Patent Description:
In a turbofan engine, high pressure exhaust from burning fuel in a combustion chamber rotates various turbines. These turbines, when rotated, in turn impart rotation on spool shafts. The spool shafts, in turn, are connected to various compressors that feed air into the combustion chamber and to a fan that propels air through a bypass chamber around the turbine. The air propelled by the fan provides a portion (often a significant portion in "high-bypass" turbofan engines) of the motive force for the turbofan engine.

During operation of a conventional turbofan engine, a mechanical gearing arrangement (e.g., planetary gears) allows the fan to rotate at a different rotational speed than the spool shaft that provides rotational forces to the fan. The mechanical gearing arrangements are often heavy and bulky, and are prone to mechanical stresses (e.g., wear, material fatigue, lubricant leaks, etc.), which requires frequent inspection and maintenance to keep in working order. Additionally, the mechanical gearing arrangements, due to physical contact between parts, can cause noise and vibration in the turbofan engine in addition to the mechanical stresses between the components of the mechanical gearing arrangement itself.

<CIT>, in accordance with its abstract, states the present disclosure provides an electrically gear turbofan that includes a fan; a first spool shaft; and an electrical gearbox including: an armature winding connected to the first spool shaft and coupled to a power source; and a magnetic receiver connected to the fan, and wherein an air gap is defined between the armature winding and the magnetic receiver. The turbines and electrical gearing enable an operator to rotate the spool shaft at a first rotational speed; power an armature winding to generate an armature magnetic field, wherein the armature magnetic field rotates at a second rotational speed; transfer rotational energy via the armature magnetic field from the spool shaft to the magnetic receiver; and rotate the fan at a third rotational speed. In some aspects, the third rotational speed is controlled via a direction and a magnitude of the second rotational speed relative to the first rotational speed.

<CIT>, in accordance with its abstract, states a gas turbine engine, in particular for an airplane, includes a bladed rotor, a shaft driven by a turbine and an electrical generator including first and second generator components that can be rotated and magnetically coupled to one another, the first one being fixed to the shaft and the second one being mechanically coupled to the bladed rotor so as to drive the bladed rotor.

<CIT>, in accordance with its abstract, states a turbomachine comprises a turbine shaft, first and second rotors, first and second propulsion stages, and a magnetic stator. The first rotor is rotationally coupled to the turbine shaft, and coaxially arranged along an axis. The first propulsion stage is rotationally coupled to the first rotor, opposite the turbine shaft. The second rotor is coaxially arranged about the first rotor, and the second propulsion stage is rotationally coupled to second rotor, opposite the turbine shaft and adjacent the first propulsion stage. The magnetic stator is coaxially arranged between the first rotor and the second rotor, forming a magnetic coupling between the first and second rotors to drive the second propulsion stage in contra-rotation with respect to the first propulsion stage.

<CIT>, in accordance with its abstract, states an electromagnetically variable transmission includes an outer rotor and an inner rotor. The inner rotor is independently rotatable within a center aperture of the outer rotor. The outer rotor is independently rotatable about the inner rotor. One of the rotors has a plurality of permanent magnets configured in pairs and facing an air gap disposed between the outer rotor and the inner rotor. The other rotor has a plurality of slots spaced about a magnetically permeable core having embedded windings. The outer and inner rotors are simultaneously rotatable in one direction. In response to rotation of the outer rotor portion and the inner rotor portion, a magnetic flux path is generated between the permanent magnet pairs, the air gap, the outer rotor core and the inner rotor portion core, to induce electrical power in the windings, which transfers power between the inner rotor portion and the outer rotor portion.

The present disclosure provides a turbofan engine in one aspect, the turbofan engine including: a first magnetic gearbox assembly connected to a fan of a turbofan engine; a second magnetic gearbox assembly connected to a spool shaft of the turbofan engine; a switch in a winding circuit in one of the gearbox assemblies for coupling and decoupling the first magnetic gearbox assembly with the second magnetic gearbox assembly; and a speed controller configured to adjust a portion of the rotational energy transferred to the fan based on a duty cycle of the switch to thereby control a rotational speed of the fan based on a rotational speed of the spool shaft by selectively coupling and decoupling the first magnetic gearbox assembly with the second magnetic gearbox assembly.

A system may comprise: a first magnetic gearbox assembly connected to a fan of a turbofan engine; a second magnetic gearbox assembly connected to a spool shaft of the turbofan engine; and a speed controller configured to adjust a rotational speed of the fan based on a rotational speed of the spool shaft by selectively coupling and decoupling the first magnetic gearbox assembly with the second magnetic gearbox assembly.

