• 태양에너지
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• 제15권1호
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• pp.53-71
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• 1995

형상비가 다른 3개의 사각노즐을 이용한 충돌 수분류가 등열유속 조건($q=10^5W/m^2$)으로 가열된 수평 평판에 충돌하였을 때, 형상비(AR=6.67, 15, 26.67)와 노즐의 출구 유속($V_0=3.3m/s{\sim}78m/s$) 및 노즐과 전열면과의 무차원거리($Z/W=6{\sim}40$)에 따른 열전달 특성을 규명하기 위한 실험을 하였다. 원형 수분류에서 나타난 제2의 열전달 극대치(scondary peaks)가 사각 수분류에서도 나타나고 있으며 그 위치가 형상비에 따라 변한다. 정체점의 열전달계수도 형상비의 영향을 받고 있으며, 정체점 열전달 게수가 가장 좋은 노즐의 최적위치와 정체점 열전달 무차원 관계식을 제시하였다.

• 한국추진공학회지
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• 제4권3호
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• pp.11-18
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• 2000

초음속 노즐 뒤에서 형성되는 과소팽창 제트(Underexpanded jet)가 분사될 때 베럴 충격파(Barrel shock), 팽창과(Expansion fan), 마하 디스크(Mach disc), 제트 경계면(Exhaust-gas jet boundary), 그리고 반사 충격파(Reflected shocks)와 같은 구조의 풍격파 셀(Shock cell)이 연속적으로 나타난다. 이러한 충격파 셀은 난류 소산에 의해 희미해지며 거리가 멀어지면 사라진다. 과소팽창 제트가 수직 평판에 충돌하게 되면 챔버 압력 및 출구 마하수 등 여러 인자들에 따라 달라지는 복잡한 유동장을 형성하게 된다. 본 논문에서는 평판에 충돌하는 과소팽창 제트가 형성하는 유동장을 압축성 Navier-Stokes 방정식에 유한체적법을 적용하여 수치적으로 구한 해존 실험 데이터와 비교 검증하였다. 실험 데이터와 계산 결과의 압력구배 및 유동가시화 사진 비교 견과 노즐과 평판이 가까운 경우에 충돌제트유동을 잘 예측할 수 있었으며, 과소팽창비가 작을 때 과소팽창비에 따른 충돌제트 유동분포의 영향은 자게 나타남을 알 수 있었다.

• Journal of Biosystems Engineering
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• 제34권3호
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• pp.167-174
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• 2009

This study was conducted to develop an agaricus bisporus washing machine which uses compressed air to remove foreign materials attached on the surface of agaricus bisporus. A prototype of the washing machine was constructed, and performance of removing foreign materials was tested. Research results are as follows: 1. Several transferring methods including PE roller rotation, brush roller rotation, PE screw rotation, vibration plate, and belt conveyor were evaluated. Roller, screw, and vibration methods caused damages on the surface of the products, but belt conveyor method caused the least damages. 2. For air jet, a stationary nozzle type and a rotational type were evaluated. The best air jet nozzle was the jet-type nozzle, and the rotational type was more effective than stationary type nozzle. 3. With the conveyer belt, box type moving method and the rotational air jet nozzle, the washing machine showed the best performance when higher than 5.4${\times}$105 Pa of air jet pressure and lower than 0.047 m/s of moving speed was used. Working performance of the system was 650 kg/h, and the damaging rate was 1.2 %.

• 한국농공학회지
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• 제15권3호
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• pp.3053-3058
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• 1973

1. This study was conducted to examine the effects of change of the short range nozzle hole on the travelling distance. The results of this study are summarized as follows; a) Effect of change of the cap hole diameter on the travelling distance of sprayed particles was generally a linear, the increasing rate was about 0.27. b) When the difference between the sectional area of cap hole and that of grooves of swirl plate, was small the travelling distance was decreased by the decreasing of spraying speed at cap hole. 2. This study was conducted to examine the effects of change of the short range nozzle hole on the size of spraying particles. The results of this study are summarized as follows; a) The diameter of sprayed particles on travelling distances in the short range nozzle did not coincide with the kinetic energy principle derived from the momentum and the resistance. b) The average diameter of sprayed particle between 1m and 3m in which amount of sprayed particle was particularly a great deal, was big, because that some of sprayed particles were absorbed each other on the way to fall c) Effect of increase of cap hole diameter was generally enlarged the average diameter of sprayed particle with small rate.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.611-616
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• 2004

