Fatigue failure analysis of semi-open impeller with mistuning considered

High fatigue failure of blades, resulting from excessive vibration stress caused by wake excitation, is the main reason for failures of centrifugal compressor impeller such as fracture. However, a problem usually neglected is the mistuning phenomenon induced by random deviation in processing or operation. Inevitably, it will cause vibration localization and even greatly promote fatigue failure, and that's why some blades of semi-open impeller are primary to fracture first. The present paper aims at this problem based on numerical and experimental methods to conduct research on dynamic characteristic and fatigue failure of fractured blades of a realistic semi-open impeller. A finite element reduced order model (ROM) and vibration frequency response measurement system are established to support dynamic response analysis of impeller. Notably, attention is paid to the effect of mistuning on vibration stress local amplitude amplification and fatigue number in various conditions. In addition, in view of the deterioration of harsh environment for mistuning magnitude, a further analysis of fatigue life impacted by mistuning level is performed. Results demonstrate that the mistuning also results in blade failure because the increased vibration stress greatly contributes to the reduction of failure period. The present methodology and results are applicable to estimate operation security in some cases.