Numerical analysis of aerodynamic damping for centrifugal impeller

In order to carry out the numerical analyses of the flow fields with moving boundaries in centrifugal impellers, the codes for the grid deformation and the unsteady flow simulations were developed independently, by which the calculations of the aerodynamic damping of centrifugal impellers were realized. By adopting the compactly supported radial basis function to carry out the data transfer of surface deformation from the structure mesh to the flow mesh, and utilizing the binomial tree technique to fulfill the wall distance calculations, the computation efficiencies of grid deformation and flow-field analyses were greatly increased. According to the test cases of an oscillating cascade and a centrifugal impeller, the correctness of the code for the simulations of the flow-fields with moving boundaries and the flows in centrifugal impellers was validated. Then taking a centrifugal impeller as the research object, the calculations of modal aerodynamic damping ratios were carried out. Results showed that, the aerodynamic damping ratios of two selected modes were both positive. The modal aerodynamic damping ratio had no relationship with the oscillating amplitude under small oscillations. For the disk vibration mode, the value of aerodynamic damping ratio decreased as the operating condition shifted towards the stall point.