Translating nacelle wall for an aircraft tail mounted fan section

The present disclosure is directed to a fan section positioned on a tail section of an aircraft, in which the fan section defines a circumferential direction, a radial direction, and an axial direction. The fan section includes a fan and a nacelle. The fan includes a plurality of fan blades and a fan shaft, in which the plurality of fan blades are rotatable with the shaft. The nacelle includes a wall at least partially enclosing the fan. The wall includes a first portion and a second portion. The first portion translates relative to the second portion between a first, closed position in which the wall of the nacelle circumferentially encloses the fan and a second, open position in which at least a portion of the fan is unenclosed by the wall of the nacelle.

FIELD OF THE INVENTION

The present invention relates generally to a fan section of an aircraft tail section.

BACKGROUND OF THE INVENTION

Aircraft and engine designs are challenged to drive ever-increasingly toward lower fuel consumption and emissions. One known solution to increase aircraft efficiency is to mount a hybrid-electric fan section at or near the tail-section of an aircraft.

However, similar to a conventional, under-wing fan configuration, a diameter of a fan section is limited by the available ground clearance of an aircraft during takeoff roll and landing. A known solution is to remove the fan nacelle to provide an open-rotor configuration. However, removing a fan nacelle may reduce fan efficiency. Additionally, fan nacelles provide noise suppression and fan blade containment protection, without which the benefits of an open-rotor configuration may be offset by increased noise and loss of fan blade containment capability.

Therefore, a need exists for a fan section mounted to an aircraft tail section that may overcome fan diameter restrictions due to aircraft ground clearance while also providing aircraft efficiency, noise suppression, and/or fan blade containment benefits.

BRIEF DESCRIPTION OF THE INVENTION

The present disclosure is directed to a fan section positioned on a tail section of an aircraft, in which the fan section defines a circumferential direction, a radial direction, and an axial direction. The fan section includes a fan and a nacelle. The fan includes a plurality of fan blades and a fan shaft, in which the plurality of fan blades are rotatable with the shaft. The nacelle includes a wall at least partially enclosing the fan. The wall includes a first portion and a second portion. The first portion translates relative to the second portion between a first, closed position in which the wall of the nacelle circumferentially encloses the fan and a second, open position in which at least a portion of the fan is unenclosed by the wall of the nacelle.

A further aspect of the present disclosure is directed to an aircraft including a fuselage defining an aft end and an engine attached to the fuselage at the aft end of the fuselage. The engine includes a fan section defining a circumferential direction, a radial direction, and an axial direction. The fan section includes a fan, including a plurality of fan blades rotatable with a fan shaft, and a nacelle. The nacelle includes a wall, including a first portion and a second portion, at least partially enclosing the fan. The first portion translates relative to the second portion between a first, closed position in which the wall of the nacelle circumferentially encloses the fan and a second, open position in which at least a portion of the fan is unenclosed by the wall of the nacelle.

DETAILED DESCRIPTION OF THE INVENTION

A fan section positioned on an aircraft tail section including a nacelle with a translating wall is generally provided. The fan section including the nacelle with a translating wall may overcome fan section diameter restrictions due to aircraft ground clearance by translating a first portion of the nacelle wall relative to a second portion. The first portion is translatable between a first, closed position in which the wall circumferentially encloses the fan, and a second, open position in which at least a circumferential portion of the fan is unenclosed. Translating the first portion of the wall to the open position may provide sufficient ground clearance during aircraft takeoff roll and landing while enabling larger diameter fan sections to be mounted at the tail section of the aircraft. The large diameter fan section may capture and energize low momentum boundary layer fluid from a surface of a fuselage of the aircraft, thereby increasing aircraft efficiency and reducing fuel consumption and emissions.

Referring now to the drawings,FIGS. 1A, 1B, and 1Care perspective views of an exemplary embodiment of a fan section100. Specifically,FIG. 1Aprovides a perspective view of the exemplary fan section100mounted onto a tail section of an aircraft10, with a first portion of a wall in a closed position;FIG. 1Bprovides a perspective view of the exemplary fan section100, with the first portion of the wall in an open position; andFIG. 1Cprovides a perspective view of the exemplary fan section100, with one or more of a plurality of fan blades in the retracted position.

