• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.499-505
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• 2001

The objective of the paper was to measure the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron & Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of $2{\times}10^4$. The effective parameters for the pressure drop and the recirculation region were the conical orifice's inclined angle (${\theta}$) against the wall, the interval(L) between orifices, the relative angle of rotation(${\alpha}$) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area. It was found that the shape of the orifice's hole affected the pressure drop and the flow field a lot, But the other parameters did not make much differences to the pressure drop. The PISO algorithm with FLUENT code was employed.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.105-110
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• 2002

Experimental study was conducted to reveal the instability such as leakage flow and rotating stall in an axial flow fan. For this study, unsteady total pressure probe and multi-hole pressure probe were specially designed for measuring the flow field upstream and downstream of rotor. The measured pressure signal was analyzed by Single and Double Phase Locked Averaging Technique. From the result of total pressure fields at inlet and outlet of the rotor, the useful information on the structure of the stall cell in radial direction was provided. Also, detailed flow measurements were carried out with a specially designed high frequency multi-hole pressure probe, providing some insight to the leakage flow and their interation.

• 대한기계학회논문집B
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• 제22권8호
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• pp.1132-1140
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• 1998

The disintegration process of initial spray from high-pressure swirl injector was investigated at different injection pressures. The transient breakup phenomena that were difficult to observe at high injection pressure were easily observed at the low injection pressure of 0.4MPa. The effect of fuel remained inside a nozzle hole volume on the penetration of initial spray was also investigated. The disintegration process of initial spray could be classified four regions: the formation of mushroom shape, the first collision, the second collision, and the development of spray, The liquid film of cup shape was particularly found in the second collision region, and the growth ratio of its length and width at low and high injection pressures were compared.

• Tribology and Lubricants
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• 제30권1호
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• pp.46-51
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• 2014

In this study, we attempted to characterize the physical meaning of the design parameters used for automobile passive dampers by considering the slit, disc, and hole, which influence the pressure characteristics. We also analyzed the change in the pressure characteristics when mixing various slits and discs. Finally, we used a computer simulation to implement lag according to nitrogen gas and analyzed the dependence of frequency on the nitrogen gas pressure.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.345-348
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• 2006

In sheet metal forming process using press and draw die some defect can be made because of the high pressure of air pocket between draw die and the product. The purpose of this study is to develop a program to decide an optimal combination of air vent hole size and number to prevent those defect on product. The air inside air pocket is considered as ideal gas and the compression and expansion is assumed as isentropic process. The mass flow is computed in two flow condition: unchocked and chocked condition. The present computation obtains required cross-sectional area of air vent hole for not exceeding the user specified pressure such as the pressure for yielding strength of the product or the pressure for unchocked flow. To validate the program the present results are compared with the results of other researchers and commercial CFD code.

• 에너지공학
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• 제24권2호
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• pp.17-21
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• 2015

다공 및 다단오리피스열을 해석할 수 컴퓨터코드를 사용하여 원자력발전소 내 공급 및 배출장치의 수축오리피스를 설계하였다. 원래 단공 오리피스가 설치되었으나 다공 오리피스 설치가 필요하여 설계 변경되었다. 오리피스 사이 거리는 충분한 압력회복거리로 유지되었다. 최소 정압은 공동현상 방지를 위하여 그 온도에 상응하는 증기압 이하로 유지되도록 설계하였다. 오리피스 설치 배관의 직경은 운전시 강성을 유지할 수 있도록 원래 크기보다 증가시켰다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.53-58
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• 2008

Film cooling effectiveness on a flat plate was measured with pressure sensitive paint. The pressure sensitive paint(PSP) changes the intensity of its emissive light with pressure and the characteristic was used in film cooling effectiveness measurement. The film coolants were air and nitrogen, and by comparing the intensity of PSP coated surface with each coolant, the film cooling effectiveness was calculated. Three blowing ratio of 0.5, 1, and 2 were tested with two mainstream turbulence intensities. Results clearly showed the effect of blowing ratio and mainstream turbulence intensity. As the blowing ratio increases, the film cooling effectiveness was decreased near the film cooling holes. However, the film cooling effectiveness far downstream from the injection hole was higher for higher blowing ratio. As the mainstream turbulence intensity increased, the film cooling effectiveness was decreased at far downstream from the injection hole.

• 항공우주기술
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• 제4권1호
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• pp.150-161
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• 2005

발사체의 노즈 페어링 벤트 홀 크기 결정 기법의 정확도를 검증하기 위한 시험을 수행하였다. 한국항공우주연구원 우주비행시험그룹이 보유한 열진공 챔버(Bake-Out Chamber)를 이용하여 챔버 내부 압력을 대기압에서 진공으로 떨어뜨렸으며, 그 속에 다양한 벤트홀이 설치된 모델을 넣고 모델 내외부의 압력 및 온도 변화를 측정하였다. 시험 과정에서 나타난 시험 설비 및 측정 장비의 특성을 검토하고 이들이 얻어진 시험 데이터의 정확도 및 신뢰도에 미치는 영향을 분석하였다. 설비 및 측정 장비의 한계 내에서 최대한의 정확도를 얻을 수 있도록 데이터를 처리하였으며, 이렇게 얻어진 시험 결과로부터 벤트 홀 면적 및 배치에 따르는 영향을 분석하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.749-752
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• 2004

In a liquid-fueled ramjet engine, the insufficient mixing and evaporation result in the low combustion efficiency and combustion instability. Improving its spray characteristics and devising a means of mixing fuel droplets with air may compensate these disadvantages of liquid fuel ramjet engine. The jet penetrations of various fuel injectors were measured to investigate the spray characteristics of a liquid-fueled ramjet engine under high pressure air-stream conditions. The penetrations in high pressure conditions are smaller than the values calculated from Inamura's or Lee's equations, and, in the high pressure conditions, the jet penetrations are similar each other. In the dual hole injectors, the jet penetrations of rear orifice is rapidly increased due to the reduction of the drag, which is created by the jet column of front orifice. The jet penetration of rear orifice is increased because of the drag reduction created by the jet column of the front orifice. And, because of the drag reduction formed by the column of jet, the jet penetration in the rear orifice of dual hole injector is much larger than the jet penetration of single hole injector. As the distances of the orifice are increased, the jet penetrations of the rear orifice decrease.

• 동력기계공학회지
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• 제10권4호
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• pp.56-64
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• 2006

This paper shows the development process of a straight-type five-hole pressure probe for measuring three-dimensional flow velocity components. The data reduction method using a bi-cubic curve-fitting program in a new calibration map was introduced in this study. This new calibration map can be applied up to the application angle, ${\pm}55^{\circ}$ of a probe. As a result, for the application angle of ${\pm}45^{\circ}$, an error for yaw and pitch angles appeared from $-1.76^{\circ}\;to\;1.83^{\circ}$ and from $-1.91^{\circ}\;to\;1.75^{\circ}$, respectively. Moreover, an error for a vector magnitude and a static pressure compared with a dynamic one showed from -7.83% to 4.87% and from -0.73 to 0.77, respectively. Even though this data reduction method showed unsatisfactory errors in a vector magnitude, it resulted in an easy and simple application method. Especially, when it was applied to an actual flow field including a swirling flow, a good result came out on the whole. However, in order to obtain a better result, it is thought that a more sophisticated interpolation method needs to be introduced.