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Unsteady aerodynamic noise prediction of contra-rotating open rotor using meshless method
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作者 Zhiliang HONG Meng SU +3 位作者 Haitao ZHANG Zerui XU Lin DU Lingfeng CHEN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2024年第8期144-165,共22页
The Contra-Rotating Open Rotor(CROR)design confronts significant noise challenges despite being one of the possible options for future green aeroengines.To efficiently estimate the noise emitted from a CROR,a three-di... The Contra-Rotating Open Rotor(CROR)design confronts significant noise challenges despite being one of the possible options for future green aeroengines.To efficiently estimate the noise emitted from a CROR,a three-dimensional unsteady prediction model based on the meshless method is presented.The unsteady wake flow and the aerodynamic load fluctuations on the blade are solved through the viscous vortex particle method,the blade element momentum theory and vortex lattice method.Then,the acoustic field is obtained through the Farassat’s formulation 1A.Validation of this method is conducted on a CROR,and a mesh-based method,e.g.,Nonlinear Harmonic(NLH)method,is also employed for comparison.It is found that the presented method is three times faster than NLH method while maintaining a comparable precision.A thorough parametric analysis is also carried out to illustrate the effects of rotational speed,rotor-rotor spacing and rear rotor diameter on the noise level.The rotor speed is found to be the most influencing factor,and by optimizing the speed difference between the front and rear rotors,a notable noise reduction can be expected.The current findings not only contribute to a deeper comprehension of the CROR’s aeroacoustic properties but also offer an effective tool for engineering applications. 展开更多
关键词 Contra-Rotating Open Rotor(CROR) Aerodynamic noise blade element momentum theory Viscosity vortex particle method Farassat’s formulation 1A
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Influence of differential longitudinal cyclic pitch on flight dynamics of coaxial compound helicopter 被引量:3
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作者 Yanqin ZHAO Ye YUAN Renliang CHEN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2023年第9期207-220,共14页
The Differential Longitudinal Cyclic Pitch(DLCP)in coaxial compound helicopter is found to be useful in mitigating low-speed rotor interactions and improving flight performance.The complex mutual interaction is simula... The Differential Longitudinal Cyclic Pitch(DLCP)in coaxial compound helicopter is found to be useful in mitigating low-speed rotor interactions and improving flight performance.The complex mutual interaction is simulated by a revised rotor aerodynamics model,where an improved Blade Element Momentum Theory(BEMT)is proposed.Comparisons with the rotor inflow distributions and aircraft trim results from literature validate the accuracy of the model.Then,the influence of the DLCP on the flight dynamics of the aircraft is analysed.The trim characteristics indicate that a negative DLCP can reduce collective and differential collective inputs in low speed forward flight,and the negative longitudinal gradient is alleviated.Moreover,a moderate DLCP can reduce the rotor and total power consumption by 4.68%and 2.9%,respectively.As DLCP further increases,the increased propeller power and unbalanced thrust allocation offset the improvement.In high-speed flight,DLCP does not improve the performance except for extra lateral and heading stick displacements.In addition,the tip clearance is degraded throughout the speed envelope due to the differential pitching moment and the higher thrust from the lower rotor.Meanwhile,the changed rotor efficiency and induced velocity alter low-speed dynamic stability and controllability.The pitch and roll subsidences are slightly degraded with the DLCP,while the heave subsidence,dutch roll and phugoid modes are improved.Lastly,the on-axis controllability,including collective,differential collective pitch,longitudinal and lateral cyclic pitches,varies with DLCP due to its effect on rotor efficiency and inflow distribution.In conclusion,a reasonable DLCP is recommended to adjust the rotor interaction and improve aircraft performance,and further to alter the flight dynamics and aerodynamics of aircraft. 展开更多
关键词 blade element momentum theory Coaxial compound helicopter Differential longitudinal cyclic pitch Interaction model Tip clearance
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Study on the Rotor Design Method for a Small Propeller-Type Wind Turbine
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作者 Yasuyuki Nishi Yusuke Yamashita Terumi Inagaki 《Journal of Thermal Science》 SCIE EI CAS CSCD 2016年第4期355-362,共8页
Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goa... Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goal of this research is to establish high-performance design guidelines and design methods for small propeller-type wind turbines.To that end,we designed two rotors:Rotor A,based on the rotor optimum design method from the blade element momentum theory,and Rotor B,in which the chord length of the tip is extended and the chord length distribution is linearized.We examined performance characteristics and flow fields of the two rotors through wind tunnel experiments and numerical analysis.Our results revealed that the maximum output tip speed ratio of Rotor B shifted lower than that of Rotor A,but the maximum output coefficient increased by approximately 38.7%.Rotors A and B experienced a large-scale separation on the hub side,which extended to the mean in Rotor A.This difference in separation had an impact on the significant decrease in Rotor A's output compared to the design value and the increase in Rotor B's output compared to Rotor A. 展开更多
关键词 Wind Turbine Propeller-Type Horizontal Axis blade element momentum theory Rotor Design Method
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