Abstract: Modal analysis is an analytical method used to avoid resonance in the working state of moving link. The natural frequency and vibration shapes of the 6PBT impeller in static mode and prestressed mode are analyzed by using bidirectional fluid-structure interaction calculation method. The working medium of the prestress modal analysis is carried out in a xanthan gum solution (a typical pseudoplastic fluid) having a rheological index of n＝0.9, n＝0.7, n＝0.5 respectively. The results show that the fluid rheology property of the pseudoplastic fluid has little effect on vibration shapes and modal frequency of the blade. The distribution of the vibration shapes of the 6PBT impeller are basically the same in static mode and prestressed mode. Between the steps of 1st and 6th, the blade mode appears torsional; between the steps of 7th to 10th, the blade modal shape appears bending. The modal frequency of the blade does not change much, indicating that the coupling effect between the stirring medium and the blade does not affect the mode of the 6PBT paddle much. Therefore, the natural frequency and vibration shapes distribution of the 6PBT impeller is stable under the pseudoplastic fluid of different rheological index, which reduces the probability of the resonance phenomenon during the agitation process greatly.

Key words: fluid-structure interaction, impeller of perturbed six-bent-bladed turbine (6PBT), pseudoplastic fluid, model analysis