Optionally, in combination with any example system above or below, the first magnetic gearbox assembly includes a permanent magnet array; the second magnetic gearbox assembly includes a rotor winding separated from the permanent magnet array by an air gap; and the speed controller is configured to selectively couple and decouple the first magnetic gearbox assembly with the second magnetic gearbox assembly via opening and closing a switch in a winding circuit with the rotor winding.

Optionally, in combination with any example system above or below, the second magnetic gearbox assembly includes a permanent magnet array; the first magnetic gearbox assembly includes a rotor winding separated from the permanent magnet array by an air gap; and the speed controller selectively is configured to couple and decouple the first magnetic gearbox assembly with the second magnetic gearbox assembly via opening and closing a switch in a winding circuit with the rotor winding.

Optionally, in combination with any example system above or below, the first magnetic gearbox assembly is positioned coaxially within a cavity defined by the second magnetic gearbox assembly.

Optionally, in combination with any example system above or below, the second magnetic gearbox assembly is positioned coaxially within a cavity defined by the first magnetic gearbox assembly.

Optionally, in combination with any example system above or below, the first magnetic gearbox assembly and the second magnetic gearbox assembly are electromagnetically linked via a coaxial magnetic field.

Optionally, in combination with any example system above or below, the speed controller is configured to decouple the first magnetic gearbox assembly from the second magnetic gearbox assembly by at least opening a switch via a switch driver powered by a current generated by the first magnetic gearbox assembly rotating relative to the second magnetic gearbox assembly.

Optionally, in combination with any example system above or below, the speed controller is configured to adjust the rotational speed of the fan based on a difference between a reference speed for the fan and a measured speed of the fan.

Optionally, in combination with any example system above or below, the speed controller further comprises a speed sensor, the speed sensor including at least one of: a Hall-effect sensor; an inductive sensor; or an opto-isolator sensor.

Optionally, in combination with any example system above or below, the system further includes an engine thrust controller configured to transmit the reference speed to the speed controller via contactless communication.

The present disclosure provides a turbofan engine according to claim <NUM>.

Optionally, in combination with any example turbofan engine above or below, the first magnetic gearbox assembly includes a permanent magnet array and the second magnetic gearbox assembly includes a winding circuit defining a rotor winding; and the speed controller is configured to reduce a duty cycle of a switch in the winding circuit to reduce the first rotational speed relative to the second rotational speed.

Optionally, in combination with any example turbofan engine above or below, the first magnetic gearbox assembly includes a winding circuit defining a rotor winding and the second magnetic gearbox assembly includes a permanent magnet array; and the speed controller is configured to reduces a duty cycle of a switch in the winding circuit to reduce the first rotational speed relative to the second rotational speed.

Optionally, in combination with any example turbofan engine above or below, the air gap is one of: coaxial to the first spool shaft defined by disposing the second magnetic gearbox assembly in a first cavity defined by the first magnetic gearbox assembly; coaxial to the first spool shaft defined by the first magnetic gearbox assembly in a second cavity defined by the second magnetic gearbox assembly; and perpendicular to an axis of rotation for the first spool shaft defined by disposing the first magnetic gearbox assembly parallel to the second magnetic gearbox assembly.

The present disclosure provides a method according to claim <NUM>.

Optionally, in combination with any example method above or below, the method further includes: measuring the second rotational speed; and in response to the second rotational speed not matching within a threshold of a reference speed for the fan, adjusting the duty cycle of the switch while continuing to rotate the spool shaft at the first rotational speed.

The present disclosure provides a computer program product according to claim <NUM>.

So that the manner in which the above recited features can be understood in detail, a more particular description, briefly summarized above, may be had by reference to examples, some of which are illustrated in the appended drawings.

The present disclosure provides for controllable electrically geared turbofan engines, which substitute the mechanical gearing arrangement between the spool shafts and the fans for electromagnetic couplings. An electromagnetic coupling allows for the transfer of rotational energy/torque without physical contact between the gear components, which can reduce the weight and size of turbofan engine assemblies as well as reduce the maintenance needs of the gearing arrangement compared to mechanical gearing arrangements.

A speed controller is provided that adjusts an effective "gear ratio" between the spool shaft and the fan, which enables more continuous control of the rotation speed (e.g., revolutions per minute (RPM)) of the fan. Stated differently, the rotational speed of the fan can be controlled independently of the rotational speed of the spool shaft so that the fan may be driven at a variable rate while driving the spool shaft at a relatively more constant rate that is optimized for various performance characteristics of the turbofan engine. Beneficially, the electromagnetic gearbox and speed controller of the present disclosure can provide greater fuel efficiency over a wider range of the thrust and speed of the turbofan engine than is provided by conventional statically-geared turbofan engines.