In this study, microfabrication of a micro-arcjet nozzle with Fifth-harmonic generation Nd：YAG pulses (wavelength 213 nm) and its thrust performance tests were conducted. A micro-arcjet nozzle was machined in a 1.2 mm thick quartz plate. Sizes of the nozzle were 0.44 mm in width of the nozzle exit and constrictor diameter of 0.1 mm. For an anode, a thin film of Au (~100 nm thick) was deposited by DC discharge PVD in vacuum on divergent part of the nozzle. As for a cathode, an Au film was also coated on inner wall surface. In operational tests, a stable discharge was observed for mass flow of 1.0mg/sec, discharge current of 6 ㎃, discharge voltage of 600 V, or 3.6 W input power (specific power of 3.6 MW/kg). In this case, plenum pressure of the discharge chamber was 80 ㎪. With 3.6 W input power, thrust obtained was 1.4 mN giving specific impulse of 138 sec with thrust efficiency of 24 %.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.463-467
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• 2004

This paper presents the fabrication possibility of the micro actuator which uses a micro-thermal bubble, generated b micro-heater under pulse heating. The valve-less micropump using the diffuser/nozzle is consists of the lower plate, he middle plate, the upper plate. The lower plate includes the channel and chamber are fabricated on high processability silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The middle plate includes the chamber and diaphragm d the upper plate is the micro-heater. The Micropump is fabricated by bonding process of the three layer. This paper resented the possibility of the PCR chip operation by the fabricated micropump.

• 한국항공우주학회지
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• 제42권9호
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• pp.745-751
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• 2014

멀티 노즐로 구성된 추진기관의 경우, 각 노즐별 노즐마개 파열압력의 편차가 초기 분력을 유발하고 유도탄의 비행안정성에 영향을 미친다. 따라서 노즐마개 설계 시 먼저 형태별로 파열거동을 분석하여 원하는 파열압력에서 균일하게 파열되는지를 확인해야 한다. 본 연구에서는 평판형, "+" 노치형 노즐마개에 대한 파열거동을 실험적, 해석적인 방법으로 분석하였다. 실험 시 저장온도, 노치의 유무, 노치방향에 따른 노즐마개 파열압력 및 편차를 분석하였다. 그리고 유한요소해석을 통해 노즐마개의 파열거동을 순차적으로 분석하고, 그 결과를 실험값과 비교하여 정확성을 검증하고자 하였다. 해석 시 상용프로그램인 Abaqus/Explicit를 사용하였고, 파손모델은 Johnson-cook 전단파손모델을 적용하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.271-275
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• 2010

연소기 재생냉각 챔버 노즐확장부의 외피구조물 제작을 위한 성형치구 설계에 대한 연구를 수행하였다. 연소기 챔버에서 두께가 얇은 외피구조물은 판재의 성형을 이용하여 제작한다. 노즐확장부 외피구조물의 성형에서 노즐확장부와 동일한 형상의 치구로 성형하면 성형 후 구조물의 형상이 노즐확장부와 일치하지 않고 탄성복원에 의하여 그 형상이 변화한다. 따라서 노즐확장부 형상과 동일한 형상으로 성형을 완성하기 위해서는 탄성복원을 고려한 성형치구의 설계가 필요하다. 본 연구에서는 초기 성형 후 탄성복원에 의한 노즐형상과 실제 구조물의 형상과의 오차를 없애기 위하여 오차를 보상한 새로운 성형치구용 형상을 생성하였다. 구조해석 결과 설계 수정된 성형치구로 성형하면 노즐 형상과 성형된 구조물과의 형상 오차가 매우 작게 감소함을 확인할 수 있었다.

• 설비공학논문집
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• 제19권12호
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• pp.821-830
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• 2007

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, 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 steam 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 the comparisons between the numerical results using the FLUENT code and the down scale experimental data on effect of geometry of the impingement baffle plate on the shell wall thinning. Additionally, a new type impingement baffle plate was installed above the impingement baffle plate in the feedwater heater and then the numerical and experimental study were performed in the same progress.

• 한국분무공학회지
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• 제13권1호
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• pp.9-15
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• 2008

This experimental study was carried out to examine the heat transfer characteristics of impinging air jet on a flat plate with a set of right angled triangle rods. Each right angled triangle rod in the array was positioned normal to the flow direction and parallel to the flat plate surface. The clearances from a right angled triangle rod to flat plate surface (C=1, 2 and 4 mm) and the distance from nozzle exit to flat plate (H=100 and 500 mm) were changed for the pitch between each right angled triangle rods (P=40 mm). As a result, heat transfer shows best performance at the clearance of C=1 mm, in case clearance changed, and the average heat transfer enhancement rate increased up to 47% compared to the result of a flat plate without a right angled triangle rod.