Aircraft propulsion system and method

Abstract

This application provides an aircraft propulsion system including a boundary layer intake (BLI) fan system disposed at the rear end of the aircraft. The BLI fan system includes a fan configured to rotate about an axial centerline of the BLI fan system along a first rotation direction. The BLI fan system includes blades positioned at a first pitch angle and configured to rotate together with the fan. An electric mechanism operatively coupled to the BLI fan system causes the rotation direction of the fan to change to a different second rotation direction. An actuator operatively coupled to the BLI fan system is configured to position the fan blades at different second pitch angles.

Description

[0001] This application is a divisional application of the invention patent application filed on August 21, 2018, with application number 201810953864.3 and invention title "Aircraft Propulsion System and Method". Technical Field

[0002] The topic discussed in this article concerns the propulsion systems of aircraft. Background Technology

[0003] A typical commercial aircraft generally consists of a fuselage, a pair of wings, and a propulsion system that provides thrust. The propulsion system typically includes at least two aircraft engines, such as turbofan engines. Each turbofan engine is mounted on a corresponding wing of the aircraft, e.g., in a suspended position below the wing, separate from the wing and fuselage. This configuration allows the turbofan engines to interact with a separate free-flowing airflow unaffected by the impact of the wing and / or fuselage. This configuration reduces turbulence in the air entering the inlet of each respective turbofan engine, positively impacting the aircraft's net thrust.

[0004] Drag on an aircraft, including a turbofan jet engine, affects the aircraft's net propulsive thrust. The total drag on an aircraft, including skin friction and form drag, is generally proportional to the difference between the free-flow velocity of air approaching the aircraft and the average velocity of the wake downstream of the aircraft due to drag. Systems have been proposed to counteract the effects of drag and / or improve the efficiency of turbofan jet engines. For example, some propulsion systems include boundary layer intake systems to send a relatively slow-moving portion of air forming a boundary layer across the fuselage and / or wing into the turbofan jet engine upstream of the fan section. This configuration can re-excite the boundary layer airflow downstream of the aircraft, which may have a non-uniform or distorted velocity distribution.

[0005] One problem with known aircraft propulsion systems is generating and providing reverse thrust to the aircraft to reduce its speed. For example, during landing, the aircraft moves at high speeds, which strains the braking system. Conventional thrust reverser systems that help the braking system slow or stop the aircraft involve heavy equipment, adding weight to the aircraft and reducing the system's fuel efficiency. Therefore, improved systems offer improved fuel efficiency, improved propulsion efficiency, thus reducing operating and maintenance costs and extending the aircraft's lifespan. Summary of the Invention

[0006] In one embodiment, an aircraft propulsion system includes a boundary layer intake (BLI) fan system disposed at the rear end of the aircraft. The BLI fan system includes a fan configured to rotate about an axial centerline of the BLI fan system in a first direction of rotation. The BLI fan system includes blades positioned at a first pitch angle and configured to rotate with the fan. An electric mechanism operatively coupled to the BLI fan system causes the direction of rotation of the fan to change to a different second direction of rotation. An actuator operatively coupled to the BLI fan system is configured to position the fan blades at different second pitch angles.

[0007] In one embodiment, a method includes positioning a boundary layer intake (BLI) fan system at the rear end of an aircraft propulsion system. The BLI fan system includes a fan configured to rotate about an axial centerline of the BLI fan system along a first direction of rotation. The BLI fan system includes blades positioned at a first pitch angle and configured to rotate with the fan. The method further includes changing the direction of rotation of the fan to a different second direction of rotation using an electric motor operably coupled to the BLI fan system, and changing the position of the fan blades to be positioned at different second pitch angles using an actuator operably coupled to the BLI fan system.

[0008] In one embodiment, an aircraft propulsion system includes a boundary layer intake (BLI) fan system disposed at the rear end of the aircraft. The BLI fan system includes a fan configured to rotate about an axial centerline of the BLI fan system along a first direction of rotation. The BLI fan system includes blades positioned at a first pitch angle and configured to rotate with the fan. An electric mechanism operatively coupled to the BLI fan system causes the direction of rotation of the fan to change to a different second direction of rotation. An actuator operatively coupled to the BLI fan system is configured to position the fan blades at different second pitch angles. When the fan rotates along the first direction of rotation and when the blades are positioned at the first pitch angle, the direction of airflow through the BLI fan system is configured to be along the first direction, and when the fan rotates along the second direction of rotation and when the blades are positioned at the second pitch angle, the direction of airflow through the BLI fan system is configured to be along a different second direction.

[0009] This application's technical solution 1 relates to an aircraft propulsion system, comprising: a boundary layer intake (BLI) fan system disposed at the rear end of the aircraft, the BLI fan system including a fan configured to rotate about an axial centerline of the BLI fan system along a first rotation direction, the BLI fan system including blades positioned at a first pitch angle and configured to rotate together with the fan, wherein an electric mechanism operably coupled to the BLI fan system causes the rotation direction of the fan to change to a different second rotation direction, and wherein an actuator operably coupled to the BLI fan system is configured to change the position of the fan blades to be positioned at different second pitch angles.

[0010] Technical solution 2 of this application relates to a system according to technical solution 1, wherein when the fan rotates along the first rotation direction and when the blade is positioned at the first pitch angle, the direction of the airflow through the BLI fan system is configured to be along a first direction, and wherein when the fan rotates along the second rotation direction and when the blade is positioned at the second pitch angle, the direction of the airflow through the BLI fan system is configured to be along a different second direction.

[0011] This application's technical solution 3 relates to a system according to technical solution 1, wherein each blade includes a leading edge and a trailing edge, and air is configured to flow through the BLI fan system in a direction from the leading edge toward the trailing edge.

[0012] This application relates to a system according to the present invention, wherein the motor includes a phase switch configured to change the rotation direction of the fan.

[0013] This application's technical solution 5 relates to a system according to technical solution 1, further comprising a pair of jet engines suspended below the wings of the aircraft propulsion system, and a generator electrically connected to the jet engines, the electric motor, and the actuator, wherein the generator mechanism causes the rotational energy from the jet engines to be converted into electrical energy.

[0014] This application relates to a system according to claim 1, wherein the BLI fan system is configured to provide thrust to the aircraft propulsion system.

[0015] This application's technical solution 7 relates to a system according to technical solution 6, wherein the thrust provided by the BLI fan system is configured as one or more of forward thrust or reverse thrust.

[0016] This application relates to a system according to claim 1, wherein the electric mechanism causes a change in the rotational speed of the fan.

[0017] This application's technical solution 9 relates to the system described in technical solution 1, and further includes a flare disposed at the rear end of the BLI fan system, wherein the flare is configured to guide airflow into the BLI fan system.