As is depicted, the fan section100generally defines an axial direction A, a radial direction R, and a circumferential direction C. Further, the fan section100includes a fan101and a nacelle110. The fan101includes a plurality of fan blades102and a shaft106. Each fan blade102defines an outer end120along the radial direction, relative to a longitudinal axis108of the fan section100. At least one fan blade102of the fan section100translates from an extended position, wherein the fan blade102is in a first radial position121(shown inFIG. 1A), to a retracted position, wherein the fan blade102is in a second radial position122(shown inFIG. 1C). Additionally, each fan blade102is rotatable with the shaft106. In one embodiment, each fan blade102is coupled to a hub104, which in turn is attached to the shaft106. As is depicted, each of the plurality of fan blades102is spaced generally along the circumferential direction. The hub104, the shaft106, and plurality of fan blades102are each rotatable about the longitudinal axis108.

The nacelle110includes a wall112that at least partially encloses the fan101. The wall112includes a first portion114and a second portion116. The first portion114translates relative to the second portion116. More specifically, the nacelle110translates the first portion114of the wall112from a first, closed position (shown inFIG. 1A) to a second, open position (shown inFIGS. 1B and 1C). When the first portion114of the wall112is in the closed position, the wall112circumferentially encloses the fan101. By contrast, when the first portion of the wall112is in the second position, at least a portion of the fan101in the circumferential direction C is unenclosed.

Referring still toFIGS. 1A, 1B and 1C, the nacelle110may translate at least a portion of the first portion114of the wall112into the second portion116of the wall112along the circumferential direction C, such that at least a segment of the first portion114is nested within the second portion116. Additionally, for the embodiment depicted, the first portion114of the wall112includes a first section162and a second section164. The first section162translates clockwise along the circumferential direction (as viewed from an aft end, such as in the view ofFIGS. 1A through 1B) to overlap, or nest within, at least a segment of the second portion116of the wall112. The second section164translates counterclockwise (as viewed from an aft end, such as in the view ofFIGS. 1A through 1B) to overlap, or nest within, a segment of the second portion116of the wall112. It should be appreciated, however, that in other exemplary embodiments, the first portion114may not include two sections (i.e., sections162,164), and instead, the first portion as a whole may translate relative to the second portion116to open up the nacelle110.

The first and second sections162,164define a split160when the first portion114translates to the open position (shown inFIGS. 1B and 1C). In one embodiment, the first section162defines a first length166along the circumferential direction and the second section164defines a second length168along the circumferential direction. In the embodiments shown inFIGS. 1A, 1B and 1C, the first length166may be approximately equal to the second length168along the circumferential direction C. The first length166and the second length168of the first portion162of the wall112may together define an approximately 120 degree segment of the wall112along the circumferential direction C when the first portion162is in the open position.

In one embodiment, the split160between the first and second sections162,164may be at about a bottom dead center (BDC) position (i.e. 180 degrees relative to a vertical reference line109). In other embodiments, the split160between the first section162and the second section164of the first portion114of the wall112may define the first length166to be unequal to the second length168along the circumferential direction C. In one embodiment in which the first length166and second length168together define a 120 degree segment of the wall112along the circumferential direction C, the split160may be defined at other than BDC such that the first length166defines at least a 60 degree segment and the second length168defines at most a 60 degree segment.

Referring to the embodiments shown inFIGS. 1A and 1B, the nacelle110may further include a nacelle locking mechanism141to lock the first section162and/or second section164to a circumferentially stationary position. For example, the nacelle locking mechanism141may be a pin attached to the second portion116of the wall112of the nacelle110and extendable into an opening defined by the first portion114of the wall112. The nacelle locking mechanism141may lock the first section162and/or the second section164of the first portion114of the wall112in a circumferentially stationary position such that the first portion114may be locked from rotating over the first and second lengths166,168when in the open position.

Referring still to the embodiments shown inFIGS. 1A, 1B, and 1C, the outer end120of each fan blade102is the outermost portion of the fan blade102along the radial direction R relative to the longitudinal axis108(e.g. the airfoil tip). In the embodiments shown inFIGS. 1A and 1B, the first radial position121refers to a position of the outer end120of the fan blade102at its outermost position. The second radial position122refers to a position of the outer end120of the fan blade102at its innermost position. For the embodiment depicted, the fan blades102each translate generally along the radial direction R between an extended position (at the first radial position121) and a retracted position (at the second radial position122). Notably, for the embodiment depicted inFIG. 1C, when in the retracted position, the outer end120of each fan blade102is positioned proximate the hub104such that the second radial position122may be approximately equal to an outer diameter of the hub104. It should be appreciated, however, that although not depicted, in other exemplary embodiments, the second radial position122may be less than the outer diameter of the hub104, such that the fan blade102is completely retracted within the hub104when in the retracted position.