Although the examples provided in the present disclosure primarily illustrate a turbofan of an aircraft, the electrical gearing arrangements described in the present disclosure may be used in conjunction with turbofan engines in various other vehicles.

<FIG> illustrate cross-sectional views of turbofan engines <NUM>, (individually, turbofan engine 100A and turbofan engine 100B), which include an electrical gearbox <NUM>, according to the present disclosure. The turbofan engines <NUM> include a turbine enclosure <NUM> defining an air intake <NUM> at an upstream end, a compression section <NUM> downstream of the air intake <NUM>, a combustion section <NUM> downstream of the compression section <NUM>, a turbine section <NUM> downstream of the combustion section <NUM>, and an exhaust <NUM> at a downstream end. In various examples, the turbine enclosure <NUM> is included inside of a nacelle <NUM> (also referred to as a housing), and a bypass flow chamber <NUM> is defined between an outer surface of the turbine enclosure <NUM> and an inner surface of the nacelle <NUM>. A fan <NUM> is positioned in the nacelle <NUM> upstream of the air intake <NUM> of the turbine enclosure <NUM>, and during operation rotates to propel air inward to the air intake <NUM> of turbine enclosure <NUM> as well as through the bypass flow chamber <NUM>, thus providing intake charge and thrust.

<FIG> illustrates a turbofan engine <NUM> that includes a first spool shaft 160A (generally, spool shaft or shaft <NUM> or collectively, shaft assembly) and a second spool shaft 160B. <FIG> illustrates a turbofan engine that includes a first spool shaft 160A, a second spool shaft 160B, and a third spool shaft 160C, although in various examples a turbofan engine <NUM> can include one, two, three, or more spool shafts <NUM>.

In the depicted examples, each shaft <NUM> extends coaxially with the other shafts <NUM>, and rotates during operation at different rates relative to one another due to the ejection of high pressure exhaust rotating the turbines 180A-B (generally, turbine <NUM>) per <FIG> or turbines 180A-C per <FIG>, which in turn drive the associated compressors 170A-B (generally, compressor <NUM>) per <FIG> or compressors 170A-C per <FIG> at different rates via the connected spool shafts <NUM>. For example, a first spool shaft 160A rotates (due to forces imparted by the first turbine 180A) to drive the rotation of a first compressor 170A at a first rotational speed, while a second spool shaft 160B rotates (due to forces imparted by the second turbine 180B) to drive the rotation of a second compressor 170B at a second rotational speed. Although not illustrated, various bearings or low friction surfaces may be located between the shafts <NUM> to improve rotational characteristics of the shafts <NUM> (e.g., to reduce friction).

The compressors <NUM> are disposed in the compression section <NUM> of the turbine enclosure <NUM>, and may each include several fan blades arranged in one or more rows. The turbines <NUM> are disposed in the turbine section <NUM> of the turbine enclosure <NUM>, and may each include several turbine blades arranged in one or more rows.

As illustrated, the first spool shaft 160A is a low-pressure shaft relative to the high-pressure shaft of the second spool shaft 160B. Accordingly, the first compressor 170A is located upstream of the second compressor 170B, and rotates at a lower rotational speed than the second compressor 170B during operation of the turbofan engine <NUM>. Additionally, the first turbine 180A is located downstream of the second turbine 180B, and rotates at a lower rotational speed than the second turbine 180B during operation of the turbofan engine <NUM>. Similarly, with reference to <FIG>, the second compressor 170B is located upstream of the third compressor 170C, and rotates at a lower rotational speed than the third compressor 170C during operation of the turbofan engine <NUM>. Additionally, the second turbine 180B is located downstream of the third turbine 180C, and rotates at a lower rotational speed than the third turbine 180C during operation of the turbofan engine <NUM>.

The rotation of the low-pressure first spool shaft 160A is transferred to a fan <NUM> via the electrical gearbox <NUM>. The fan <NUM>, when rotated, forces air through the bypass flow chamber <NUM> of the turbofan engine <NUM> to provide motive force (e.g., thrust) to a vehicle using the turbofan engine <NUM>. The fan <NUM> includes a plurality of fan blades <NUM> extending from a central hub <NUM>, and is generally larger in radius than the corresponding blades of the compressors <NUM> (and turbines <NUM>) in the turbofan engine <NUM>. As such, if rotated at the same angular velocity or rotational speed (e.g., in revolutions per minute) as the compressors <NUM>, the fan <NUM> would be subject to higher velocities (and mechanical stresses) at the distal ends of the fan blades <NUM> than the blades of the compressors <NUM> and turbines <NUM>. For example, the tips of the blades of the compressors <NUM> (and turbines <NUM>) may travel at subsonic speeds, but the tips of the fan <NUM> rotating with the subsonic compressors <NUM> (and turbines <NUM>) may travel at supersonic speeds due to the greater radius of the fan <NUM>, which can cause noise and vibration issues (in addition to mechanical stresses) as the tips of the fan blades <NUM> break the sound barrier.

