How can we prevent the centrifugal impeller's natural frequency from coupling with the airflow excitation frequency and causing resonance?
Preventing the coupling between the natural frequency of a centrifugal impeller and airflow excitation forces (resonance) is a critical aspect of turbomachinery design. This phenomenon, often analyzed using Campbell Diagrams, can lead to High Cycle Fatigue (HCF) and catastrophic failure. To prevent this coupling, engineers employ a combination of design, operational, and testing strategies. Here are the primary methods: 1. Stiffness and Material Modification (Shifting Natural Frequencies) The most direct method is to ensure that the impeller’s natural frequencies do not intersect with the excitation orders within the operating speed range. Increase Stiffness: Modify the impeller geometry to increase its stiffness without adding excessive mass. Backplate Thickness: Increasing the thickness of the impeller backplate raises the natural frequencies of the primary bending