An Analysis System for Turbomachine Blade Forced Vibration

Hsiao-Wei D. Chiang ； Meng-Hsuan Chung

《中華民國振動與噪音工程學會論文集》 1997 (1997/05) Pp. 539-557

https://doi.org/10.30028/CSSVANNUAL.199705.0539

並列摘要

A frequent cause of turbomachinery blade failure is excessive forced vibration. The most common excitation source is the nonuniform flow field generated by inlet distortion and pressure disturbances from adjacent blade rows. The standard method for dealing with this problem is to avoid resonant conditions using a Campbell diagram. Unfortunately, it is impossible to avoid all resonant conditions. Therefore, judgments based on past experience are used to determine the acceptability of a blade design.
Anew analysis system has been developed to predict blade forced vibration. The system provides a design tool, over and above the standard Campbell diagram approach, for predicting potential forced vibration problems. The incoming excitation sources are modeled using measured data for inlet distortion, and a 2D CFD code for pressure disturbances. Using these aerodynamic stimuli, and the blade natural frequencies and mode shapes from a finite element model, the unsteady aerodynamic modal forces and the aerodynamic damping are calculated. A modal response solution is then performed.
This system has been applied to current engine designs. A recent investigation involved fan blade vibration due to inlet distortion. An aeromechanical test had been run with two different distortion screens. The resulting distortion entering the fan was measured. With this as input data, the predicted vibration agreed well with the measured data. In another application, the vibration of a rotor blade due to downstream pressure disturbances was determined. In this case the blades were excited by the static pressure distortion from the downstream stator vanes and struts. Effects of strut &vane modifications are examined using the analysis. Recent testing of the strut modification shows exceptional correlation with the analysis.