Abstract

Improvements made to the high cycle fatigue life of an industrial compressor rotor blade for tip active modes through aerodynamic design changes and aero-mechanical assessments are presented in this paper. Typical aero-mechanical computations involved utilising an in-house linear-harmonic solver to compute the aero damping. In parallel, a novel hybrid model with whole-anulus domain for the blade rows of interest followed by a single passage domain for the rest of the compressor was used to compute the modal forcing. In addition to the standard blade passing resonances, low engine order excitations due to vane number differences, were analysed. This was achieved within a time frame consistent with the product design cycle by using TurboStream, a GPU based non-linear time domain unsteady flow solver. The excitation due to low engine order resonance was found to be influenced by a harmonic of upstream blade passing frequency. When considering a design change targeting HCF life, the calculated reserve factors showed significant improvements for the tip modes of interest. The subsequent engine tests carried out with tip timing agreed closely with the predictions thus validating not only the design but also the forced response prediction process.

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