• 한국추진공학회지
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• 제25권3호
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• pp.42-55
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• 2021

본 연구에서는 중심선 방정식 선정에 따른 노즐 성능 영향성을 확인하고자 하였다. 곡선 방정식과 설계 형상 파라미터를 활용하여 S-형 노즐 3조와 Double S-형 노즐 3조를 설계하였고 노즐 차폐 성능은 차폐율 정의를 이용하여 평가하였다. 그리고 내부 유동을 분석하기 위해 속도 분포도와 압력분포도로 특성을 연구하였고, 노즐 성능 계수로는 총 추력 비(f)와 노즐 단열 효율계수(η)를 통해 노즐의 성능을 평가하였다. 중심선에 따른 S-형 노즐의 성능 영향성을 분석한 결과 출구에서 급격한 곡률 변화가 있는 중심선은 노즐 성능이 우수한 반면 차폐율이 낮은 특징이 있다. 반면에 입구에서 급격한 곡률 변화가 있는 중심선은 노즐 성능이 낮아지고 차폐율이 높은 특징이 있다. Double S-형 노즐은 첫 번째 곡률에서 완만한 특징을 보이는 중심선을 사용하는 것이 노즐 성능과 차폐율이 우수하였다.

• 수산해양기술연구
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• 제56권4호
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• pp.395-406
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• 2020

The objectives of this study were to develop the optimal structures of recirculating aquaculture tank for improving the removal efficiency of solid materials and maintaining water quality conditions. Flow analysis was performed using the CFD (computational fluid dynamics) method to understand the hydrodynamic characteristics of the circular tank according to the angle of inclination in the tank bottom (0°, 1.5° and 3°), circulating water inflow method (underwater, horizontal nozzle, vertical nozzle and combination nozzle) and the number of inlets. As the angle in tank bottom increased, the vortex inside the tank decreased, resulting in a constant flow. In the case of the vertical nozzle type, the eddy flow in the tank was greatly improved. The vertical nozzle type showed excellent flow such as constant flow velocity distribution and uniform streamline. The combination nozzle type also showed an internal spiral flow, but the vortex reduction effect was less than the vertical nozzle type. As the number of inlets in the tank increased, problems such as speed reduction were compensated, resulting in uniform fluid flow.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.324-330
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• 2005

For axial-type turbines which operate at partial admission, a performance prediction model is developed. In this study, losses generated within the turbine are classified to windage loss, expansion loss and mixing loss. The developed loss model is compared with experimental results. Particularly, if a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. For this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model quite well agrees with the experimental results. So the developed model could be applied to predict the performance of axial-type turbines which operate at various partial admission rates or with different nozzle shape.

• 한국유체기계학회 논문집
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• 제9권4호
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• pp.13-19
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• 2006

For axial-type turbines which operate at partial admission, a performance prediction model is developed. In this study, losses generated within the turbine are classified to windage loss, expansion loss and mixing loss. The developed loss model is compared with experimental results. Particularly, if a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. For this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model quite well agrees with the experimental results. So the developed model could be applied to predict the performance of axial-type turbines which operate at various partial admission rates or with different nozzle shape.

• 한국분무공학회지
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• 제4권2호
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• pp.47-52
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• 1999

The prediction of the critical Reynolds number in the stability curie of liquid jet was mainly analyzed by the empirical correlations and the experimental data through the literature. The factors affecting the critical Reynolds number include Ohnesorge number, nozzle length-diameter ratio, ambient pressure and nozzle inlet type. The nozzle inlet type was divided into two groups according to the dependence of the critical Reynolds number on the length-to-diameter ratio of nozzle. The empirical correlations for the critical Reynolds number as a function of above factors mentioned are newly proposed.

• 한국화재소방학회논문지
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• 제17권3호
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• pp.55-60
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• 2003

본 연구에서는 관창의 유동특성예측을 위한 해석이론을 정립하고 수치해석으로부터 방수량과 방수형태를 예측하였다. 예측 데이터로부터 관창의 방수형태가 노즐과 니들의 위치에 따라 결정됨을 알 수 있었고, 관창의 유동특성은 노즐과 니들의 형상에 따라 그 특성이 결정됨을 알 수 있었다. 관창의 유동특성과 예측 데이터로부터 화재진압의 효율성을 극대화할 수 있는 새로운 관창의 모델이 제시되었다. 본 연구의 결과가 새로운 모델의 관창을 개발하는데 필요한 자료로 활용할 수 있을 것으로 보며, 또한 관창의 원천기술 확보, 동종업계의 기술력 파급효과 증대 및 소방분야의 기술개발 활성화 등에 이바지하고 자 한다.

• 오토저널
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• 제12권5호
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• pp.26-35
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• 1990

This is an experimental study to investigate the characteristics of Diesel spray and Diesel engine performance using ultrasonic injection nozzle (A, B type) and conventional commercial injection nozzle (C type). The results are obtained as follows: 1. SMD and range of size distribution of Diesel spray using the ultrasonic nozzle are smaller than those using the conventional injection nozzle, and spray angle is spread. 2. Because of the difference of the ultrasonic vibration energy transfer in the same condition, the effects of A-type ultrasonic vibration are larger than those of B-type ultrasonic vibration. 3. Attaching the ultrasonic vibrator to the conventional injection nozzle of the Diesel engine, engine performances i.e. BMEP, BSFC, and cylinder peak pressure are improved.

• International Journal of Fluid Machinery and Systems
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• 제5권1호
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• pp.30-37
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• 2012

A two dimensional Darrieus-type turbine has been proposed for the hydropower utilization of extra-low head less than 2m. In a practical use of Darrieus-type hydro-turbine, head and flow rate may be varied temporally and seasonally. Considering that the cost advantage is required for the low head hydro turbine system, the Darrieus turbine should be operated with high efficiency in the wider range of flow rate possibly by using an additional device with simpler mechanism. In the present paper, an adjustment of inlet nozzle section by lowering the inlet nozzle height is proposed to obtain the preferable inlet velocity in low flow rate conditions. Effects of resulting spanwise partial inlet flow are investigated. Finally, an effective modification of inlet nozzle height over flow rate variation is shown.

• 반도체디스플레이기술학회지
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• 제4권1호
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• pp.35-41
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• 2005

An air levitation type wafer transfer system is composed of control and transfer track. Wafer transfer speed is mainly affected by air velocity of propulsion nozzle. In this study, the propulsion force coefficient was evaluated experimentally for the nozzle with 0.5mm, 0.8mm, and 1.0mm diameter. As a result, the propulsion force was largest in the smallest size of nozzle at same air velocity. The propulsion force coefficient of nozzle increases with reducing diameter of nozzle. This increment of propulsion force coefficient was enlarged remarkably at the 0.5mm diameter of nozzle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.400-405
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• 2001

Nozzle of the double-plated grid plays the role of the spring to support a fuel rod as well as to provide the coolant path in grid. The nozzle was known to be necessary to reduce the spring stiffness for supporting performance. In this study the contact analysis between the fuel rod and the nozzle type spacer grid was performed by using ABAQUS standard to propose the preferable shape in tenn of spring performance. Two small cuts at the upper and lower part of the nozzle appeared to have a minor effect in decreasing the nozzle stiffness. A long slot at the center of the nozzle was turned out not only to decrease the spring constant as desired but also to increase the elastic displacement.