Experimental study of damping flexural vibrations in tapered turbofan blades

In this paper, the results of the experimental investigations into damping of flexural vibrations in turbofan blades with trailing edges tapered according to a power-law profile are reported. Edges of power-law profile (wedges), with small pieces of attached absorbing layers, materialise one-dimensional acoustic black holes for flexural waves that can absorb a large proportion of the incident flexural wave energy. The NACA 1307 aerofoil was used as a base model for experimental samples. This model was modified to form four samples of non-enginespecific model fan blades. Two of them were then twisted, so that a more realistic fan blade could be considered. All model blades, the ones with tapered trailing edges and the ones of traditional form, were excited by an electromagnetic shaker, and the corresponding frequency response functions have been measured. The results show that the fan blades with power-law tapered edges have the same pattern of damping that can be seen for plates with attached wedges of power-law profile, when compared to their respective reference samples. The resonant peaks are reduced substantially once a power-law tapering is introduced to the sample. The obtained results demonstrate that power-law tapering of trailing edges of turbofan blades can be a viable method of reduction of blade vibrations.