Rotor disks used in some turbofan engines can have blades removably mounted in circumferentially-disposed blade retention slots provided at their periphery. These blades have blade roots that are somewhat loose in their corresponding blade retention slots when the engine is shut down. However, when the engine is running rotor disk rotates at high speeds and the centrifugal force pushes the blades radially outwardly for a firm connection between the blade roots and the respective blade retention slots.
Windmilling is the passive rotation of an engine spool at very low speeds when the gas turbine engine is not operating (i.e. on the ground) in response to environmental wind blowing on the engine. The clearance between a blade root and its blade retention slot can cause the blade root to flop around in the blade retention slot. After many hours of windmilling, the mating surfaces on the blade root and the blade retention slot will be subject to wear. This wear can have a detrimental impact on the low cycle fatigue life of the rotor disk and of the blades.
It is known to provide devices to bias the blades outwardly so as to reduce blade friction wear while windmilling, but known devices are often relatively complex to assemble. Room for improvements thus exists.
USPTO Backgrounds
USPTO Backgrounds