Impact of variable stator vane schedule on nonsynchronized vibration

In multi-stage compressors, the Variable Stator Vane (VSV) schedule significantly influences performance and stability. This study examines the part-span rotating stall in a multi-stage axial compressor which can lead to Non-Synchronised Vibration (NSV). Unsteady aerodynamic simulations were performed using URANS CFD for an axial compressor that experienced high vibration levels during the operation. For the original VSV schedule, steady-state simulations revealed the formation of short-length-scale disturbances near the tip of the first stage rotor. Full-annulus unsteady simulations demonstrated that these disturbances coalesce into rotating stall cells propagating around the annulus. The frequency of the unsteadiness caused by rotating structures was close to blade’s first mode natural frequency which could potentially cause NSV. Based on the findings, a new VSV schedule was developed, effectively eliminating the flow separation near the tip of the first-stage rotor and consequently rid the compressor of part-span rotating stall and NSV.