[0018] This application's technical solution 10 relates to a system according to technical solution 1, wherein when the fan rotates along a second rotation direction and when the blades are positioned at the second pitch angle, the movement and configuration of the aircraft are such that the airflow direction through the BLI fan system is in the same direction.

[0019] This application's technical solution 11 relates to a method comprising: placing a boundary layer intake (BLI) fan system at the rear end of an aircraft propulsion system, the BLI fan system including a fan configured to rotate about an axial centerline of the BLI fan system along a first rotation direction, the BLI fan system including blades positioned at a first pitch angle and configured to rotate together with the fan; changing the rotation direction of the fan to a different second rotation direction using an electric motor operably coupled to the BLI fan system; and changing the position of the fan blades to be positioned at different second pitch angles using an actuator operably coupled to the BLI fan system.

[0020] This application's technical solution 12 relates to a method according to technical solution 11, wherein when the fan rotates along the first rotation direction and when the blade is positioned at the first pitch angle, the direction of the airflow flowing through the BLI fan system is configured to be along a first direction, and wherein when the fan rotates along the second rotation direction and when the blade is positioned at the second pitch angle, the direction of the airflow flowing through the BLI fan system is configured to be along a different second direction.

[0021] This application's technical solution 13 relates to the method according to technical solution 11, wherein each blade includes a leading edge and a trailing edge, and wherein air is configured to flow through the BLI fan system in a direction from the leading edge toward the trailing edge.

[0022] This application's technical solution 14 relates to the method according to technical solution 11, and further includes using a phase switch of the motor including a phase switch to change the rotation direction of the fan.

[0023] This application's technical solution 15 relates to the method according to technical solution 11, further comprising suspending a pair of jet engines under the wings of the aircraft propulsion system, and electrically connecting a generator to the jet engines, the electric motor, and the actuator, wherein the generator mechanism causes the rotational energy from the jet engines to be converted into electrical energy.

[0024] This application's technical solution 16 relates to the method according to technical solution 11, wherein the BLI fan system is configured to provide thrust to the aircraft propulsion system.

[0025] This application's technical solution 17 relates to the method according to technical solution 16, wherein the thrust provided by the BLI fan system is configured as one or more of forward thrust or reverse thrust.

[0026] This application's technical solution 18 relates to the method according to technical solution 11, further comprising using the electric motor to change the rotational speed of the fan.

[0027] This application's technical solution 19 relates to the method according to technical solution 11, wherein when the fan rotates along a second rotation direction and when the blades are positioned at the second pitch angle, the movement and configuration of the aircraft are such that the airflow direction through the BLI fan system is in the same direction.

[0028] This application's technical solution 20 relates to an aircraft propulsion system, comprising: a boundary layer intake (BLI) fan system disposed at the rear end of the aircraft, the BLI fan system including a fan configured to rotate about an axial centerline of the BLI fan system along a first rotation direction, the BLI fan system including blades positioned at a first pitch angle and configured to rotate together with the fan, wherein an electric mechanism operably coupled to the BLI fan system causes the rotation direction of the fan to change to a different second rotation direction, wherein an actuator operably coupled to the BLI fan system is configured to position the fan blades at different second pitch angles, and wherein when the fan rotates along the first rotation direction and when the blades are positioned at the first pitch angle, the direction of the airflow through the BLI fan system is configured to be along a first direction, and wherein when the fan rotates along the second rotation direction and when the blades are positioned at the second pitch angle, the direction of the airflow through the BLI fan system is configured to be along a different second direction. Attached Figure Description

[0029] The subject matter of the invention will be better understood by referring to the accompanying drawings and by reading the following description of non-limiting embodiments, hereinafter referred to as the drawings:

[0030] Figure 1 A top view of an aircraft system according to one embodiment is shown;

[0031] Figure 2 An embodiment is shown. Figure 1 Side view of the aircraft system in the image;

[0032] Figure 3A cross-sectional perspective view of a boundary layer intake (BLI) fan system according to one embodiment is shown;

[0033] Figure 4A A blade having a first pitch angle is shown according to one embodiment. Figure 3 A partial perspective view of the BLI fan system in the image;

[0034] Figure 4B A blade having a first pitch angle is shown according to one embodiment. Figure 3 A partial front view of the BLI fan system in the image;

[0035] Figure 4C An embodiment is shown. Figure 4A and 4B Side view of the BLI fan system in the middle;

[0036] Figure 5A A blade with a second pitch angle is shown according to one embodiment. Figure 3 A partial perspective view of the BLI fan system in the image;

[0037] Figure 5B A blade with a second pitch angle is shown according to one embodiment. Figure 3 A partial front view of the BLI fan system in the image;

[0038] Figure 5C An embodiment is shown. Figure 5A and 5B Side view of the BLI fan system; and

[0039] Figure 6 A flowchart of a method according to one embodiment is shown. Detailed Implementation

[0040] One or more embodiments of the subject matter of this invention relate to systems and methods for efficiently providing thrust to an aircraft propulsion system. The system and method alter the rotation direction of a fan in a boundary layer intake (BLI) fan system. The system and method use an electric motor to change the position of the fan blades. By altering the rotation direction of the BLI fan system's fan and the position of its blades, the system and method change the direction of the airflow through the BLI fan system. This change in the airflow direction allows the BLI fan system to provide both forward and reverse thrust to the aircraft propulsion system. One technical advantage of the subject matter described herein is the ability to manage the desired amount and direction of thrust that can be provided to the aircraft system by the BLI fan system. Another technical advantage of the subject matter described herein is the ability to improve the deceleration of the aircraft system during landing, deceleration, etc. (e.g., faster deceleration), thereby extending the component life of the aircraft's braking system.

[0041] As used herein, the terms “first,” “second,” and “third” are used interchangeably to distinguish one component from another and are not intended to indicate the location or importance of individual components. The terms “front” and “rear” refer to the location of a component based on its actual or intended direction of travel. For example, “front” may refer to the front of an aircraft based on its intended direction of travel, and “rear” may refer to the rear of an aircraft based on its intended direction of travel. Furthermore, the terms “upstream” and “downstream” refer to the relative directions of fluid flow in a fluid path. For example, “upstream” refers to the direction from which fluid flows, while “downstream” refers to the direction to which fluid flows.

[0042] Figure 1 A top view of an aircraft system 10 according to one embodiment is shown. Figure 2 A side view of an aircraft system 10 according to one embodiment is shown. This document will describe it in detail together. Figure 1 and 2 .

[0043] Aircraft system 10 includes an aircraft 13 having a fuselage 12 extending longitudinally between a front end 16 and a rear end 18 of the aircraft 13. The aircraft 13 defines a longitudinal centerline 14 extending through the vertical direction V and the lateral direction L. The aircraft 13 defines a bisector 15 extending between the front end 16 and the rear end 18 of the fuselage 12. As used herein, the term "fuselage" generally includes the entire body of the aircraft 13, such as the tail fin. Furthermore, as used herein, "bisector" refers to a midpoint line extending along the length of the aircraft 13, without considering appendages of the aircraft system 10 (e.g., wings 20 and stabilizers, which will be described in more detail herein).

