The present application is related to the following copending applications filed on the same day as this application: “RACK AND PINION VARIABLE VANE SYNCHRONIZING MECHANISM FOR INNER DIAMETER VANE SHROUD” by inventors J. Giaimo and J. Tirone III (attorney docket number U73.12-002); “SYNCH RING VARIABLE VANE SYNCHRONIZING MECHANISM FOR INNER DIAMETER VANE SHROUD” by inventors J. Giaimo and J. Tirone III (attorney docket number U73.12-003); “GEAR TRAIN VARIABLE VANE SYNCHRONIZING MECHANISM FOR INNER DIAMETER VANE SHROUD” by inventors J. Giaimo and J. Tirone III (attorney docket number U73.12-004); “LIGHTWEIGHT CAST INNER DIAMETER VANE SHROUD FOR VARIABLE STATOR VANES” by inventors J. Giaimo and J. Tirone III (attorney docket number U73.12-006). All of these applications are incorporated herein by this reference.
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.
The present invention comprises a first drive vane arm and a second drive vane arm for driving a first variable vane array and a second variable vane array, respectively, of a stator vane section of a gas turbine engine. The first drive vane arm and second drive vane arm are connected to each other at a first end by a linkage. The first drive vane arm and second drive vane arm are connected at a second end to a first drive vane and a second drive vane, respectively, of the first and second variable vane arrays. The first drive vane arm and second drive vane arm respond in unison to a single actuation source connected to one of the first drive vane arm and second drive vane arm.
Stator vane section 10 is divided into first and second sub-assemblies. Fan case 12 is comprised of a first fan case component 24A and second fan case component 24B. Vane shroud 14 is similarly comprised of first vane shroud component 26A and second vane shroud component 26B. Stator vane array 16 is also comprised of a first array component 28A and second array component 28B component. In one embodiment, the fan case components, the vane shroud components and the vane array components comprise upper and lower assemblies for use in a split fan configuration. The first and second sub-assemblies come together at first split line 30A and second split line 30B. First array component 28A and second array component 28B operate independently from one another. The synchronizing mechanism contained within vane shroud 14 does not synchronize the rotation of the first array component 28A and second array component 28B because of the discontinuity caused by first split line 30A and second split line 30B.
First variable stator vane array 28A includes first stator vanes 22A that pivot within first fan case portion 24A at their outer diameter end. First stator vanes 22A are connected inside first vane shroud 24A by a synchronizing mechanism such that they all rotate in unison when any individual vane (e.g. drive vane 20A) is rotated. Second variable stator vane array 28B includes second stator vanes 22B that pivot within second fan case portion 24B at their outer diameter end. Second stator vanes 22B are connected inside second vane shroud 24B by a synchronizing mechanism such that they all rotate in unison when any individual vane (e.g. drive vane 20B) is rotated. First variable stator vane array 28A and second variable stator vane array 28B operate independently of each other. Examples of synchronizing mechanisms are described in the previously mentioned copending applications, which are incorporated by reference.
Actuator 18 is connected to a drive mechanism (not shown) that causes up and down motion (as shown in
First variable stator vane array 28A is connected to first arm 38A through drive vane 20A. First arm 38A is connected to second arm 38B by linkage 36. As second arm 38B is rotated by actuator 18, linkage 36 rotates first arm 38A. First arm 38A provides a moment arm for rotating drive vane 20A. Preferably, drive vane 20A is selected to be next to or near split line 30A. As a result of drive vane 20A being rotated, follower vanes 22A also rotated by the synchronizing mechanism inside second vane shroud 26A. Thus, a single actuator, actuator 18, drives both first variable stator vane array 28A and second variable stator vane array 28B.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
This invention was made with U.S. Government support under contract number N00019-02-C-3003 awarded by the United States Navy, and the U.S. Government may have certain rights in the invention.