As shown in the embodiments inFIGS. 1A, 1B, and 1C, the fan section100may be configured to translate the first portion114of the wall112of the nacelle110from the first, closed position (shown inFIG. 1A) to the second, open position (shown inFIGS. 1B and 1C) to provide sufficient ground clearance during takeoff roll and landing. Additionally, the outer ends120of the fan blades102may translate between the extended position (at the first radial position121, shown inFIGS. 1A and 1B) and the retracted position (at the second radial position122, shown inFIG. 1C). In one embodiment, the plurality of fan blades102each translate inwardly along the radial direction R to a retracted position representing at least a 25% decrease in a radius of the respective fan blade102from the extended position. Translating the outer end120of the fan blades102may provide clearance between the outer end120and the wall112of the nacelle110during translation of the wall112from the first, closed position (shown inFIG. 1A) to the second, open position (shown inFIGS. 1B and 1C). Additionally, translating the outer end120of the fan blades102may provide additional ground clearance for the aircraft10during takeoff or landing when the wall112is retracted to the second, open position.

Referring still to the embodiments shown inFIGS. 1A, 1B, and 1C, the fan section100may include a locking mechanism140to position the plurality of fan blades102in a circumferentially stationary position (i.e. the fan section100not rotating about the longitudinal axis108). For example, the locking mechanism140may be a pin attached to a circumferentially stationary portion of the fan section100or the fuselage12(shown inFIG. 2) and extendable into an opening defined by the hub104by an actuator. The locking mechanism140may lock the fan blades102in a circumferentially stationary position such that an extended fan blade102may be locked from rotating over the first and second lengths166,168in the open position.

Referring now toFIG. 2, a top view of an exemplary aircraft10as may incorporate various embodiments of a fan section100described herein is provided. Additionally,FIG. 3provides a port side view of the aircraft10as illustrated inFIG. 2. As shown inFIGS. 2 and 3collectively, the aircraft10includes a powerplant90, a fuselage12, and a plurality of wings20. The aircraft10further includes an engine99at an aft end18of the fuselage12. The engine99includes the fan section100, according to various embodiments shown inFIGS. 1-4and described herein, positioned aft of a vertical stabilizer30included with the fuselage12.

Referring still toFIGS. 2 and 3, the aircraft10defines a longitudinal centerline14that extends therethrough, a vertical direction V, a lateral direction L, a forward end16, and an aft end18. Moreover, the aircraft10defines a mean line15extending between the forward end16and aft end18of the aircraft10. As used herein, the “mean line” refers to a midpoint line extending along a length of the aircraft10, not taking into account the appendages of the aircraft10(such as the wings20and stabilizers discussed below).

The engine99, including the fan section100, is mounted at the aft end18of the aircraft10. More specifically, for the embodiment depicted, the fan section100is aft of the vertical stabilizer30. Further, the fan section100depicted may ingest and consume at least a portion of air forming a boundary layer over the fuselage12of the aircraft10. Specifically, for the embodiment depicted, the fan section100is fixedly connected to the fuselage12at the aft end18, such that the fan section100is incorporated into a tail section at the aft end18, and such that the mean line15extends therethrough.

Still more specifically, the fan section100may be positioned at a region of the aft end18of the fuselage12at the tail section where thick fluid boundary layers from the outer surface38of the fuselage12create a relatively large region of low momentum fluid. The placement of the fan section100at the aft end18of the fuselage12to ingest a relatively low momentum boundary layer fluid increases the efficiency of the aircraft10. The translating fan blades102of the fan section100may avoid contact with the ground during aircraft takeoff roll and landing. In another embodiment, the translating fan blades102may position the first radial position121of the outer end120of the fan blades102within 100% of the fluid boundary layer, or a lesser portion thereof to maximize efficiency. In yet another embodiment, the translating fan blades102may position the second radial position122of the outer end120of the fan blades102to avoid ground contact during takeoff roll or landing, and position the first radial position121within a portion of the fluid boundary layer that may yield maximum efficiency. For example, the translating fan blades102may position the outer end120within 60% of the fluid boundary layer, or 50%, or 45%, etc. during takeoff or landing while avoiding contact with the ground. Still further, as boundary layer conditions change, the fan section100may re-position the outer end120of the fan blades102from the first radial position121to the second radial position122to maximize efficiency. Notably, in this embodiment, or in other embodiments, the fan section100may further include a locking mechanism (not shown) for locking the fan blades102in a desired radial position. The locking mechanism may be operable with the fan blades102directly (e.g., a pin or clamp member), or alternatively may be operable with an actuator configured to translate the fan blades102.