[0044] The aircraft 13 includes a pair of wings 20. A first wing extends laterally along the port side 22 of the fuselage 12 in a lateral direction L, and a second wing extends laterally along the right chord side 24 of the fuselage 12. Each wing 20 includes one or more leading-edge flaps 26 and one or more trailing-edge flaps 28. Optionally, the wings 20 may not include leading-edge flaps 26 and / or trailing-edge flaps 28. The aircraft 13 includes a vertical stabilizer 30 and a pair of horizontal stabilizers 34 at its rear end 18. The vertical stabilizer 30 has rudder flaps 32 for yaw control, and each horizontal stabilizer 34 has elevator flaps 36 for pitch control of the aircraft system 10. The fuselage 12 includes an outer surface or skin 38. Figure 1 and 2 An embodiment of the aircraft system 10 is shown. Alternatively, the aircraft system 10 may include any alternative configuration such as a stabilizer, wing, etc., which may extend from the aircraft 13 away from the centerline 14 and / or the bisector 15 in the vertical direction V, the horizontal or lateral direction L, or any alternative direction.

[0045] Aircraft system 10 includes aircraft propulsion system 100. Aircraft propulsion system 100 includes a pair of aircraft engines, at least one mounted on each of a pair of wings 20, and a rear engine. In the illustrated embodiment, the aircraft propulsion system 100 engines may be configured as turbofan jet engines 102, 104, suspended below the wings 20 in an underwing configuration. Alternatively or additionally, jet engines 102, 104 may be located at different positions between the front end 16 and the rear end 18 of the aircraft 13, may be located above the wings 20, or may be located at any alternative position. Optionally, aircraft propulsion system 100 may include any number and / or configuration of jet engines, including non-limiting examples of turbofans, turboprops, turbojet engines, etc. For example, aircraft propulsion system 100 may not include underwing-mounted jet engines 102, 104 and may include any alternative energy source (e.g., a power source) for powering aircraft system 10.

[0046] The rear engine is a fan configured to draw in and consume air forming the boundary layer on the fuselage 12 of the aircraft 13. The rear engine may be referred to herein as a boundary layer intake (BLI) fan system 106. The BLI fan system 106 is mounted to the fuselage 12 at a location aft of the wing 20 and / or jet engines 102, 104, such that a bisector 15 extends through the BLI fan system 106. For example, this configuration positions the central axis of the BLI fan system 106 above the centerline 14 along the vertical direction V. Furthermore, the BLI fan system 106 may be mounted parallel to or at an angle to the centerline 14 along the lateral direction L. For example, the centerline of the BLI fan system 106 may define an angle with the centerline 14. The BLI fan system 106 is fixedly connected to the fuselage 12 at the rear end 18, such that the BLI fan system 106 is incorporated into or mixed with the tail section of the aircraft system 10 at the rear end 18. Alternatively, the BLI fan system 106 can be positioned at any alternative location near the rear end 18 of the aircraft 13.

[0047] Jet engines 102, 104 are configured to provide power to generator 108 and / or energy storage device 110 of aircraft propulsion system 100. For example, one or more jet engines 102, 104 may be configured to provide mechanical power from a rotating shaft (e.g., a low-pressure shaft or a high-pressure shaft) to generator 108. In the illustrated embodiment, jet engines 102, 104 are operatively coupled to a single generator 108. Alternatively, jet engines 102, 104 may be operatively coupled to two or more generators. Generator 108 may convert the rotational energy generated by jet engines 102, 104 into electrical energy. Additionally or alternatively, generator 108 may convert mechanical energy into electrical energy and provide the converted electrical energy to energy storage device 110.

[0048] The aircraft propulsion system 100 includes an electric motor 40 operatively coupled to the BLI fan system 106. For example, the electric motor 40 can electrically control one or more operations of the BLI fan system 106. Optionally, the electric motor 40 can be operatively coupled to one or more components of the BLI fan system 106. Furthermore, a generator 108 and / or an energy storage device 110 are electrically coupled to the electric motor 40. For example, the generator 108 can provide converted power to the electric motor 40. The electric motor 40 can use the power generated by the generator 108 and supplied to the electric motor 40 to control the operation of the BLI fan system 106.

[0049] In the illustrated embodiment, the generator 108, energy storage device 110, and electric motor 40 are separate from the jet engines 102 and 104. Alternatively, one or more of the generator 108, energy storage device 110, or electric motor 40 may be constructed together with the jet engines 102 and 104. Optionally, the aircraft propulsion system 100 may include multiple generators 108. Each generator 108 may be operatively coupled to each jet engine 102 and 104. Optionally, one or more jet engines 102 and 104 may be high-bypass turbofan jet engines, wherein the generator is driven by one or more shafts of the turbofan jet engine.

[0050] Figure 3 A cross-sectional perspective view of a BLI fan system 106 according to one embodiment is shown. The BLI fan system 106 is mounted to the aircraft 13 near the rear end 18 of the aircraft system 10. The BLI fan system 106 defines a radial direction R and an axial direction A. The axial direction A extends along a longitudinal axial centerline 202, which extends through the center of the BLI fan system 106 between the front end 248 and the rear end 250 of the outer nacelle 206. The outer nacelle 206 includes an inlet 220 at the front end 248 and an outlet 230 at the rear end 250. For example, during cruise operation of the aircraft system 10, boundary layer air may flow into the inlet 220 at the front end 248 and out of the BLI fan system 106 from the outlet 230 at the rear end 250 of the outer nacelle 206. For example, the outer nacelle 206 defines a pathway through which air is configured to flow.

[0051] Aircraft Propulsion System 100 ( Figure 1 and 2 The system also includes an actuator 218 operatively coupled to the BLI fan system 106. The actuator 218 may be an electric motor, mechanical actuator, hydraulic actuator, hydraulic pump, etc. In the illustrated embodiment, a single actuator 218 is operatively coupled to the BLI fan system 106. Alternatively, the propulsion system 100 may have one or more actuators 218 operatively coupled to the BLI fan system 106. The actuator 218 is located within the fuselage 12 at the rear end 18 of the aircraft system 10. Alternatively, the actuator 218 may be located at alternative locations within the aircraft system 10.

[0052] Actuator 218 electrically and / or mechanically controls the operation of BLI fan system 106. Additionally, generator 108 and / or energy storage device 110 are electrically connected to actuator 218. For example, generator 108 can supply converted power to actuator 218. Actuator 218 can use the power generated by generator 108 and supplied to actuator 218 to control one or more operations of BLI fan system 106.

