• Journal of computational fluids engineering
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• v.16 no.3
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• pp.22-28
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• 2011

Laminar Flow over an equilateral triangular cylinder is studied for several inflow angles. Under an uniform flow of $Re_d$=50,75,100,125,150, the triangular cylinder is rotated by ${\theta}$=$0^{\circ}$,$15^{\circ}$,$30^{\circ}$,$45^{\circ}$,$60^{\circ}$,$75^{\circ}$,$90^{\circ}$,$105^{\circ}$. The governing equations are solved by the PISO algorithm based on the finite volume method of the unstructured grid system. The effects of the inflow angle on the vortex-shedding flows are investigated. The Strouhal number shows a minimum at ${\theta}$=$60^{\circ}$. It is closely related to the variation of pressure and flow structure induced by the movement of separation points.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1061-1066
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• 2011

In this study, the flow characteristics of an injection nozzle installed in a high-pressure holder for improving productivity were determined. The inlet velocity, nozzle inflow angle, and nozzle outlet diameter were selected as design factors having an influence on the flow characteristics, and numerical analysis was conducted for these factors. As the inlet velocity is high and the nozzle outlet diameter is small, the pressure and velocity of the injected flow are high. In the case of the nozzle inflow angle, the variation of flow characteristics according to angle was slight, but the highest pressure and velocity were found at $15^{\circ}$. In addition, the possibility of chip elimination by the injected flow was analyzed on the basis of the numerical results.

• 기계와재료
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• v.24 no.2
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• pp.80-93
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• 2012

본 연구는 5,000PS급 선박용 SCR 촉매시스템에 관한 내부 유동특성을 전산유체역학(CFD)을 통해 예측하고 설계에 반영하기 위한 기초를 확보하기 위함이다. 따라서 SCR 촉매반응기 내부 유동특성을 수치해석하기 위한 기법을 소개하였고, 촉매 Cell에 대한 수학적 모델링을 제시한 후 SCR 촉매시스템에서 NOx를 환원시켜 주는 촉매담체에 대한 압력강하를 실험과 수치해석을 통해 비교하였다. 그 결과 수치해석 결과가 실험에 매우 근접함을 확인할 수 있었다. SCR 촉매반응기에 대한 유동특성을 수치해석을 수행하여 각 지점에 대한 압력과 속도분포를 확인하였다. 또한 촉매 담체로 배기가스가 유입되는 입구부의 유동균일도를 예측하기 위해 Inlet pipe의 $90^{\circ}$ 각도에서 유입길이를 변화시켜 수치해석을 수행하였다. 그 결과 각도와 길이에 영향을 받는 것으로 나타났다.

• Journal of Energy Engineering
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• v.11 no.1
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• pp.26-33
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• 2002

In this paper, incompressible and compressible flow characteristics around the butterfly valve have been investigated. In order to simplify the problem, a flat disk valve with various valve disk angles and pressure ratios is considered in the present calculations. It was found that as the disk angle increases, the stagnation point on the front surface of the disk moves to the center of the surface and the inflow velocity decreases. The maximum flow velocity occurs at the downstream of throat because of the formation of vents contracta. As the pressure ratio decreases, compressibility effects increase and the jet formed between the throttle body wall and the disk edge becomes supersonic. This flow also builds up as a shock cell structure. The increase of disk angle and pressure ratio makes the mass flow at the inlet decrease, while the increase of disk angle and the decrease of pressure ratio make the pressure loss coefficient increase.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.426-430
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• 2012

