Reduced Order Model Formulation for the Study of the Free and Forced Response of a Mistuned Impeller with Two Blade Geometries

Abstract

Numerous works have presented techniques for obtaining reduced order models (ROMs) of mistuned bladed disks. Most of these works focus in only one rotor’s stage, though some also include several stages and even the rotor shaft. However, to the authors’ knowledge, the ROM techniques presented consider only one blade geometry by stage. This paper shows an adaptation of a previously published reduced order modelling technique in order to allow its application to the case of an impeller incorporating two different blade geometries (main and splitter blade). The technique is based in Craig and Bampton’s component mode synthesis, and it permits to introduce different mistuning patterns for each blade geometry, while the disk is considered as a cyclic symmetric structure.
The proposed technique is applied to an impeller’s simplified model, in order to assess its precision and validity. Validation is carried out by comparison of predictions for the free and forced response of the mistuned impeller, obtained by means of the ROM and the finite element parent model. Results show that the ROM properly represents the dynamic features of the parent model in the frequencyrange of interest, with minimal computational cost. Furthermore, the ROM properly captures the localization phenomenon when it occurs, in both, the normal modes and the forced response.