[0053] BLI fan system 106 includes inlet guide vanes 208 and outlet guide vanes 222. Optionally, in one or more embodiments, BLI fan system 106 may not have inlet guide vanes 208 and / or outlet guide vanes 222. Alternatively, inlet guide vanes 208 may be referred to as inlet guide vanes 208, and outlet guide vanes 222 may be referred to as outlet guide vanes 222. For example, inlet guide vanes 208 and outlet guide vanes 222 may be similar in shape and size to or unique to fan blades 212. Inlet guide vanes 208 are fixedly coupled to outer nacelle 206 and are positioned near the front end 248 of outer nacelle 206 along axial centerline 202. Outlet guide vanes 222 are fixedly coupled to outer nacelle 206 and are positioned near the rear end 250 of outer nacelle 206 along axial centerline 202. For example, a fan 210 is positioned between inlet guide vanes 208 and outlet guide vanes 222. Alternatively or concurrently, the inlet guide vane 208 and / or the outlet guide vane 222 may be variable guide vanes. One or more of the inlet guide vanes 208 and / or one or more of the outlet guide vanes 222 may rotate about a guide vane axis (not shown) corresponding to each inlet guide vane 208 and / or each outlet guide vane 222. For example, an actuator 218 may be operatively coupled to the inlet guide vane 208 and / or the outlet guide vane 222 and may provide electrical or mechanical power to rotate the inlet guide vane 208 and / or the outlet guide vane 222 from a first pitch angle to a different second pitch angle. Optionally, a first actuator may be operatively coupled to the inlet guide vane 208 and control the position of the inlet guide vane 208, and different second actuators may be operatively coupled to the outlet guide vane 222 and control the position of the outlet guide vane 222.

[0054] The inlet guide vane 208 and outlet guide vane 222 are shaped, sized, and oriented within the outer nacelle 206 to guide and / or regulate the airflow through the BLI fan system 106. For example, compared to a BLI fan system 106 without inlet guide vane 208 and / or outlet guide vane 222, the inlet guide vane 208 and outlet guide vane 222 can improve the efficiency of the BLI fan system 106, reduce air distortion entering the BLI fan system 106, and add strength and / or stiffness to the BLI fan system 106, etc.

[0055] BLI fan system 106 includes a fan 210 comprising a rotating fan shaft 216 rotatable about an axial centerline 202 within an outer nacelle 206. BLI fan system 106 includes a plurality of fan blades 212 spaced substantially evenly relative to each outer fan blade about the axial centerline 202. In one or more embodiments, the fan blades 212 may be fixedly attached to the fan shaft 216 or rotatably attached to the fan shaft 216. For example, the fan blades 212 may be attached to the fan shaft 216 such that the pitch angle of each blade 212 can be changed (e.g., aligned or disaligned) by an actuator 218 to guide the blades 212 to rotate about or about the blade axis of each fan blade 212. In one or more embodiments, the pitch angle of the fan blades 212 may be changed by the actuator 218, by a hydraulic pump (not shown), or by an alternative mechanism. Compared to a BLI fan system 106 that does not change the pitch of the fan blades 212, changing the pitch of multiple fan blades 212 can improve the efficiency of the BLI fan system 106, allowing the BLI fan system 106 to achieve the desired thrust, etc. For example, the BLI fan system 106 can be called a variable pitch fan. The pitch angle of the fan blades 212 will be discussed in more detail below.

[0056] The fan shaft 216 of the BLI fan system 106 is operably connected to the motor 40. Figure 1 and 2 (In the middle). The electric motor 40 can change one or more of the rotational speed of the fan shaft 216, the rotational direction of the fan shaft 216 of the fan 210, etc. Compared to the BLI fan system 106 which does not change the rotational speed and / or direction of the fan 210, changing the rotational direction and / or speed of the fan 210 can improve the efficiency of the aircraft propulsion system 100, improve the efficiency of the BLI fan system 106, and allow the BLI fan system 106 to achieve the desired direction and / or amount of thrust, etc. The rotational direction of the fan 210 will be discussed in more detail below.

[0057] BLI fan system 106 includes a tail cone 224 and a nozzle 226. The nozzle 226 is positioned between the outer nacelle 206 and the tail cone 224 at the rear end 250 of the nacelle 206. The tail cone 224 is shaped and sized to guide airflow through the outlet 230 of the BLI fan system 106. The nozzle 226 generates thrust from the airflow through the BLI fan system 106, and the tail cone 224 is shaped to minimize drag on the BLI fan system 106. Alternatively, the tail cone 224 may have alternative shapes and / or sizes and may be positioned at alternative locations within the BLI fan system 106 (e.g., between the inlet 220 and the outlet 230), etc.

[0058] Figure 4AA partial perspective view of a BLI fan system 106 having fan blades 212 positioned at a first pitch angle, according to one embodiment, is shown. Figure 4B A partial front view of a BLI fan system 106 having blades 212 positioned at a first pitch angle, according to one embodiment, is shown. Figure 4C A side view of the BLI fan system 106 is shown. It will be described in detail together. Figure 4A , 4B and 4C.

[0059] Fan 210 and a plurality of fan blades 212 rotate about an axial centerline 202 of BLI fan system 106 in a first rotational direction 402. Each fan blade 212 has a pressure side 432 and a suction side 434 opposite to the pressure side 432. The pressure side 432 and the suction side 434 are interconnected by a leading edge 430 and a trailing edge 440 opposite to the leading edge 430. Between the leading edge 430 and the trailing edge 440, the pressure side 432 is generally concave and the suction side 434 is generally convex. For example, the generally concave pressure side 432 and the generally convex suction side 434 provide aerodynamic surfaces on which fluid flows over BLI fan system 106.

[0060] exist Figure 4A and 4B In one embodiment, the blade 212 is positioned at a first pitch angle 436 relative to the blade axis 214 corresponding to each blade 212. For example, as Figure 4B As shown, the first pitch angle 436 may be less than 90 degrees to the horizontal axis. For example, the first pitch angle 436 may be defined as the angle between the horizontal axis and the blade chord.

[0061] When the blade 212 is positioned at the first pitch angle 436 and the fan 210 is positioned around the axial centerline 202 of the BLI fan system 106 along the first rotation direction 402 (e.g., along...), Figure 4A When the airflow rotates clockwise (within the system), air flows through the BLI fan system 106 along the first airflow direction 404. The airflow along the first airflow direction 404 enters the inlet 220 at the front end 248 of the outer nacelle 206 and exits the BLI fan system 106 through the outlet 230 at the rear end 250 of the outer nacelle 206. Furthermore, as the airflow flows through the BLI fan system 106 along the first airflow direction 404, the inlet guide vane 208 and the outlet guide vane 222 (… Figure 3 (As shown) can be positioned at the first inlet pitch angle and the first outlet pitch angle (not shown), respectively.

