BLEED DUCT FOR LAMINAR FAN DUCT FLOW

A disclosed gas turbine engine includes a fan including a plurality of fan blades rotatable about an engine axis and core engine disposed within a core nacelle for driving the fan. A bypass passage is defined between the core nacelle and an outer or fan nacelle. A duct mounted within the core nacelle defines a bleed air flow path for directing bleed air from the core engine into the bypass passage. The bleed air duct includes a plurality of airfoils disposed at a defined chord angle for directing bleed airflow into the bypass passage to minimize disruption to bypass airflow.

BACKGROUND

Bypass airflow generated by the fan section flows through a bypass passage defined around the core engine. Bypass airflow provides a substantial portion of the overall propulsive thrust generated by the gas turbine engine. During operation, bleed air may be directed from the compressor section to improve efficiency. The bleed air is typically directed into the bypass passage to intermix with bypass airflow. Obstructions and disruptive airflows can disturb bypass airflow and effect propulsive efficiencies.

Turbine engine manufacturers continuously seek further improvements to engine performance including improvements to thermal, transfer and propulsive efficiencies.

SUMMARY

A gas turbine engine according to an exemplary embodiment of this disclosure, among other possible things includes a fan including a plurality of fan blades rotatable about an engine axis, a core engine disposed within a core nacelle for driving the fan, a fan nacelle circumscribing the fan, a bypass passage defined between the core nacelle and the fan nacelle, and a duct mounted within the core nacelle defining a bleed air flow path for directing bleed air from the core engine into the bypass passage. The duct includes a plurality of airfoils that define a corresponding plurality of passages through the core nacelle bounded on one side by a suction side of one airfoil and a pressure side of an adjacent airfoil.

In a further embodiment of the foregoing gas turbine engine, the plurality of airfoils are disposed at a chord angle of between about 40° and about 55° for directing bleed airflow into the bypass passage.

In a further embodiment of any of the foregoing gas turbine engines, the chord angle is between about 45° and about 50°.

In a further embodiment of any of the foregoing gas turbine engines, the duct includes a forward side and an aft side wherein each of the forward side and the aft side include a partial airfoil shape corresponding to the shape of the plurality of airfoils.

In a further embodiment of any of the foregoing gas turbine engines, the plurality of airfoils are orientated transverse to the engine axis.

In a further embodiment of any of the foregoing gas turbine engines, the core engine includes a compressor section and the duct is disposed proximate the compressor section for exhausting bleed air flow into the bypass passage.

In a further embodiment of any of the foregoing gas turbine engines, the core nacelle includes at least one panel defining a plurality of openings and the duct includes a plurality of ducts corresponding to the plurality of openings.

A duct for defining a passage for bleed air flow according to an exemplary embodiment of this disclosure, among other possible things includes a frame defining an outer periphery, and a plurality of airfoils defining a corresponding plurality of bleed air passages. The plurality of bleed air passages through the duct are bounded on one side by a suction side of one airfoil and a pressure side of an adjacent airfoil.

In a further embodiment of the foregoing duct, each of the airfoils includes a chord angle of between about chord angle of between about 40° and about 55° for directing bleed airflow.

In a further embodiment of any of the foregoing ducts, the chord angle is between about 45° and about 50°.

In a further embodiment of any of the foregoing ducts, the duct includes a forward side and an aft side wherein each of the forward side and the aft side include a partial airfoil shape corresponding to the shape of the plurality of airfoils.

In a further embodiment of any of the foregoing ducts, the frame includes a ridge about the periphery for aligning the duct within an opening through a nacelle panel.

In a further embodiment of any of the foregoing ducts, includes an adhesive for mounting duct to the nacelle panel within the opening.

In a further embodiment of any of the foregoing ducts, the duct includes a thermoplastic material.

A method of defining a bleed air flow path into a bypass airflow passage according to an exemplary embodiment of this disclosure, among other possible things includes configuring a frame to define a desired flow area, and configuring a plurality of airfoils across the flow area to define a plurality of bleed air passages. The plurality of bleed air passages are bounded on one side by a suction side of one airfoil and a pressure side of an adjacent airfoil.

In a further embodiment of the foregoing method, each of the plurality of airfoils include a chord angle of between about 40° and about 55° for defining a bleed air flow into the bypass airflow passage.

In a further embodiment of any of the foregoing methods, the chord angle is between about 45° and about 50°.

In a further embodiment of any of the foregoing methods, includes defining the frame to include a forward side and an aft side. Each of the forward side and the aft side include a partial airfoil shape corresponding to the shape of the plurality of airfoils.

In a further embodiment of any of the foregoing methods, includes defining the bleed airflow into the bypass passage to provide a laminar flow that minimizes disruption of bypass airflow.

