In view of the reduction of hovering efficiency near high tension when a helicopter rotor hovers,a numerical simulation method of lifting rotor hovering aerodynamic characteristics based on leading edge droop is estab...In view of the reduction of hovering efficiency near high tension when a helicopter rotor hovers,a numerical simulation method of lifting rotor hovering aerodynamic characteristics based on leading edge droop is established in this paper. It is dominated by Reynolds average N-S equation in integral form. Firstly,VR-12 airfoil is taken as the research object,and the influence of leading edge droop angle on the aerodynamic characteristics of two-dimensional airfoil is studied. Secondly,the modified 7 A rotor is taken as the research object,and the effects of different leading edge droop angles at the position of blade r/R=0.75—1 on the aerodynamic characteristics in hover are explored. It is found that the leading edge droop can significantly improve the aerodynamic characteristics of two-dimensional airfoil and three-dimensional hovering rotor near high angle of attack,and can effectively inhibit the generation of stall vortex.展开更多
Shaftless ducted rotor(SDR)is a new type of ducted rotor system designed with ducted-rotor-motor integration,which is quite different from traditional ducted rotor(DR)in aerodynamic characteristics.The sliding mesh ba...Shaftless ducted rotor(SDR)is a new type of ducted rotor system designed with ducted-rotor-motor integration,which is quite different from traditional ducted rotor(DR)in aerodynamic characteristics.The sliding mesh based on unstructured grid is used to simulate the aerodynamic characteristics of SDR and DR.Then,the effects of five key parameters,namely,the rotor disk height,the number of blades,the spread angle of the duct,the central hole radius and the ducted lip radius on the aerodynamic characteristics of the SDR are investigated.It is found that the same-sized SDR produces a larger total lift than the DR in hovering,but the lift proportion of its duct is reduced.In the forward flight,a large low-speed region is generated behind the SDR duct,and the reflux vortex in blade root above the advancing blade has the trend for inward diffusion.The rotor disk height has similar effects on SDR and DR.Increasing the number of blades can effectively increase the total lift of SDR,which also increases the lift proportion of duct.Increasing the spread angle of the duct will lead to the rotor lift coefficient decrease,reducing the central hole radius can increase the total lift,but the component lift coefficient decreases.Appropriately increasing the ducted lip radius can increase the total lift,which begins to decrease after reaching a certain value.展开更多
As one of the most important steps in the design of bearing-less rotor systems,the design of flexible beam has received much research attention.Because of the very complex working environment of helicopter,the flexibl...As one of the most important steps in the design of bearing-less rotor systems,the design of flexible beam has received much research attention.Because of the very complex working environment of helicopter,the flexible beam should satisfy both the strength and dynamic requirements.However,traditional optimization research focused only on either the strength or dynamical characteristics.To sufficiently improve the performance of the flexible beam,both aspects must be considered.This paper proposes a two-stage optimization method based on the Hamilton variational principle:Variational asymptotic beam section analysis(VABS)program and genetic algorithm(GA).Consequently,a two-part analysis model based on the Hamilton variational principle and VABS is established to calculate section characteristics and structural dynamics characteristics,respectively.Subsequently,the two parts are combined to establish a two-stage optimization process and search with GA to obtain the best dynamic characteristics combinations.Based on the primary optimization results,the section characteristics of the flexible beam are further optimized using GA.The optimization results show that the torsional stiffness decreases by 36.1%compared with the full 0°laying scheme without optimization and the dynamic requirements are achieved.The natural frequencies of flapping and torsion meet the requirements(0.5 away from the passing frequencies of the blade,0.25 away from the excitation force frequency,and the flapping and torsion frequencies keep a corresponding distance).The results indicate that the optimization method can significantly improve the performance of the flexible beam.展开更多
基金supported by the National Natural Science Foundation of China(No.11972190)the Aeronautical Science Foundation of China(No. 20185752)
文摘In view of the reduction of hovering efficiency near high tension when a helicopter rotor hovers,a numerical simulation method of lifting rotor hovering aerodynamic characteristics based on leading edge droop is established in this paper. It is dominated by Reynolds average N-S equation in integral form. Firstly,VR-12 airfoil is taken as the research object,and the influence of leading edge droop angle on the aerodynamic characteristics of two-dimensional airfoil is studied. Secondly,the modified 7 A rotor is taken as the research object,and the effects of different leading edge droop angles at the position of blade r/R=0.75—1 on the aerodynamic characteristics in hover are explored. It is found that the leading edge droop can significantly improve the aerodynamic characteristics of two-dimensional airfoil and three-dimensional hovering rotor near high angle of attack,and can effectively inhibit the generation of stall vortex.
基金supported by the National Defense Science and Technology Key Laboratory Fund(No.6142220180511)Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Shaftless ducted rotor(SDR)is a new type of ducted rotor system designed with ducted-rotor-motor integration,which is quite different from traditional ducted rotor(DR)in aerodynamic characteristics.The sliding mesh based on unstructured grid is used to simulate the aerodynamic characteristics of SDR and DR.Then,the effects of five key parameters,namely,the rotor disk height,the number of blades,the spread angle of the duct,the central hole radius and the ducted lip radius on the aerodynamic characteristics of the SDR are investigated.It is found that the same-sized SDR produces a larger total lift than the DR in hovering,but the lift proportion of its duct is reduced.In the forward flight,a large low-speed region is generated behind the SDR duct,and the reflux vortex in blade root above the advancing blade has the trend for inward diffusion.The rotor disk height has similar effects on SDR and DR.Increasing the number of blades can effectively increase the total lift of SDR,which also increases the lift proportion of duct.Increasing the spread angle of the duct will lead to the rotor lift coefficient decrease,reducing the central hole radius can increase the total lift,but the component lift coefficient decreases.Appropriately increasing the ducted lip radius can increase the total lift,which begins to decrease after reaching a certain value.
基金supported by the Foundation of National Key Laboratory of Rotorcraft Aeromechanics,Nanjing University of Aeronautics and Astronautics(No.614222004030917)。
文摘As one of the most important steps in the design of bearing-less rotor systems,the design of flexible beam has received much research attention.Because of the very complex working environment of helicopter,the flexible beam should satisfy both the strength and dynamic requirements.However,traditional optimization research focused only on either the strength or dynamical characteristics.To sufficiently improve the performance of the flexible beam,both aspects must be considered.This paper proposes a two-stage optimization method based on the Hamilton variational principle:Variational asymptotic beam section analysis(VABS)program and genetic algorithm(GA).Consequently,a two-part analysis model based on the Hamilton variational principle and VABS is established to calculate section characteristics and structural dynamics characteristics,respectively.Subsequently,the two parts are combined to establish a two-stage optimization process and search with GA to obtain the best dynamic characteristics combinations.Based on the primary optimization results,the section characteristics of the flexible beam are further optimized using GA.The optimization results show that the torsional stiffness decreases by 36.1%compared with the full 0°laying scheme without optimization and the dynamic requirements are achieved.The natural frequencies of flapping and torsion meet the requirements(0.5 away from the passing frequencies of the blade,0.25 away from the excitation force frequency,and the flapping and torsion frequencies keep a corresponding distance).The results indicate that the optimization method can significantly improve the performance of the flexible beam.
