• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.107-115
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• 2002

In this paper, spray and combustion characteristics of a liquid-fueled ramjet engine were experimentally investigated. The spray penetrations were measured to clarify the spray characteristics of a liquid jet injected transversely into the subsonic vitiated airstream, which Is maintained a high velocity and temperature. The spray penetrations are increased with decreasing airstream velocity, increasing airstream temperature, and increasing air-fuel momentum ratio. To compensate our results of penetrations, the new experimental equation were modified from Inamura's equation. In the case of insufficient penetration, the combustion phenomenon in ram-combustor were unstable. Therefore, the sufficient penetration must be considered to make a stable flame.

• 발명특허
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• v.26 no.10 s.306
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• pp.76-83
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• 2001

본 발명은 승화성 고체 미립자 제트를 이용한 분사로 표면의 오염물을 제거하는 공정이다. 이는 극저온에서 고화된 입자가 표면에 고속 충돌 후 오염물을 제거하고 자신은 승화되어 잔사를 남기지 않는 청정 세척 공정을 말하는데 반도체 장비, 정밀 제품, 인쇄회로 기판 등의 다양한 표면의 각종 오염막 제거에 널리 사용될 수 있다. 본 장치의 특징은 세정 매체인 $CO_2$와 Carrier gas인 $N_2$를 사용하였고 현재 특허에 출원되어 있는 단순한 액체$CO_2$를 이용한 세정범위를 넘어 다양한 세정매체 즉, 복합인자($CO_2$ + ice, Ar + ice)를 이용하여 세정효율의 다변화를 이루었고 자체 개발한 냉동기를 이용하여 고화율이 액체 $CO_2$보다 상대적으로 낮은 기체 $CO_2$의 고화율을 증대 시킴으로써, 세정매체의 소모시간이 현격히 감소되어 원가절감 효과를 증대 시켰다. 세정대상물을 효과적으로 제거하기 위해 주 세정 매체인 $CO_2$의 수농도를 조절할 수 있는 Multi-Nozzle의 개발과 이로 인하여 세정력의 강도를 조절하도록 하였다. 세정 후 발생되는 오염입자를 효과적으로 제거하도록 국부 Exhaust를 Nozzle전단에 달아 재 오염의 방지효과를 극대화 시켰다.

• Journal of Korea Ship Safrty Technology Authority
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• v.17
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• pp.24-43
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• 2005

최근 우리나라 어선어업은 한중일 어업협정, 연안 어업자원 감소 및 연안오염 등 사회적, 환경적 변화가 급변하고 있어 이들을 고려한 어선 선형개발이 필요로 한다. 현재 우리나라의 어선 중 연안지역에서 조업하는 5톤 미만의 소형어선은 전체 어선 중 $65\%$ 이상으로 구성되어 있으나 선박의 크기가 작고 부가가치가 낮은 관계로 지금까지 전문적인 연구는 거의 없었던 것이 현실이다. 한편, 서$\cdot$남해 연안에서 작업 및 항해하는 연안어선들의 해양사고 발생율은 전체사고의 $69.6\%$로 매년 증가하고 있는 추세이다. 전체 어선 안전사고 중 부유폐어망, 로프 등이 추진기에 감긴 사고는 전체 사고의 $10.4\%$로 매년 증가하고 있다. 이에, 추진기 손상에 의한 어선 사고와 연관하여 추진기를 보호하기 위한 장치로서 물분사 추진기(Water-Jet), 펌프제트(Pump-Jet)장치들이 있으나 이들은 고가 수입품으로서 영세한 어민들의 소형어선에 장착하기에는 한계가 있어, 본 연구에서는 폐그물, 로프 등 해상 부유물에 의한 추진기 손상이 발생되지 않는 프로펠러 보호터널 부착 추진장치를 개발을 목적으로 한다. 프로펠러 부착 추진장치는 기존 선미를 수정하여 추진기를 선체 안쪽으로 배치하며 돌출되는 부분은 덕트로 보호하고 있으며 이러한 추진기는 워터제트 추진기와는 달리 가격이 싸고 그물이나 부유물에 걸리지 않고 고장 시 신속한 대응이 쉬워 소형 연안어선에 적합할 뿐만 아니라 그물, 부유물, 갯벌이 많은 국내의 서$\cdot$남해 연안에서 작업 및 항해 시 매우 유용할 것으로 판단된다. 본 연구는 `프로펠러 보호터널 부착 연안어선의 선형개발`을 최종목표로 수행하였으며, 연구개발 내용은 기존 소형 연안어선의 분류 및 특성 조사 연구, 프로펠러 보호터널형 선미 선형 개발, 기존 선형 및 보호터널형 선형의 모형시험, 개발선의 구조강도 특성, 프로펠러 설계 및 단독시험, 보호터널 부착 추진기의 효율 검증 및 개발 대상 어선의 조선공학적 제 계산, 설계도작성 등을 실시하였다. 주요 요소 기술로서는 프로펠러 보호터널 부착 선형의 모형시험을 통하여 선미선형을 개발하며 FRP판부재의 구조강도 특성을 분석하고 그 결과를 활용하여 4톤급 연안어선의 시제선을 건조하고 시운전을 통하여 주요성능을 확인하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.324-333
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• 1998

