• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.225-227
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• 2011

핀/슬롯 그레인 및 내삽노즐을 가진 고체로켓모터 내부와 동일한 기하학적 형상을 가진 축소형 표면 분사 시험모델을 사용하여 연소유동장을 모사하였다. 내삽노즐 인접부에서의 복잡한 유동패턴에 대한 유동가시화가 수행되었으며, 내부유동들 간의 상호작용으로 추정되는 슬롯 출구에서의 대칭 와류구조 및 원주방향 유동이 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1601-1604
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• 2005

The demand increasing of optical applications like as display devices derives interest for fabrication process. The product s development is apt to fabricate numerous thin and wide surfaces with micro pattern. Naturally that needs injection molding fabrication for the mass production. In existing manufacturing, the product quality is controlled by input fabrication condition from the outside. That can be called as a try and error method and not fundamentally solve the troubles; imperfect replication, war page, short shot, etc. To understand the cause and bring a solution, it is needed that check of changing in the cavity. This study can catch them. Data acquisition system about temperature and pressure distribution is settled and can get some data. From this research, other studies related with DAQ in cavity can start on the easier step.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.676-679
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• 2008

Numerical simulations of fluid injection into particulate materials were conducted to observe cavity initiation and propagation using distinct element method. After generation of initial particles and wall elements, confining stress was applied by servo-control method. The fluid scheme solves the continuity and Navior-Stokes equations numerically, then derives pressure and velocity vectors for fixed grid by considering the existence of particles within the fluid cell. Fluid was injected as 7-step into the assembly in the x-direction from the inlet located at the center of the left boundary under confining stress condition, 0.1MPa and 0.5MPa, respectively. For each simulation, movement of particles, flow rate, fluid velocity, pressure history, wall stress including cavity initiation and propagation by interaction of flulid-paricles were analyzed.

• Design & Manufacturing
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• 제1권1호
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• pp.27-32
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• 2007

In the optical application demand for high quality lens is increasing. Plastics lenses are demanded more than glass lenses for large size lenses as well as micro-size lenses. It is difficult to apply typical straight cooling channels of injection mold to lens molding due to its non-uniform temperature distribution. In this study, we manufactured molds for plastic lenses with the conventional cooling channels and conformal cooling channels produced by the DMLS process. We evaluated cooling performance for the 2 molds by injection molding experiment. Also, uniformity of the temperature distribution was tested by infrared camera and temperature monitoring. We confirmed that the cooling performance and temperature uniformity with the conformal cooling channels is much improved from the ones with the conventional. The cooling time with the conformal cooling channels was reduced 30% compared with the conventional cooling channels.

• Design & Manufacturing
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• 제10권3호
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• pp.1-7
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• 2016

In the semiconductor industry the memory and chip were developed to high density memory and high performance chip, so circuit design was also high integrated and the test bed was needed to be thin and fine pitch socket. LGA(Land Grid Array) IC socket with thin wall thickness was designed to satisfy this requirement. The LGA IC socket plastic part was manufacture by injection molding process, it was needed accuracy, stiffness and suit resin with high flowability. After injection molding process the side gates were needed to remove for further assembly process. ln this study, the cold press cutting process was applied to remove the gates. For design of punch and die, the cold press cutting analysis was implemented by$DEFORM-2D^{TM}$ ln consideration of the simulation results, an adequate punch and die was designed and made for the cutting unit. In order to verify the performance of cutting process, the roughness of cutting section of the part was measured and was satisfied in requirement.

• International Journal of Fluid Machinery and Systems
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• 제2권1호
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• pp.55-60
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• 2009

The present study investigated temperature and thermal stress distributions in a film cooling system with normal injection cooling flow. 3D-numerical simulations using the FEM commercial code ANSYS were conducted to calculate distributions of temperature and thermal stresses. In the simulations, the surface boundary conditions used the surface heat transfer coefficients and adiabatic wall temperature which were converted from the Sherwood numbers and impermeable wall effectiveness obtained from previous mass transfer experiments. As a result, the temperature gradients, in contrast to the adiabatic wall temperature, were generated by conduction between the hot and cold regions in the film cooling system. The gradient magnitudes were about 10~20K in the y-axis (spanwise) direction and about 50~60K in the x-axis (streamwise) direction. The high thermal stresses resulting from this temperature distribution appeared in the side regions of holes. These locations were similar to those of thermal cracks in actual gas turbines. Thus, this thermal analysis can apply to a thermal design of film cooling holes to prevent or reduce thermal stresses.

