Numerical Simulation of Aerodynamic Damping for Flutter Analysis of Turbomachinery Blade Rows

Abstract

This paper describes the calculation of aerodynamic damping for prediction of e utter characteristics of turbomachinery bladerows.Theunsteady aerodynamicbladeloadsareobtainedbysolving theNavier ‐Stokesequations on a dynamically deforming, body-e tted grid. Phase-lagged boundary conditions are used to model the nonzero interbladephaseangleoscillations,and theenergy exchangemethod isused to calculatetheaerodynamicdamping. The analysis is applied to calculate e utter of a transonic forward-swept fan cone guration, which showed e utter at part speed conditions in wind-tunnel tests. The analysis successfully identie ed the most critical mode and the e ow characteristics responsible for the observed e utter. The location of shock wave and variation of its strength were found to strongly ine uence the aerodynamic damping, with outboard stations providing the main contribution. The results also demonstrate that changes in blade shape impact the calculated aerodynamic damping, indicating the importance of using an accurate blade operating shape under centrifugal and steady aerodynamic loading. Sensitivity of thecalculated aerodynamic damping to variation in inlet and exit conditions, the computational time steps, and blade natural frequency are also reported.