Patent Application
20210039777
The present invention relates to electric tip-jet engines for powering rotary-wing and VTOL fixed-wing aircraft, and particularly to systems and methods that eliminate the potential of gyroscopic effect caused by electric fans and electric motor components spinning on the rotor blades.
A growing market for urban and interurban point-to-point ‘flying taxi’ or ‘flying car’ service requires efficient, non-polluting and quiet aircraft. Concepts have been proposed for electrically-powered rotary-wing aircraft, i.e., single- and multi-rotor helicopters, as well as VTOL fixed-wing aircraft with multiple rotors. A classical Tip Jet helicopter is designed as having a propulsion device installed at the tips of its rotor, applying thrust perpendicular to the rotor-blade, torqueing it and supplying the energy needed to hover, climb or fly forward. Since the torque is applied directly to the rotor and not originated from the helicopter fuselage, there is no counter-torque applied on the fuselage and there is no need for a tail-rotor (or a tail).
In addition, the main rotor transmission is not needed, and for a battery powered helicopter there is no need for main-engine installed in the fuselage. The whole propulsion system of an aircraft that could employ a electric tip-jet system consists of a battery pack and a number of electric-tip-jet-engines equal to the number of rotor blades. All this reduces the empty-weight of the helicopter, allows more weight for the batteries and increases the payload or the endurance of the vehicle.
A simple electric tip-jet will have a fan turned by an electric motor typically spinning at a rate of 10,000-15,000 RPM. If mounted at a tip of a rotor-blade turning at a rate of 300-600 RPM, a very large gyroscopic moment will develop, applying a twist moment around the rotor-blade longitudinal axis, and probably destroying the rotor. Thus, there is a need for an electric tip-jet solution for turning aircraft rotors without the disadvantage of the gyroscopic effect.
According to embodiments of the invention, an electrically-powered tip-jet engine system for turning an aircraft rotor blade comprises: (a) first and second fan assemblies having substantially the same moment of inertia and configured to rotate at the same angular speed, each fan assembly comprising a respective plurality of fan blades and a respective electric motor rotor; and (b) a rigid frame assembly comprising an electric motor stator assembly and configured for mounting to the aircraft rotor blade, wherein (i) the first fan assembly is effective to create thrust in a thrust direction by rotating clockwise with respect to the thrust direction, and (ii) the second fan assembly is effective to create thrust in the thrust direction by rotating counter-clockwise with respect to the thrust direction.
In some embodiments, the rotation in opposing directions of the first and second fan assemblies can be effective to eliminate gyroscopic effect on the aircraft rotor blade.
In some embodiments, the first and second fan assemblies can be disposed such that the respective motor rotors are adjacent to, and located on opposite sides of, the stator assembly, the stator assembly being configured as a common stator assembly for both fan assemblies.
In some embodiments, the tip-jet engine system can comprise two stator assemblies, each stator assembly being disposed adjacent to a respective one of the first and second fan assemblies so as to form respective first and second electric motor units.
In some embodiments, the first and second fan assemblies can be arranged coaxially.
In some embodiments, the tip-jet engine system can additionally comprise a static guide-vane ring installed between the first and second fan assemblies. In some embodiments, the respective pluralities of fan blades are configured to operate together as a two-stage counter-rotating axial fan.
In some embodiments, the first and second motor units can be configured to be arranged side-by-side when mounted to the aircraft rotor blade. In some embodiments, the first and second motor units can be configured to be arranged substantially one atop the other when mounted to the aircraft rotor blade.
In some embodiments, the fan assemblies can be ducted.
According to embodiments, an aircraft configured to carry passengers comprises: (a) an onboard electrical power source; an aircraft rotor comprising a plurality of aircraft rotor blades; and a plurality of electrically-powered tip-jet engine systems for turning the aircraft rotor, each tip-jet engine system comprising: (i) a rigid frame assembly mounted to a respective aircraft rotor blade and comprising an elctric motor stator assembly, and (ii) first and second fan assemblies having substantially the same moment of inertia and configured to rotate at the same angular speed, each fan assembly comprising a respective plurality of fan blades and a respective electric motor rotor, wherein (A) the first fan assembly is effective to create thrust in a thrust direction by rotating clockwise with respect to the thrust direction, and (B) the second fan assembly is effective to create thrust in the thrust direction by rotating counter-clockwise with respect to the thrust direction.
In some embodiments, the aircraft can be a helicopter. In some embodiments, the aircraft can be a VTOL fixed-wing aircraft.
