Locking vane shims together: A NEW METHOD AVOIDS VIBRATORY STRESSES AND COLLATERAL DAMAGE FROM LOOSE AND PROTRUDING SHIMS

摘要

In recent years, the design of axial compressors has pushed the envelope on compressor air flow, pressure ratio, complex blade shapes, and large blade sizes. These factors have amplified new failure mechanisms that were not problematic in the past. As compressors evolve to meet greater power demands, protrusion or liberation of stator vane shims (Figure 1) and vane-fretting wear are becoming common failure events that can lead to severe collateral damage costing USD10 million to USD20 million. In some compressor designs where stator vanes have a square-base blade attachment, shims serve as spacers between the vane bases. Often, the vanes wear due to relative motion and as a result the shims protrude out, setting up excitation forces on downstream rotating blades. If the shims liberate, they could cause domestic object damage.