Analysis of the Influence of Intentional Mistuning on the Forced Response Characteristics of the Splittered Impeller via ROM

To investigate the influence of intentional mistuning on the forced response characteristics of impellers with splitter blades, the wave-based substructuring method is developed and a high precision reduced order model (ROM) is established. Compared with the full finite element model of the impeller, the total number of degrees of freedom (DOF) of the ROM is reduced over 99.8%. Based on the ROM, the intentional mistuning of harmonic pattern is applied to the main and the splitter blades respectively. The normalized resonant response amplitude envelope is calculated for the ideal intentional mistuned state with mistuning patterns of different harmonic indices and intentional mistuning amplitudes, which is used as a guide to select the appropriate harmonic mistuning pattern to minimize the response amplitude. With the appropriate intentional mistuning pattern identified and applied, additional random mistuning of different amplitudes is introduced to simulate the practical intentional mistuned state. The statistical forced response characteristics are calculated and compared for both the practical intentional mistuned state and the random mistuned state by Monte Carlo method, and the 0.95-quantiles of the maximum amplitude is used to evaluate the effect of vibration reduction. The results show when the excitation frequency locates within the frequency band of the main (or splitter) blade dominated mode family, it is feasible to introduce harmonic mistuning only to the main (or splitter) blades to reduce the mistuned response amplification. Besides, harmonic mistuning for main (or splitter) blades could barely affect the forced response characteristics within the frequency band corresponding to the splitter (or main) blade dominated modes. Furthermore, the maximum resonant amplitude could be reduced lower than that of the tuned impeller by choosing an appropriate harmonic mistuning pattern.