The electrical gearbox <NUM>, described in greater detail in regard to <FIG>, <FIG>, and <FIG>, couples the first spool shaft 160A with the hub <NUM> of the fan <NUM>, and allows the first spool shaft 160A (and the associated first compressors 170A) to rotate at one rotational speed, and the fan <NUM> to rotate at an independent rotational speed. The independent rotational speeds can include cases in which the fan <NUM> rotates faster than, slower than, or the same speed as the first spool shaft 160A. In some examples, an operator can also cause the speeds of the fan <NUM> and the first spool shaft 160A to change relative to one another (e.g., speeding up or slowing down the fan <NUM>).

The electrical gearbox <NUM> electromagnetically couples the first spool shaft 160A with the fan <NUM>, using magnetically coupled components as a gearing system, rather than physically interlocking gears, so that the portions of the electrical gearbox <NUM> physically connected to the first spool shaft 160A and the fan <NUM> are not in physical contact with one another. Instead, controllable electromagnetic fields selectively link the first spool shaft 160A and the fan <NUM> over an air gap. An operator controls whether a winding circuit is open or closed, thus selectively coupling and decoupling the components of the electrical gearbox <NUM> to set an effective gearing ratio based on a duty cycle of the winding circuit. In various examples, control signals can be transmitted to the electrical gearbox <NUM> to thereby alter a duty cycle and the ratio between the fan speed and the shaft speed to control the fan speed.

Accordingly, the electrical gearbox <NUM> is configured to transfer rotational energy from the spool shafts <NUM> to the fan <NUM>. In some examples, the electrical gearbox <NUM> is configured to maintain a static gearing ratio, or is controlled via the shaft-speed without further control signal inputs. The power to create these electromagnetic fields can be supplied by a power distribution bus <NUM> or other power transfer mechanism for a vehicle in which the turbofan engine <NUM> is disposed (e.g., via a transfer cable <NUM> or wireless resonant power transmitter), such as in <FIG> an 1B, or via an electrical generator <NUM> connected between two spool shafts <NUM>, such as in <FIG>, which is discussed in greater detail in regard to <FIG>. In some examples using an electrical generator <NUM>, the power distribution bus <NUM> and/or transfer cable <NUM> can be omitted.

The electrical gearbox <NUM> thereby allows the spool shafts <NUM> to rotate at a constant rate and the fan <NUM> to rotate at a different rate (either constant or based on a variable fan reference speed) by selectively coupling and decoupling the fan <NUM> from the first spool shaft 160A.

In some examples, such as in <FIG>, an electrical generator <NUM> is disposed at the interface between the first spool shaft 160A and the second spool shaft 160B (and/or the interface between the second spool shaft 160B and the third spool shaft 160C) to extract electrical energy based on the different rotational speeds of the spool shafts <NUM>. By attaching components of the electrical generators <NUM> to two different spool shafts (e.g., 160A and 160B) or to two different compressors (e.g., 170A and 170B) at the respective interfaces therebetween, the electrical generator <NUM> can, based on the differential rotational speed, convert rotational energy into electrical energy via a series of induced magnetic fields that can then be transferred to various systems within and outside of the turbofan engine <NUM> without requiring physical contact between the generator components rotating at different rates. The electrical generators <NUM> capitalize on the different rotational speeds of the compressors <NUM> attached to different shafts <NUM> to rotate the components relative to one another using the operational rotation of the components of the turbofan engine <NUM>. The construction of the electrical generator <NUM> is discussed in greater detail in regard to <FIG>.

<FIG> illustrate cross-sections for various configurations of the electrical gearbox <NUM>, according to the present disclosure. As will be appreciated, the electrical gearbox <NUM> can include a housing or other cover that protects internal components from debris, reduces air resistance, etc., mounting hardware to secure the electrical gearbox <NUM> to the fan <NUM> and/or spool shaft <NUM>, etc. Such mechanical features have been omitted from the Figures for clarity in discussing the electromagnetic components and the operation thereof.

