倾转旋翼机螺旋颤振稳定性研究

Study on whirl-flutter stability of a tiltrotor aircraft

为揭示旋翼设计对倾转旋翼机气动弹性稳定性的影响机制,探索通过改进桨尖形状提升机翼颤振稳定性的方法,采用Hamilton能量原理推导了旋翼/短舱/机翼耦合动力学方程,建立了适用于气动弹性稳定性分析的配平与特征值求解方法。以XV-15倾转旋翼机为例,计算了风车状态下机翼的模态特性,结果表明当前进比超过0.9,机翼的一阶弦向和法向模态先后进入不稳定区域;经与参考文献数据对比,验证了理论模型的有效性。研究了旋翼桨尖后掠角、下反角以及尖削比对倾转旋翼机螺旋颤振稳定性的影响,结果表明后掠与下反设计有利于增强机翼模态阻尼。最后通过对比不同设计组合,总结了提升倾转旋翼机螺旋颤振稳定性的旋翼桨尖设计方法。

In order to reveal the influence of rotor design on the aeroelastic characteristics and explore the ways to enhance the whirl flutter stability through blade tip improving of a tilt rotor aircraft, an analytical model including tiltrotor/nacelle/wing system is formulated. Moreover, the corresponding methods for trim and eigenvalue solution are developed. Byusing XV-15 as an example, the wing modal characteristics under the windmill condition are calculated. The results show that the wing＇s bending modes get into an unstable state when the advance ratio exceeds 0.9. These results are in good agreement with the data in references. The influence of the rotor blade tip sweep, droop and taper on the whirl flutter stability is studied. It is indicated that the modal damping of the wing is enhanced significantly due to the swept angle and drooped angle of the blade tip. The method of improving the whirl flutter stability is obtained through comparative analysis.