Patent Application
20080273965
The present invention relates to systems and methods for controlling variable vane stator assemblies for gas turbine engines.
Gas turbine engines often include stator assemblies with variable-position vanes, which are sometimes referred to as variable vane or vari-vane assemblies. These stator assemblies are positioned in a primary engine gaspath, and can be located in a cold section of an engine, such as in a compressor section. The vanes of the stator assembly are static in the sense of being non-rotating parts, but are variable in their angle of attack relative to fluid flow in the primary engine gaspath, the variation of which adjusts an effective area between adjacent vanes in the stator assembly. Typically, all of the vanes are connected to a single positioning ring through conventional mechanical coupling mechanisms generally located outside the primary engine gaspath. The position of all of the vanes can be affected simultaneously by moving a positioning ring. Movement of the positioning ring is produced using an hydraulic actuator having a piston that is mechanically coupled to the positioning ring through a bellcrank, lever or other conventional mechanical coupling mechanism assemblies.
Known stator assemblies allow detection of a position of the actuator piston. Positions of the positioning ring and the vanes are not sensed directly, but instead only the position of the actuator piston is detected. This approach is not very precise, because it assumes that movement of the actuator piston translates perfectly into movement of the vanes and positioning ring through extensive mechanical linkages according to original design specifications. However, wear, damage, engine operating conditions, and other factors may cause the actual positions of vanes or positioning rings to deviate from anticipated positions under perfect conditions.
A variable vane control system for use with a gas turbine engine includes a plurality of vanes, an actuation assembly, a mechanical linkage assembly, and a sensor. Each of the plurality of vanes has an airfoil portion disposed in a gas flowpath of the gas turbine engine, and a position of each of the vanes is adjustable with respect to an angle of attack of the airfoil portion of each vane. The actuation assembly is configured for generating actuation force to position the plurality of vanes. The mechanical linkage assembly operably connects the actuation assembly to at least one of the plurality of vanes. The sensor is configured to sense the position of at least one of a plurality of vanes and the mechanical linkage assembly, and to generate a position output signal.
In general, the present invention provides a system and method for sensing and controlling the positions of vanes in a stator assembly of a gas turbine engine. The positions of airfoils, positioning rings, bellcranks, levers, coupling mechanisms, or other structures of the stator assembly can be monitored in order to sense vane position. The present invention thus provides a relatively precise indication of actual vane position relative to a primary gas flowpath in essentially real time, and decreases or eliminates reliance upon assumptions of vane position that are based upon a blueprint mechanical configuration of the stator assembly. In other words, the present invention permits more direct sensing of vane positioning. The system and method of the present invention further enables dynamic adjustment of the positioning of the vanes based upon comparison between a sensed vane position feedback signal (or signals) and a position command signal that indicates desired vane positioning.
The stator assembly 12 enables variable positioning of the vanes 24 relative to fluid flow of a primary flowpath of the gas turbine engine. As will be understood by those of ordinary skill in the art, the vanes 24 are static in the sense of being essentially non-rotating engine components (as opposed to rotating turbine blades), but have a variable angle of attack for adjusting an effective area between adjacent vanes 24 in the stator assembly 12. The actuator 14, in response to a control signal, produces mechanical force used to position the vanes 24 as desired. The coupling mechanisms 22A mechanically link the piston 16 of the actuator 14 to the positioning ring 20 via the bellcrank 18, and the coupling mechanism 22B mechanically links the positioning ring 20 to each of the vanes 24. Movement of the actuator piston 16 thereby causes substantially simultaneous movement of all of the vanes 24. The mechanical connecting structures of the stator assembly 12 are shown in simplified schematic form in
As shown in
The sensor 34 is positioned adjacent to the positioning ring 20, outside the primary gaspath, in order to detect a position of the ring 20. The sensor 34 can be of any type, such as one of the types described above with respect to the sensors 32. The sensor 34 enables sensing the positions of the vanes 34 indirectly, by directly sensing the position of the positioning ring 20 and enabling the positions of the vanes 24 to be determined based upon the mechanical relationship of the vanes 24 to the positioning ring 20.
The sensor system 10 can utilize both sensors 32 and 34 as described above. However, it should be understood that fewer sensors can be used than are shown in the exemplary embodiment illustrated in
The sensors 32 and 34 are operably connected to a controller unit 46, which receives vane position feedback signals from the sensors 32 and 34. The controller unit 46 is also operably connected to the actuator 14, and can send control signals to the actuator 14 for controlling movement of the actuator piston 16. As explained further below, the controller unit 46 can utilize position feedback to dynamically adjust the control signals to harmonize position feedback with desired vane positioning.
The controller unit 46 includes a comparator 54, a stabilizing controller module 56, and a diagnostics module 58. The non-contact position measuring sensor(s) 52 each generate a position feedback signal, indicating actual sensed vane position as described above, that are sent to both the comparator 54 and the diagnostics module 58. The comparator 54 compares the position feedback signal(s) with the position command signal from the position command source 50, indicating desired vane positioning, and then generates a bias signal sent to the stabilizing controller module 56. The stabilizing controller module 56 interprets the bias signal, determines if adjustment of actual vane position is necessary, and sends appropriate control signals to the actuator 14 in order to harmonize actual positions of the vanes 24 (associated with the position feedback signal(s)) with desired positions of the vanes 24 (associated with the position command signal).
The actuator position measuring sensor 48 generates an actuator position feedback signal that is sent to the diagnostics module 58 along with the position feedback signal(s) from the non-contact position measuring sensor(s) 52. The diagnostics module 58 can generate a diagnostic output signal, which can indicate a health condition of the stator assembly 12 of the gas turbine engine. The diagnostics module 58 can generate the diagnostic output signal on demand, such as during a regular maintenance interval when diagnostic equipment is connected to the controller unit 46. Alternatively, the diagnostic output signal could be sent to the EEC on a periodic or substantially continuous basis. Furthermore, the diagnostics module 58 can electronically store position data over time, enabling tending data to be collected and included with the diagnostic output signal. Thus, the diagnostics module 58 facilitates engine health monitoring and maintenance, and can help identify vane positioning error sources in the stator assembly 12.
In one embodiment, the diagnostics module 58 can be used to only record a limited amount of position data over time, and can have the ability to transmit that position data on a periodic basis to an optional ground based unit 60 (e.g., wirelessly or through a periodic physical uplink) that could store and trend all the historic position data. This would allow a cost effective solution where the on-board controller unit 46 could be less complex and memory storage and decision making capabilities would primarily reside on the ground (with the ground based unit 60).
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.
