High turning fan exit stator

A turbine engine includes a fan section that rotates about a longitudinal axis and a compressor section. The turbine engine also includes a fan exit stator located between the fan section and the compressor section, the fan exit stator including an airfoil. The airfoil defines an entrance angle with respect to a leading edge of the airfoil and a line parallel to the longitudinal axis, and the airfoil defines an exit angle with respect to a trailing edge of the airfoil and a line parallel to the longitudinal axis. A difference between the entrance angle and the exit angle is between about 45° and about 65°. The turbine engine also includes a turbine section, and a portion of the compressor section is driven by a portion of the turbine section.

BACKGROUND OF THE INVENTION

Gas turbine engines can have multiple low pressure compressor stages closed coupled with a fan. A fan exit stator (the first core stream stator behind a fan blade) of the low pressure compressor is closed coupled with a following airfoil and determines an inlet swirl profile of air flowing into the following airfoil. Air exiting a traditional fan exit stator has 15 to 25 degrees of co-rotating swirl when the air arrives at the following airfoil.

SUMMARY OF THE INVENTION

A turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a fan section that rotates about a longitudinal axis and a compressor section. The turbine engine also includes a fan exit stator located between the fan section and the compressor section, the fan exit stator including an airfoil. The airfoil defines an entrance angle with respect to a leading edge of the airfoil and a line parallel to the longitudinal axis, and the airfoil defines an exit angle with respect to a trailing edge of the airfoil and a line parallel to the longitudinal axis. A difference between the entrance angle and the exit angle is between about 45° and about 65°. The turbine engine also includes a turbine section, and a portion of the compressor section is driven by a portion of the turbine section.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a front center body duct that slopes radially inwardly with respect to a longitudinal axis.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a low pressure turbine and a low pressure compressor, and the fan section is driven through a geared architecture by the low pressure turbine.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a fan section and a low pressure compressor that counter-rotate.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a geared architecture that is a star gear system.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a geared architecture that is located radially inwardly of a fan exit stator.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a portion of a pressure side of an airfoil that is substantially parallel to a longitudinal axis.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a portion of a pressure side of an airfoil is located near a trailing edge of the airfoil.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include an entrance angle that is between about 45° to about 55°.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a difference between an air inlet angle and an air outlet angle between about 45° and about 60°.

A turbine engine according to another exemplary aspect of the present disclosure includes, among other things, a fan section that rotates about a longitudinal axis and a compressor section including a low pressure compressor and a high pressure compressor. The turbine engine includes a fan exit stator located between the fan section and the compressor section, the fan exit stator including an airfoil. The airfoil defines an entrance angle with respect to a leading edge of the airfoil and a line parallel to the longitudinal axis, and the airfoil defines an exit angle with respect to a trailing edge of the airfoil and a line parallel to the longitudinal axis. A difference between the entrance angle and the exit angle is between about 45° and about 65°. The turbine engine includes a combustor in fluid communication with the compressor section and a turbine section in fluid communication with the combustor. The turbine section includes a low pressure turbine and a high pressure turbine, and the fan section is driven through a geared architecture by the low pressure turbine.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a front center body duct that slopes radially inwardly with respect to a longitudinal axis.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a low pressure turbine and a low pressure compressor, and the fan section is driven through a geared architecture by the low pressure turbine.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a fan section and a low pressure compressor that counter-rotate.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a geared architecture that is a star gear system.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a geared architecture that is located radially inwardly of a fan exit stator.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a portion of a pressure side of an airfoil that is substantially parallel to a longitudinal axis.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a portion of a pressure side of an airfoil is located near a trailing edge of the airfoil.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include an entrance angle that is between about 45° to about 55°.

