High speed rotorcraft propulsion configuration
11577831 · 2023-02-14
Assignee
Inventors
Cpc classification
F02C7/04
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
B64C27/14
PERFORMING OPERATIONS; TRANSPORTING
B64C29/0033
PERFORMING OPERATIONS; TRANSPORTING
B64C27/30
PERFORMING OPERATIONS; TRANSPORTING
B64D35/02
PERFORMING OPERATIONS; TRANSPORTING
F05D2220/329
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F05D2220/323
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F02C7/36
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F02C6/206
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F05D2240/12
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
B64C11/28
PERFORMING OPERATIONS; TRANSPORTING
B64C27/28
PERFORMING OPERATIONS; TRANSPORTING
F05D2260/40
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
B64C29/00
PERFORMING OPERATIONS; TRANSPORTING
F02C7/04
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F02C7/36
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
B64C11/28
PERFORMING OPERATIONS; TRANSPORTING
B64C27/14
PERFORMING OPERATIONS; TRANSPORTING
B64D35/02
PERFORMING OPERATIONS; TRANSPORTING
F02C6/20
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Abstract
A tiltrotor aircraft having a propulsion configuration that divorces the engine core power from the thrust fan, using a combined gearbox with a plurality of clutches to couple and decouple one or more rotor systems and one or more thrust fans. The aircraft can be operable for vertical takeoff and landing (VTOL) in a helicopter mode, forward flight in a proprotor mode, and high-speed forward flight in an airplane (jet) mode. The propulsion configuration provides shaft horsepower (SHP) to rotors for VTOL flight, while also providing SHP to the thrust fan for high speed flight. Allowing the rotor and the thrust fan to be clutched on and off, sequentially, enables transition from rotor-borne VTOL flight to wing-borne thrust fan flight, and back.
Claims
1. A tiltrotor aircraft, comprising: an engine core; a thrust fan; a rotor system; an inlet guide vane configured to modulate airflow to the thrust fan; and a combined gearbox operably coupled to the engine core and the thrust fan, the combined gearbox having a rotor clutch configured to selectively couple the rotor system to the engine core and a fan clutch configured to selectively couple the thrust fan to the engine core.
2. The aircraft of claim 1, wherein the fan clutch includes a friction clutch.
3. The aircraft of claim 1, wherein the rotor clutch includes a friction clutch.
4. The aircraft of claim 1, further comprising a variable area nozzle configured to modulate the thrust of the thrust fan.
5. The aircraft of claim 1, wherein the rotor clutch includes a lockshaft spline.
6. The aircraft of claim 1, wherein the fan clutch includes a lockshaft spline.
7. An aircraft comprising: a combined gearbox, the combined gearbox comprising: a rotor clutch coupled to an engine core and selectively coupled to a rotor system; and a fan clutch coupled to an engine core and selectively coupled to a thrust fan having airflow modulated by an inlet guide vane.
8. The aircraft of claim 7, wherein the rotor clutch is engaged and the fan clutch is disengaged when the aircraft is in a helicopter mode.
9. The aircraft of claim 7, wherein the rotor clutch transfers the power from the engine core to the rotor systems by engaging a rotor drive shaft.
10. The aircraft of claim 7, wherein the fan clutch transfers the power from the engine core to the thrust fan by engaging a fan drive shaft.
11. The aircraft of claim 7, wherein the rotor clutch is disengaged and the fan clutch is engaged when the aircraft is in an airplane mode.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION
(13) The preferred versions of the inventions are presented in the following written description and the various features and advantageous details thereof are explained more fully with reference to the non-limiting examples included in the accompanying drawings and as detailed in the description which follows. Descriptions of well-known components and processes and manufacturing techniques are omitted so as to not unnecessarily obscure the principle features of the inventions as described herein. The examples used in the description which follows are intended merely to facilitate an understanding of ways in which the inventions may be practiced and to further enable those skilled in the art to practice the inventions. Accordingly, the examples should not be construed as limiting the scope of the claimed inventions.
