航空发动机离心叶轮高阶模态振动故障研究

High order mode vibration failure of an aero-engine centrifugal impeller

研究某航空发动机离心叶轮叶片高周疲劳断裂掉块故障。采用有限元计算分析,确定叶轮激振频率范围内的振动模态及应力分布,选取了对叶片各阶振动模态具有足够敏感性的位置安装应变计。叶片动应力测试获得了叶片大应力振动对应的叶轮共振频率、共振转速及激振源。利用计算和试验获得的数据进行叶片高周疲劳强度分析,提出排故措施并验证。研究结果表明:叶片断裂掉块故障原因是叶轮的高阶模态共振在叶片故障部位形成大应力,超过了其许用应力水平,提出的排故措施有效。发动机研制过程中应通过计算分析和动应力测试充分研究构件在激振频率范围内的各阶振动。

The reason of an aero-engine centrifugal impeller blade rupture was investigated.A finite element model of the impeller was built to analyze the vibration modes and stress distributions covering the main band of exciting frequencies during operation.The strain gauges were positioned on the blade with appropriate strain sensitivity for all the modes.The impeller resonant frequencies,resonant speeds and exciting engine orders that caused high level stress were identified from the results of dynamic stress measurements.According to the blade HCF strength analysis based on the numerical and test results,subsequently targeted solutions for getting rid of the possible troubles were proposed and verified.The investigation results show that the blade rupture is caused by a high order mode resonance of the impeller inducing stresses higher than the permitted stress around the rupture area.The solutions were validated to be effective.All modes of the structure within the range of exciting frequencies need to be investigated completely by numerical analysis and dynamic stress measurement during the engine development.