Measurements of the local heat transfer coefficients on a hemispherically concave surface with a round oblique impinging jet were made. The liquid crystal transient method was used for these measurements. This method, which is a variation of the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystal for the surface temperature measurements. The Reynolds number used was 23,000 and the nozzle -to -jet distance was L/d=2, 4, 6, 8 and 10 and the jet angle was $\alpha$=0$^{\circ}$, 15$^{\circ}$, 30$^{\circ}$and 40$^{\circ}$. In the experiment, the maximum Nusselt number at all region occurred at L/d(equation omitted)6 and Nusselt number decreases as the inclined jet angle increases. For the normal jet the contours of constant Nusselt number are circular and as the jet is inclined closer and closer to the surface the contours become elliptical shape. The decreasing rate of the Nusselt number at X/d＞ 0(upstream) on a surface curvature are higher than those on a flate plate and the decreasing rate of the Nusselt number at X/d ＜0(downstream) on a surface curvature are lower than those on a flate plate. And also, the decreasing rate of local Nusselt number distribution at X/d ＜0(upstream) exhibit lower than with X/d ＜0(downstream) as jet angle increases. The second maximum Nusselt number occurred at long distance from stagnation point as jet angle increases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.846-854
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• 1999

Measurements of the local heat transfer coefficients were made on a hemispherically convex surface with a round oblique impinging jet. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystal for the surface temperature measurements. The Reynolds number used was 23000 and the nozzle-to-surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was $\alpha$=$0^{\circ}\; 15^{\circ}\;30^{\circ}C\; and \;40^{\circ}C$. In the experiment, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit Secondary maxima at $0^{\circ}C\re $\alpha$\re 15^{\circ}C, L/d\le6$ for X/d＜0(upstream) and at $0^{\circ}C\re $\alpha$40^{\circ}C,\;L/d\le4\;and\; at\; 30^{\circ}C\re $\alpha$$\leq$40^{\circ}C,\;L/d\le 6 $for X/d＞0(downstream). The secondary maxima occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. The Y-axis Nusselt number distributions exhibit secondary maxima at Y/d=$\pm$2 for $0^{\circ}C\le a\le30^{\circ}C\; and\; L/d\le4, and \;for\;$\alpha$=40^{\circ}C$and L/d=2. The displacement of the maximum Nusselt number from the stagnation point increases as the jet angle increases or the nozzle-to-surface distance decreases and the maximum distance is about 0.67 times of the nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.53-58
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• 2021

Based on surrogate model, a hydrocarbon mixture was analyzed by visualizing the impinging break up mechanism in subcritical and supercritical conditions. Decane and methylcyclohexane with different critical pressures and temperatures were selected as experimental fluids. The impinging injector was installed inside the chamber, and the spray was visualized through a speed camera in subcritical and supercritical conditions. The injection condition of the mixture and chamber was kept constant at Pr(P/P_c) = 1, and Tr(T/T_c) was increased from 0.48 to 1.02. As Tr increased, the spray angle increased, and the sheet length decreased as the properties of the mixture reached each critical point. In addition, when the mixture approached the near critical point, it was shown that the change in density gradient was largely observed out of the impinging break up mechanism.

