• 한국추진공학회지
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• 제8권1호
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• pp.44-53
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• 2004

본 논문에서는 슬릿형 분사노즐의 출구 종횡비에 따라 3차원 화학반응 유동장을 수치적 계산을 통하여 그 특성을 조사하고 연소／혼합 촉진 방법을 고찰하였다. 내부유입유동과 슬릿측면 와동들 둘 다 혼합관점에서 고려되어야 한다는 것을 보여 주었다. 연소효율은 종횡비1.0을 기준으로 작은 경우가 낮고 압력손실 역시 종횡비가 작은 경우가 적다. 모든 결과들은 유동방향으로 긴 슬릿이 연소와 압력손실에 대해 바람직함을 나타내고 있다.

• Advances in aircraft and spacecraft science
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• 제6권6호
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• pp.515-528
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• 2019

The structural vibrations of a flat plate induced by fluctuating wall pressures within wall-bounded transonic jet flow downstream of a high-aspect ratio rectangular nozzle are simulated. The wall pressures are calculated using Hybrid RANS/LES CFD, where LES models the large-scale turbulence in the shear layers downstream of the nozzle. The structural vibrations are computed using modes from a finite element model and a time-domain forced response calculation methodology. At low flow speeds, the convecting turbulence in the shear layers loads the plate in a manner similar to that of turbulent boundary layer flow. However, at high nozzle pressure ratio discharge conditions the flow over the panel becomes transonic, and the shear layer turbulence scatters from shock cells just downstream of the nozzle, generating backward traveling low frequency surface pressure loads that also drive the plate. The structural mode shapes and subsonic and transonic surface pressure fields are transformed to wavenumber space to better understand the nature of the loading distributions and individual modal responses. Modes with wavenumber distributions which align well with those of the pressure field respond strongly. Negative wavenumber loading components are clearly visible in the transforms of the supersonic flow wall pressures near the nozzle, indicating backward propagating pressure fields. In those cases the modal joint acceptances include significant contributions from negative wavenumber terms.

• 한국추진공학회지
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• 제20권5호
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• pp.1-8
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• 2016

배기노즐 형상변화에 따른 엔진성능특성 변화와 그에 따른 적외선 신호특성을 이해하기 위하여 마이크로 터보제트 엔진을 이용한 성능특성 및 적외선 신호 측정 연구를 수행하였다. 엔진 배기노즐은 원형노즐과 가로세로비가 서로 다른 5개의 사각형 노즐을 제작하여 실험을 진행하였다. 엔진의 추력 및 연료소모율은 배기노즐 형상에 따라 큰 차이를 나타내지는 않았다. 그러나 배기가스에서 방출되는 적외선 신호의 경우 가로세로비가 큰 사각형 노즐에서 적외선 신호가 점차 감소하는 경향을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1522-1527
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• 2004

The purpose of this study is to investigate the effect of swirler angle and swirl chamber aspect ration of nozzle on the characteristics of single and twin spray. The performances of nozzle has been investigated by measurements of spray angle, droplet size, velocity and Weber number at a water pressure 0.4MHz. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the smaller swirler angle, the larger axial velocity became. It was also shown that the larger aspect ratio, the smaller droplet diameter became.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1194-1197
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• 2005

Micro nozzle is employed as a dynamic passive valve in micro fluidic devices. Micro nozzle array is used in micro droplet generation in bio-medical applications and propulsion device for actuating satellite and aerospace ship in vacuum environments. Aperture angle and the channel length of the micro nozzle affect its retification efficiency, and thus it is needed to produce micro nozzle precisely. MEMS process has a limit on making a micro nozzle with high-aspect ratio. Reactive ion etching process can make high-aspect ratio structure, but it is difficult to make the complex shape. Focused ion beam deposition has advantage in machining of three-dimensional complex structures of sub-micron size. Moreover, it is possible to monitor machining process and to correct defected part at simultaneously. In this study, focused ion beam deposition was applied to micro nozzle production.

• International Journal of Automotive Technology
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• 제6권1호
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• pp.9-14
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• 2005

An experimental investigation has been carried out to reveal the atomization process of the diesel fuel spray. The spray injected through a single hole nozzle was taken by a camera on the opposite side of a stroboscope for macroscopic observation or a nanolite for microscopic observation. The effect of nozzle aspect ratio was analyzed with disintegration phenomena of the diesel spray. Based on the enlarged spray photograph, atomization process was observed in detail and further the spray cone angle was measured under various ambient pressures. The result shows that atomization of diesel spray in early stage of injection is mainly progressed in the vicinity of spray periphery region except the region close to the nozzle exit and spray head region. The spray cone angle is nearly constant under the pressurized condition, while it decreases with elapsing time under the atmospheric condition.

• 한국분무공학회지
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• 제26권1호
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• pp.33-39
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• 2021

Y-jet nozzle has a wide fuel flow rate range and turn-down ratio, thus, it is used in industrial boilers, furnace and agricultural atomizer. However, it has asymmetrical spray characteristics due to the nozzle design factors. Therefore, in this study, asymmetric spraying characteristics of the elliptical Y-jet nozzle was studied by using the lab-scale spray apparatus. As a result, the elliptical Y-jet nozzle had lower gas mass flow rate than circular Y-jet nozzle at same gas pressure, because of bigger shear stress due to the wider inner surface at the elliptical Y-jet nozzle. Larger SMD was measured on the elliptical Y-jet nozzle than the circular Y-jet nozzle. When SMD was measured in the X_Axis direction at the same gas mass flow rate, the elliptical Y-jet nozzle with an aspect ratio of 2:1 showed greater asymmetry than the others.

• 한국항공우주학회지
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• 제46권2호
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• pp.150-158
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• 2018

항공기 추진기관의 적외선 저감기술을 개발할 목적으로 축소모델인 마이크로 터보제트 엔진의 열유동장에 대한 전산해석 및 실험적 연구를 수행하였다. 이를 위해 원형의 기본노즐과 세장비에 따른 5개의 사각형 형상변형 노즐을 고려하였다. 먼저 엔진 성능 분석을 통하여 전산해석을 위한 계산조건을 도출하였다. 또한 전동식 온도 측정 장치를 이용하여 노즐의 정 후방 특정 위치별 열유동장 분포를 측정하였다. 세장비가 5인 사각 노즐의 추력손실은 원형노즐 대비 약 1.8%이었으며, 노즐 출구의 세장비가 커짐에 따라 추력은 대체적으로 감소하는 경향을 확인하였다. 열유동장의 경우, 세장비가 커짐에 따라 해석에 비해 실험에서 배기 플룸이 더 넓게 형성되었다.

• 설비공학논문집
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• 제3권5호
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• pp.395-403
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• 1991

The purpose of this investigation was to characterize nucleate boiling and burn-out heat flux for rectangular free jet with saturated water impinging perpendicularly and upward against a flat uniform heat flux surface. Heat flux measured for Reynolds number based on rectangular nozzle width and for aspect ratio. The result of nucleate boiling heat transfer was presented nondimensional experimental equation including Nusselt, Boiling, Subcooling, Reynolds and Weber number. The effect of aspect ratio of heated surface in the burn-out heat flux had not appeared distinctly. But for the same aspect ratio, burn-out heat flux increased linearly with increment of nozzle exit velocity.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.751-752
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• 2009