In some embodiments, the aircraft can additionally comprise: (d) a plurality of electrically conductive wires, each respective wire disposed in an aircraft rotor blade for delivering electricity to the tip-jet engine system; and (e) a slip ring connected to the aircraft rotor for transmitting electric power from the power source to the plurality of wires.
In some embodiments, the rotation in opposing directions of the first and second fan assemblies of each tip-jet engine system can be effective to eliminate gyroscopic effect on the respective aircraft rotor blade.
In some embodiments, the first and second fan assemblies of each tip-jet engine system can be disposed such that the respective motor rotors are adjacent to and on opposite sides of the stator assembly, the stator assembly being configured as a common stator assembly for both the first and second fan assemblies.
In some embodiments, it can be that (i) each tip-jet engine system comprises two stator assemblies, and (ii) each stator assembly is disposed adjacent to a respective one of the first and second fan assemblies of the respective tip-jet engine system so as to form respective first and second electric motor units.
In some embodiments, the first and second fan assemblies of each tip-jet engine system can be arranged coaxially.
In some embodiments, each tip-jet engine system can additionally comprise a static guide-vane ring installed between the respective first and second fan assemblies.
In some embodiments, the respective pluralities of fan blades of the first and second fan assemblies of each tip-jet engine system can be configured to operate together as a two-stage counter-rotating axial fan.
In some embodiments, the first and second motor units of each tip-jet engine system can be arranged side-by-side. In some embodiments, the first and second motor units of each tip-jet engine system can be arranged substantially one atop the other.
In some embodiments, it can be that the fan assemblies of at least one of the plurality of tip-jet engines are ducted.
A method is disclosed for operating an aircraft comprising a plurality of electrically-powered tip-jet engine systems mounted to respective rotor blades of the aircraft, each tip-jet engine system comprising first and second fan assemblies, the method comprising: (a) delivering electric power from on onboard source to the plurality of tip-jet engine systems; (b) causing respective first fan assemblies of the tip-jet engine systems to rotate clockwise with respect to respective thrust directions and thereby create thrust in the thrust directions; and (c) causing respective second fan assemblies of the tip-jet engine systems to rotate counter-clockwise with respect to the thrust directions and thereby create thrust in the thrust directions, wherein the respective first and second fan assemblies of each tip-jet engine system have substantially the same moment of inertia and rotate at substantially the same angular speed.
In some embodiments, it can be that each of the fan assemblies (i) comprises a respective plurality of fan blades and a respective electric motor rotor, and (ii) is disposed adjacent to an electric motor stator assembly which is mounted to a respective aircraft rotor blade.
In some embodiments, the aircraft can be a helicopter. In some embodiments, the aircraft can be a VTOL fixed-wing aircraft.
In some embodiments, the aircraft can additionally comprise: (a) an onboard electrical power source; (b) a plurality of electrically conductive wires respectively disposed in aircraft rotor blades for delivering the electric power to the tip-jet engine systems; and (c) a slip ring connected to the aircraft rotor for transmitting the electric power from the power source to the plurality of wires.
In some embodiments, the rotating in opposing directions by the first and second fan assemblies of each tip-jet engine system can eliminate gyroscopic effect on the respective aircraft rotor blades.
In some embodiments, the first and second fan assemblies of each tip-jet engine system can be disposed such that the respective motor rotors are adjacent to and on opposite sides of the stator assembly, the stator assembly being configured as a common stator assembly for both the first and second fan assemblies.
In some embodiments, it can be that (i) each tip-jet engine system comprises two stator assemblies, and (ii) each stator assembly is disposed adjacent to a respective fan assembly so as to form respective first and second electric motor units.
In some embodiments, the first and second fan assemblies of each tip-jet engine system can be arranged coaxially.
In some embodiments, each tip-jet engine system can additionally comprise a static guide-vane ring installed between the respective first and second fan assemblies.
In some embodiments, the respective pluralities of fan blades of the first and second fan assemblies can be configured to operate together as a two-stage counter-rotating axial fan.
In some embodiments, the first and second motor units of each tip-jet engine system can be arranged side-by-side. In some embodiments, the first and second motor units of each tip-jet engine system can be arranged substantially one atop the other.
In some embodiments, it can be that the fan assemblies of at least one of the plurality of tip-jet engines are ducted.
The invention will now be described further, by way of example, with reference to the accompanying drawings, in which the dimensions of components and features shown in the figures are chosen for convenience and clarity of presentation and not necessarily to scale. Also, in some drawings the relative sizes of objects, and the relative distances between objects, may be exaggeratedly large or small for the sake of convenience and clarity of presentation. In the drawings:
The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Throughout the drawings, like-referenced characters are generally used to designate like elements.
