鼠笼式弹性支承的柔度计算及影响因素分析

Flexibility Calculation and Influencing Factors Analysis of Squirrel-cage Elastic Support

鼠笼式弹性支承常用于现代航空发动机调整临界转速以实现振动抑制。针对理论公式在工程应用中预测柔度较小的鼠笼式弹性支承的柔度时存在一定误差的问题,基于有限元法进行了鼠笼式弹性支承柔度数值计算。讨论了弹支数值仿真计算边界条件的合理性,分析了笼条根部倒圆、非笼条鼓筒及工艺简化导致笼条截面形状改变等因素对鼠笼式弹性支承柔度的影响;将非笼条局部增大刚度模型的仿真计算结果与理论公式计算结果进行了对比,以验证有限元数值计算的可靠性。结果表明:由非笼条局部增大刚度模型得到的数值仿真计算结果与理论公式得到的理论解吻合很好;理论公式未考虑的非笼条鼓筒部分、笼条根部倒圆等因素对柔度预测有一定的影响。采用有限元数值仿真方法进行弹支结构的柔度设计,可以克服理论解析方法无法考虑倒角等结构细节特征影响的局限性,从而获得更逼近真实条件的鼠笼式弹性支撑结构设计方案。

The squirrel-cage elastic support is often used in modern aeroengines to adjust the critical speed and suppress vibration.In view of the fact that significant error exists in using the theoretical formula to predict the flexibility of the squirrel-cage elastic support with lower flexibility in engineering applications,numerical calculation of the flexibility of the squirrel-cage elastic support was conducted based on the finite element method.The rationality of the boundary conditions for the numerical simulation of the elastic support was discussed,and the influencing factors on the flexibility of the squirrel cage elastic support,such as the cage bar root fillet,the non-cage bar drum,and the change of the cross-sectional shape of the cage bar due to process simplification,were analyzed.In order to verify the accuracy of finite element numerical calculation,the simulation results of the local stiffness increase of the non-cage bars were compared with the results of the theoretical formula.The results show that the numerical simulation results obtained by the non-cage bar local stiffness increase model are in good agreement with the theoretical solution obtained by the theoretical formula.Factors such as the non-cage bar drum part,the cage bar root fillet,etc.are not considered by the theoretical formula,so the flexibility prediction results are affected.It should be emphasized that the use of the finite element numerical simulation method for the flexibility design of the elastic support structure can overcome the limitation of the theoretical analysis method which ignores the influence of the structural details such as chamfers,so as to obtain a more realistic design of the squirrel-cage elastic support structures.