• 한국연소학회지
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• 제5권1호
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• pp.43-53
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• 2000

Experimental studies on determination of the supply leading time of propellants to combustion chamber have been made to stably and efficiently guarantee the ignition process with liquid rocket engine. The propellant used is a Jet A-1 as fuel and a liquid oxygen as oxidizer. Unlike impinging FOOF type of injectors are arranged radially and the designed O/F ratio is 2.34. The present experiment program also includes the stability on the quadlet type of ignitor using the triethylalumimum as an ignition source and injector life tests. Experimental results clarifies that the propellant supply through LOx leading to combustion chamber is proper for stable ignition and combustion processes based on the fuel and oxidizer manifold pressures, combustion chamber pressure, and the variation of flame length from the nozzle exit with lapse time, and shows that the leading supply time of propellants affects the engine performance little. The effect of positioning cooling holes is remarkable to protect the injector face.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.1-9
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• 2002

Simultaneous PIV and OH PLIF measurements are used for shear strain rates and flame locations, respectively. It is believed that the shear strain rates represent flow characteristics such as turbulence intensity and the OH intensity indicates the flame characteristics such as burning velocities. However, these are still lack of geometric information, which may be very important to flame quenching Hence, fractal dimensions 'Df) of the OH images are adopted as an additional information. Finally, the flame structure diagram proposed in this research has three parameters, which consist of strain rates, OH intensities and fractal dimensions. The results show that this diagram classifies turbulent premixed flames more effectively based on flame structures. The regime of weak turbulence is limited to narrow strain ranges and has the fractal dimension of about 2 In the regime of moderate turbulence, OH intensities increase as strain rates increase and the values of fractal dimensions are 1.8 Df 1.95. The regimes of thickened reaction and flame extinction (quenching) show bell-shaped and their values of fractal dimensions are 1.5 Df 1.7 and 0.9 Df 0.6, respectively.

• 열처리공학회지
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• 제25권4호
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• pp.181-189
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• 2012

The demand on quantitative measurement of the heat flux is motivated in making higher-quality steel product through a water quenching process of plate mill. To improve a spatial degree of heat flux measurement, the multi-point heat flux measurement was carried out by a unique experimental technique that has a combination of the existing single-point heat flux gauge. The corresponding heat flux can be easily determined by Fourier's law in a conventional way. The multi-point heat flux gauge developed in this study can be applicable to measure the surface heat flux, the surface heat transfer coefficient during a water quenching applications of steelmaking process. The results exhibit different heat transfer regimes; such as single-phase forced convection, nucleate boiling, and film boiling, that are occurred in close proximity on the multi-point heat flux gauge quenched by water impinging jet.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1997년도 제9회 학술강연회논문집
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• pp.8-9
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• 1997

산업의 발달과 환경에 대한 관심이 높아짐에 따라 고효율, 저공해인 가스터빈의 응용범위가 넓어지고 있는 추세이다. 가스터빈 기관의 효율을 높이기 위해서는 터빈 입구온도를 높이는 것이 필수적인데 이는 재질에 의해 제한 받게 되고 이 때문에 효과적인 냉각방법의 필요성이 대두되었다 충돌제트는 국소적으로 높은 열/물질 전달 효과를 얻을 수 있어서 터빈 블레이드 냉각과 연소기 벽면 냉각에 효과적으로 응용 될 수 있다. 이러한 충돌제트의 냉각효과는 제트출구의 초기조건에 매우 민감한데 Kelvin-Helmholts 불안정은 불안정한 자유전단층에서 자연적인 와류생성(roll up)과 개개의 와류고리 형성의 원인이 되고 이 고리의 성장과 병합(pairing)은 제트의 유동특성에 상당히 영향을 미친다. 제트주위에 생성되는 이러한 와류에 의해 제트중심에서 속도와 난류강도가 변하게 된다. 이러한 제트초기의 불안정성은 하류에서의 와류성장에 영향을 끼치기 때문에 와류의 조절에 의한 충돌 면에의 열 전달 효과 상승을 기대할 수 있다. 이 조절방법은 크게 두 가지로 나눌 수 있는데 하나는 제트주의 환형관에 이차유동을 가하여 와류를 직접 제어함으로써 자유전단류(free shear layer flow)의 안정성 원리를 이용하여 열 전달을 촉진하는 것이고 다른 하나는 음향여기(acoustic exitation)를 사용하여 제트주위의 와류형성을 조절하는 것인데, 자연적으로 형성되는 와류의 주파수(와류의 고유주파수)나 부조화 주파수(subharmonic)로 음향여기 시키는 경우 제트 주위 와류는 더욱 증폭되고 그렇지 않은 경우 제트주위 와류의 형성이 억제되어 더 긴 제트코어의 길이 및 제트코어 주위에서 작은 크기의 와류들이 형성된다.

• 설비공학논문집
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• 제21권9호
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• pp.483-495
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• 2009

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction stream line-inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.