In each of the configurations illustrated in <FIG>, a first magnetic gearbox assembly 210A (generally, magnetic gearbox assembly <NUM>) is connected to the fan <NUM> and a second magnetic gearbox assembly 210B is connected to the first spool shaft 160A. As will be described in greater detail in regard to <FIG> and <FIG>, one of the magnetic gearbox assemblies <NUM> includes a permanent magnet array, and the other magnetic gearbox assembly <NUM> includes a winding circuit with a rotor winding (shown in greater detail in <FIG> or <FIG>). The magnetic gearbox assemblies <NUM> are part of the electrical gearbox <NUM>, and are separated from one another by an air gap <NUM> that is selectively bridged by electromagnetic fields between the magnetic gearbox assemblies <NUM>.

In <FIG>, the second magnetic gearbox assembly 210B defines a first cavity 240A (generally, cavity <NUM>) in which the first magnetic gearbox assembly 210A is positioned. The first cavity 240A is coaxial to the spool shafts <NUM> so that the first magnetic gearbox assembly 210A and the second magnetic gearbox assembly 210B so that the magnetic gearbox assemblies <NUM> rotate about a shared axis of rotation <NUM> at different points along the length of the axis of rotation <NUM> so as to be clear of the orbit (i.e., not physically contacting) of the other magnetic gearbox assembly <NUM>.

In <FIG>, the first magnetic gearbox assembly 210A defines a second cavity 240B in which the second magnetic gearbox assembly 210B is positioned. The second cavity 240B is coaxial to the spool shafts <NUM> so that the first magnetic gearbox assembly 210A and the second magnetic gearbox assembly 210B so that the magnetic gearbox assemblies <NUM> rotate about a shared axis of rotation <NUM> at different points along the length of the axis of rotation <NUM> so as to be clear of the orbit (i.e., not physically contacting) of the other magnetic gearbox assembly <NUM>.

In <FIG>, the first magnetic gearbox assembly 210A and the second magnetic gearbox assembly 210B are positioned in a facing relationship to one another with an air gap <NUM> between the physical components thereof. The first magnetic gearbox assembly 210A and the second magnetic gearbox assembly 210B are coaxially aligned with one another, the hub <NUM>, and the first spool shaft 160A, and are arranged facially to one another so that the magnetic fields between the magnetic gearbox assemblies <NUM> are projected coaxially to link the magnetic gearbox assemblies <NUM>. The first magnetic gearbox assembly 210A is arranged in parallel to the second magnetic gearbox assembly 210B so that the air gap <NUM> is perpendicular to an axis of rotation <NUM> for the spool shafts <NUM> to define a planar air gap 240C (rather than a cavity in which one magnetic gearbox assembly <NUM> envelopes the other), over which the magnetic gearbox assemblies <NUM> are selectively linked via coaxial magnetic fields.

The relative sizes and positions of the electromagnetically coupled components in <FIG> have been illustrated for easy identification and differentiation. However, in various examples, the relative sizes, shapes, and orientations of these components may be altered based on the physical properties of the turbofan engine <NUM> in which the components are installed (e.g., length, thickness, circumference, gap distance, rotational torque, speed, operating temperature, etc.), the desired power transfer characteristics for the extracted rotational energy (e.g., gearing ratios, field strengths, relative speeds), and the like. The lengths of the components along the axis of the shafts <NUM> determined based on the torque and/or power rating requirements of the vehicle from the turbofan engine <NUM>, and the relative sizes and distances of individual components are sized to optimize torque production and speed from the turbofan engine <NUM> and power transfer efficiency in the electrical gearbox <NUM> within the physical confines of the turbofan engine <NUM>. Thus, <FIG> are intended to demonstrate the concepts of operation, and not necessarily a specific implementation, which may be modified based on the power requirements, thrust requirements, turbofan engine <NUM> specific fuel consumption, and material properties of various components, to name a few considerations.

<FIG> and <FIG> illustrate various arrangements of the first magnetic gearbox assembly 210A relative to the second magnetic gearbox assembly 210B, according to examples of the present disclosure. <FIG> illustrate a winding circuit <NUM>, including a rotor winding <NUM> and a switch <NUM>, internal to a permanent magnet array <NUM>, while <FIG> illustrate the winding circuit <NUM> external to the permanent magnet array <NUM>. Although illustrated with arrays having one pair of magnetic poles (i.e., one North (N) and one South (S) pole), rotor windings <NUM> and permanent magnet arrays <NUM> may include additional pairs of magnetic poles in other examples.

Depending on the configuration of the first magnetic gearbox assembly 210A relative to the second magnetic gearbox assembly 210B (per <FIG>), a first one of the winding circuit <NUM> and the permanent magnet array <NUM> are included in the first magnetic gearbox assembly 210A and the second one of the winding circuit <NUM> and the permanent magnet array <NUM> are included in the second magnetic gearbox assembly 210B. For example, when the second magnetic gearbox assembly 210B encompasses the first magnetic gearbox assembly 210A (as in <FIG>), the second magnetic gearbox assembly 210B may include the winding circuit <NUM> (as in <FIG>) or the permanent magnet array <NUM> (as in <FIG>).

<FIG> and <FIG> are illustrated in a plane perpendicular to the axis of rotation <NUM> for the spool shafts, and the rotation speed of the internal element (i.e., the winding circuit <NUM> in <FIG> or the permanent magnet array <NUM> in <FIG>) is illustrated as ωi, while the rotation speed of the external element (i.e., the winding circuit <NUM> in <FIG> or the permanent magnet array <NUM> in <FIG>) is illustrated as ωe. When the switch <NUM> is closed, completing the circuit including the rotor winding <NUM>, rotation of the permanent magnet array <NUM> relative to the rotor winding <NUM> induces a current in the winding circuit <NUM>, which generates a magnetic field in the rotor winding <NUM>. The magnetic fields of the permanent magnet array <NUM> and the winding circuit <NUM> interact, resulting in the transfer of rotational forces (e.g., torque) from the spool shaft <NUM> to the fan <NUM>.

<FIG> and <FIG> illustrate the respective winding circuits <NUM> and permanent magnet arrays <NUM> in a neutral position, where the respective winding circuits <NUM> and permanent magnet arrays <NUM> are not offset from one another. However, as the components rotate due to forces transferred from the rotation of the spool shafts <NUM>, the external component may lag or lead the external component by an angle θ. <FIG> and <FIG> illustrate the respective winding circuits <NUM> and permanent magnet arrays <NUM> with the external element lagging the internal element by an angle of θlag (e.g., <NUM> radians < θlag < π/<NUM> radians) in the direction of rotation. <FIG> and <FIG> illustrate the respective winding circuits <NUM> and permanent magnet arrays <NUM> with the external element leading the internal element by an angle of θlead (e.g., -π/<NUM> radians < θlead < <NUM> radians).

In some examples, the first magnetic gearbox assembly 210A connected to the first spool shaft 160A includes the permanent magnet array <NUM> and is external to the second magnetic gearbox assembly 210B that includes the winding circuit <NUM> (e.g., per <FIG> and <FIG>). In the present and other examples, when the permanent magnetic array <NUM> lags the rotor winding <NUM>, as in <FIG>, a current is generated in the rotor winding <NUM>, which in turn generates a rotor magnetic field that is pushed by the permanent magnetic field generated by the permanent magnet array <NUM>. Similarly, when the permanent magnetic array <NUM> leads the rotor winding <NUM>, as in <FIG>, a current is generated in the rotor winding <NUM>, which in turn generates a rotor magnetic field that is pulled by the permanent magnetic field inherent to the permanent magnet array <NUM>. Accordingly, rotational energy is transferred from the first spool shaft 160A to the fan <NUM> without requiring an external power source to energize the rotor winding <NUM>.

In other examples, the first magnetic gearbox assembly 210A connected to the first spool shaft 160A includes the winding circuit <NUM> and is external to the second magnetic gearbox assembly 210B that includes the permanent magnet array <NUM> (e.g., per <FIG> and <FIG>). In the present and other examples, when the rotor winding <NUM> lags the permanent magnetic array <NUM>, as in <FIG>, a current is generated in the rotor winding <NUM>, which in turn generates a rotor magnetic field that is pushed by the permanent magnetic field generated by the permanent magnet array <NUM>. Similarly, when the rotor winding <NUM> leads the permanent magnetic array <NUM>, as in <FIG>, a current is generated in the rotor winding <NUM>, which in turn generates a rotor magnetic field that is pulled by the permanent magnetic field inherent to the permanent magnet array <NUM>. Accordingly, rotational energy is transferred from the first spool shaft 160A to the fan <NUM> without requiring an external power source to energize the rotor winding <NUM>.

The switch <NUM> included in the winding circuit <NUM> selectively interconnects one end of the rotor winding <NUM> with the other end to open or close the winding circuit <NUM>. When closed, the switch <NUM> allows for the current to flow through the rotor winding <NUM> to generate the rotor magnetic field, thus allowing the permanent magnetic field to push or pull the rotor magnetic field. When open, the switch <NUM> interrupts the flow of current through the rotor winding <NUM> and thereby disrupts generation of the rotor magnetic field, thus decoupling the magnetic gearbox assemblies <NUM>. Depending on the duty cycle for how often (and for how long) the switch <NUM> is open or closed, the rotor winding <NUM> can alternate between lagging or leading the permanent magnet array <NUM>. Regardless of whether the rotor winding <NUM> is lagging or leading the permanent magnet array <NUM>, the forces are transferred to rotate the fan <NUM> in the same direction as the first spool shaft 160A.

