rated at 145kV 40kA. The results for a cold gas flow agree with the experimental measurement well. The other results such as pressure rise, arc temperature, post-arc current and so forth am also reasonable and show the possibility that the combined program can be applied to the design of UHV interrupters.

• Journal of Mechanical Science and Technology
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• 제19권9호
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• pp.1811-1820
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• 2005

Thermo-acoustic instability of methane/ air flames in an industrial gas-turbine combustor is numerically investigated adopting CFD analysis. The combustor has 37 EV burners through which methane and air are mixed and then injected into the chamber. First, steady fuel! air mixing and flow characteristics established by the burner are investigated by numerical analysis with single burner. And then, based on information on the flow data, the burners are modeled numerically via equivalent swirlers, which facilitates the numerical analysis with the whole combustion system including the chamber and numerous burners. Finally, reactive flow fields within the chamber are investigated numerically by unsteady analysis and thereby, spontaneous instability is simulated. Based on the numerical results, scaling analysis is conducted to find out the instability mechanism in the combustor and the passive control method to suppress the instability is proposed and verified numerically.

• 한국가스학회지
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• 제25권5호
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• pp.37-51
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• 2021

가스 레귤레이터에 동일한 유량을 공급할 때 발생하는 압력 강하 현상을 분석하였다. 레귤레이터는 특정 범주의 환경에서 일정한 압력을 토출하기 위해 피스톤 상/하부에 작용하는 힘과 스프링 장력 간의 상호 작용으로 피스톤의 위치를 이동시켜 압력을 유지하는 특성이 있다. 레귤레이터 내부의 유체의 체적이 변화함에 따른 레귤레이터의 유동특성과 압력제어과정을 수치해석기법을 통해 분석하였다. 피스톤과 피스톤 시트 사이의 간격이 감소함에 따라 압력 강하가 증가하고 유속이 증가하였다. 압력-유량시험과 동일한 조건(입구압력 3MPa, 출구압력 0.8MPa, 유량 70kg/h)에서 피스톤이 0.12mm에 위치함을 수치해석을 통해 검증하였다.