In a further non-limited embodiment of any of the foregoing turbine engine embodiments, the turbine engine may include a difference between an air inlet angle and an air outlet angle between about 45° and about 60°.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1schematically illustrates a gas turbine engine20. The gas turbine engine20is disclosed herein as a two-spool turbofan that generally incorporates a fan section22, a compressor section24, a combustor section26and a turbine section28. Alternative engines might include for example, a three-spool design, an augmentor section, and different arrangements of sections among other systems or features.

Although depicted as a geared turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with geared turbofans as the teachings may be applied to other types of turbine engines.

The fan section22drives air along a bypass flowpath B while the compressor section24drives air along a core flowpath C for compression and communication into the combustor section26then expansion through the turbine section28.

The low speed spool30generally includes an inner shaft40that interconnects a fan42, a low pressure compressor44and a low pressure turbine46. The inner shaft40is connected to the fan42through a geared architecture48to drive the fan42at a lower speed than the low speed spool30. The geared architecture48connects the low pressure compressor44to the fan42, but allows for rotation of the low pressure compressor44at a different speed and/or direction than the fan42.

The high speed spool32includes an outer shaft50that interconnects a high pressure compressor52and a high pressure turbine54.

A combustor56is arranged between the high pressure compressor52and the high pressure turbine54.

A mid-turbine frame58of the engine static structure36is arranged generally between the high pressure turbine54and the low pressure turbine46. The mid-turbine frame58further supports bearing systems38in the turbine section28.

The inner shaft40and the outer shaft50are concentric and rotate via bearing systems38about the engine central longitudinal axis A which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor44then the high pressure compressor52, mixed and burned with fuel in the combustor56, then expanded over the high pressure turbine54and low pressure turbine46. The mid-turbine frame58includes airfoils60which are in the core airflow path. The turbines46,54rotationally drive the respective low speed spool30and high speed spool32in response to the expansion.

The engine20is in one example a high-bypass geared aircraft engine. In a further example, the engine20bypass ratio is greater than about six (6:1) with an example embodiment being greater than ten (10:1). The geared architecture48is an epicyclic gear train (such as a planetary gear system or other gear system) with a gear reduction ratio of greater than about 2.3 (2.3:1). The low pressure turbine46has a pressure ratio that is greater than about five (5:1). The low pressure turbine46pressure ratio is pressure measured prior to inlet of low pressure turbine46as related to the pressure at the outlet of the low pressure turbine46prior to an exhaust nozzle.

In one disclosed embodiment, the engine20bypass ratio is greater than about ten (10:1), and the fan diameter is significantly larger than that of the low pressure compressor44. The low pressure turbine46has a pressure ratio that is greater than about five (5:1). The geared architecture48may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 (2.3:1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans.

A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section22of the engine20is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 feet, with the engine at its best fuel consumption, also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’),” is the industry standard parameter of lbm of fuel being burned per hour divided by lbf of thrust the engine produces at that minimum point.

“Fan pressure ratio” is the pressure ratio across the fan blade alone. The fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.6.

“Low corrected fan tip speed” is the actual fan tip speed in feet per second divided by an industry standard temperature correction of [(Tambient deg R)/518.7)0.5]. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 feet per second (351 meters per second).

The low pressure compressor44and the fan42are driven by a common low pressure turbine46. The geared architecture48includes components that spin and move in opposing directions and allows for rotation of the low pressure compressor44at a different speed and/or direction than the fan42. Therefore, the geared architecture48can allow for counter-rotation of the fan42and the low pressure compressor44, which can increase the amount of swirl in the airflow. In one embodiment, the system has a star gear system so that the fan42and the low pressure compressor44counter-rotate.