• 한국분무공학회지
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• 제1권2호
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• pp.24-32
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• 1996

Most of the research of small engines to date focused on developing spark ignition engines occupied much parts. Recently the number of a small direct injection diesel engine applied in small cars has been increased and considered as a next generation power source for passenger cars because of its high efficiency. Therefore the combustion chamber becomes smaller and the fuel injection pressure goes higher, which makes fuel sprays impinged easily on the combustion chamber walls. When strong swirls are not induced, the fuel may not mix with air because of fuel deposition on the wall. As a positive way, the combustion chamber systems which is using spray wall impaction has been introduced and assessed by an experimental or a simulate manner. In these systems the raised lands are positioned in tile chamber for spray impaction in order to break up the fuel drops into much smaller and direct them into desirable direction. This study addresses to the effects of rho position and size of the raised land or glow plug to help the chamber design using spray wall impaction. The characteristics of the spray impinged on various lands are investigated and compared with each other. Then the chamber shapes are discussed with the characteristics and their proper position and size is proposed in any chamber volume.

• International Journal of Automotive Technology
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• 제5권3호
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• pp.155-164
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• 2004

The direct injection gasoline spray-wall interaction was characterized inside a heated pressurized chamber using various visualization techniques, including high-speed laser-sheet macroscopic and microscopic movies up to 25,000 frames per second, shadowgraph, and double-spark particle image velocimetry. Two hollow cone high-pressure swirl injectors having different cone angles were used to inject gasoline onto a heated plate at two different impingement angles. Based on the visualization results, the overall transient spray impingement structure, fuel film formation, and preliminary droplet size and velocity were analyzed. The results show that upward spray vortex inside the spray is more obvious at elevated temperature condition, particularly for the wide-cone-angle injector, due to the vaporization of small droplets and decreased air density. Film build-up on the surface is clearly observed at both ambient and elevated temperature, especially for narrow cone spray. Vapor phase appears at both ambient and elevated temperature conditions, particularly in the toroidal vortex and impingement plume. More rapid impingement and faster horizontal spread after impingement are observed for elevated temperature conditions. Droplet rebounding and film break-up are clearly observed. Post-impingement droplets are significantly smaller than pre-impingement droplets with a more horizontal velocity component regardless of the wall temperature and impingement angle condition.

• 대한기계학회논문집B
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• 제22권12호
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• pp.1735-1745
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• 1998

Oil-film surface flow visualizations and three-dimensional flow measurements using a straight five-hole probe have been conducted for a circular impinging jet which is normally oriented to the crossflow in a channel. Throughout the experiments, the ratio of channel height to injection hole diameter, H/D, is fixed to be 1.0, and blowing ratio is varied to be 1.0, 2.0, 3.0 and 4.0. From the surface flow visualizations for both top wall(target plate) and bottom wall, impinging jet region on the target plate can be clearly identified, and for the small value of H/D = 1.0, presence of the bottom wall changes the near-hole flow structure, significantly. The three-dimensional flow measurements show that in the dawnstream region of the injection hole, there exist a pair of counter-rotating vortices, called "scarf vortices", and the strength of the vortices strongly depends on the blowing ratio. In addition, a new flow model in the flow symmetry plane has been proposed for H/D = 1.0.

• 한국추진공학회지
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• 제15권3호
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• pp.31-39
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• 2011

핀/슬롯 그레인 및 내삽노즐을 가진 고체로켓모터 내부와 동일한 기하학적 형상을 가진 표면분사 시험모델을 사용하여 연소유동장을 모사하고, 스모크 와이어를 이용하여 유동장을 가시화하였다. 그레인 전방부 투영창을 통해 촬영하는 기법 등에 이용하여 획득된 내삽노즐 선단 인접부의 반경방향 평면상에서의 유동가시화 이미지 분석을 통해, 슬롯출구 반경방향유동, 핀베이스 축방향유동 및 상류그레인포트 축방향유동의 상호 전단작용에 의한 반경방향 운동량 전달이 노즐 인접부에서의 선회류 유동 및 와류튜브 구조를 발생시키는 것으로 나타났다.