High Fidelity Transient Forced Response Analysis of Mistuned Bladed Disks Under Complex Excitation and Variable Rotation Speeds

An effective method is developed for efficient calculations of the transient vibration response for mistuned bladed disks under complex excitation and varying rotation speeds. The method uses the large-scale finite element modelling of the bladed disks allowing the accurate description of the dynamic properties of the mistuned bladed disks. The realistic distributions of the excitation forces are considered, which resulted in the multiharmonic excitation loads.

The effects of the varying rotation speed on the natural frequencies and mode shapes of the mistuned bladed disk and its effects on the amplitude and the spectral composition of the loading are allowed for. The different functions of the rotation speed variation can be analyzed.

The transient response calculation is based on the analytically derived expressions for the transient forced response and the effective method used for the model reduction.    

Numerical studies of the transient forced response and the amplitude amplification in mistuned bladed disks are studied when the resonance regimes are passed during gas-turbine engine acceleration or deceleration. The effects of different types of excitation force and mistuning on transient amplitude amplification are illustrated by a large number of the computational results and comparative analysis. These results and analysis of transient forced response are shown on an example of two realistic mistuned bladed disks: (i) a turbine bladed disk of 86 blades (whose natural frequencies are high); (ii) a fan bladed disk of 20 blades (with significantly lower natural frequencies).