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(15) The aircraft 100 can include one or more engines 102, a combined gearbox (CGB) 108, and a thrust fan 116. The CGB 108 preferably includes a rotor clutch 110 and a fan clutch 114. The thrust fan 116 is operably connected to an inlet guide vane (IGV) 119 on a first end and a variable area nozzle (VAN) 120 on a second end. The engines 102 are operatively coupled to the CGB 108 via engine drive shafts 112. The rotor systems 104 are operatively coupled to CGB 108 via rotor drive shafts 106. The thrust fan 116 is operatively coupled to the CGB 108 via a fan drive shaft 118.
(16) As discussed in more detail below the aircraft 100 can convert from a helicopter mode for VTOL to an airplane mode for forward flight. Additionally, the aircraft 100 can transition from a proprotor to an airplane (jet) by folding the rotors into a stowed mode to effectively eliminate the aerodynamic issues associated with the rotor blades. Such an aircraft requires a special propulsion system that can provide full shaft torque to the rotors while in full helicopter mode and operate like a jet in airplane mode. For any sort of efficient high speed flight, a thrust producing (bypass) fan is preferable.
(17) A convertible engine is a type of propulsion engine that can convert between using shaft horsepower output and thrust output by incorporating an engine core 102 and a thrust fan 116. In one exemplary embodiment, the convertible engine preferably includes two engine cores 102 disposed fore of a combined gearbox 108, which is fore of a thrust fan 116. However, other exemplary embodiments can include any suitable number of engine cores 102 and thrust fans 116 in any suitable location on the aircraft 100. Typically in a jet, you have an engine core 102 and a thrust fan 116 that produces thrust. In a helicopter, thrust is typically generated by rotor system that is operatively connected to a turbo shaft. In order to incorporate both aspects of a jet and a helicopter, the convertible engine weight must be balanced and the engine power directed to either the thrust fan 116 or the rotor systems 104.
(18) The thrust fan 116 leverages IGV 119 to control the airflow into the thrust fan 119. When IGV 119 chokes-off the airflow to the thrust fan 116, instead of the fan absorbing the power produced by the engine cores 102, the rotor drive shaft 106 can absorb the power and the shaft is operably coupled to the rotor systems 104 to drive the rotor systems 104. When transitioning to airplane mode, the power generated by the engines 102 is preferably transferred to the thrust fan 116. The rotors can be stopped, and the IGV 119 opened, such that the thrust fan 116 can produce the thrust again. The engine core 102 and the thrust fan 116 are mechanically coupled via the CGB 108.
(19) Each engine core 102 is operably coupled to an engine drive shaft 112, which is operably coupled to the CGB 108. The CGB 108 can transfer the power from the engines to either the rotors system 104 (via rotor drive shafts 106) or the thrust fan 116 (via fan drive shaft 118). The gearbox includes a rotor clutch 110, which can selectively engage and disengage the rotor systems 104. The rotor clutch 110 can include a friction clutch that provides a course rotational speed matching of the engine core 102 with the rotor system 104. A spline can then be utilized to match and maintain the rotational speed of the engine core 102 with the rotor system 104.
(20) During VTOL, the aircraft 100 is in helicopter mode. The engine cores 102 transfer their power to the CGB 108 via engine drive shafts 112. The CGB 108 engages the rotor drive shaft 106, which is operably coupled to the CGB 108 via the rotor clutch 110, and transfers the power from the engine core 102 to the rotor systems 104. The aircraft 100 can then take-off, hover, and land in helicopter mode. While in helicopter mode, the rotor clutch 110 is engaged to drive the rotor system 104. Advantageously, the fan clutch 114 is dis-engaged, with the IGV 119 closed, while the aircraft 100 is in helicopter mode, such that there is no power transferred to the thrust fan 116. By disengaging the thrust fan 116, all of the power generated by the engine cores 102 can be transferred to the rotor systems 104, thereby eliminating the traditional 20% power loss associated with conventional convertible engines. Further, as the thrust fan is de-clutched from the system, it is free to rotate at its natural (slower) rotational speed to maintain aeroelastic stability.
