• Solar Energy
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• v.17 no.3
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• pp.59-66
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• 1997

The present study adopted the PTV method for the velocity acquisition. The system consists of an image grabber built-in a personal computer and a laser-based sheet light projector and particle identification softwares. Velocity vectors are obtained, by PTV and they are used as velocity components for Poisson equation for pressure. Related boundary conditions and no-slip condition at solid wall and the linear velocity extrapolation on the upper side of cavity are well examined for the present study. For calculation of pressure, resolution of grid is basically $40{\times}40$ and 2-dimensional uniform mesh using MAC staggered grid is adopted. The result of experiment reveal that, newly suggested measuring method is capable of estimating pressure and velocity distribution of flow field reasonably.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.3815-3821
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• 2012

The LCD frame is an important part which supports the BLU of medium/large sized TFT-LCD. To produce it efficiently, it is necessary to achieve the molding process improvement from 1 cavity to 2 cavity system. Because 2 cavity mold is compact and its hot-runner zone is broadened, it is difficult to control the temperature on the mold. In this study, injection molding analysis on the frame in 2 cavity process with FEA(Finite Element Analysis) software is carried out to estimate its quality. The calculated injection molding pressures and maximum deflection in 1 and 2 cavity processes are 41.13 MPa and 1.62 mm, 40.49 MPa and 1.66 mm respectively. The measured maximum flexure load and surface roughness of the left and right frame of 2 cavities are 209 N and 0.08 ${\mu}m$, 193 N and 0.10 ${\mu}m$ while those in 1 cavity are 140 N and 0.13 ${\mu}m$. Thermal image shows that the maximum standard deviation of the temperature on left and right side of 2 cavity mold is $1.23^{\circ}C$. The simulation and measurement results show that the quality of the frame in 2 cavity injection molding process as a whole is not worse than that of 1 cavity system. But maximum flexure loads of the frame in 2 cavity process are far greater than that in 1 cavity process.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.1
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• pp.43-47
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• 1985

윤활에서 캐비테이션 문제는 가장 오래된 것 중의 하나이며, 현재 많이 사용되고 있는 레이놀즈 경제조건(캐비테이션)은 유막내의 인장력발생가능성 때문에 그 진실성이 문제되고 있다. 본 논 문에서는 복합 저어널 베어링 실험장치를 이용하여 그 가능성이 연구되었다. 이 장치에서 측정된 최저 압력은 -7바 정도였으며 베어링 축회전수에 따라 캐비티가 발생하지 않는 안정영역, 불 안정한 음압력 및 캐비티가 존재하는 영역과 두 영역 사이의 천이영역으로 구분할 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.769-772
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• 2009

Diaphragm compressors are used for a hydrogen compression because it can achieve high gas pressure with high purity. But diaphragm's lifetime may depend on the shape of the cavity and deflection from fluctuation the pressure change, which is necessary to monitored. In this study, the gas and hydraulic oil pressure in the cavity were measured as piston speed varies for diaphragm compressor. The results show pressure change quantities were reduced and maximum pressure points are delayed as the piston moves faster. And the hydraulic pressure were elevated as gas pressure elevated. And the compression period was more faster than expansion period.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.147-156
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• 2001

본 연구에서는 칩 캡슐화 성형 공정 중의 패들 변형을 해석하기 위한 방법론이 연구되었다. 헬레쇼오 근사 모델에 근거한 유한요소법이 칩 캐비티에서의 유동 해석을 위해 사용되었다. 리드 프레임 상의 구멍을 통한 통과 유동해석을 위한 근사모델이 제안되었다. 본 연구에서 제시된 해석모델에 의해 계산된 값과 실험 값은 잘 일치하였다. 유동해석을 통하여 리드프레임과 패들에 의해 경계를 이루고 있는 상, 하 캐비티간의 압력차가 계산되었다. 최종적으로 패들 변형이 압력차 계산 값을 이용하여 계산되게 된다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.227-232
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• 1995

