BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A shows a prior art gas turbine engine.
FIG. 1B shows one portion of a convergent-divergent axisymmetric nozzle for the gas turbine engine.
FIG. 2 shows the inventive structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1A shows a gas turbine engine 10. As known, a fan section 11 moves air and rotates about an axial center line 12. A compressor section 13, a combustion section 14, and a turbine section 15 are also centered on the axial center line 12. A nozzle section 16 of the turbine discharges gas downstream. FIG. 1A is a highly schematic view, however, it does show the main components of the gas turbine engine. Further, while a particular type of gas turbine engine is illustrated in this figure, it should be understood that the present invention extends to other types of gas turbine engines.
As also shown in FIG. 1A, a plurality of flaps 31 at the end of the nozzle 16 can be pivoted radially inwardly or outwardly to control the cross-sectional area at the nozzle. This is as known in the art, and an actuation structure for pivoting the flaps 31 is shown in FIG. 1B. As shown, a hydraulic actuator 41 drives a sync ring 44 through a connection at 46. Air pressure 40 within the nozzle acts on an inner surface of the flaps 31, while an ambient pressure 42 outside the flaps 31 acts on an outer surface of the flaps 31. Typically, the air pressure at 40 is much greater than the ambient air pressure 42. This imbalance creates forces on the sync ring 44. Thus, pressurized air is delivered through openings 48 to the rear surface of the sync ring 44 to assist in handling the load.
At times, however, the pressure ratio between the areas 40 and 42 will be lower. This occurs, for example, at low altitude/low speed flying. In such instances, the force supplied through the openings 48 through the pressurized air on the rear surface of the sync ring 44 can be unduly high and can itself create undesirable loads and stresses on the various connections.
Thus, as shown in FIG. 2, in an inventive nozzle control 60, an air supply tube 62 is provided with a valve 64, and which is controlled by a control 66. Control 66 may trigger the valve 64 either through a simple delta pressure control based upon the pressures at 40 and 42, or the control can be based upon an electronic control. In one application, it may be the controller for the entire engine. Essentially, should the pressure ratio between areas 40 and 42 be lower (e.g., less than three), then it would be desirable to block airflow to the sync ring 44, and instead open the cavity to a lower pressure source (e.g., atmosphere) as shown at 66. Notably, the hydraulic actuator 41 is omitted from the view but would preferably be included.
In this manner, the higher pressure forces on the sync ring 44 at certain conditions are lowered to atmospheric pressure or less.
A preferred and more detailed valve is disclosed in concurrently filed U.S. patent application Ser. No. ______, entitled “Combined Control for Supplying Cooling Air and Support Air in a Turbine Engine Nozzle.”
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
Patent Application
20080072604
