Simulation of Non-synchronous Blade Vibration of an Axial Compressor Using a Fully Coupled Fluid/strcuture Interaction

In this paper non-synchronous vibration (NSV) of a GE axial compressor is simulated using a fully coupled fluid/strcuture interaction (FSI). Time accurate NavierStokes equations are solved with a system of 5 decoupled structure modal equations in a fully coupled manner. A 3rd order WENO scheme for the inviscid flux and a 2nd order central differencing for the viscous terms are used to resolve nonlinear interaction between vibrating blades and fluid flow. 1/7th annulus is used with a time shifted phaselag (TSPL) boundary condition to reduce computational efforts. A fully conservative rotor/stator sliding boundary condition is employed to accurately capture unsteady wake propagation between the rotor and stator blades. The predicted dominant frequencies using the blade tip response signals are not harmonic to the engine order, which is the NSV. The blade vibration is torsionally coupled with highly oscillating blade pressure and is not damped out during the NSV. No resonance to the blade natural frequencies is found. The instability of tornado vortices in the vicinity of the rotor tip due to the strong interaction of incoming flow, tip vortex and tip leakage flow is the main cause of the NSV observed in this study.