Research on dynamic characteristics of distributed multi-rotor/tilting wing aeroelastic coupling
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摘要:
基于准线性化隐式气弹建模方法，建立适用于分布式多旋翼/倾转机翼飞行器的耦合柔性多体动力学模型，研究其气弹耦合动力学特性。基于中等变形梁模型和准定常理论，采用Pitt-Peters动态入流模型和Floquet理论，建立求解多旋翼/大展弦比柔性倾转机翼气弹耦合系统动特性的计算方法。在验证理论模型正确性的基础上，研究分布式多旋翼/倾转机翼耦合系结构动特性、回转颤振特性和气弹耦合动响应特性。结果表明：旋翼和短舱对机翼扭转模态影响最大，旋翼与机翼耦合情况下会加大旋翼整体模态振型；增加旋翼个数并将升力桨展开可提高系统低速状态下的稳定性，但增加旋翼个数会降低机翼扭转频率，进而降低颤振速度，增加旋翼有效迎角和机翼攻角可提高系统颤振速度，而增加旋翼转速则会降低系统颤振速度；随前飞速度增加，系统先发生机翼扭转失稳后发生机翼弦向弯曲失稳的回转颤振现象，系统振动响应经历了振动收敛、小幅极限环颤振和大幅多频极限环颤振，其中，机翼颤振形式是垂向、弦向弯曲和扭转运动耦合，其三维耦合效应显著，而旋翼与机翼的模态耦合程度也在不断加深。
Abstract:Based on the quasi-linear implicit aeroelastic modeling method, a coupled flexible multibody dynamics model suitable for distributed multi-rotor/tilting wing aircraft was established, and its aeroelastic coupling dynamics characteristics were studied. Based on the moderately deformed beam model and quasi-steady theory, the Pitt-Peters dynamic inflow model and Floquet theory were used to establish a calculation method for solving the dynamic characteristics of the aeroelastic coupling system of the multi-rotor/high aspect ratio flexible tilting wing. On the basis of verifying the correctness of the theoretical model, the dynamic characteristics of the distributed multi-rotor/tilting wing coupling system, the whirl flutter characteristics, and the dynamic response characteristics of aeroelastic coupling were studied. The results show that the rotor and the nacelle have the greatest influence on the torsional mode of the wing, and the coupling between the rotor and the wing will increase the overall mode shape of the rotor; increasing the number of rotors and deploying the lift blades can improve the stability of the system at low speed. However, increasing the number of rotors will reduce the torsional frequency of the wings and thus reduce the flutter speed; increasing the effective angle of attack of the rotors and the angle of attack of the wings can increase the flutter speed of the system, and increasing the rotor speed will reduce the flutter speed of the system; as the flying speed increases, the system first occurs the torsional instability of the wing and then the chordwise bending instability of the wing. The vibration response of the system has experienced vibration convergence, small-amplitude limit-cycle flutter, and large-scale multi-frequency limit-cycle flutter. The form of wing flutter is the coupling of vertical and chordwise bending and torsional motion, and its three-dimensional coupling effect is remarkable. The degree of modal coupling between the rotor and the wing is also deepening.
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图 7 旋翼个数和升力桨收放对一阶扭转的影响
Figure 7. Influence of number of rotors and lift blade retraction on first order torsion
图 10 系统颤振速度随旋翼有效迎角和转速的变化
Figure 10. Variation of system flutter speed with speed and effective angle of attack of rotor
图 11 系统颤振速度随机翼攻角的变化
Figure 11. Variation of system flutter speed with angle of attack of wing
图 12 分布式多旋翼/倾转机翼飞行器前飞气动力
Figure 12. Aerodynamic forces on distributed multi-rotor/tilting wing aircraft in forward flight
图 13 n3z系统翼尖响应（前飞速度为31 ～32 m/s）
Figure 13. Wing tip response of n3z system (forward flight speed 31～32 m/s)
图 15 n3系统翼尖响应（前飞速度为120～150 m/s）
Figure 15. Wing tip response of n3 system (forward flight speed 120～150 m/s)
表 1 XV-15倾转旋翼机主要动力学参数
Table 1. Main dynamics parameters of XV-15 tilt-rotor
部件 参数 数值 旋翼 片数 3 洛克数 3.83 半径/m 3.82 预锥角/(º) 2.5 转速/(r·min−1) 458 机翼/短舱 一阶垂向弯曲频率q1/Hz 2.4 一阶弦向弯曲频率q2/Hz 5.1 一阶扭转频率p1/Hz 5.9 
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表 2 耦合系统主要动力学参数
Table 2. Main dynamics parameters of coupling system
参数 数值 旋翼半径R/m 0.7 旋翼片数 4 额定转速Ω /（r·min−1） 1300 短舱质量mp/kg 3.8 短舱长度h/m 0.35 机翼半展长RW/m 4 推进桨一阶挥舞$\beta^{\;t}_{1} $频率/Hz 33.75 升力桨一阶挥舞$\beta^{\;{\mathrm{s}}}_{1} $频率/Hz 42.25 一阶垂向弯曲q1耦合频率/Hz 3.68 一阶弦向弯曲q2耦合频率/Hz 9.97 二阶垂向弯曲q3耦合频率/Hz 19.07 一阶扭转p1耦合频率/Hz 25.91
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表 3 半展系统固有频率
Table 3. Natural frequency of half-spread system
Hz 模态 取值 推进桨一阶挥舞后退型βt−1频率 13.04 推进桨一阶挥舞集合型βt1频率 35.77 升力桨一阶挥舞后退型βs−1频率 18.74 升力桨一阶挥舞集合型βs1频率 40.73 机翼一阶垂向弯曲q1频率 3.337 机翼一阶弦向弯曲q2频率 9.122 机翼二阶垂向弯曲q3频率 16.488
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