• International Journal of Ocean System Engineering
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• 제1권1호
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• pp.46-51
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• 2011

In a line heating process for hull forming, the phase of the steel transforms from austenite to martensite, bainite, ferrite, or pearlite depending on the actual speed of cooling following line heating. In order to simulate the water cooling process widely used in shipyards, a heat transfer analysis on the effects of impinging water jet, film boiling, and radiation was performed. From the above simulation it was possible to obtain the actual speed of cooling and volume percentage of each phase in the inherent strain region of a line heated steel plate. Based on the material properties calculated from the volume percentage of each phase, it should be possible to predict the plate deformations due to line heating with better precision. Compared to the line heating experimental results, the simulated water cooling process method was verified to improve the predictability of the plate deformation due to line heating.

• 대한기계학회논문집B
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• 제30권3호
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• pp.262-269
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• 2006

Segregation algorithms of the incompressible Wavier-Stokes equations using P1P1/P2P1 finite element formulation are newly proposed. P1P1 formulation allocates velocity and pressure at the same nodes, while P2P1 formulation allocates pressure only at the vertex nodes and velocity at both the vertex and the midpoint nodes. For a comparison of both the elapsed time and the accuracy between the two methods, they have been applied to the well-known benchmark problems. The three cases chosen are the two-dimensional steady and unsteady flows around a fixed cylinder, decaying vortex, and impinging slot jet. It is shown that the proposed P2P1 semi-segregation algorithm performs better than the conventional P1P1 segregation algorithm in terms of both accuracy and computation time.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.453-456
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• 2011

합성가스를 이용한 충돌제트 버너에서 신장된 예혼합 화염의 열전달 특성에 관한 실험적 연구를 수행하였다. 본 연구에서는 석탄을 가스화하는 과정에서 추출되는 수소와 일산화탄소를 혼합한 합성가스를 연료로 사용하였다. 정체점에서의 열유속은 전체 신장율이 증가함에 따라 증가하다 다시 감소하는 것이 관찰되었다. 또한 정체점에서의 열유속이 노즐로부터 충돌판까지 거리가 증가함에 따라 증가하는 것을 확인하였다. 본 연구는 석탄에서 발생하는 부생가스의 주성분인 수소와 일산화탄소를 실용화하는 연구 중 기초 연구이다.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1547-1554
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• 2017

VESTA (Verification of Ex-vessel corium STAbilization) and VESTA-S (-small) test facilities were constructed at the Korea Atomic Energy Research Institute in 2010 to perform various corium melt experiments. Since then, several tests have been performed for the verification of an ex-vessel core catcher design for the EU-APR1400. Ablation tests of an impinging $ZrO_2$ melt jet on a sacrificial material were performed to investigate the ablation characteristics. $ZrO_2$ melt in an amount of 65-70 kg was discharged onto a sacrificial material through a well-designed nozzle, after which the ablation depths were measured. Interaction tests between the metallic melt and sacrificial material were performed to investigate the interaction kinetics of the sacrificial material. Two types of melt were used: one is a metallic corium melt with Fe 46%, U 31%, Zr 16%, and Cr 7% (maximum possible content of U and Zr for C-40), and the other is a stainless steel (SUS304) melt. Metallic melt in an amount of 1.5-2.0 kg was delivered onto the sacrificial material, and the ablation depths were measured. Penetration tube failure tests were performed for an APR1400 equipped with 61 in-core instrumentation penetration nozzles and extended tubes at the reactor lower vessel. $ZrO_2$ melt was generated in a melting crucible and delivered down into an interaction crucible where the test specimen is installed. To evaluate the tube ejection mechanism, temperature distributions of the reactor bottom head and in-core instrumentation penetration were measured by a series of thermocouples embedded along the specimen. In addition, lower vessel failure tests for the Fukushima Daiichi nuclear power plant are being performed. As a first step, the configuration of the molten core in the plant was investigated by a melting and solidification experiment. Approximately 5 kg of a mixture, whose composition in terms of weight is $UO_2$ 60%, Zr 10%, $ZrO_2$ 15%, SUS304 14%, and $B_4C$ 1%, was melted in a cold crucible using an induction heating technique.

• 태양에너지
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• 제13권1호
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• pp.11-21
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• 1993

이차원(二次元) 충돌공기분류계(衝突空氣噴流系)에서 흐름방향과 수직(垂直)이 되게 설치한 평판전열면(平板傳熱面) 전방(前方)에 난류촉진체(亂流促進體)인 정4각(正4角) 로드군(群)(로드폭=4mm, 로드피치=50mm)을 설치하고 로드와 전열면(傳熱面)사이의 간극(間隙)(C=1, 2, 4, 6mm), 노즐출구와 전열면간(傳熱面間) 거리(H/B=2, 6, 10, 14) 및 Re수($Re=6.410{\times}10^3{\sim}5.769{\times}10^4$)를 변화시켜 실험한 결과, 평판(平板)에서 열전달계수(熱傳達系數)의 감소율이 큰 영역에서도 로드를 설치하므로써 높은 열전달계수(熱傳達係數)를 얻을 수 있었으며, 실험범위내의 Re수와 H/B에 대하여 열전달계수(熱傳達係數)가 최대(最大)가 되는 최적간극(最適間隙)은 C=1mm이고, 최대(最大) 열전달증진율은 H/B=2, C=1mm에서 로드를 설치하지 않은 평판(平板)보다 약 43% 증진한다.