非均匀桨结合后掠桨尖的旋翼厚度噪声研究

针对普通直升机存在噪声大的问题，分析了一种将桨叶间距非均匀与桨尖后掠二者相结合的旋翼的厚度噪声。通过FW-H方程的Formulation1A公式计算了该旋翼在不同桨叶间距和桨尖后掠角情况下的厚度噪声。计算结果表明，在桨盘平面内距离桨毂中心3m处，桨尖后掠角度为80°时的厚度噪声约比无后掠的普通旋翼的厚度噪声降低3dB，采用将非均匀桨与桨尖后掠二者相结合的旋翼可以在降低厚度噪声的同时明显减小特征线谱的幅值，此外还可明显改变旋翼在桨盘平面内的指向性。

Research on Thickness Noise of Helicopter Rotor with Uneven Blade Spacing and Swept Tip

In view of loud noise of common helicopter,the thickness noise generated from a rotor with uneven blade spacing and swept tip is analyzed.Through the Formulation 1A of FW-H equation,the thickness noise from the rotor with various blade spacing and swept tip at different angles are calculated.The numerical results show that:for the measured point located in rotor disc plane which is 3m from the center of hub in distance,when the angle of swept tip is 80 degree,the thickness noise is reduced by 3 dB compared with that from the rotor without swept tip.For the rotor with uneven blade spacing and swept tip,its spectral character of noise is obscured while its sound pressure level of thickness noise is reduced.In addition,its directivity of noise in rotor disc plane is changed remarkably after the spacing of rotor is modulated.