基于自由尾迹方法的复合材料无铰式旋翼气弹稳定性分析

基于有限元理论及自由尾迹方法,建立了一套适用于各向异性复合材料无铰式旋翼的气弹稳定性分析方法.为了模拟复合材料旋翼气弹特性,截面特性参数采用二维线性有限元方法分析得到,展向一维梁则采用考虑剪切变形的23自由度非线性梁单元模拟,并将自由尾迹分析模型用于计算旋翼菲均匀诱导速度场,基于升力线模型构建了一个高效且较为精细的气动分析模块.在此基础上开展了无铰式旋翼气弹稳定性分析,算例计算及验证表明建立的模型能有效地用于复合材料旋翼非定常气动载荷预估及进行气弹稳定性分析.最后细致分析并获得了复合材料铺层角对无铰式旋翼气弹稳定性参数的影响规律,结果表明:算例在小拉力系数(0.0025)下,截面竖直铺层角在10°到25°会发生气弹稳定性问题,这在真实型号设计中应当注意避免.

Aeroelastic stability analysis of composite hingeless rotor based on free-wake model

Based on finite element method (FEM) and free-wake method, an aeroelastic stability analysis model of composite hingeless rotor was developed. In order to simulate the aeroelastic behavior of composite rotor, 2-D linear FEM analysis was employed to obtain the sectional properties, and 1-D beam was modeled by 23 degree of freedom (DOF) nonlinear beam element which included transverse shears. The free-wake model was adopted to calculate non-uniform induced velocity field, and a highly-efficient and accurate aerodynamics analysis module was established by using lifting-line theory. On the basis of these, the stability analysis for composite hingless rotor was carried out. It is demonstrated by numerical simulation that the present model is capable to predict unsteady airloads and aeroelastic stability characteristics of composite rotor. Finally, the effect of material ply orientation on hingless rotor aeroelastic stability was analyzed, and it can be seen from the results that under the condition of low thrust coefficient (0.0025), the rotor aeroelastic instability may occur when ply angle of the vertical wall varies between 10°and 25°, which should be avoided in rotor design.