机动飞行中旋翼尾迹畸变效应实验

Experiments of rotor wake distortion in pitching maneuvers

为准确计算机动飞行时的旋翼他轴响应,气动模型应计入尾迹畸变效应。体现此效应的关键在于推出时变的尾迹弯曲参数KR。本文通过烟流实验,得出随旋翼前进比、拉力系数和机动角速率变化的KR表达式,并分析指出,国外文献采用固定KR值不足以体现机动效应。为了给理论预测提供参考,本文还测量了机动旋翼的空气动力时间历程,表明旋翼轴接受准阶跃输入后,同轴及他轴的空气动力响应有过冲,且俯仰速率愈大,过冲幅值愈大;本实验中他轴响应为主响应的15%。

To compute accurately the off-axis response of maneuvering rotors, rotor aerodynamic model should introduce the wake distortion effect. The key to represent this effect is a time-accurate wake curvature parameter KR. This paper obtained a KR expression with advance ratio, rotor thrust coefficient and maneuvering angular rate as variables. Then this paper concludes that a fixed wake curvature parameter is inadequate to reflect the maneuver-related effects. Besides, the aerodynamic load history of maneuvering model rotor was tested so as to provide theoretical prediction with reference data. Experimental results show that after the rotor shaft receives a quasi-step angular input, both the rotor on-axis and off-axis aerodynamic responses assume an overshoot whose amplitude increases with the pitching rate ; and that the off-axis response amplitude is about 15% of the major axis one.