The rotational force that is applied as a torque from the first spool shaft 160A to the fan <NUM> that is proportional to the induced current in the rotor winding <NUM>. By controlling the duty cycle of the switch <NUM>, the average value for the induced current over time can be matched to a desired torque. For a given moment of inertia of a rotor P, the dynamic equation governing the speed thereof is given according to Formula <NUM>, where J is the moment of inertia of the rotor, Tis the torque produced by the interaction of the magnetic fields, and b is the friction coefficient.

Assuming a constant friction coefficient b with a rotor under a steady state (i.e., not accelerating), Formula <NUM> provides a simplified version of Formula <NUM>.

Accordingly, the rotational speed of the fan <NUM> is proportional to the averaged value of the induced current in the rotor winding <NUM> over time.

<FIG> illustrate a speed controller <NUM> for an electrical gearbox <NUM>, according to the present disclosure. The speed controller <NUM> sets the duty cycle for the switch <NUM> to control the induced current in the rotor winding <NUM>, and thereby the speed of the fan <NUM>. The speed controller <NUM> is co-located with the winding circuit <NUM> to control the switch <NUM> included therein. <FIG> illustrates an example where the speed controller <NUM> is located on the fan <NUM> (i.e., when the first magnetic gearbox assembly 210A includes the winding circuit <NUM>) and receives power from an external power supply <NUM>. <FIG> illustrates an example where the speed controller <NUM> is located on the first spool shaft 160A (i.e., when the second magnetic gearbox assembly 210B includes the winding circuit <NUM>) and receives power from an external power supply <NUM>. <FIG> shows an example where the speed controller <NUM> is located on the first spool shaft 160A (i.e., when the second magnetic gearbox assembly 210B includes the winding circuit <NUM>) and receives power from a power supply <NUM> located on the spool shafts <NUM>, in contrast to the examples discussed in relation to <FIG> and <FIG> where the power is received from a power supply <NUM> that transmits power through the engine case and intervening space to the fan <NUM>.

The speed controller <NUM> receives a reference (or target) speed for the fan <NUM> from an engine thrust controller <NUM> and a measured speed for the fan <NUM> from a speed sensor <NUM>. In various examples, the engine thrust controller <NUM> is disposed in the nacelle <NUM> or the body of the vehicle controlling the turbofan engine <NUM>, and determines the reference speed for the fan <NUM> based on the operating conditions of the turbofan engine <NUM> (e.g., altitude, temperature, number of engines employed by the vehicle, etc.) and a desired speed or thrust profile for the vehicle. In some examples, the engine thrust controller <NUM> transmits the reference speed to the speed controller <NUM> via contactless communications (e.g., light or radio waves). Thus, examples may include a contactless transmitter 570A paired with a contactless receiver 570B used by the speed controller <NUM> to receive the reference speed.

The speed sensor <NUM> measures a rotation speed of the fan <NUM>, and may include several different types of sensors deployed at various positions in the turbofan engine <NUM>. In some examples, the speed sensor <NUM> includes a Hall-effect sensor that measures a magnitude of a magnetic field (e.g., produced by a permanent magnet connected to the fan <NUM>) to track the rotation speed of the fan <NUM> based a frequency of periodic changes in the magnitude of that magnetic field. In other examples, the speed sensor <NUM> includes an inductive sensor, which measures variations in magnetic flux in a generated or induced magnetic field due to changes in proximity to elements of the fan <NUM> (e.g., as the fan blades <NUM> are angled) or the magnetic elements included in the first magnetic gearbox assembly 210A. In other examples, the speed sensor <NUM> includes an opto-isolator sensor that includes a light transmitter and a light receiver to measure how frequently the transmitter and receiver are aligned with one another (e.g., based on a transmitted light beam between transmitters/receivers located separately on the fan <NUM> and spool shaft <NUM>) or based on reflected signal (e.g., off of a reflective surface of the fan <NUM> to a reflective pair of transmitters/receivers located on the spool shaft <NUM>) determine the speed of the fan <NUM>.

A comparator <NUM> compares the reference speed against the measured speed, and provides the difference to a control loop <NUM>, such as a Proportional Integral Derivative (PID) controller, which uses the difference as feedback for how to adjust the duty cycle of the switch <NUM>. For example, when the difference indicates that the measured speed is less than the reference speed, the control loop <NUM> indicates that the duty cycle should be increased so that the switch <NUM> stays closed for longer, closed more often, or combinations thereof compared to a current duty cycle. In other examples, when the difference indicates that the measured speed is greater than the reference speed, the control loop <NUM> indicates that the duty cycle should be decreased so that the switch <NUM> stays open for longer, open more often, or combinations thereof compared to a current duty cycle. Accordingly, the switch <NUM> is controlled to selectively decouple or selectively couple the magnetic gearbox assemblies <NUM> of the electrical gearbox <NUM> in response to the duty cycle indicated by the control loop <NUM>.

