• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2007년도 추계학술대회
• /
• pp.71-76
• /
• 2007

Flow visualization of a droplet passing through a straight channel and a diverging channel has been carried out using micro-PIV. Diverging channel is frequently used in lab-on-a-chip and microfluidic devices, where flow pattern inside the droplet passing is quite different from that through a straight channel. In the present study, we visualized the droplet flow in three different regions. The first region is where the droplet has a wide contact area with the channel wall, the second region is characterized with a narrow contact area and the third region is where droplet is detached from the channel wall. Visualization results show that the internal flow inside the droplet passing through the straight channel moves in the opposite direction to the droplet velocity in the near wall exhibiting complex flow patterns. But in the diverging channel the internal flow inside the droplet moves in the same direction as the droplet velocity due to the shear induced by oil phase flow exhibiting rather simple flow pattern.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2011년 춘계학술대회논문집
• /
• pp.14-19
• /
• 2011

Two difference cavitation models based on the homogeneous mixture model are used to study cavitating flows through converging-diverging channel. Here, the cloud cavities, pressure distributions and other results have been obtained and compared to evaluate two cavitation models. What's more, differences are observed in the simulated results, due to the differences in characteristics of each model. Analytical results shows that the new improvement cavitation model is validated to have better effects on simulating cavitating flows

• 동력기계공학회지
• /
• 제17권1호
• /
• pp.64-70
• /
• 2013

The heat transfer and friction factor characteristics of turbulent flows in three stationary channels have been investigated experimentally to check out the effect of divergence ratio. These are a constant cross-sectional channel and two diverging channels with ratio of divergence(Dho/Dhi) of 1.16 and 1.49. The measurement was conducted within the range of Reynolds numbers from 15,000 to 89,000 and the dimension of uniform cross-sectional test section is $100mm{\times}100mm$ at the cross section and 1,000 mm in length. The measurements of heat transfer coefficients and friction factors in the uniform channels were conducted as a reference. Because of the streamwise flow deceleration, the heat transfer and friction factor characteristics in the diverging channel were quite different from those of the constant cross-sectional channel. The effective friction factors and convective heat transfer coefficients increased with increasing the ratio of divergence of the channel.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.1604-1610
• /
• 2004

A steady dilute premixed combustion at transonic speeds in a diverging channel is investigated. The model explores the nonlinear interactions between the near-sonic speed of the flow, the small changes in geometry from a straight channel, and the small heat release due to the one-step first-order Arrhenius chemical reaction. The reactive flow can be described by a nonhomogeneous transonic small-disturbance (TSD) equation coupled with an ordinary differencial equation for the calculation of the reactant mass fraction in the combustible gas. The asymptotic analysis results in the similarity parameters that govern the reacting flow problem. The model is used to study transonic combustion at various amounts of incoming, reactant mass, reaction rates, and channel geometries.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
• /
• pp.91-94
• /
• 2014

In this study, the laminar burning velocities of SNG fuel were studied using both experimental measurements and kinetic simulations. They were measured using the angle method of Bunsen flame configuration and the annular diverging channel combustor. And they were also numerically calculated by CHEMKIN Package with GRI 3.0 mechanisms. Spectrometer was used for characteristics of flame chemiluminescence of SNG fuels. From results of this work, first, we found that according to adding $H_2$ contents in the fuels the laminar burning velocities of SNG fuels were increased. And second, we also discovered existence of OH*, CH*, $C_2*$, HCO*, $CH_2*$ radicals and their correlation.

• 멤브레인
• /
• 제7권3호
• /
• pp.142-149
• /
• 1997

비대칭형 막기공을 통한 뉴톤 유체의 발산흐름(diverging flow)에 대한 심도있는 해석 결과를 제시하였다. 막기공 모델의 일반적 형태인 슬릿(slit)과 원뿔(cone)형 채널에 대해 미동흐름(creeping flow)을 적용하여 유속분포 관계식을 구하였다. 유속분포의 고찰로부터 발산각도 $\alpha$$\longrightarrow$0 인 경우는 윤활근사법(lubrication approximation)이 적용되어 Poiseuille 흐름으로 되는 것을 확인하였고, 발산각도가 증가할수록 벽면부근에서의 유속분포는 결핍(depletion)됨과 아울러 전체유속은 감소하였다. 구해진 속도분포와 압력분포의 관계식으로부터 투과유량에 대한 이론식을 도출하였다. 예측된 결과는 기공의 비대칭성이 증가할수록 그에 따른 투과유량은 점차 증가하는 거동을 보였다. 본 연구의 이론결과는 궁극적으로 막여과에의 응용 측면과 밀접하게 연관되어 있다.

• 한국항공우주학회지
• /
• 제33권11호
• /
• pp.65-73
• /
• 2005

천음속 미교란 모델과 1단계 1차 Arrhenius 화학반응식을 이용하여 반응유체의 압축성 유동에 대하여 연구하였다. 유체 유동은 적은 열방출을 수반하는 희박 예혼합 반응에 국한시켰다. 천음속 연소에 끼치는 채널형상과 채널입구 마하수의 영향 등을 수치해석을 이용하여 조사하였다. 수치결과에서 채널확대는 주어진 채널길이 내에서 화학반응을 증가시키고 있음에 반하여 채널수축은 출구 근처에서 화학반응을 억제시키고 있음을 보여주고 있다. 확대형 채널 내에서 입구유동 마하수 증가는 고정된 반응속도에서 유동을 가속시켰으며 불활성 유체 경우에는 나타나지 않는 약한 충격파가 나타났다. 또한 확대형 채널 출구 근처의 압력과 온도를 증가시키고 주어진 채널길이 내에서 반응체의 소비를 도와준다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 학술대회
• /
• pp.148-154
• /
• 2008

Diverging channel from gas burner exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B) of 300 kW HRSG system, two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of boiler(Case C) and uniformity has been improved considerably. Secondly, the diverging channel length can be further reduced for compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.

• 한국전산유체공학회지
• /
• 제14권3호
• /
• pp.1-8
• /
• 2009

Diverging channel from gas engine exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B), two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of the boiler(Case C) and uniformity in velocity and temperature distribution has been improved considerably. Secondly, the diverging channel length can be further reduced to compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.1172-1177
• /
• 2008

Diverging channel from gas burner exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW steam supply and power generation system. Three different test geometries have been chosen for the numerical simulation. The existing design for 300 kW HRSG system (CASE B) has been improved by geometry and position changes of inlet guide vanes along with gas velocity entrance angle at the diverging channel inlet (CASE C). Both cases has been compared with the case where hot combustion gas is directly injected without any guide vanes (CASE A). Improved design shows overall uniform velocity and temperature distribution compared to existing design.