复合环境下直升机旋翼动力特性分析

Research on dynamic characteristics of helicopter rotor under combined environment

考虑直升机旋翼旋转时声场、应力刚化、几何大变形等复合运行环境,对多种影响因素下的旋翼动力特性进行研究。通过实验测试数据建立了直升机旋翼结构的动力有限元模型,对旋翼在静止、应力刚化影响下的动力特性进行了分析;建立旋翼声振耦合动力学模型,考虑外声场和旋翼几何非线性影响因素,深入研究旋翼动力特性的变化规律,分析了其内在机理。研究分析发现:考虑声场影响后结构前三阶的固有频率误差分别减小了0.46%、0.82%、0.45%,更接近实验值,旋翼桨叶的振幅峰值明显降低;应力刚化对旋翼模态影响较大,随着其转速的增加固有频率呈二次曲线上升趋势;几何非线性使旋翼的共振频率值略微增大、振幅极值减小。

Considering the combined performance environment of a helicopter rotor, i.e. the flow field, the stressstiffening and geometric large deformation, it is necessary to research the dynamic characteristics of the rotor under the influence of various factors. In this paper,the dynamic finite element model of the rotor structure is established according to the corresponding experiment data. The dynamic characteristics of the helicopter rotor are studied under the condition of un-rotation or the stress stiffening. And then, the actual sound field and the geometric nonlinearity of the rotor are taken into account for the acoustic-vibration coupling dynamics modeling. The variation of dynamic characteristics of the helicopter rotor and its inherent mechanism is investigated in detail. It is found that the frequencies obtained from the rotor model with the sound field are closer to the experiment data than that without the sound field. The amplitude value of rotor blade is reduced remarkably due to the effect of the sound field. The influence of the stress stiffening on natural frequencies of rotor is significant, and the natural frequencies raise as a quadratic curve with the increase of rotational speed. The effect of the geometric nonlinear slightly increases the resonant frequencies of the rotor, and reduces the displacement amplitude.