Note: Throughout this disclosure, subscripted reference numbers (e.g., 101 or 10A) may be used to designate multiple separate appearances of elements of a single species, whether in a drawing or not; for example: 101 is a single appearance (out of a plurality of appearances) of element 10. The same elements can alternatively be referred to without subscript (e.g., 10 and not 101) when not referring to a specific one of the multiple separate appearances, i.e., to the species in general.
For convenience, in the context of the description herein, various terms are presented here. To the extent that definitions are provided, explicitly or implicitly, here or elsewhere in this application, such definitions are understood to be consistent with the usage of the defined terms by those of skill in the pertinent art(s). Furthermore, such definitions are to be construed in the broadest possible sense consistent with such usage.
The embodiments herein are equally applicable to all kinds of aircraft which use a rotor, e.g., spinning in a roughly horizontal plane for lift and/or hovering and, optionally, for forward propulsion and maneuvering, and the use of the term ‘helicopter’ should be interpreted to encompass any and all such aircrafts for the purposes of understanding the scope of the present invention. The present disclosure uses the terms ‘helicopters’ and VTOL (vertical take-off and landing) aircraft. A helicopter is also a type of VTOL aircraft and any semantic distinction does not limit the present invention in any way. The term ‘helicopter’ as used herein can mean rotary-wing aircraft (rotorcraft) including traditional helicopters or multi-lift-rotorcraft such as quadricopters (also known as quadcopters), or it can mean any rotor-equipped aircraft including a VTOL aircraft. The term ‘VTOL’ as used herein means only VTOL aircraft other than helicopters, such as fixed-wing aircraft with one or more lift rotors, or tilt-rotor aircraft.
The terms ‘tip-jet’ and ‘tip-jet engine’ are used broadly to encompass devices for vehicles adapted for flight using rotors, where the lift of the rotor blades is accomplished by creating thrust at or near the distal tips of the rotor blades, whether by actual ‘jets’ or not. The term ‘stator assembly’ is intended to include at least the stator and any magnets or electromagnetic windings (or coils) provided within.
The term ‘fan assembly’ as used herein means a rotatable assembly comprising a fan, or a plurality of fan blades, and the rotor of an electric motor. The terms ‘fan’ and ‘fan assembly’ should be regarded as including propellers and propeller blades substituting for fans and fan blades in the case of an engine design without a duct shell. The term ‘motor unit’ as used herein means a combination of a fan assembly with an electric motor stator. In other words, a ‘motor unit’ as defined herein comprises at least the two key components of an electric motor (stator and rotor) along with a fan or a plurality of fan blades. A ‘rigid frame assembly’ as used herein means a rigid frame suitable for mounting a tip-jet engine system to the rotor blade of an aircraft, where the frame comprises a stationary component of an electric motor of the tip-jet engine system, such as, without limitation, a stator or stator assembly.
The term ‘tip-jet engine system’ as used herein means a tip-jet engine mounted on a rotor blade, or multiple tip-jet engines mounted on a single rotor blade so as to operate together. It is to be understood that a tip-jet engine system includes an electric motor, a fan assembly which may include a cowling for aerodynamics and/or equipment protection, a fan duct in those embodiments in which the fan assembly/tip-jet engine is ducted, a guide vane ring in those embodiments in which multiple coaxial fan assemblies or motor units are assembled in a fan duct, and a rigid frame mounting the tip-jet engine system to the aircraft rotor blade.
According to embodiments of the invention, an electrically-powered tip-jet engine uses an electric motor to generate torque in an aircraft rotor, in order to spin a fan connected to the aircraft rotor. The electrically-powered tip-jet engine is preferably positioned to create thrust at or near the distal tips of a rotor blade. The attached figures all illustrate, for convenience, brushless direct current (DC) motors built with an outer-rotor design, the motors all illustrated as having electromagnetic coils in a stator assembly and external permanent magnets in a rotor. This is not meant to exclude other types of suitable motors for electrically-powered tip-jet engines according to the embodiments of the present invention; in other examples which are not illustrated, the electric motors of the tip-jet engine can include, and not exhaustively, alternating current (AC) induction motors, switched reluctance motors or other designs of brushless DC motors. Non-limiting examples of other suitable DC motors include those with permanent magnets in the stator assembly and electromagnetic windings in the rotor(s). Permanent magnets in the rotor can be external or internal to the rotors.