A gas turbine engine according to an exemplary embodiment of this disclosure, among other possible things includes a fan including a plurality of fan blades rotatable about an engine axis, a core engine disposed within a core nacelle for driving the fan. a fan nacelle circumscribing the fan, a bypass passage defined between the core nacelle and the fan nacelle, and a duct mounted within the core nacelle defining a bleed air flow path for directing bleed air from the core engine into the bypass passage. The duct includes a plurality of airfoils disposed at an acute chord angle relative to the free stream flow.

In a further embodiment of the foregoing gas turbine engine, the plurality of airfoils are disposed at a chord angle of between about 40° and about 55° for directing bleed airflow into the bypass passage.

DETAILED DESCRIPTION

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 section28as well as setting airflow entering the low pressure turbine46.

In one disclosed embodiment, the gas turbine engine20includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor44. It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines.

Referring toFIG. 2, with continued reference toFIG. 1, a bypass passage18is defined between a core nacelle16and an outer or fan nacelle14. Fan exit guide vanes98orientate airflow through the bypass passage18to improve propulsive efficiencies. The core nacelle18includes a plurality of panels66(FIG. 2). The panels66include ducts70that define openings62for bleed airflow64from the compressor section24into the bypass passage18.

The disclosed ducts70include features for directing bypass airflow64into the bypass passage18that reduces disruptions in the bypass airflow B. The example duct70is mounted within panels proximate to the low pressure compressor44, but may also be placed in other locations within the bypass flow passage where airflow is exhausted into the bypass flow B.

The duct70is provided in panels spaced circumferentially about the engine axis. In this example eight inserts are provided in four different panels66. However, other numbers of ducts70could be utilized and are within the contemplation of this disclosure. Moreover, in the disclosed example, each of the ducts70is disposed within a common plane normal to the engine axis A.

Bypass airflow B through the bypass passage18provides a substantial portion of the overall propulsive forces generated by the engine20. The core nacelle16includes an inner surface75that extends from just aft of the fan blades42, to the aft portion of the engine20. The panels66define a forward portion of the core nacelle16and in this example cover an engine compartment containing the low pressure compressor44. Bleed air64from the low pressure compressor44is in some instances exhausted into the bypass flow B to improve compressor efficiency.

Referring toFIGS. 2 and 3, the example panel66supports two ducts70. The example ducts70include a plurality of airfoils74that direct bleed air flow64into the bypass passage18. A frame72defines an outer boundary of the duct70and supports the airfoils74. The example louver assembly70is secured to the panel66using an adhesive material such as scrim supported epoxy78. It should be understood that although the disclosed panels66are supported by an adhesive, other attachment processes are also within the contemplation of this disclosure.

The duct70is fabricated from a plastic material. In this example the duct70is fabricated from a polyethermide 30% glass filled. It should be appreciated that the duct70could be fabricated from other materials that are compatible with the environment within which it is desired to operate.

Referring toFIGS. 4-8, the example duct70includes a plurality of airfoils74supported within the frame72. The ducts include a forward side80and an aft side82referenced relative to the orientation of duct70when mounted within the panel66.

The airfoils74define passages84for the bleed airflow64into the bypass passage18. The airfoils74include a pressure side90, a suction side92, a leading edge86and a trailing edge88. A pressure side90of one airfoil74defines one side of the passage84and a suction side92of an adjacent airfoil defines a second side of the passage84. The forward side80includes a shape similar to the pressure side90of the airfoils such that the passage84at the front side80is substantially the same as passages84defined between adjacent airfoils74. Moreover, the aft side82includes a shape that is substantially the same shape as the suction side92of the airfoils to provide the aft most passage84with the same profile as those passages84between adjacent airfoils74.

The duct70includes edges76that fit within the inner side of the openings68defined within the panels66(FIG. 3). The edges76orientate and align the duct70and thereby the airfoils70within the panel66that provides for alignment of the bleed airflow64into the bypass passage18. The duct70includes a curvature96that corresponds with a shape of the panels66to provide a desired fit. The matching curvature96provides a tight fit between the panel and duct70such that bleed air flow64is only directed through the passages84defined between the airfoils74.

The airfoils74include a chord angle94of between about 40° and about 55° for directing bleed airflow into the bypass passage. In another disclosed example, the chord angle94is between about 45° and about 50°. The disclosed chord angle94defines the direction of bleed airflow64into the bypass passage18to minimize disruption to the bypass flow B.

Referring toFIGS. 9,10and11, an interaction between the bypass flow B and bleed airflow64is schematically shown. The airfoils74direct airflow64such that it lays down along the inner surface75of the core nacelle16instead of flowing perpendicular to the bypass flow B. Laying down, or directing the bleed airflow transverse to the duct70with the airfoils74reduces disruptions. Guide vanes98direct airflow toward the ducts70into the bypass flow B.

Accordingly, the example duct70minimizes flow disturbances in the bypass passage18and reduces the acoustic impact of the bleed air and minimizes flow pressure losses from within the bypass passage18caused by bleed air.

Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure.