旋翼气动载荷的简化求法

目前,在工程应用上迫切要求发展一种简化的旋翼载荷估算法。 本文从旋翼的广义经典涡流理论出发,通过环量对诱导速度的贡献的简化处理,推导出旋翼诱导速度的二阶分布。然后,根据叶素理论,建立起封闭形式的环量方程,计及桨叶挥舞条件,得出了估算旋翼载荷的简化公式;特别是在挥舞系数的表达式中,考虑了诱导速度的变化,但直接与桨叶参数和飞行参数有联系。 最后,算例表明,本文这些公式适用于直升机气动分析和初步设计。

A SIMPLIFIED METHOD FOR PREDICTING ROTOR BLADE AIRLOADS

At present, a simplified approach to the prediction of rotor blade airloads is urged to be developed in the engineering application.In this paper, firstly, relations of first two harmonic induced velocities to the lower and same-order harmonic circulations are obtained from the generalized classical vortex theory of the rotor. Then, based on the blade element theory, a closed form of equations for circulation is established and, by taking the flapping condition into account, simplified formulae for predicting rotor blade airloads are set up. In particular, expressions of flapping coefficients are derived, including the effect of variable induced velocity distribution but in terms of blade parameters and flight parameters only.Finally, a calculation of a typical example is made and comparisions of airloads with those from the more accurate numerical solution are shown that the present method is fairly suitable for aerodynamic analysis and preliminary design of helicopters.