This invention relates generally to gas turbine engines and more particularly to variable stator vane assemblies for use in such engines.
Gas turbine engines operate by combusting a fuel source in compressed air to create heated gases with increased pressure and density. The heated gases are ultimately forced through an exhaust nozzle, which is used to step up the velocity of the exiting gases and in-turn produce thrust for driving an aircraft. The heated air is also used to drive a turbine for rotating a fan to provide air to a compressor section of the gas turbine engine. Additionally, the heated gases are used for driving rotor blades inside the compressor section, which provides the compressed air used during combustion. The compressor section of a gas turbine engine typically comprises a series of rotor blade and stator vane stages. At each stage, rotating blades push air past the stationary vanes. Each rotor/stator stage increases the pressure and density of the air. Stators serve two purposes: they convert the kinetic energy of the air into pressure, and they redirect the trajectory of the air coming off the rotors for flow into the next compressor stage.
The speed range of an aircraft powered by a gas turbine engine is directly related to the level of air pressure generated in the compressor section. For different aircraft speeds, the velocity of the airflow through the gas turbine engine varies. Thus, the incidence of the air onto rotor blades of subsequent compressor stages differs at different aircraft speeds. One way of achieving more efficient performance of the gas turbine engine over the entire speed range, especially at high speed/high pressure ranges, is to use variable stator vanes which can optimize the incidence of the airflow onto subsequent compressor stage rotors.
Variable stator vanes are typically circumferentially arranged between an outer diameter fan case and an inner diameter vane shroud. A synchronizing mechanism simultaneously rotates the individual stator vanes in response to an external actuation source.
In some situations, it is advantageous to divide the compressor section into upper and lower halves to expedite maintenance of the gas turbine engine. It is particularly advantageous, for example, in military applications when maintenance must be performed in remote locations where complete disassembly is imprudent. However, in dividing the compressor section into halves, the synchronizing mechanism must also be split apart. This creates two synchronizing mechanisms that must be actuated in unison to orchestrate simultaneous operation of all of the stator vanes. Synchronizing mechanisms that are located on the outer case can be accessed and spliced together easily. However, this is not the case for inner diameter synchronizing mechanisms, which cannot be accessed after assembly to attach the synchronizing mechanisms together. Thus, there is a need for an apparatus for coordinating actuation of split inner diameter synchronizing mechanisms.