12th European Conference on Turbomachinery Fluid dynamics & Thermodynamics

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Federico Vanti - University of Florence
Lorenzo Pinelli - University of Florence
Francesco Poli - University of Florence
Andrea Arnone - University of Florence


In modern turbomachinery design, one of the main objectives of aviation industry is the continuous research for higher performance with lighter engines. This trend leads to a re-duction in the number of blades, which become increasingly thin and loaded, with a conse-quent increase in the occurrence of aeroelastic phenomena, compromising the structural integrity. This paper aims to present a numerical flutter assessment of two different types of blade assembly: a turbine cluster system typical of stator segments and an intentionally mistuned row representing an up-to-date low pressure turbine rotor. The numerical re-sults obtained by a time-accurate CFD solver with vibrating blades will be compared with experimental data measured in the context of the EU project FUTURE. The first part of the paper will describe the study of a stator turbine cascade assembly, whose blades are mounted in packets and vibrate as a cluster mode. The comparison between numerical and experimental data showed an excellent agreement and further validated the aeroelas-tic solver. Then, the attention will be focused on the flutter analysis of an intentionally mis-tuned turbine rotor bladerow in comparison with a traditional row consisting of identical blades: this highlights how this type of assembly may stabilize the bladerow. The results of the numerical blade stability analysis show a flutter instability for the first bending mode which becomes stable, once the modal mistuning is introduced by adding masses at the tip of alternate blades. This numerically predicted flutter stabilization was confirmed by the experimental campaigns.

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