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합성제트를 이용한 풍력터빈 에어포일의 유동 제어에 관한 수치적 연구
이학민(H.M. Lee),권오준(O.J. Kwon) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.3
In the present study, a numerical study about flow control of a wind turbine airfoil was performed using computational fluid dynamics (CFD). Two dimensional unsteady Reynolds-Averaged Navier-Stokes (RANS) solver was used to solve the flow around a wind turbine airfoil. Synthetic jets were applied to the DU 35 airfoil used in the inboard section of the NREL 5MW wind turbine. In order to simulate the synthetic jets, suction/blowing boundary condition was applied. The flow characteristics of synthetic jets were investigated according to the injection speed and injection angle. The injection velocity is 1, 2, and 3 times the freestream and the injection angle is 45 degrees. As the injection speed increases, more energy is transferred into the boundary layer. Therefore, the performance of the DU 35 airfoil is most improved when the injection speed is 3 times the freestream. In the case of the injection angle, the flow analysis was performed at 0 degrees, 45 degrees, and the direction perpendicular to the surface. The injection speed at this time is 3 times. The size and shape of the vortices generated by the synthetic jets depend on the injection angle. When the injection angle is 45 degrees, the performance enhancement of the DU 35 airfoil is the greatest.
아음속 수직분사제트에서 분사각도 영향에 대한 분무특성 연구
김민기(Min-Ki Kim),송진관(Jinkwan Song),이장수(Jangsu Lee),윤영빈(Youngbin Yoon) 한국항공우주학회 2009 韓國航空宇宙學會誌 Vol.37 No.2
본 연구에서는 횡단류 아음속유동장에서 연료가 여러 분사각도를 가지고 수직 분무시 나타나는 액주영역의 궤적과 분열지점에 관한 연구를 수행하였다. 직접 사진촬영 방법과 평면레이저유도형광(PLLIF) 기법으로 정방향 분사각도의 분무에서 액주영역의 제적식과 분열지접까지의 거리에 대한 경험식을 도출하여 기존 연구결과와 비교 분석하고 대향분사의 액주 궤적식과 분열지점까지의 거리에 대한 경험식을 도출하였다. 실험을 통하여 액주영역의 궤적과 분열지점까지의 거리는 분사차압, 공기의 유속, 인젝터 지름 크기, 분사각도에 의하여 결정됨을 확인하였다. The liquid column trajectory and column breakup length characteristics have been experimentally studied in angled jets injected into subsonic crossflow. Pulsed shadowgraph photography and Planar Liquid Laser Induced Fluorescence measurements were used to determine the angled effects. And the main objectives of this research are to get a empirical formula of liquid column trajectory and breakup length with below the 90° degree injection angle conditions, and were compared with previous results. It was also found that the empirical formula, which reversed injection conditions of air streanl. As the result, This has been shown that liquid column trajectories and column breakup length were spatially dependent on various injection angle, normalized injector exit diameter, air-stream and fuel injection velocity. Furthermore, the empirical formula of liquid column trajectories and breakup length has been some different of drag coefficient results between normal angled injection and reversed injection in subsonic crossflow.
중수소 분사각에 따른 불화중수소 화학레이저의 성능향상에 관한 수치적 연구
박준성(Jun Sung Park),백승욱(Seung Wook Baek) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.1
환형 노즐을 갖는 불화중수소 화학레이저 시스템에서 레이저빔 발진은 불소 원자와 중수소 분자의 혼합을 통해서 얻어진다. 초음속 연소기에서 연료의 분사각이 성능에 큰 영향을 미친다는 연구에 근거하여, 혼합률을 증진시키기 위한 연구로서 주유동과 일정각을 가지고 분사되는 중수소의 불소 원자와의 혼합률 증진에 대한 수치적 연구를 수행하였다. 중요 결과로서 중수소 분사각(10, 20, 40도)이 커짐에 따라서 최대 소신호 광학이득계수와 레이저 공동내의 압력이 상승하게 된다. 또한, 광학이득계수와 공동압력의 관점에서 불화중 수소 화학레이저 발진을 위한 최대 성능은 20~40도 사이의 중수소 분사각에서 나타난다. In the chemical laser system with a radial expansion nozzle array, the laser beam generation is achieved by mixing F atom from supersonic nozzle and D₂ molecule from holes of round-bended supply line. Based on that the fuel injection angle with main stream has a great influence of performance on supersonic combustor, the effects of D₂ injection angles with the main F flow on mixing enhancement are numerically investigated. The results are discussed by comparison with three cases of D₂ injection angles; 10˚, 20˚ and 40˚ with the main flow direction. Major results reveal that as the D₂ injection angle increases, the maximum small signal gains and the static pressure in the laser cavity become higher. Consequently, the D₂ injection angle between 20˚ and 40˚ is recommended as an optimized geometric parameter in consideration of both of high gains and low cavity pressure.