[0062] Air flowing along the first airflow direction 404 flows in a direction from the leading edge 430 of each blade 212 to the trailing edge 440 of each blade 212. For example, the first relative velocity 410 of the airflow moving along the first airflow direction 404 is configured to be directed toward the leading edge 430 of each blade 212.

[0063] Fan blades 212 positioned at a first pitch angle 436 and fan 210 rotating along a first rotation direction 402 generate forward thrust 408, which propels the aircraft system 10 along its forward movement direction 406. For example, during operation of the aircraft system 10 in cruise and / or acceleration (e.g., during takeoff), the BLI fan system 106 provides forward thrust 408 to the aircraft system 10. The BLI fan system 106 assists the jet engines 102, 104 in moving the aircraft system 10 along its travel direction in the forward movement direction 406.

[0064] Figure 5A Figures 5B and 5C show the changes in the position of blade 212 and the changes in the rotation direction of fan 210. Figure 5A A partial perspective view of a BLI fan system 106 having blades 212 positioned at different second pitch angles according to one embodiment is shown. Figure 5B A partial front view of a BLI fan system 106 having blades 212 positioned at a second pitch angle, according to one embodiment, is shown. Figure 5C A side view of the BLI fan system 106 is shown. It will be described in detail together. Figure 5A , 5B and 5C.

[0065] exist Figure 5A and 5B In this embodiment, the blades 212 are positioned at different second pitch angles 536 relative to the blade axis 214 corresponding to each blade 212. An actuator 218 of the aircraft propulsion system 100 operably controls the blades 212 to change the position of the blade 212's pitch angle from a first pitch angle 436 to a second pitch angle 536. For example, the actuator 218 may include a switch (not shown) and alternative electrical or mechanical components that electrically or mechanically control the position of the blades 212. The switch may be manually controlled by an onboard operator of the aircraft system 10, by an offboard operator of the aircraft system 10, or autonomously controlled by one or more systems of the aircraft system 10. Each blade 212 rotates about each corresponding blade axis 214 from a position of the first pitch angle 436 to a position of the second pitch angle 536 (e.g., Figure 5A The clockwise direction shown is 514). For example, generator 108 ( Figure 1The mechanical energy from jet engines 102 and 104 can be converted into electrical energy used by actuator 218 to change the position of blades 212. Alternatively, a hydraulic pump or alternative mechanism can change the position of blades 212. Optionally, each blade 212 can be aligned with... Figure 5A The rotation direction 514 shown is opposite to the rotation from the position of the first pitch angle 436 to the position of the second pitch angle 536. For example, the blade 212 can rotate in a counterclockwise direction.

[0066] The motor 40 rotates the fan 210 about the axial centerline 202 of the BLI fan system 106 from a first rotation direction 402 (e.g., Figure 4A The clockwise rotation direction 502 changes to a different second rotation direction (for example, shown as...). Figure 5A (Counterclockwise in the context of the fan rotation). For example, motor 40 may include one or more phase switches (not shown), or alternative electrical components, that can electrically change the direction of fan rotation. The phase switches may be manually operated by an onboard operator of aircraft system 10, by an offboard operator of aircraft system 10, or autonomously controlled by one or more systems of aircraft system 10. Optionally, motor 40 may change the direction of fan rotation 210 to a second direction of rotation 502, and may increase and / or decrease the rotational speed of fan 210. For example, motor 40 may guide the fan speed to decrease (e.g., to a predetermined lower fan speed limit threshold, stop, etc.), and then change the direction of fan rotation to the second direction of rotation 502. Optionally, the direction of fan rotation may remain unchanged when blades 212 are configured to rotate in a counterclockwise direction (e.g., opposite to the direction of rotation 514).

[0067] Optionally, in one or more embodiments, actuator 218 is operatively controllable to change the position of the pitch angle of inlet guide vane 208 and / or outlet guide vane 222 to a different second pitch angle. For example, actuator 218 may include one or more switches (not shown) or alternative electrical components that electrically control the position of inlet guide vane 208 and / or outlet guide vane 222. Actuator 218 can change the position of inlet guide vane 208 and outlet guide vane 222 from a first inlet pitch angle to a different second inlet pitch angle, and from a first outlet pitch angle to a different second outlet pitch angle, respectively. For example, inlet guide vane 208 may have a first inlet pitch angle that is unique to the first outlet pitch angle of outlet guide vane 222 and unique to the first pitch angle 436 of fan blade 212. Furthermore, actuator 218 can change the position of inlet guide vane 208 to a second inlet pitch angle, which is unique to the second outlet pitch angle of outlet guide vane 222 and unique to the second pitch angle 536 of fan blade 212. For example, actuator 218 can change the positions of inlet guide vane 208, outlet guide vane 222, and fan blade 212 to unique and / or common positions. Optionally, propulsion system 100 may include three actuators 218 operably controlling the positions of inlet guide vane 208, fan blade 212, and outlet guide vane 222. For example, a first actuator may be operably coupled to fan blade 212 to change the position of the pitch angle of fan blade 212, a second actuator may be operably coupled to inlet guide vane 208 to change the position of the pitch angle of inlet guide vane 208, and a third actuator may be operably coupled to outlet guide vane 222 to change the position of the pitch angle of outlet guide vane 222. Alternatively, actuator 218 may include three switches. For example, a first switch may be operatively connected to fan blade 212 to change the position of the pitch angle of fan blade 212, a second switch may be operatively connected to inlet guide vane 208 to change the position of the pitch angle of inlet guide vane 208, and a third switch may be operatively connected to outlet guide vane 222 to change the position of the pitch angle of outlet guide vane 222.

[0068] Changing the position of the blades 212 of the BLI fan system 106 from a first pitch angle 436 to a second pitch angle 536, and changing the rotation direction of the fan 210 from a first rotation direction 402 to a second rotation direction 502, changes the airflow direction through the BLI fan system 106 from a first airflow direction 404 to a different second airflow direction 504. The airflow along the first airflow direction 504 flows into the outlet 230 at the rear end 250 of the outer nacelle 206, and flows out of the BLI fan system 106 through the inlet 220 at the front end 248 of the outer nacelle 206.

[0069] The air flowing along the second airflow direction 504 flows in a direction from the leading edge 430 of the blade 212 to the trailing edge 440 of each blade 212. For example, the second relative velocity 510 of the airflow moving along the second airflow direction 504 is configured to be directed toward the leading edge 430 of each blade 212.

