• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.5
• /
• pp.1234-1243
• /
• 1990

Double coaxial are jets(annular and coaxial air jets) between which propane gas is fed was selected to study the structure of diffusion flames in turbulent shear flow. Schlieren and direct photographs are taken to visualize the flame structure. Mean and fluctuating temperatures and ion currents were measured to investigate the macroscopic and the instantaneous flame structure. The objective of this study is to understand the interaction between combustion and mixing process especially in the transition region of turbulent shear flow. The investigation reported in this paper focuses on the macroscopic and the instantaneous structures of three flames obtained. The increased mixing effect resulting from increase of Reynolds number of central air jet makes the flame bluish and short. When the velocity of surrounding air stream is higher than that of central air jet, the instantaneous flame structure is composed of coherent structure. It is considered that the flame structure of transitional region of mixing layer depends on the structure of mixing layer of non-reacting conditions.

• Journal of Advanced Marine Engineering and Technology
• /
• v.21 no.1
• /
• pp.43-48
• /
• 1997

The present study is aimed to investigate experimentally on the hydrodynamic behaviours of air ~ pulverized coal flow in rectangular combustor with cavity. Mean velocity, density and tur¬bulent properties of pulverized coal in rectangular entrained flow combustor were measured by PDA. Experimental results show that the flow reattachment point at the lower plane in the com¬buster chamber has been developed near X/D= 15. The similarities at each section are found after the flow reattachment point. The maximum values of turbulent intensity and Reynolds shear stress have been shown near Y/D=6, which is higher than centerline. The maximum density of the pulverized coal sited in the range ofY/D=6~8.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.1
• /
• pp.110-120
• /
• 1986

45.deg. corss jet flow, at the mixing of two jet flows, was experimentally studied. For this study, only the statistical turbulent characteristics and high order moments will be analysed by on-line computer system (hot-wire anemometer system, dynamic analyser and computer system, plotting and printing system). Since mean velocity distributions, intensities of turbulence, Reynolds stresses, correlation coefficients, and other general results were already studied and presented. One dimensional probability density distributions of u', v', and w' were analysed comparing with Gaussian curve, which showed skew and flat tendency according to the Y and Z directions. For the analysis of the joint flow of turublent components, the joint probability density distributions were examined. The fagures were drawn so as to be read joint probabilities, joint probability densities, fluctuating velocities u', v', and w'. For further detailed examination of the variations of skewness and flatness phenomena, iso-joint probability density contours obtained from the profiles of the joint probability density distributions were studied. According to the displacement of positions from the center of the mixing flow and the directions, the flatness and skewness factors were increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.6 no.4
• /
• pp.427-438
• /
• 1994

This experimental study was earned out to examine the heat transfer characteristics of a 2-dimensional impinging air jet on a flat plate with a set of square rods. The objectives of the study were to investigate the flow and heat transfer characteristics caused by the square rods and to find out the optimum rods arrangement. Experiment was carried out first without using the rods to establish the baseline heat transfer performance. Then, rods of different widths and clearances were installed to cause the turbulence on the fluid flow.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.6
• /
• pp.1215-1222
• /
• 1989

본 논문의 목적은 공기 유동장내에 가스분류의 거동을 조사하고 실용 가스 기관의 설계시에 필요한 기초적 데이타를 제공하고자 하는데 있다.본 연구와 관련 된 후래의 연구를 보면 자문등은 열선농도프로브를 사용하여 정상분류중의 농도측정을 행하였고, 분류내의 내부구조를 상세히 조사하였다. 특히, 종래에는 일정하게 보였 던 분류코아 부의 농도변동값의 경향을 구체적으로 나타내었다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.1761-1764
• /
• 2008