Referring now to the figures,
An electrically-powered helicopter is powered from an onboard power source 180 that can be flown by the helicopter 150 and that contributes to the total weight of the aircraft. The position shown in
As discussed hereinabove, previous attempts to use the electrically-powered tip-jet engine concept have encountered the problem of a large gyroscopic moment developing so as to apply a twist moment around the longitudinal axis of each of the rotor blades. The gyroscopic effect is due to the spinning of a tip-jet fan engine system at a high rotational speed at or near the tips of the spinning rotor blades. The gyroscopic moment is equal to angular momentum of the rotating body (the fan assembly including electric motor rotor components)—which is the moment of inertia of the rotating body multiplied by its angular velocity—multiplied by the angular velocity of the rotor blade. This gyroscopic effect can be serious enough to damage or even destroy the rotor. In the embodiments disclosed herein, the gyroscopic effect is eliminated, or ‘zeroed-out’, or simply not created, due to the provision of a second fan (i.e., fan assembly) on each rotor blade. The moment of inertia and angular spin of the second fan assembly can be set so that the product (angular momentum) is the same, but with a different sign because the direction of the velocity vector is reversed. The angular speed of the aircraft rotor is treated as a constant in this discussion. It can be desirable to establish that angular momentum is substantially the same for the two fan assemblies on each rotor blade by configuring the fan assemblies to have substantially the same moment of inertia, and to rotate (e.g., to be configured to rotate) at the same angular speed. Obviously, the angular velocities are in opposite directions and so it is angular speed, the directionless scalar value of angular velocity, that is set as equal. In some embodiments, angular momentum of both fan assemblies is kept constant so as to eliminate the gyroscopic effect, but the two factors of angular momentum, i.e., angular speed and moment of inertia, are not. According to embodiments, each respective second fan assembly has substantially the same moment of inertia and rotates (or is configured to rotate) at the same angular speed (e.g., in revolutions per minute, or RPM) as the corresponding first fan assembly of a given tip-jet engine system—but in the opposite direction, and no gyroscopic ‘effect’, i.e., gyroscopic moment, is created by the spinning fan assemblies.
We now refer to
Each of the rotors 3, 4 comprises an array of permanent magnets 11. The common stator 5 comprises electromagnetic windings 10 in the form of coils. A support element 82 is one of three rigid members shown attaching the tip-jet engine system 100 to the helicopter rotor blade 18 (which can be the same as, or similar to, any of the rotor blades 117 shown in
The tip-jet engine system 100 shown in
Referring now to
In some embodiments, any of the fan assemblies, motor units or tip-jet engine systems described or illustrated hereinabove can be provided without fan ducts and, consequently, without guide vanes. In some embodiments there is no duct shell and the fans are replaced by two propellers designed accordingly.
In an example, a rotary-wing aircraft 150 is fitted with tip-jet engine systems 100. The helicopter 150 has four rotor blades 117 connected to a single rotor 130. Therefore four tip-jet engine systems 100 are deployed. The tip-jet engine systems 100 were required to create 60 kg of thrust, a requirement that was a key input to the design.
The following table shows ranges for values of design and operating parameters of one of the four tip-jet engine systems 100 based on the design criterion of 60 kg thrust. The table represents just one example of a combination of parameters, out of a potentially infinite number of combinations, and should therefore be viewed as an illustration of a suitable specification for a 60-kg system. In some cases, the parameter values shown have been calculated (e.g., electric power) and in other cases they reflect that design choices have also been factored in (e.g., physical dimensions of the tip-jet engine system).
In another example, a much larger helicopter requiring, for example, thrust of 100-120 kg would require up to two times the electric power to the tip-jet engine systems, and tip-jet engines would be up to two times larger at least in terms of mass. The helicopter rotor blades could be 1.5 times longer with the same rotor blade tip velocity.
Referring now to
Step S01, delivering electric power from on onboard source 180 to the plurality of tip-jet engine systems 100;
Step S02, causing respective first fan assemblies of the tip-jet engine systems 100 to rotate clockwise with respect to respective thrust directions DT and thereby create thrust in the thrust directions DT; and
Step S03, causing respective second fan assemblies of the tip-jet engine systems 100 to rotate counter-clockwise with respect to the thrust directions DT and thereby create thrust in the thrust directions DT.
According to the method, each of the respective first and second fan assemblies of each tip-jet engine system 100 have substantially the same moment of inertia and rotate at substantially the same angular speed.
