直升机旋翼旋转噪声的估算

准确地预估直升机噪声水平是直升机噪声研究的主要目标之一。本义以Farassat的亚音速时域公式1A为基础,给出了旋翼旋转噪声的估算方法,适用于任意观察位置和各种直线飞行状态。在不考虑桨叶弹性的条件下,导出了用于数值计算的延迟时间方程和声压计算公式中各被积函数的表达式。本文以国内Z—8直升机旋翼和国外1/4缩比的UH—1旋翼模型为算例,对悬停飞行条件下的旋翼旋转噪声进行了计算。在此基础上,讨论了桨叶叶尖马赫数、桨盘载荷和桨叶翼型对噪声的影响。

Prediction of Helicopter Rotor Rotational Noise

To predict accurately helicopter noise levels is one of the main goals of the helicopter noise researches. Based on Farassat Formulation 1A for subsonic time domain, a method which is valid for arbitrary observer position and all linear flight conditions is developed in this paper to predict the rotor rotational noise. Without considering the elasticity of the blade, the retarded time equation and all of the integrands in the Formulation lA are derived and expressed as the proper form for numerical calculation. As examples, the noise calculation of the Helicopter Z-8 rotor and 1/4 scale UH-1 rotor in hover are carried out and discussions on the influence of rotor parameters, such as the tip Mach number, the disc loading and the blade airfoil, arc presented.