[0070] Fan blades 212 positioned at a second pitch angle 536 and fan 210 rotating in a second rotation direction 502 generate a counter-thrust 508 that counteracts the propulsion of the aircraft system 10 in the forward movement direction 406 of the aircraft system 10. For example, during aircraft system 10 operation at landing, BLI fan system 106 provides counter-thrust 508 to aircraft system 10. BLI fan system 106 assists the braking system (not shown) of aircraft system 10 by slowing, reducing, or stopping the forward movement 406 of aircraft system 10.

[0071] like Figure 4C As shown, when fan 210 rotates along the first rotation direction 402, the blades are positioned at the first pitch angle 436, and air flows through the BLI fan system 106 along the first airflow direction 404, the first airflow direction 404 through the BLI fan system 106 is the opposite direction to the movement direction 406 of the aircraft system 10. Alternatively, as Figure 5C As shown, when the fan 210 rotates along the second rotation direction 502, the blades are positioned at the second pitch angle 536, and air flows through the BLI fan system 106 along the second airflow direction 504, the second airflow direction 504 passing through the BLI fan system 106 is in the same direction as the movement direction 406 of the aircraft system 10. Optionally, when the airflow passes through the BLI fan system 106 along the first airflow direction 404, the inlet guide vane 208 and the outlet guide vane 222 may be positioned at a first inlet pitch angle and a first outlet pitch angle, respectively (e.g., a first inlet pitch angle that may be the same as or different from the first pitch angle 436, and a first outlet pitch angle that may be the same as or different from the first pitch angle 436). When the airflow passes through the BLI fan system 106 along the second airflow direction 504, the inlet guide vane 208 and the outlet guide vane 222 may be positioned at different second inlet pitch angles and different second outlet pitch angles, respectively (e.g., a second inlet pitch angle that may be the same as or different from the second pitch angle 536, and a second outlet pitch angle that may be the same as or different from the second pitch angle 536).

[0072] In one or more embodiments, the BLI fan system 106 includes a flare 420 disposed at the rear end 250 of the outer nacelle 206. The flare 420 extends around the perimeter of the outer nacelle 206. The flare 420 is shaped and sized to direct an airflow flowing in a second airflow direction 504 into the outlet 230 of the BLI fan system 106. For example, the flare 420 includes an inner flare surface 422 disposed near the outlet 230 of the outer nacelle 206, and an outer flare surface 424 disposed distal to the inner flare surface 422 in the outer nacelle 206. The outer flare surface 424 has a diameter larger than that of the inner flare surface 422. For example, when the BLI fan system 106 provides reverse thrust (e.g., reverse thrust 508) to the aircraft system 10, the flare 420 can direct non-boundary layer air into the outlet 230 of the BLI fan system 106.

[0073] Figure 6 A flowchart illustrating one embodiment of a method 600 for providing a propulsion system for an aircraft is shown. At 602, a boundary layer intake (BLI) fan system (e.g., BLI fan system 106) is positioned at the rear end of the aircraft system. The BLI fan system includes a fan 210 comprising a plurality of blades 212. The fan 210, having blades 212, rotates about an axial centerline 202 of the BLI fan system 106. The BLI fan system 106 consumes or ingests boundary layer air from the aircraft system 10. Alternatively or additionally, the BLI fan system 106 may be positioned at alternative locations on the aircraft system and may consume or ingest free-flow air or air not twisted by the fuselage, wings, etc., of the aircraft system. The BLI fan system 106 provides forward and reverse thrust to the aircraft system 10. For example, when the aircraft system 10 takes off, cruises, or accelerates, the BLI fan system 106 may provide forward thrust (e.g., Figure 4C The forward thrust 408 is transmitted to the aircraft system 10, and the BLI fan system 106 can provide reverse thrust (e.g., when the aircraft system 10 lands, decelerates, etc.) to the aircraft system 10. Figure 5C The reverse thrust 508) is sent to the aircraft system 10.

[0074] At 604, the electric motor 40 is operatively connected to the BLI fan system 106. For example, the electric motor 40 may be located within the fuselage 12 of the aircraft system 10 and electrically connected to the BLI fan system 106. Furthermore, the actuator 218 is operatively connected to the BLI fan system 106. For example, the actuator 218 may be located within the fuselage 12 of the aircraft system 10 and electrically connected to the BLI fan system 106. In one or more embodiments, the electric motor 40 and the actuator 218 may receive electrical energy from the generator 108, energy storage device 110, etc. For example, the generator 108 may convert mechanical energy from jet engines 102, 104 into electrical energy that can be used by the electric motor 40 and / or the actuator 218. Alternatively, the electric motor 40 and / or the actuator 218 may receive electrical energy from alternative power sources such as batteries. Furthermore or alternatively, batteries may provide power to the aircraft during takeoff, provide power to the electric motor, etc. In one or more embodiments, the propulsion system 100 may include a number of electric motors 40, actuators 218, hydraulic pumps, or any alternative power source operatively coupled to the BLI fan system 106.

[0075] At 606, the motor 40 changes the rotation direction of the fan 210 from a first rotation direction 402 to a different second rotation direction 502. For example, the motor 40 may include a phase switch, or any alternative component capable of changing the rotation direction of the fan 210. The motor 40 controls the rotation direction of the fan 210. For example, the motor 40 may reduce the rotational speed of the fan 210 while it is rotating in the first rotational direction 402 until the rotational speed of the fan 210 reaches a predetermined threshold, stops, etc. The phase switch changes the phase of the motor 40 to change the rotational direction of the fan 210 to the second rotational direction 502. The motor 40 may increase or decrease the rotational speed of the fan 210 rotating in the first rotational direction 402 or the second rotational direction 502 until the rotational speed of the fan 210 reaches a desired operating speed. The fan 210 rotating at the first rotational speed 402 provides forward thrust 408 to the aircraft system 10. The fan 210, which rotates in the second rotation direction 502, provides reverse thrust 508 to the aircraft system 10.

[0076] At 608, actuator 218 changes the position of the blades 212 of the BLI fan system 106 from a first pitch angle 436 to a different second pitch angle 536. For example, actuator 218 guides the blades 212 to rotate about the corresponding blade axis 214 of each blade 212 to the position of the second pitch angle 536. Optionally, the position of the blades 212 of the BLI fan system 106 can be changed from the first pitch angle 436 to the second pitch angle 536 and / or from the second pitch angle 536 to the first pitch angle 436 by mechanical actuators, hydraulic actuators, etc. The blades 212 positioned at the first pitch angle 436 provide forward thrust 408 to the aircraft system 10. The blades 212 positioned at the second pitch angle 536 provide reverse thrust 508 to the aircraft system 10.

[0077] Optionally, actuator 218 can change the position of inlet guide vanes 208 and / or outlet guide vanes 222. For example, by guiding inlet guide vanes 208 to rotate about a corresponding guide vane axis (not shown) of each inlet guide vane 208 to a second inlet pitch angle, actuator 218 can change the position of inlet guide vanes 208 from a first inlet pitch angle to a different second inlet pitch angle. Furthermore, actuator 218 can change the position of outlet guide vanes 222 from a first outlet pitch angle to a different second outlet pitch angle by guiding outlet guide vanes 222 to rotate about a corresponding guide vane axis (not shown) of each outlet guide vane 222 to a second outlet pitch angle.