수직분사제트에서 다양한 분사각도의 분무궤적 특성에 대한 실험적 연구
김민기(Min-Ki Kim),송진관(Jinkwan Song),황정재(Jeongjae Hwang),윤영빈(Youngbin Yoon) 한국추진공학회 2008 한국추진공학회지 Vol.12 No.6
The liquid column and spray trajectory have been experimentally studied in liquid jets injected into subsonic crossflow. With water as fuel injection velocity, injection angle were varied to provide of jet operation conditions. The Pulsed Shadowgraph Photography and Planar Liquid Laser Induced Fluorescence technique was used to determine the injection characteristics in a subsonic crossflow of air. And the mainly objectives of this research was to get a empirical formula of liquid column and spray region trajectory with forward and reversed injection of air stream. As the result, This research has been shown that each trajectories were spatially dependent on air-stream velocity, fuel injection velocity, various injection angle, and normalized injector exit diameter. Furthermore, the empirical formula of liquid column trajectories has been some different of drag coefficient results between forward and reversed angled injection.
End-burning 하이브리드 연소기 인젝터 분사각에 따른 연소 유동장의 수치적 연구
윤창진(Changjin Yoon),김진곤(Jinkon Kim),문희장(Heejang Moon) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.12
end-burning 연소실의 주요 설계인자들을 구축하기 위해 기존에 수행되었던 인젝터 배열 및 포트 직경 변화, O/F비 변화 외에 산화제 분사각 변화에 따른 연소 특성을 해석하였다. 연료면과 평행한 분사각(Case 1), 연료면을 향해 30° 기울여진 분사각(Case 2)과 노즐을 향해 기울여진 분사각(Case 3)을 설정하여 모델을 구성하였다. 연료면을 향한 분사각의 경우 상류에서 가장 효율적인 혼합특성을 보였으나 상당량의 미연가스가 노즐 밖으로 배출됨을 알 수 있었다. 반면 Case 1과 Case 3은 낮은 혼합특성을 보였으나 연소효율은 연료면을 향한 경우보다 월등한 것으로 판명되었다. Case 1, Case 3 모두 유사한 경향을 나타내었으나 노즐을 향한 Case 3은 짧은 체류시간으로 인해 연료면과 평행한 Case 1에 비해 낮은 연소 성능을 갖는 것으로 평가되었다. The effect of oxidizer injection angle on the combustion characteristics of end-burning hybrid combustor is numerically investigated. Besides the previously studied parameter(injector arrangement, port diameter and O/F ratio), three different injection angle are considered: parallel angle to fuel surface(Case 1), +30 degree inclined angle toward the fuel (Case 2) and 30 degree inclined angle toward the nozzle(Case 3). It is found that Case 2 has the best mixing pattern in the upstream area but has the worst combustion efficiency since non negligible amount of unburned fuel is expelled from the nozzle. In contrast, though Case 1 and Case 3 showed relatively low mixing effect than the Case 2, they had high combustion efficiency. The comparison of numerical results between Case 1 and Case 3 demonstrate that no major difference is encountered, however, Case 1 is expected to have the best combustion efficiency due to the low residence time of the Case 3 injector which heads toward the nozzle.
경사 슬롯의 폭과 분사각이 평판 막냉각 효율에 미치는 영향
이경태,양희문,이상선,강민석,김기문,곽재수 한국유체기계학회 2023 한국유체기계학회 논문집 Vol.26 No.4
The present study was carried out to examine the effects of slot width and injection angle of an inclined slot on the film cooling effectiveness. Three levels of variation were adopted for each design parameter (the wall thickness-to-slot width ratio H/S=5.0, 7.0, and 15.0, and injection angle α=30 °, 45 °, and 60 °). Film cooling effectiveness was measured using the pressure sensitive paint technique in a flat plate test rig under 30 m/s of mainstream velocity condition. Four blowing ratios (M=0.25, 0.5, 0.75, and 1.0) defined as the mass flux ratio between the coolant and the mainstream were considered. Carbon dioxide gas was used as the coolant, resulting in a coolant-to-mainstream density ratio of approximately 1.5. The results showed that higher film cooling cooling effectiveness was observed for a wider slot at a constant blowing ratio condition because more amount of coolant was injected through the wider injection area. In contrast, a narrower slot had a benefit for film cooling effectiveness at a constant mass flow ratio condition. Results also indicated that a steeper injection angle caused lower film cooling effectiveness due to stronger mixing between the coolant and the mainstream.
분사압력 변화에 따른 가솔린 직접분사 인젝터의 거시적 분무와 분무패턴 특성에 관한 연구
박정현 ( Jeonghyun Park ),박수한 ( Suhan Park ) 한국액체미립화학회 2018 한국액체미립화학회지 Vol.23 No.1
The purpose of this study is to investigate the macroscopic spray characteristics and spray pattern of a gasoline direct injection (GDI) injector according to the increase of injection pressure. The macroscopic spray characteristics, such as a spray tip penetration and spray angle, were measured and analyzed from the frozen spray images, which are obtained from the spray visualization system including the high-speed camera, light-source, long-distance microscope (LDM). The spray pattern was analyzed through the deviation of the center of the spray plum and images were acquired using Nd: YAG Laser and ICCD(Intensified charge coupled device) camera. From the experiment and analysis, it revealed that the injection pressure have a significant influence on the spray tip penetration and spray pattern. However, the injection pressure have little influence on the spray angle. The increase of injection pressure induced the reduction of a closing delay. In addition, the deviation of spray center increase with the increase of injection pressure and the distance from a nozzle tip.