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(22) During forward flight in proprotor mode, the engine cores 102 transfer their power to the CGB 108 via engine drive shafts 112. The CGB 108 engages the rotor drive shaft 106, which is operably coupled to the CGB 108 via the rotor clutch 110, and transfers the power from the engine core 102 to the rotor systems 104. The aircraft 100 can then utilize the forward thrust generated by the rotor systems 104 rotated into a horizontal position, coupled with the lift provided by the wing 103 for forward flight in proprotor mode. While in proprotor mode, the rotor clutch 110 is engaged to drive the rotor system 104. Advantageously, the fan clutch 114 is dis-engaged, with the IGV 119 closed, while the aircraft 100 is in proprotor mode, such that there is no power transferred to the thrust fan 116. By disengaging the thrust fan 116, all of the power generated by the engine cores 102 can be transferred to the rotor systems 104, thereby eliminating the traditional 20% power loss associated with conventional conversion engines. Further, as the thrust fan is de-clutched from the system, it is free to rotate at its natural (slower) rotational speed to maintain aeroelastic stability.
(23) When the rotor systems 104 are rotated vertically, the aircraft 100 can take-off and hover like a helicopter and as the nacelles are rotated horizontally, the aircraft 100 can accelerate in forward flight. Conversion occurs when the nacelles are tilted forward such that the aircraft 100 “converts” from essentially a helicopter into essentially a proprotor. The conversion period preferably begins when the nacelles tilt from 90° to 0° and the rotor is pointing into the air axially and you have axial flow through the rotor system 104. However, any suitable nacelle tilt angle can be utilized as the conversion period.
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(25) The transition process enables the propulsion configuration of aircraft 100. The transition process includes transferring the thrust from the rotor system 104 to the thrust fan 116. During flight, the thrust from the rotor system 104 can be transferred to the thrust fan 116 during a transition process. During the transition process, the power from the main rotors is slowly decreased and the fan clutch 114 is engaged such that the power from the engine cores 102 can be transferred to the thrust fan 116, so that steady, level flight is maintained. Ideally, transition occurs at a steady, level condition so the transition is smooth without impressing large moments or forces on the aircraft 100 during flight.
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(27) When the rotor systems 104 are mechanically de-clutched via the rotor clutch 110, the rotors are disengaged such that none of the engine power is transferred to the rotor systems 104. The CGB 108 can then engage the fan clutch 114 to transfer the power from the engine core 102 to the thrust fan 116. The IGV 119 is opened and the thrust fan 116 starts to absorb power from the engine core 102. All the power is thereby transferred to the thrust fan 116 to produce thrust, and the aircraft 100 increases speed quickly.
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(30) An air vehicle graphic 602 shows the outbound aircraft 100 transition (from proprotor mode to airplane mode) and accompanying rotor system 104 thrust vectors (in blue) and fan 116 thrust vectors (in red). During outbound transition, the primary thrust generation transitions from the rotors 104 to the fan 116. While in airplane mode, the thrust is only generated by the fan 116.
(31) An engine thrust graphic 604 shows the thrust vectors for the fan 116 and the rotor system 104. Initially, a majority of the thrust originates from the rotor 104, as the aircraft 100 is in proprotor mode. As the aircraft transitions into airplane mode, a majority of the thrust is transferred to the thrust fan 116, as the aircraft 100 is in airplane mode.
(32) A rotor position graphic 606 shows the transition of the rotor blades from operation to a stowed mode. Initially, the rotor blades produce all forward thrust, as shown via the blue vector arrows. However, as rotor thrust is reduced to zero via disengagement of the rotor clutch, the rotor blades begin to windmill from the airflow. The gimbal of the rotor system 104 is locked to stop the rotor flapping, the blades are feathered to stop rotor rotation, and the rotor folding mechanism is unlocked to allow the rotor blades to fold substantially parallel to the pylon of the rotor system 104. The rotor blades are locked in a stowed mode to end the transition process.