[0078] In one or more embodiments, the motor 40 may change one or more of the rotational speed or direction of the fan 210 from a first rotational direction 402 to a second rotational direction 502, but the actuator 218 may not change the position of the blades 212. Alternatively, the actuator 218 may change the position of the blades 212 from a first pitch angle 436 to a second pitch angle 536, but the motor 40 may not change the rotational direction and / or speed of the fan 210. Optionally, in one or more embodiments, the pitch angle of the exit guide vanes and / or inlet guide vanes may change from a reverse thrust operating mode to a forward thrust operating mode / from a forward thrust operating mode to a reverse thrust operating mode. Optionally, the propulsion system 100 may include a plurality of BLI fan systems 106. For example, the plurality of BLI fan systems 106 may control different components or systems to work together to provide forward thrust or reverse thrust to the aircraft system 10. One or more of the plurality of BLI fan systems 106 may change one or more of the rotational direction of the fan 210 or the position of the blades 212. For example, the first BLI fan system 106 may only change the rotation direction and speed of the fan 210, and the second BLI fan system 106 may change the position of the blades 212. Optionally, one or more BLI fan systems 106 may have any uniform or unique combination of changes in the rotation of the fan 210 and / or the position of the blades 212.

[0079] In the illustrated embodiment, propulsion system 100 is used to provide thrust to an aircraft system. Alternatively or additionally, propulsion system 100 can be used to provide propulsion to any alternative system, including, but not limited to, water systems, vehicle systems, clean energy systems, etc.

[0080] In one embodiment of the subject matter described herein, the aircraft propulsion system includes a boundary layer intake (BLI) fan system disposed at the rear end of the aircraft. The BLI fan system includes a fan configured to rotate about an axial centerline of the BLI fan system in a first direction of rotation. The BLI fan system includes blades positioned at a first pitch angle and configured to rotate together with the fan. An electric mechanism operatively coupled to the BLI fan system causes the direction of rotation of the fan to change to a different second direction of rotation. An actuator operatively coupled to the BLI fan system is configured to position the fan blades at different second pitch angles.

[0081] Optionally, when the fan rotates in a first direction of rotation and when the blades are positioned at a first pitch angle, the direction of the airflow through the BLI fan system is configured to be along a first direction, and when the fan rotates in a second direction of rotation and when the blades are positioned at a second pitch angle, the direction of the airflow through the BLI fan system is configured to be along a different second direction.

[0082] Optionally, each blade includes a leading edge and a trailing edge, wherein air is configured to flow through the BLI fan system in a direction from the leading edge to the trailing edge.

[0083] Optionally, the motor includes a phase switch, wherein the phase switch is configured to change the direction of rotation of the fan.

[0084] Optionally, the system includes a pair of jet engines suspended under the wings of the aircraft propulsion system, and also includes a generator, an electric motor, and an actuator electrically connected to the jet engines, wherein the generator causes the rotational energy from the jet engines to be converted into electrical energy.

[0085] Optionally, the BLI fan system is configured to provide thrust to the aircraft propulsion system. Optionally, the thrust provided by the BLI fan system is configured as one or more of forward thrust or reverse thrust.

[0086] Alternatively, the electric mechanism causes a change in the fan's rotational speed.

[0087] Optionally, the system includes a flare located at the rear end of the BLI fan system, wherein the flare is configured to guide airflow into the BLI fan system.

[0088] Alternatively, when the fan rotates in the second rotation direction and when the blades are positioned at the second pitch angle, the aircraft moves and is configured such that the direction of the airflow through the BLI fan system is the same.

[0089] In one embodiment of the subject matter described herein, a method includes positioning a boundary layer intake (BLI) fan system at the rear end of an aircraft propulsion system. The BLI fan system includes a fan configured to rotate about an axial centerline of the BLI fan system along a first direction of rotation. The BLI fan system includes blades positioned at a first pitch angle and configured to rotate with the fan. The method further includes changing the direction of rotation of the fan to a different second direction of rotation using an electric motor operably coupled to the BLI fan system, and changing the position of the fan blades to be positioned at different second pitch angles using an actuator operably coupled to the BLI fan system.

[0090] Optionally, when the fan rotates in a first direction of rotation and when the blades are positioned at a first pitch angle, the direction of the airflow through the BLI fan system is configured to be along a first direction, and when the fan rotates in a second direction of rotation and when the blades are positioned at a second pitch angle, the direction of the airflow through the BLI fan system is configured to be along a different second direction.

[0091] Optionally, each blade includes a leading edge and a trailing edge, wherein air is configured to flow through the BLI fan system in a direction from the leading edge to the trailing edge.

[0092] Optionally, the method further includes changing the rotation direction of the fan using a phase switch of the motor.

[0093] Optionally, the method also includes suspending a pair of jet engines under the wings of the aircraft propulsion system, and electrically connecting a generator to the jet engines, electric motors, and actuators, wherein the generator mechanism causes the rotational energy from the jet engines to be converted into electrical energy.

[0094] Optionally, the BLI fan system is configured to provide thrust to the aircraft propulsion system. Optionally, the thrust provided by the BLI fan system is configured as one or more of forward thrust or reverse thrust.

[0095] Alternatively, one method may also include using an electric motor to change the rotational speed of the fan.

[0096] Optionally, the method further includes providing a flare at the rear end of the BLI fan system, wherein the flare is configured to guide airflow into the BLI fan system.

[0097] Alternatively, when the fan rotates in the second rotation direction and when the blades are positioned at the second pitch angle, the aircraft moves and is configured such that the direction of the airflow through the BLI fan system is the same.

[0098] In one embodiment of the subject matter described herein, an aircraft propulsion system includes a boundary layer intake (BLI) fan system disposed at the rear end of the aircraft. The BLI fan system includes a fan configured to rotate about an axial centerline of the BLI fan system along a first direction of rotation. The BLI fan system includes blades positioned at a first pitch angle and configured to rotate together with the fan. An electric mechanism operatively coupled to the BLI fan system causes the direction of rotation of the fan to change to a different second direction of rotation, and an actuator operatively coupled to the BLI fan system is configured to position the fan blades at different second pitch angles. When the fan rotates along the first direction of rotation and when the blades are positioned at the first pitch angle, the direction of airflow through the BLI fan system is configured to be along the first direction, and when the fan rotates along the second direction of rotation and when the blades are positioned at the second pitch angle, the direction of airflow through the BLI fan system is configured to be along a different second direction.