본 연구에서는 상용 3차원 수치모형 코드인 FLOW-3D를 이용하여 난류모형에 따른 유류-유사 분리기 내에서 유체의 흐름거동을 해석하였다. 우수로 인해 발생한 유출수는 유류, 유사 및 쓰레기 등을 포함하고 있기 때문에 3차원적 거동을 하고 다양한 흐름특성을 갖는다. 유류-유사 분리기는 도심지의 지하구조물로서 이러한 유출수의 수질을 개선하여 하천이나 강으로 흘려보내는 기능을 갖는다. 분리기내에서의 복잡한 흐름 거동을 해석하기위해 정류판과 유류흡착기로 구성된 유류-유사분리기를 제작하여 수치모의를 실시하였다. 유류-유사분리기로 유입되는 유입수에 포함된 유사는 유체의 흐름이 분리기내에 설치되어있는 정류판을 지나면서 여과되도록 하였고 유사와 함께 유입수에 포함된 유류는 유류흡착기를 통해 여과되도록 하였다. 기존의 수리실험 결과와 수치모의를 통한 연구결과에서 유입수에 포함된 유사와 유류는 유류흡착기를 설치하였을 경우 유사와 유류의 분류활동이 더 활발하게 이루어지는 것을 알 수 있었다. 따라서, 본 연구에서는 유사와 유류의 포획률을 증가시키기 위한 단계로서 유류-유사분리기에 유류흡착기를 설치하고 분리기내의 복잡한 흐름을 각각의 난류모형을 이용하여 비교분석하였다. 수치모의는 $\kappa$ - 모형과 LES(Large Eddy Simulation) 모형의 두가지 난류모형을 사용하였고, FLOW-3D를 이용하여 3차원 수치모의를 실시하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1998.04a
• /
• pp.9-9
• /
• 1998

가스터빈 연소기의 난류유동장을 구성하는 기본적인 유동형태는 크게 밀폐관내의 돌연 확대를 가지는 동축제트, 선회유동, 그리고 연소공기공 및 회석공기공을 통해 연소실에 수직방향으로 유입되는 제트유동 등으로 분류할 수 있다. 실제 가스터빈 연소기내의 난류유동장을 수치해석하기 위해서는 임의의 형상을 갖는 3차원 유동장을 모사할 수 있는 수치해석법과 고차정확도를 유지하면서도 수렴안정성을 만족시키는 대류항 처리기법 등과 같은 수치모델의 개발이 선행되어야 하며, 이와 함께 복잡한 난류연소유동장을 정확히 묘사할 수 있는 난류모델 및 난류연소모델의 개발 및 검증이 가장 중요한 요인이 된다. 또한 가스터빈 연소기의 최적 설계는 넓은 작동구간에서 높은 효율, NOx 및 CO 배기량의 저감, 희박연소 가연한계의 확장, 연소계통에서의 낮은 압력강하, 낮은 연소벽면온도와 온도구배를 유지시키기 위한 공기에 의한 충분한 냉각 같은 서로 상충되는 설계조건을 만족해야 한다. 그리고, 이러한 상충된 연소설계조건들을 충족시키는 최적 연소기의 설계를 위해서는 실험적인 연구뿐만 아니라 연소기내의 물리적인 현상을 잘 반영할 수 있는 물리적 모델을 바탕으로 한 연소유동의 해석적인 연구를 필요로 한다. 본 연구에서는 원통형 가스터빈 연소기의 등온 및 연소유동장, 그리고 연소기와 연결되는 Scroll 내부의 난류유동장에 대한 수치해석을 수행하여 수치 및 물리모델의 예측능력을 검증하였고, 가스터빈 연소유동장 해석에 관련된 중요 논점들에 대하여 심도있게 분석하였다.

• Proceedings of the Korean Nuclear Society Conference
• /
• 2003.05a
• /
• pp.149.2-149.2
• /
• 2003

• Proceedings of the Korea Water Resources Association Conference
• /
• 1995.05a
• /
• pp.185-190
• /
• 1995

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.3
• /
• pp.716-724
• /
• 1990

Oblique impinging plane jets were investigated experimentally and numerically at Reynolds number 21000. The inclination angle was varied from 90.deg.(normal to the impinging plate) to 60.deg.. The distance H between the nozzle exit and the stagnation point on the impinging plate was fixed at H/D=8. The working fluid was air. The mean velocity components and turbulent quantities were measured by a hot-wire anemometer. And the static pressure distributions on the impinging plate were measured by a Pitot tube. In numerical computation, the governing partial differential equations of elliptic type were solved with conventional k-.epsilon. turbulence model. The measurements show that, after impingement, the jet half width alone the wall increases in both directions, and that similarity for each turbulent quantity such as Reynolds shear stress or turbulent kinetic energy is revealed in the wall jet region. The computed results show some deviation from experimental data in the impingement region, where streamline curvature is significant. However, the computed results agree qualitatively well with measurements.