In some embodiments of the method, the aircraft can additionally comprise an onboard electrical power source, a plurality of electrically conductive wires respectively disposed in aircraft rotor blades for delivering the electric power to the tip-jet engine systems, and a slip ring connected to the aircraft rotor for transmitting the electric power from the power source to the plurality of wires.
In some embodiments of the method, all of the steps of the method can be carried out simultaneously.
A classical Tip Jet helicopter is designed as having a propulsion device installed at the tips of its rotor, applying thrust perpendicular to the rotor-blade, torqueing it and supplying the energy needed to hover, climb or fly forward.
Since the torque is applied directly to the rotor and not originated from the helicopter fuselage, there is no counter-torque applied on the fuselage and there is no need for a tail-rotor (or a tail).
In addition, the main rotor transmission is not needed and for a battery powered helicopter there is no need for main-engine installed in the fuselage. The whole propulsion system consists of a battery pack and a number of electric-tip-jet-engines equal to the number of rotor blades. All this reduces the empty-weight of the helicopter, allows more weight for the batteries and increases the payload or the endurance of the vehicle.
A simple electric-tip-jet will have a ducted-fan turned by an electric motor spinning at a rate of 10,000-15,000 RPM. If mounted at a tip of a rotor-blade turning at a rate of 300-600 RPM, a very large gyroscopic moment will develop, applying a twist moment around the rotor-blade longitudinal axis, probably destroying the rotor. One purpose of our invention is to eliminate this problem.
Between the counter rotating fans a static guide vane ring 12 is installed, to redirect the air after first fan 1 compression. The second fan 2 is designed to accept the air after the first compression, creating a typical two stage counter rotating compressor (fan).
The magnetic rotors 3, 4 counter-rotate relative to a fixed electromagnets ring stators 5, installed at the center of the engine (a common stator for two counter-rotating rotors. The stator 5 contains a plurality of electromagnets 10 and the rotors 3, 4 contain a plurality of permanent magnets 11.
Each rotating element is equipped with main bearings 6 and pressure bearings 7 which are connected to the helicopter blade by connecting parts 8.
The incoming air 14 is guided through the outside duct shell 9 and the internal cowlings 13, the air is accelerated by the two counter rotating fans 3, 4 and creates thrust in direction 15. In an alternative embodiment there is no duct shell and the fans are replaced by two propellers designed accordingly.
Electric power is supplied to the electromagnets 10 through wires installed in the Helicopter rotor blade and a Slip-rings in the helicopter rotor shaft (not shown on the drawing).
Some of the inventive concepts related to the additional discussion include (but not exhaustively):
Inventive concept 1: An electric-tip-jet engine comprising two counter-rotating elements. The two elements having substantially the same moment of Inertia and configured to spin at the same RPM, thus eliminating the gyroscopic effect typical to a spinning mass at the tip of a turning rotor-blade.
Inventive concept 2: The electric -tip-jet engine of Inventive concept 1 wherein each counter-rotating-element comprises an aerodynamic fan and a disk containing a plurality of permanent magnets, using as electric motor rotor.
Inventive concept 3: The electric -tip-jet engine of Inventive concept 1 wherein each counter-rotating-elements is installed adjacent to common stator in which a plurality of electromagnetic coils is installed creating a typical axial flow electromagnetic motor (also called a Pancake motor).
Inventive concept 4: The electric -tip-jet engine of Inventive concept 1 wherein a static guide vanes ring is installed between the counter-rotating fans. the static vanes ring and the fans are designed to operate as a two stages counter-rotating axial fan.
Inventive concept 5: A method for propelling a helicopter or a VTOL vehicle with an electric-tip-jet -engine comprising two counter-rotating elements. The two elements having substantially the same moment of Inertia and the common stator is causing the two rotational elements to spin at the same RPM while operating.
Inventive concept 6: A vehicle adapted to flight comprising: A rotor, a plurality of Electric tip jet engines as described in Inventive concept 1 and one of Inventive concepts 2,3,4 installed at the tips of the rotor blades and an electric battery as the main power source.
Inventive concept 7: A vehicle, as claimed in Inventive concept 6 but with a hybrid electric reciprocating-engine, as main power source (instead of the battery).
The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the present invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments will occur to persons skilled in the art to which the invention pertains.
In the description and claims of the present disclosure, each of the verbs, “comprise”, “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb. As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.
For example, the term “a marking” or “at least one marking” may include a plurality of markings.
This patent application claims the benefit of U.S. Provisional Patent Application No. 62/731,984 filed on Sep. 17, 2018, which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/057761 | 9/15/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62731984 | Sep 2018 | US |