[0099] As used herein, elements or steps described in the singular and followed by the words “a” or “an” should be understood to not exclude a plurality of the said elements or steps, unless such exclusion is expressly stated. Furthermore, references to “one embodiment” in the subject matter currently described are not intended to exclude the existence of additional embodiments that also incorporate the said features. Moreover, unless expressly stated otherwise, embodiments that “comprise” or “have” one or more elements with a particular attribute may include other such elements that do not have that attribute.

[0100] It should be understood that the above description is intended to be illustrative and not restrictive. For example, the above embodiments (and / or aspects thereof) may be used in combination with each other. Furthermore, many modifications may be made to adapt particular situations or materials to the teachings of the subject matter without departing from the scope of the subject matter set forth herein. While the dimensions and types of materials described herein are intended to define parameters of the disclosed subject matter, they are by no means restrictive but rather exemplary embodiments. Many other embodiments will become apparent to those skilled in the art upon review of the above description. Therefore, the scope of the subject matter described herein should be determined by reference to the full scope of the appended claims and the equivalents claimed by such claims. In the appended claims, the terms “including” and “in which” are used as common English equivalents to the corresponding terms “comprising” and “wherein”. Furthermore, in the following claims, the terms “first,” “second,” and “third,” etc., are used only as designations and are not intended to impose numerical requirements on their objects. Furthermore, the limitations of the following claims are not prepared in the device plus function format and are not intended to be interpreted based on 35 USC §112(f), unless and until such claims are limited by the phrase “device for…” followed by no further structural functional statement.

[0101] This written description uses examples to disclose several embodiments of the subject matter set forth herein, including best modes, and also enables those skilled in the art to practice embodiments of the disclosed subject matter, including making and using the said apparatus or system and performing the said methods. The patentable scope of the subject matter described herein is defined by the claims and may include other examples that may occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that are identical to the literal language of the claims, or if such other examples include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method for operating an aircraft propulsion system, comprising: A boundary layer intake fan system is disposed at the rear end of the aircraft propulsion system. The boundary layer intake fan system includes a fan configured to rotate about the axial centerline of the boundary layer intake fan system along a first rotation direction. The boundary layer intake fan system includes blades positioned at a first pitch angle and configured to rotate together with the fan. Each of the fan blades has a pressure side and a suction side opposite to the pressure side. Between the leading edge and the trailing edge of the fan blade, the pressure side has a concave shape and the suction side has a convex shape. An flare is provided at the rear end of the boundary layer intake fan system, wherein the flare is configured to guide airflow into the boundary layer intake fan system. The rotation direction of the fan is changed to a different second rotation direction by an electric motor operably connected to the boundary layer intake fan system; and An actuator operatively coupled to the boundary layer intake fan system positions the blades of the fan at different second pitch angles, wherein each of the blades rotates about a corresponding blade axis, and wherein each blade axis is parallel to the axial centerline of the aircraft.

2. The method of claim 1, wherein when the fan rotates along the first rotation direction and when the blade is positioned at the first pitch angle, the direction of the airflow entering the fan system through the boundary layer is along a first direction, and wherein when the fan rotates along the second rotation direction and when the blade is positioned at the second pitch angle, the direction of the airflow entering the fan system through the boundary layer is along a different second direction.

3. The method of claim 1, wherein each blade includes the leading edge and the trailing edge, wherein air is configured to flow through the boundary layer into the fan system in a direction from the leading edge toward the trailing edge.

4. The method of claim 1, wherein the motor includes a phase switch, and wherein changing the rotation direction of the fan is achieved using the phase switch of the motor.

5. The method of claim 1, further comprising suspending a pair of jet engines under the wings of the aircraft propulsion system, and electrically connecting a generator to the jet engines, the electric motor, and the actuator, wherein the generator causes the rotational energy from the jet engines to be converted into electrical energy.

6. The method of claim 1, wherein the boundary layer intake fan system is configured to provide thrust to the aircraft propulsion system.

7. The method of claim 6, wherein the thrust provided by the boundary layer intake fan system is configured as one or more of forward thrust or reverse thrust.

8. The method of claim 1, further comprising using the electric motor to change the rotational speed of the fan.

9. The method of claim 1, wherein when the fan rotates along the second rotation direction and when the blades are positioned at the second pitch angle, the movement of the aircraft is configured such that the airflow direction entering the fan system through the boundary layer is in the same direction.

10. An aircraft propulsion system, comprising: A boundary layer intake fan system is configured to be positioned at the rear end of an aircraft. The boundary layer intake fan system includes a fan configured to rotate about the axial centerline of the boundary layer intake fan system along a first rotation direction. The boundary layer intake fan system also includes blades positioned at a first pitch angle and configured to rotate together with the fan. An flare is disposed at the rear end of the boundary layer intake fan system, wherein the flare is configured to guide airflow into the boundary layer intake fan system. Each of the blades rotates about a corresponding blade axis parallel to the axial centerline of the aircraft, and each of the blades has a pressure side and a suction side opposite to the pressure side, wherein the pressure side has a concave shape and the suction side has a convex shape between the leading and trailing edges of the fan blades. The actuator is operatively coupled to the boundary layer intake fan system and configured to change the position of the fan blades to different second pitch angles.

11. The system of claim 10, wherein the electric motor is operatively coupled to the boundary layer intake fan system and configured to change the rotation direction of the fan to a different second rotation direction.

12. The system of claim 11, wherein when the fan rotates along the first rotation direction and when the blade is positioned at the first pitch angle, the direction of the airflow entering the fan system through the boundary layer is along a first direction, and wherein when the fan rotates along the second rotation direction and when the blade is positioned at the second pitch angle, the direction of the airflow entering the fan system through the boundary layer is along a different second direction.

13. The system of claim 10, wherein each blade includes the leading edge and the trailing edge, wherein air is configured to flow through the boundary layer into the fan system in a direction from the leading edge toward the trailing edge.

14. The system of claim 11, wherein the motor includes a phase switch, wherein the phase switch is configured to change the rotation direction of the fan.

15. The system of claim 11 further includes a pair of jet engines suspended below the wings of the aircraft propulsion system, and a generator electrically connected to the jet engines, the electric motor and the actuator, wherein the generator causes the rotational energy from the jet engines to be converted into electrical energy.

16. The system of claim 10, wherein the boundary layer intake fan system is configured to provide thrust to the aircraft propulsion system.

17. The system of claim 16, wherein the thrust provided by the boundary layer intake fan system is configured as one or more of forward thrust or reverse thrust.

18. The system of claim 11, wherein the electric mechanism causes a change in the rotational speed of the fan.

19. The system of claim 11, wherein when the fan rotates in the second rotational direction and when the blades are positioned at the second pitch angle, the movement of the aircraft is configured such that the airflow direction entering the fan system through the boundary layer is in the same direction.

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