The fuselage12extends longitudinally from the forward end16of the aircraft10towards the aft end18of the aircraft10, and includes a plurality of wings20of the aircraft attached thereto. As used herein, the term “fuselage” generally includes all of the body of the aircraft10, including an empennage or tail section of the aircraft10. The first of such wings20extends laterally outwardly with respect to the longitudinal centerline14from a port side22of the fuselage12and the second of such wings20extends laterally outwardly with respect to the longitudinal centerline14from a starboard side24of the fuselage12. Each of the wings20for the exemplary embodiment depicted includes one or more leading edge flaps26and one or more trailing edge flaps28. The fuselage12further includes the vertical stabilizer30, including a rudder flap32for yaw control, and a pair of horizontal stabilizers34each having an elevator flap36for pitch control. The fuselage12additionally includes an outer surface or skin38. It should be appreciated however, that in other exemplary embodiments of the present disclosure, the aircraft10may additionally or alternatively include any other suitable configuration of stabilizer that may or may not extend directly along the vertical direction V or horizontal/lateral direction L. Such examples include, but are not limited to, T-tail, cruciform tail, twin or triple tails, or V-tails.

The exemplary powerplant90included in the aircraft10shown inFIGS. 2 and 3includes one or more gas turbine engines92and a fan section100. The one or more gas turbine engines92to generate an amount of thrust, and further may produce power to drive the fan section100. As will be appreciated, the fan section100is, for the embodiment depicted, attached to the aft end of the aircraft, to the fuselage of the aircraft. The fan section100may ingest and re-energize a boundary layer airflow over the fuselage of the aircraft to improve a propulsive efficiency of the aircraft. In certain embodiments, the fan section100may include one or more fan blades102that translate between an extended position and a retracted position to increase a ground clearance during takeoff and landing. More specifically, in certain embodiments, the fan section100may be configured in accordance with one or more of the embodiments described above with reference toFIGS. 1A-1C.

Referring still toFIGS. 2 and 3, the powerplant90may further include an electrical powertrain94to convert, store, and distribute electrical energy to the fan section100. In one embodiment, the engines92include electrical generators to provide energy for the aircraft10and the fan section100. In another embodiment, as shown inFIG. 2, the powerplant90includes at least one electrical generator96separate from the engines92. For example, the electrical generators96may include auxiliary power units (APUs) placed within the wings20or at the empennage near the aft end18of the aircraft10. The engines92or electrical generators96transmit electrical energy to an energy storage device95. The energy storage device95may be, for example, but not limited to, capacitors, batteries, or fuel cells to store energy for later use.

The energy storage device95may be used to provide energy to operate the fan section100to generate propulsive force or to translate the outer end120of the fan blades102independently of the power output or rotational speed of the engines92. For example, the fan section100may translate the fan blades102or provide thrust while the engines92are non-operating, or while the engines92are operating at a reduced power output, using energy transmitted from the energy storage device95.

The electrical powertrain94may further include a power conditioner97, such as, for example, a rectifier, or transformer, or alternator. However, it should be understood that electrical generators96may include a power conditioning means that may obviate the inclusion of a separate power conditioner97(e.g. a variable frequency generator system as the electrical generator96). Therefore, in other embodiments, the electrical generators96may be configured in direct communication with the energy storage device95without a separate power conditioner97therebetween. The electrical powertrain94may further include a communications apparatus98to distribute energy to the fan section100and to receive and communicate load requirements to and from the fan section100.

It should be appreciated, however, that in other embodiments the present disclosure, the fan section100may instead receive mechanical energy from a powerplant90including engines92mounted at the aft end18of the fuselage12of the aircraft10, such as e.g. at the vertical stabilizer30, or the within the tail section of the fuselage12, or along the port side22or starboard side24of the fuselage12at the aft end18of the aircraft10. The engines92may transmit mechanical energy to the fan section100by mechanically coupling the fan section100to the engine92, such as, for example, by coupling the shaft106of the fan section100to a shaft and/or gearbox of the engines92. The engines92transmitting mechanical energy to the fan section100may include e.g. turbofan, turbojet, or turboprop engines that also provide propulsive thrust for the aircraft10, or a turboshaft engine, such as an APU, to also provide electrical energy to the aircraft10.