Impact Loading of Compressor Stator Vanes By Hailstone Ingestion

Impacts of 1 inch diameter ice bullets onto stator vanes of the first stage of an axial compressor were investigated at an impact velocity of v = 257 m/s. The analytical and experimental simulations of typical hailstone ingestions were performed with special emphasis on damage effects of the thin leading edges of the hidden titanium vanes. The paper includes a comprehensive overview of the ice properties used in the analytical model regarding elastic constants, strain rate dependent strength and crack propagation under compression. The influence of different impact positions and ice properties was investigated in the analytical simulations. In all cases the highest stresses occur at the leading edge of the hidden vane. When the center of impact is placed on the leading edge plastic deformations are expected and localized microcracks cannot be excluded. When the target point is positioned on the suction side of the vane (air foil flank) the energy transfer and the loading is high, but the deformations remain elastic. For verification shooting tests of ice bullets on a complete stator were performed. The ice balls were made by freezing water in liquid nitrogen and the impacts were recorded with a high speed camera. The observed leading edge deflections are in good agreement with the calculated values, but in no case plastic deformations or cracks were detected.