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단방향 유동구조 연성해석을 활용한 노즐 구조 안전성 검토 연구
이창욱(Changwook Lee),박용석(Yongseok Park),조덕용(DuckYong Jo) 한국추진공학회 2022 한국추진공학회 학술대회논문집 Vol.2022 No.5
스텔스 성능 향상 목적으로 굴곡이 있는 노즐을 사용한다. S-형상의 노즐은 터빈 외부로 노출되는 것을 막을 수 있다. 본 연구에서 복잡한 형상의 노즐 제작 방법으로 5-축 가공을 활용하였고 제작을 수행하기 위해 링 형태로 노즐 분할하여 제작하였다. 링 형태로 제작한 노즐의 구조적 안전성을 검토하기 위해 유동-구조 연성해석을 활용하였다. 유동해석에 사용되는 프로그램은 STAR-CCM+를 사용하여 노즐 내부온도와 압력 분포를 획득하였다. 온도와 압력 분포를 구조해석 경계조건으로 입력하였고 구조해석 프로그램인 NASTRAN을 활용하여 전체 구조의 안전 마진 체결 홀에 대한 국부적인 안전 마진을 계산하여 제작 방법에 대한 타당성을 검증하였다. A curved nozze is used to improve stealth performance. The S-shape nozzle can prevent the turbine from expose to the outside. In this study, five-axis machining was used as a method for manufacturing a nozzle with a complex geometry and the nozzle was divided into a ring shape for manufacturing. To examine the structural safety of a nozzle manufactured in the form of a ring, 1-way fluid structure interaction analysis was used. The program used for fluid dynamics analysis used STAR-CCM+ to obtain nozzle internal temperature and pressure distribution. To determine the validity of the manufacturing method, Temperature and pressure distribution were set as boundary conditions for structural analysis and the overall safety margin and bearing safety margin were calculated using NASTRAN.
이창욱(Changwook Lee),박용석(Yongseok Park),조덕용(DuckYong Jo),최성만(Seong Man Choi) 한국추진공학회 2022 한국추진공학회지 Vol.26 No.5
In this study, 5-axis machining was proposed as a method for manufacturing a nozzle with a curved shape, and flow analysis and structural analysis were used for structural validation of the manufactured geometry. The program used for CFD obtained the internal temperature and pressure distribution of the nozzle using STAR-CCM+ and used it as the boundary condition for structural analysis. For structural analysis, the commercial program NASTRAN was used, and stress was calculated using the von-mises technique. Based on the maximum stress value generated, the safety margin was 0.78 and the safety margin of the bearing stress was 46.8. In addition, the creep life was calculated as 9.97 x 1012 hours using the Larson-Miller parametric method and applying the maximum stress value of 187 MPa and the exhaust gas perfectly mixed temperature of 463 K.
이창욱(Changwook Lee),박용석(Youngseok Park),진준엽(Juneyub Jin),김재원(Jaewon Kim),최성만(Seong Man Choi) 한국추진공학회 2021 한국추진공학회지 Vol.25 No.2
The Aft-deck is being applied to the latest unmanned aircraft for the purpose of shielding the gas turbine exhaust plume or spreading jets to increase the mixing rate with the ambient air, thereby reducing the temperature of exhaust gases. In this study, we would like to find out how the performance of the nozzle is affected by the design variables of the Aft-deck. The design variables of aft-deck are selected as length, expansion angle and upper deck shape. The correlation between thrust and plume shielding rate with the length variable is presented. And the correlation between the thrust and the jet diffusion range is presented according to the expansion angle. In addition, the thrust increase effect is confirmed by the removal of the upper deck and the characteristics of transverse velocity vector determined mixing performance with external flow.
DBD 플라즈마 구동기를 이용한 원통모델의 공기저항저감
이창욱(Changwook Lee),심주형(Ju-hyeong Sim),한성현(Sunghyun Han),윤수환(Su Hwan Yun),김태규(Taegyu Kim) 한국추진공학회 2015 한국추진공학회지 Vol.19 No.1
Dielectric barrier discharge (DBD) plasma actuator was designed to reduce aerodynamic drag in a cylindrical model and wind tunnel test was performed at various wind velocities. In addition, computational fluid dynamics (CFD) analysis and flow visualization were used to investigate the effect of the plasma on the flow stream in the cylinderical model. At low wind velocity, the plasma actuator had no effects because flow separation did not appear. The aerodynamic drag was reduced by 14% at 14 m/s and by 27% at 17 m/s, respectively. It was confirmed by CFD analysis and flow visualization that the DBD plasma actuator decreased in pressure difference around the cylindrical model, thus decreasing the magnitude of wake vortex.
DBD 플라즈마 엑츄에이터를 이용한 3차원 모델의 유동박리제어
이창욱(Changwook Lee),윤수환(Su Hwan Yun),김태규(Taegyu Kim) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11
3차원 모델의 유동박리제어를 위해 유연성 DBD (dielectric barrier discharge) 엑츄에이터를 설계하였다. 모델에 부착 시 형상항력이 발생하지 않도록 필름형태의 유전체를 사용하였다. 단일 DBD 엑츄에이터의 방전전압과 전극 간격에 따른 유속 성능을 평가 하였다. 3차원 형상의 고속철도 모델에 유동박리제어를 위해 플라즈마 엑츄에이터를 전두부에 부착하였다. 풍동실험을 통해서 항력저감을 검증하였으며, DBD 엑츄에이터의 위치에 따라 항력저감효과가 달라짐에 따라서 위치의 DBD 엑츄에이터의 위치가 중요함을 알 수 있었다. Flexible DBD (dielectric barrier discharge) actuator for flow separation control of 3-dimensional model was designed. A thin film was used as a dielectric barrier not to induce the profile drag when attached on the model. The ionic wind velocity of DBD actuator was measured as discharge voltages and electrode gaps. The DBD actuator was installed on the surface of the front part-to control the flow separation of the three dimensional train model. The reduction of aerodynamic drag was verified using wind-tunnel tests. The location of DBD actuator was important to improve the drag reduction, considering that the degree of drag reduction was different according to the location.
이창욱(Changwook Lee),최성만(Seong Man Choi) 한국추진공학회 2021 한국추진공학회지 Vol.25 No.6
Bell mouth inlet is applied in various industries due to the advantage of little pressure loss and accurate flow measurement. In this study, the configuration of the bell mouth intake is designed in a long radius shape, and a suitable grid size was selected to minimize thepressure drop and to prevent the engine damage by foreign objects at outdoor operating conditions. It was able to present a modified pressure drop coefficient equation from two data obtained from the computational simulation and experimental results for the total pressure loss by inlet screen installation.