Turbofan engine fan assembly with blade containment and cutter to trim fan blade tips

摘要

High bypass ratio turbofan propulsion engines have a containment system 30 encircling the fan assembly 2 to capture any part of a released fan blade 4 following foreign object damage and, in order to reduce the vibrations of the resulting unbalanced fan assembly 2, the support structure 14, 20 for the bearing 16 of the rotating assembly is constructed with frangible parts to introduce a snubber gap 26 to permit the rotating, unbalanced fan assembly 2 and bearing 16 to orbit. However, in the case of very wide chord fan assemblies, the largest acceptable snubber gap 26 is insufficient to reduce the induced vibrations. The invention incorporates into the containment system 30, and behind a fan track liner 36 encircling the fan blades 2, at least one severance member 44 having a cutting edge 46 that will impact the tips 40 of the blades 4 of an orbiting fan assembly 2 to trim the mass distribution of the fan blades 4 in order to reduce the vibrations caused by the out of balance forces. The severance members 44 may be integral with annular ribs 48, 50 around the containment casing 30 or may be separate members of harder material.