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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Formulation 1A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3 m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3 dB,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。
Aiming at the problem of large noise in conventional helicopters, the thickness noise of a rotor combining the non-uniformity of blade pitch and the swept-back of tip is analyzed. Through the Formulation 1A formula of FW-H equation, the thickness noise of the rotor under different blade pitch and tip swept angle was calculated. The calculation results show that the thickness noise at the blade tip sweep angle of 80 ° is about 3 dB lower than that of the conventional rotor without sweeping at 3 m from the hub center in the plane of the propeller disk. Rotor blades that combine tip-swept can significantly reduce the amplitude of the characteristic line spectrum while reducing thickness noise, and can significantly change the directivity of the rotor in the plane of the paddle.