• Journal of Animal Environmental Science
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• v.18 no.3
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• pp.207-220
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• 2012

There are around 7,500 manure tanks to treat the manures from pigs in Korea. In the tank, there are too much sediments deposited on the base and wall, which causes low efficiency of stock capacity and manure fermentation. In order to minimize sediments and to ferment manure effectively, we developed a 2-fluid jet mixer for mixing sediments in liquid livestock manure tank. For developing the prototype, we tested a factorial experimental system with various nozzles, and simulated CFD models with two kinds of nozzle arrangement. From the results of factorial experiment and CFD simulation, we concluded the dia. ratio of primary : secondary nozzle should be 1:2 and the nozzles should be arranged at the same distances toward to the circumferential direction. With this results, we manufactured a 2-fluid jet mixer which is consists of four 2-phase nozzles, centrifugal slurry pump and root's type air blower. And, we carried out the performance test of the prototype in the round shaped liquid manure tank in the farm. The performance test results showed that the uniformity of TS (Total Solid) and VS (Volatile Solid) was raised from 21.3 g/L, 13.3 g/L In steady state to TS and VS to 23.0 g/L, 14.1 g/L in the mixing operation. Therefore, we could conclude that the prototype of 2-fluid mixer could make the solid material which could be sediments in the tank not to be deposited in the tank and to be contacted to air bubbles which could enhance the efficiency of the fermentation of livestock manure.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.93-98
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• 2007

The air velocity flowing in inner combustion chamber of SCramjet is supersonic and the time of its stay is very short as a few milliseconds. Within this short time, fuel injection， air-fuel mixing, and combustion process should be accomplished. Several methods are suggested for mixing enhancement. Among these, cavity is selected to study for mixing characteristics. The numerical simulation is performed in the case of freestream Mach number of 2.5 and cavity located in front of fuel jet injection. 3 different sized cavities of the same length-height ratio were used in order to recognize the effect about cavity size. Also, the case without cavity was analyzed to find the effect of cavity. Used code compared with the result of experiment under identical conditions and it was verified. Through this comparison and verification, mixing enhancement by cavity size could be confirmed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.81-86
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• 2007

The air velocity flowing in inner combustion chamber of Scramjet is supersonic and the time of its stay is very short as a few milliseconds. Within this short time, fuel injection, air-fuel mixing, and combustion process should be accomplished. Several methods are suggested for mixing enhancement. Among these, cavity is selected to study for enhancement of mixing. The numerical simulation is performed in the case of freestream Mach number of 2.5 and cavity located in front of fuel jet injection. 8 different sized cavities of length-height ratio were used in order to recognize the effect about cavity size. Also, the case without cavity was analyzed to find the effect of cavity. Used code compared with the result of experiment under identical conditions and it was verified. Through this comparison and verification, mixing enhancement by cavity could be confirmed.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.1
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• pp.1-11
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• 2022

In a gas turbine, fuel is exposed to a high temperature environment until it is fed to the combustor through the injector. Hydrocarbon fuels can coke under high temperature conditions, which can cause coking material to deposit on fuel lines or block the injector passages. In this study, a specimen simulating a fuel line located inside a gas turbine and Jet A-1 were heated using electric devices. Jet A-1 coking tests were performed by changing the wall temperature of the stainless steel specimen and the temperature of Jet A-1 supplied to the specimen. After the coked specimens were cut, the coking material and the inner surface were analyzed using an energy dispersive X-ray spectrometer and a field emission scanning electron microscope.