사출성형(Injection Molding)은 생산성이 좋으며 마무리가공을 거의 필요로 하지 않는 정형 형태( net shape)로 제조가 가능하고 복잡한 형상을 만들 수 있어 고분자 재료의 대부분이 사출성형법에 의해 성형 되고 있다. 최근들어 가볍고 강도가 매우 높은 고분자재료의 개발로 전기전자 제품은 물론 자동차, 항공기 등의 생산에 이르기까지 사출성형의 중요성은 더욱 가속화되고 있다. 본 연구에서는 복잡한 형상과 여러 형상의 캐비티를 갖는 경우에는 동시에 충진이 완료되기가 어렵다. 따라서, 다른 캐비티가 충진되고 있는 동안에 먼저 충진이 된 캐비티에서 고분자 수지는 압축을 받고있기 때문에 사출성형품의 치수정밀도를 향상시키기 위한 좀더 정확한 압력과 온도분포를 예측하기 위하여 기존 의 충진과정과 충진후과정(보압, 냉각과정)을 분리하여 해석 하는 것이 아니라 충진과정과 충진후과정을 동시에 해석할 수 있는 프로그램(program)을 만들었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.90-97
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• 2019

Sparkjet actuator, also known as plasma synthetic jet actuator (PSJA), is an active flow control device that has possibility of controling supersonic flow. This actuator utilizes arc plasma to deposit energy onto the gas inside the cavity to raise temperature and pressure. A change in the state of the fluid inside the cavity generates pressure waves and momentum jet, and they are exhausted through out the orifice exit and disturb external flow field. Since the cavity flow is affected by arc plasma, which is an equilibrium plasma and have generated equilibrium flow, the equilibrium state of air should be considered in order to analyze the flow of sparkjet actuator. In this study, numerical program for equilibrium flow was developed for the use of sparkjet actuator analysis. The developed program was validated by comparing the time - accurate jet front positions with the reference result. Then, impulse characteristics of the actuator in the atmospheric quiescent air were explained.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.305-308
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• 2010

본 연구에서는 사출 성형에서 Cavity내의 압력을 측정하여 사출 성형기에서의 설정한 변수 즉, 사출 압력에 따라 Cavity내의 압력이 사출 공정동안 어떠한 추이를 나타내는지 관찰하였다. 이를 CAE 해석과 비교 분석하여 결과에 따른 점도 함수와의 관계를 알아보았다. 우선 Cavity의 압력을 측정하기 위하여 Cavity 내에 압력센서를 설치하고, 이를 시간에 따른 압력측정 결과를 보기 위하여 압력센서 시스템을 제작 하였다. 실제 사출성형하면서 Cavity 내 압력을 측정하고 CAE 해석 결과의 압력 변화와 비교한다. 이때 일반적으로 CAE 해석과 실험결과가 일치하지 않으므로 새로운 점도 곡선을 추정하여 CAE 소프트웨어 D/B(Data Base) 파일에 입력하여 다시 해석하고 실험 결과와 비교하여 압력변화가 일치할 때까지 반복해서 수행한다. 이때 점도는 Power Law로 가정하여 D/B 파일에서 K와 n값을 조절할 수 있고 일반적으로 n값은 Base Resin과 동일하므로 K값의 변화만을 고려하여 압력변화를 해석한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.104-111
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• 2016

The flame stabilization is one of the topics which have to be solved for the airbreathing propulsion systems, using the entering air which is supersonic velocity as an oxygen sources. Making a recirculation zone with an eddy flow, installed the reducing velocity devices such as the bluff body, is the typical method of the flame stabilization. Recently using a cavity flame stabilization at the wall is an emerging technique as an effective method which extends the stabilization zone, and the related research papers have been published on the flow separation and reattachment, pressures and oscillations including length/depth ratios in the cavities. Even though, still there are lots of topics to study more in the cavity flame stabilization field as the preceding techniques, as well as the research and the development of the airbreathing propulsion system itself.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1982-1987
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• 2011

In this study, we proposed a new method that can estimate viscosity curves of unknown samples or high viscous resins like LFT(Long Fiber Thermoplastics). First, we built the system that could detect the pressure of melt during filling the cavity in a mold. It consists of both pressure sensors which are installed in a mold and the Kit which can convert analog signal to digital signal. The kit measures the melt pressure in mold cavity. We could also simulate the cavity pressure during filling process with commercialized CAE softwares(ex, Moldflow). If the viscosity data in CAE Database were correct, the simulated pressure profile coincided with the measured one. According to our proposed algorithm, we obtained correct viscosity data by iterating the process of comparing the simulated profile with the measured one until both coincided each other. In order to verify this algorithm, we selected well-defined PP resin and concluded that the experimental profile comply with the CAE profile. We could also estimate the optimized viscosity curves for PP-LFT by applying our method.