Blade Vibration Measurements in a Multi-Stage Axial Turbine with Geometric Variations

摘要

In jet engines, blade repair is often more economical than the replacement of damaged blades with spare parts. Besides such a regeneration of turbine blades, blade rubbing and erosion also lead to a deviation from the original blade geometry. Typical regeneration and wear-specific geometric variations of turbine blades are applied to turbine vanes and blades of a five-stage axial air turbine. These geometric variations introduce non-uniform flow conditions, which in turn lead to an excitation of the blades. The vibration amplitudes of the turbine blades are measured with an optical blade tip-timing system. Additionally, an optical tip clearance probe is implemented to verify the accurately measure the tip clearance size simultaneously with the tip-timing measurements. The geometric variations lead to a change of the aerodynamic excitation, which results in a remarkable change of the vibration amplitude determined by the blade tip-timing system. This variation is shown to dependent on the geometric variations and the investigated operating points.