본 연구에서는 3차원 수치 해석 기법으로 SDR 반응기 내 유동 특성을 모사하여 유동 분포 및 체류 시간등을 확인하고 혼합 특성 개선을 위한 방법에 대해 연구하였다. 본 연구 대상 SDR 반응기는 입구 덕트와 반응기 본체의 접속 구간에 가이드 베인(Guide vane)이 설치되어 있고 그 바로 하부 지점에 흡수제를 분무하는 노즐이 설치되어 있다. 이는 처리가스가 반응기로 유입될 때 가이드 베인에 의해 선회류를 형성하여 분무된 흡수제와의 혼합을 촉진시키기 위한 목적으로 설치하였다. 시간당 1,971$m^3/min$ at $260^{\circ}C$의 처리가스가 반응기 상부로 유입되어 가이드 베인을 거쳐 선회류를 형성한 후흡수제와 혼합되어 하부로 배출되는 구조이다. 유동 특성을 분석한 결과, 처리가스가 반응기 중앙으로 강하게 편중되고 있었으며 반응기 양 측면으로 부상 기류가 형성되고 있음을 확인할 수 있다. 또한 강한 편류에 의해 체류시간도 매우 짧은 것으로 판단되는 바, 가이드 베인의 기류 안내 각도가 적합하지 못함을 확인할 수 있었다. 이는 곧 혼합 특성 저하에 따른 미반응 액적의 다량 발생과 함께 고착에 의한 스케일 형성 가능성이 매우 클 것으로 예상되므로 혼합 특성을 개선할 수 있는 설계 변경이 필요할 것으로 판단되었다. 따라서 편류를 해소하고 노즐 근처에서의 체공시간을 확보할 수 있도록 가이드 베인의 안내 각도를 더 크게 변경한 결과, 기존 설계상에서 본체 중앙에 형성되는 편류가 해소되고 선회류의 전개 각도가 커지면서 체류시간 역시 약 5초 이상으로 유지되고 있음을 확인할 수 있었다. 따라서 가이드 베인의 각도만 변경하더라도 본체 형상의 추가적인 변경없이 유동의 혼합 특성을 개선시킬 수 있을 것으로 판단되었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.161-169
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• 2017

The present study investigated the effect of the rib arrangement and a guide vane for enhancing internal cooling of the blade. Two types of rib arrangements were used in the first and second passage in parallel. Aspect ratio of the channel was 5 and a fixed Reynolds number based on hydraulic diameter was 10,000. The attack angle of rib was $60^{\circ}$, rib pitch-to-height ratio (p/e) was 10, and the rib height-to-hydraulic-diameter ratio ($e/D_h$) was 0.075. The effect of an interaction between Dean vortices and the secondary vortices from the first passage was observed. Overall, the attack angle of rib in the first passage was dominant factor to heat transfer and flow patterns in turning region. Also, the channel with a guide vane showed enhanced heat transfer at the tip surface with reducing flow separation and recirculation.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1485-1490
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• 2003

This paper is the analysis of thermal and fluid in solar concentration absorber with various tilt angle and opening ratio of absorber entrance. The purpose of this study is to develop optimum solar concentration absorber, and the parameters for the study are the opening ratio of absorber entrance and the tilt angle. The aspect ratio of absorber was fixed at 0.64, and opening ratio was changed from 0.1 to 1.0. The finite volume method with SIMPLE computational algorithm are used and analyzed the heat transfer in absorber inside walls.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.666-674
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• 2021

A selective catalyst reduction system (SCR) with an integrated bypass unit is proposed. Through simulations of the SCR, variations in flow to the catalyst due to the particular shape of the bypass shutting device in the SCR are also studied. The commercial software Ansys Fluent is used to develop the simulations. For the simulations, the catalyst of the SCR is modeled using the porous media method to reduce the calculation time and number of meshes, which is necessary because of the detailed modeling of the catalyst. Simulations are performed based on changes to the entrance angle to the catalyst and the size of the bypass shutting device. Finally, simulation results are used to compare and analyze the average velocity and uniformity of the flow to the catalyst.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1496-1502
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• 2012

The fuel pump mounted on the engine in the vehicle is consist of the outer and inter rotors, and which inhales fuel from the inlet port and supplies it to the outlet port. In this study, it is carried out the analysis and test of the fuel pump with rotors to evaluate its performance. It is analyzed the flow characteristics of the fuel pumps with numerical simulation in their inlet-outlet angles of 0, 15, 30 degree. After it is determined whether it has the best flow characteristics, its vibration characteristics is analyzed. The flow rate of a pump in the inlet-outlet angles of 0 degree is 191.0 LPH(Liter per hour) which is the largest. and its vibration is calculated to be 0.866 $^m/s^2$. In the results of vibration test, it is known that the vibration of the research pump is smaller than that of the existing one. And the natural frequencies of two pumps is nearly same. Therefore it is known that the performance of the research pump is superior.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.341-349
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• 2001

Numerical calculation has been performed to investigate the fluid flow, heat transfer and local mass fraction of chemical species in the MOCVD(metalorganic chemical vapor deposition) manufacturing process. The mixing of reactants (trimethylgallium with hydrogen gas and ammonia) was presented by the concentration of each reactant to predict the uniformity of film growth. Effects of inlet size, location, mass flow rate and susceptor/cold wall tilt angle on the concentration were reported. From the numerical calculation, the concentration of reactants could be qualitatively predicted by the Nusselt number(heat transfer) and the optimum mass flow rate, wall tilt angle and inlet condition were considered.