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RISS 인기검색어
- 검색키워드
- 저자 : Chenkai Cao (검색결과 5 건)
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- 유료
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Optimization of Duct Shape for Improving Aerodynamic Performance of Ducted Tail Rotor
Chenkai Cao,Bo Wang,Guoqing Zhao,Qijun Zhao 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.2
Numerical simulations on the aerodynamics of helicopter ducted tail rotor in hover are conducted, and a surrogate-based optimization framework is employed for the duct shape design in this work, by considering interactions between rotor and duct. The CFD analyses of ducted tail rotor are performed using the helicopter code CLORNS, including the momentum source method and high-fidelity CFD methods. The SA365N1 Dauphin fenestron in a test case is simulated by CFD methods and the duct shape is selected as baseline design for optimization. Parametric researches are conducted to investigate the relationship between the aerodynamic loads of ducted tail rotor and the variations of duct shape. Besides, the influence of duct shape on the flow details of rotor blade is obtained by resolving the flowfield based on high-fidelity CFD, and detailed analyses of the flow separation phenomenon downstream the rotor with large collective pitches are presented. Then, the multi-optimization of duct shape with different collective pitches is conducted by employing a surrogate-based optimization framework. Compared with the baseline design, the hovering efficiency of optimized design is improved because of a better negative pressure distribution on the duct wall.
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Aeroacoustic Characteristic Analyses of Coaxial Rotors in Hover and Forward Flight
Bo Wang,Chenkai Cao,Qijun Zhao,Xin Yuan,Zheng Zhu 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.6
A numerical method combining computational fluid dynamics (CFD) method and Ffowcs Williams–Hawkings (FW–H) equations is established for predicting acoustic characteristics of the coaxial rigid rotor in hovering and forward flight. The unsteady Reynolds-averaged Navier–Stokes (URANS) solver coupled with the moving-embedded grid technique is established to obtain sound source information in the flowfield with high accuracy. On the basis of the accurate solution for the coaxial rotor flowfield, the blade–vortex interaction (BVI) noise in hovering state and the high-speed impulsive (HSI) noise in high-speed forward flight are estimated by the Farassat 1A formula and the FW–H equation with a penetrable data surface (FW–Hpds), respectively. Then the sound pressure distribution characteristics and sound radiation pattern for the coaxial rotor in a hovering state and in a forward flight are obtained through the comparative analysis of the sound pressure time histories and the distribution of sound pressure levels of the upper rotor, lower rotor, and coaxial rotor. The simulation results indicate that significant unsteady characteristics appear in blade aerodynamic loading due to the Venturi effect, blade–vortex interaction phenomenon, and action of the downwash existing in the coaxial rotor flowfield, causing the loading noise of the coaxial rotor to occupy the dominant position in hovering state; the counter-rotating characteristics of the upper and lower rotors cause a significant phase difference between their respective sound pressure waveforms, and the phase difference is determined by the angle between the observation point and the intersection position of the upper and lower blades; the difference with the single rotor in terms of the severe HSI noise generated in the high-speed forward flight is that the noise radiation intensity of the coaxial rotor along both sides in the forward direction exhibits an approximately symmetrical distribution.
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Adaptive Separation Model for Electromagnetic Pulse Coupling Signals of Engine Digital Controllers
Chen Kai,Wei Minxiang,Cao Jie,Chen Xinda,Li Shunming 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.4
The engine digital controller is vulnerable to attacks of wide-spectrum and uncertain electromagnetic pulses (EMPs). To address this issue, herein, we propose a novel “internal cluster evaluation cluster” clustering integrated signal separation method and establish an adaptive separation model for EMP coupling signals of engine digital controllers. Specifi cally, the proposed method mainly includes generation of base clusterings to form a candidate pool of base clusterings, evaluation of the uncertainty of clusters, and establishing an integration strategy. To verify the model, we adopt two types of EMP coupling signal data for simulation and actual measurement. The proposed method is compared with fi ve typical clustering ensemble methods in terms of their normalized mutual information (NMI) values. For the simulated EMP coupled signal data, the hyperparameter is 0.4, and the NMI values of fi ve sets of data are 0.721, 0.576, 0.329, 0.201, and 0.466. For the measured data, the hyperparameter is 0.8, and the NMI values of fi ve sets of data are 0.738, 0.555, 0.377, 0.511, and 0.485. The NMI values of the two types of EMP coupling signal data of the proposed method are generally better than those of the other classical methods. The results confi rm the superior separation eff ect of the proposed method on EMP coupled signals.
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