Gas turbine engine and an airflow control system

#The present disclosure relates to a gas turbine engine, and more particularly to an engine having an airflow control system.

#Gas turbine engines, such as those which power modern military aircraft, include a compressor section to pressurize a supply of air, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases and generate thrust. Downstream of the turbine section, an augmentor section, or “afterburner”, is operable to selectively increase the thrust. The increase in thrust is produced when fuel is injected into the core exhaust gases downstream of the turbine section and burned with the oxygen contained therein to generate a second combustion.

#Variable cycle gas turbine engines power aircraft over a range of operating conditions yet achieve countervailing objectives such as high specific thrust and low fuel consumption. The variable cycle gas turbine engine essentially alters a bypass ratio during flight to match requirements. This facilitates efficient performance over a broad range of altitudes and flight conditions to generate high thrust for high-energy maneuvers yet optimize fuel efficiency for cruise and loiter.

#Various features will become apparent to those skilled in the art from the following detailed description of the disclosed, non-limiting, embodiments. The drawings that accompany the detailed description can be briefly described as follows:

#FIG. 1 is a schematic cross-section of a gas turbine engine of the present disclosure;

#FIG. 2 is a cross section of a turbine exhaust case of the engine taken along line 2-2 in FIG. 1; and

#FIG. 1 schematically illustrates a gas turbine engine 20. The gas turbine engine 20 is disclosed herein as a two-spool turbo fan that generally incorporates a fan section 22, a compressor section 24, a combustor section 26, a turbine section 28, and a turbine exhaust case 30 (TEC). In a downstream direction from the TEC 30, the engine 20 may further include an augmentor section 32, an exhaust duct section 34 and a nozzle section 36. The fan section 22 drives air along a second flowpath while the compressor section 24 drives air along a core flowpath for compression and communication into the combustor section 26 then expansion through the turbine section 28. The fan, compressor and turbine sections 22, 24, 28 may each include various architectures that, for example, include a plurality of stages, each with or without various combinations of blades and variable or fixed guide vanes orientated about an engine axis A.

#Variable cycle gas turbine engines power aircraft over a range of operating conditions and essentially alters a bypass ratio during flight to achieve objectives that may be countervailing (such as high specific thrust for high-energy maneuvers) yet optimizes fuel efficiency for cruise and loiter modes of operation. Although depicted as an augmented low bypass turbofan in the disclosed, non-limiting, embodiment, it is understood that the concepts described herein are applicable to other types of turbine engines including non-augmented engines, geared architecture engines, high bypass and/or direct drive turbofans, turboshafts, and three-spool (plus fan) turbofans wherein an intermediate spool includes an intermediate pressure compressor (“IPC”) between a Low Pressure Compressor (“LPC”) and a High Pressure Compressor (“HPC”), and an Intermediate Pressure Turbine (“IPT”) between the High Pressure Turbine (“HPT”) and the Low Pressure Turbine (“LPT”).

#The engine 20 generally includes a low spool 38 and a high spool 40 mounted for rotation about the engine axis A, and relative to an engine core case 42, via several bearing structures (not shown). The low spool 38 generally includes an inner shaft that interconnects at least one leading fan stage 44 of the fan section 22, a LPC 46 of the compressor section 24 and a LPT 48 of the turbine section 28. The inner shaft of the low spool 38 drives the leading fan stage 44 directly, or through a geared architecture 50 to drive the leading fan stage 44 at a lower speed than the low spool 38. An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system.