Referring toFIGS. 2 and 3, with continued reference toFIG. 1, the gas turbine engine20includes a plurality of fan exit stators62positioned around the longitudinal axis A. The fan exit stators62function as high turning airfoils to remove a substantial circumferential flow component from air exiting the fan section22.FIG. 2illustrates a top view of an airfoil72of a fan exit stator62when viewed along an axis D.FIG. 3illustrates a perspective view of a plurality of airfoils72attached to an outer surface of a fixed case88. The fixed case88extends circumferentially around the longitudinal axis A, and the plurality of airfoils72circumferentially surround the longitudinal axis A. The airfoil72ofFIG. 2is shown from a tangential perspective with respect to the longitudinal axis A (that is, the airfoil72is shown as a top view with respect toFIG. 1). An axis E is perpendicular to both the axis D and the longitudinal axis A (shown extending into the page ofFIG. 1).

The airfoil72includes a body portion82having a suction side84, a pressure side86, a leading edge74where the suction side84and the pressure side86contact, and a trailing edge76where the suction side84and the pressure side86contact.

A forward section78of the airfoil72located near the leading edge74extends at an angle relative to the longitudinal axis A, while slightly curving toward a plane perpendicular to the longitudinal axis A. In one example, an aft section80of the airfoil72located near the trailing edge76includes a profile that curves toward a plane perpendicular to the longitudinal axis A until the pressure side86is substantially parallel to the longitudinal axis A.

Continuing to refer toFIGS. 2 and 3, air enters the fan exit stators62in a direction G. The pressure side86of the aft section80of the airfoil72guides the entering air so that upon exiting the fan exit stator62, the air flow is in an axial direction F. The turn of air flow provided by the example fan exit stators62reduces the circumferential components, or swirl in the air flow before exiting the fan exit stators62. Air then flows through a front center body duct64along the path C in an axial direction with little or no circumferential swirl. In one example, there is less than about 5° of swirl relative to an axial direction remaining in the air when exiting the fan exit stators62. In one example, there is less than about 10° of swirl relative to an axial direction remaining in the air when exiting the fan exit stators62.

In one example, as shown inFIG. 2, air enters the fan exit stators62in the direction G at an angle H° with respect to a line parallel to the longitudinal axis A. Air exits the fan exit stators G in the direction F at an angle I° with respect to a line parallel to the longitudinal axis A. In one example, a difference between the angle H° and the angle I° is between about 45° and about 60°. In another example, a difference between the angle H° and the angle I° is between about 45° and about 65°. In one example, the air exits the fan exit stators at an angle I° between about 0 and about 10°. In another example, the air exits the fan exit stators at an angle I° between about 0 and about 5°

With reference toFIG. 4, the airfoil60defines an entrance angle J° with respect to the leading edge74of the airfoil72and a line parallel to the longitudinal axis A and an exit angle K° with respect the trailing edge76of the airfoil72and a line parallel to the longitudinal axis A. In one example, the entrance angle J° is about 45° to about 55°, and a difference between the entrance angle J° and the exit angle K° is between about 45° and about 65°. In another example, the entrance angle J° is about 45° to about 55°, and a difference between the entrance angle J° and the exit angle K° is between about 45° and about 60°

Air exiting the fan section22flows to the low pressure compressor44. The air entering the low pressure compressor44first flows past the fan exit stators62and then through a front center body duct64. The front center body duct64slopes radially inwardly towards the longitudinal axis A in the direction of airflow, reducing both the distance that the air flowing along the flow path C must travel in the front center body duct64and pressure losses in the front center body duct64. Moreover, reducing the circumferential component of airflow through the front center body duct reduces aerodynamic loading on the front center body duct64. Although the air flow is directed inwardly by the front center body duct64, air flows substantially parallel to the longitudinal axis A when viewed with respect to the axis D.

The air with reduced swirl then flows through inlet guide vanes66and first rotors68of the low pressure compressor44. If the low pressure compressor44is counter-rotating, the fan exit stators62reduce the turning requirement of the air by the inlet guide vanes66to reduce pressure losses through the variable inlet guide vane66. The air exiting the low pressure compressor44flows through an intermediate case70and then enters the high pressure compressor52.

The foregoing description is only exemplary of the principles of the invention. Many modifications and variations are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than using the example embodiments which have been specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.