The Local Aerodynamic Effect due to Miss-Staggering in Variable Stator Vanes

Abstract Multistage axial compressors require variable stator vanes to allow operability over a wide range of operating conditions. The vane profile is therefore restaggered through local rotation around the spindle axis. Multiple vanes of one blade row are linked through a ring and a mechanical gear. Within this mechanism some backlash will be present and will increase over operating time due to wear. This may lead to a deviation of the stagger angle of all vanes of a ring, as well as a local miss-staggering of individual vanes. To investigate the influence of these local deviations on the aerodynamic behavior of the compressor, tests have been conducted in a linear compressor cascade at engine representative Mach numbers. The cascade setup will be introduced and experimental results of stagger angle variation, including a local miss-staggering of the central profile, will be discussed. The tests include an opened and closed staggering of all profiles of the cascade combined with an additional local variation of stagger angle of the central vane to load and unload the vane. To guide the interpretation of the experimental results, numerical simulations using the RANS approach of the cascade setup were performed. Discussion of the experimental and numerical results will reveal the effect on the loss characteristic and turning of the three central vanes and separate the aerodynamic response of the individual vane passages on the local miss-staggering of the central vane.