(33) A thrust vs. time diagram 608 shows the thrust transfer between the thrust from the thrust fan 116 (red) and the thrust from the rotor system 104 (blue). As the thrust is transferred from the rotor system 104 to the thrust fan 116, the rotor thrust actually becomes drag as the rotor blades windmill. As the rotor blades are feathered to turn the edge parallel to the airflow, the drag turns into minimal thrust. As the rotor blades transition into a stowed mode, the thrust drops to effectively zero.
(34) In helicopter mode, the fan 116 is completely de-clutched from the fan clutch 114. So, as forward flight begins, the IGV 119 is still closed to prevent the fan 116 from spinning (windmiling) to an extent that it creates drag. Once a sufficient airspeed is attained, such that it is possible to pass the thrust from the rotor systems 104 to the thrust fan 116, the IGV 119 is opened in front of the thrust fan 116. The rotor systems 104, change the thrust by collectively changing the pitch on all the rotor blades via a swash plate, thereby mechanically changing the rotor blade angle of attack. Typically on thrust fans 116, the angle of attack is fixed as they spin a lot faster, are placed together, and packaged more closely. Thrust fans 116 modulate thrust via IGVs 119 that block and open the airflow. Thrust fans can utilize a variable area nozzle (VAN) 120 to control the exit pressure to modulate the thrust.
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(37) An air vehicle graphic 802 shows the inbound aircraft 100 transition (from airplane mode to proprotor mode) and accompanying rotor system 104 thrust vectors (in blue) and fan 116 thrust vectors (in red). During inbound transition, the primary thrust generation transitions from the fan 116 to the rotors 104. While in airplane mode, the thrust is only generated by the fan 116.
(38) An engine thrust graphic 804 shows the thrust vectors for the fan 116 and the rotor system 104, effectively working in reverse from the outbound transition process disclosed in
(39) A rotor position graphic 806 shows the transition of the rotor blades from a stowed mode into operation. As the rotor blades unfold, they deploy in the feathered state and produce a small drag increase. As the blades unfeather, the rotor spins up to match the rotation speed of the engine and drag substantially increases.
(40) A thrust vs. time diagram 808 shows the thrust transfer between the thrust from the thrust fan 116 (red) and the thrust from the rotor system 104 (blue). As the thrust is transferred from the thrust fan 116 to the rotor system 104, the fan thrust experiences a boost as the blades are unfeathered and spin up. Once the rotor clutch is engaged, after the engine and rotor RPMS equalize, the fan thrust decreases as the fan clutch is disengaged.
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(44) During the outbound transition process, the IGV 119 will start in a closed position and gradually open to allow airflow through the thrust fan 116, causing the fan 116 to spin up aerodynamically. As the fan 116 spins up aerodynamically the thrust fan's 116 rotation speed is increased to substantially the same rotation speed of the engine cores 102. Once the thrust fan's 116 RPMs effectively match the engine cores' 102 RPMs, the fan clutch 114 can be engaged. Because the two components have a minimal rotation speed difference, a friction clutch can be utilized, as there is only a small amount of RPM to overcome. That small rotational speed difference allows the fan clutch to be sized for a small amount of torque, thereby greatly reducing the weight requirement typical in conventional systems. The fan clutch 114 brings the engine 102 and the fan 116 to the same speed and a spline shaft slides into position to transfer the entirety of the torque. The friction clutch of the fan clutch 114 is a heavy component, so the aircraft 100 propulsion system is designed so the thrust fan 116 and the engine core 102 engage and disengage at the minimum torque possible, essentially synchronizing the two speeds with some differential RPM. The fan clutch 114 is sized to be as small and as light as possible. This minimal clutch sizing is possible because, aerodynamically, the thrust fan 116 is spun up to speed to match the engine's 102 RPMs before the clutch is engaged. Once the fan clutch 114 is engaged the collective pitch on rotor system 104 are varied, the IGV 119 is further changed such that the power from the main rotor system 104 is transferred to the thrust fan 116 and the rotors are retracted into a stowed mode. Once the rotors are disengaged, their rotation is halted and the rotor blades are feathered and retracted.
