Sensitivity Analysis and Modal Mechanism Analysis of Centrifugal Impeller Constraints

To clarify the influence of assembly constraint methods on the modal characteristics of centrifugal impellers, a specific centrifugal impeller was selected as the research object. The natural frequencies and mode shape characteristics of the impeller under different vibratory nodal diameters were systematically compared under two distinct constraint conditions. The accuracy of the simulation results was validated through optical fiber tip amplitude testing experiments. The results indicate that the third-order nodal diameter vibration is insensitive to the constraint method, with highly consistent calculation outcomes under different constraints. In contrast, the first-order nodal diameter vibration is significantly affected by the constraint method; only some modes exhibit correspondence between the two constraint schemes. Among them, Constraint Method A aligns better with the actual operating conditions, yielding resonant speeds consistent with experimental measurements. Mechanism analysis reveals that low-order nodal diameter modes involve global cooperative motion, where boundary conditions significantly alter the system’s overall stiffness matrix. Conversely, high-order nodal diameter modes exhibit localization characteristics, primarily depending on the blades’ inherent stiffness, and are insensitive to remote boundary conditions.