(45) During the inbound transition process, the transition process works in reverse of the outbound transition process. The thrust fan 116, creates the thrust for the aircraft while in airplane mode. The rotor blades are deployed and collectively pitched spin-up and produce thrust. The IGV 119 is slowly closed to decrease the airflow to the fan 116 and decreasing the power absorbed, but the thrust fan 116 is still spinning at the same speed because everything is connected mechanically. Both the fan clutch and corresponding high torque spline and the rotor clutch and corresponding high torque spline are engaged at the same time. Once the rotors 104 are producing all the thrust and the fan is still spinning at its nominal speed, the fan 116 can be de-clutched and the IGV 119 can be closed. The fan 116 stops spinning so all the power and all the torque is transferred to the rotor system 104, in proprotor mode. The aircraft 100 can then convert back into helicopter mode. The aircraft can land or hover.
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(47) At step 1204, an inlet guide vane opens to direct airflow to a thrust fan. The method then proceeds to step 1206.
(48) At step 1206, the thrust fan's rotation speed is increased to substantially the same rotation speed of an engine cores (at the clutch connect point. The actual fan and engine will be separated in speed by the gear ratio). The method then proceeds to step 1208.
(49) At step 1208, the engine core and the rotor system are coupled to a fan by selectively engaging a fan clutch when the thrust fan's rotation speed effectively matches the engine core's rotation speed (at the clutch engage location). The method then proceeds to step 1210.
(50) At step 1210, the rotor system can be de-clutched to transfer full engine core power to the thrust fan. The method then proceeds to step 1212.
(51) At step 1212, the rotor blades can be retracted into a stowed mode, substantially parallel to a rotor system nacelle.
(52) The inventions of the present disclosure achieve at least the following advantages: 1. Provides SHP to rotors for VTOL flight, provides SHP to thrust fan for high speed, turbofan flight; 2. Allows rotor and fan to be clutched on and off sequentially to enable transition from rotor-born VTOL flight to wing-born fan flight, and back. De-clutched fan: a. Generates no residual thrust, and b. Does not rob engine power available from rotors in VTOL mode; 3. Outbound flight transition: a. Rotor powered turbo-prop mode, IGV open to aerodynamically spin up thrust fan, b. Clutch and spline lock engage fan, engine powers both fan and rotor, c. IGVs, VAN and rotor collective pitch adjusted to transfer thrust from rotor to fan, d. Rotor de-clutched at zero torque condition, and e. Rotor stopped, folded, for high-speed, turbofan powered flight; 4. Since fan and engine are separated, allows more engine options, independent of thrust fan; does not require a special engine type; 5. Separate inlet treatment of engine core flow, enables use of inlet barrier filter (IBF); 6. Thrust fan can utilize inlet guide vanes (IGVs) and variable area nozzle (VAN) to modulate thrust independent of engine rpm; 7. Engine and fan can operate at different, optimal rpms; 8. De-clutching thrust fan provides greater power to rotors in hover/VTOL mode and no residual thrust; 9. Centralized fan is easier to hide forward facing fan face with bi-furcated inlets; 10. Upward directed hot exhaust ducting is shielded/hidden from bottom/side view, preventing thermal detection; and 11. Thrust fan can be located to ideally shape inlets without adverse CG placement implications.
(53) While the inventions have been shown in specific embodiments, they are not thus limited and are susceptible to various changes and modifications without departing from the spirit thereof. Persons skilled in the art will understand that these concepts are susceptible to various changes and modifications, and may be implemented or adapted readily to other types of environments. Further, the individual elements of the claims are not well-understood, routine, or conventional. Instead, the claims are directed to the unconventional inventive concepts described herein.