In various examples, the output from the control loop <NUM> is passed through an integrator <NUM> to remove spikes in the output, maintain the output within a specified range, and prevent oscillating changes (e.g., alternating small increases and decreases in duty cycle below a threshold adjustment size or within a specified window of time) to reduce jerk or strain on the fan <NUM> via rapid or frequent changes in the duty cycle.

A power switch driver <NUM> receives the output from the speed controller <NUM> to implement the duty cycle for the switch <NUM>. In various examples, the power switch driver <NUM> is powered via a current generated in the winding circuit <NUM> or another inductive loop to open and close the switch <NUM> according to the selected duty cycle. In various examples, the power switch driver <NUM> supplies the power to open a normally-closed switch that closes when the power is no longer supplied, supplies the power to close a normally open-switch that opens when the power is no longer supplied, or supplies the power to change the state of a switch that remains in a current state (i.e., open or closed) when the power is no longer supplied.

In <FIG> and <FIG>, the power provided to the electrical components of the speed controller <NUM> and power switch driver <NUM> is received from a power supply <NUM> external to the spool shafts <NUM> and electrical gearbox <NUM>, which may be mounted to the turbine enclosure <NUM> or nacelle <NUM> in some examples. When mounted externally from the electrical gearbox <NUM>, the power is transferred wirelessly over an air gap from a power transmitter 590A that is located with the power supply <NUM> to a power receiver 590B that is located on the spool shafts <NUM>, the fan, or the electrical gearbox <NUM>. In various examples, the power transmitter 590A and power receiver 590B can include various near-field coupled devices (e.g., inductive or capacitive coupled devices) or far-field coupled devices (e.g., microwave and laser power beaming devices) according to the distances between the power transmitter 590A and power receiver 590B and intervening objects (including additional power transmitters/receivers for forwarding power between different locations).

In <FIG>, the power provided to the electrical components of the speed controller <NUM> and power switch driver <NUM> is received from a power supply <NUM> co-located with the spool shafts <NUM> or electrical gearbox <NUM>. In various examples, the power supply <NUM> of <FIG> can be a battery or other power storage and release device, such as a super capacitor. In some examples, the power supply <NUM> of <FIG> receives input power from a generator <NUM> connected at an interface between the first spool shaft 160A and the second spool shaft 160B, as is described in greater detail in regard to <FIG>.

<FIG> is a flowchart of a method <NUM> for controlling a turbofan engine <NUM> having an electrical gearbox <NUM>, according to the present disclosure.

Method <NUM> begins at block <NUM>, where the spool shafts <NUM> of the turbofan engine <NUM> rotates. In a turbofan engine <NUM>, an operator may cause spool shafts <NUM> to rotate by engaging the turbofan engine <NUM> to produce thrust for a vehicle; inducing rotational energy upon spool shafts <NUM> by the combustion of fuel in a combustion chamber and expelling the exhaust through a turbine section <NUM>, thus causing the turbines <NUM> to rotate the corresponding spool shafts <NUM>. Depending on the number of spool shafts <NUM> in the turbofan engine <NUM>, the thrust requirements of the vehicle using the turbofan engine <NUM>, the altitude of the vehicle using the turbofan engine <NUM>, etc., the spool shafts <NUM> may rotate at various different speeds.

At block <NUM>, the electrical gearbox <NUM> transfers rotational energy from the first spool shaft 160A of the turbofan engine <NUM> to the fan <NUM>. A first magnetic gearbox assembly 210A of the electrical gearbox <NUM> is connected to the first spool shaft 160A, and includes one of a winding circuit <NUM> or a permanent magnet array <NUM>. A second magnetic gearbox assembly 210B of the electrical gearbox <NUM> is connected to the fan <NUM>, and includes a different one of the winding circuit <NUM> or the permanent magnet array <NUM> from what is included in the first magnetic gearbox assembly 210A. The magnetic gearbox assemblies <NUM> are separated from one another via an air gap <NUM>, but are (selectively) electromagnetically coupled over the air gap <NUM> via a rotor magnetic field selectively generated by a rotor winding <NUM> and a permanent magnetic field generated by a permanent magnet array <NUM>.

By rotating the first spool shaft 160A (and the connected first magnetic gearbox assembly 210A) at a first rotational speed, a current is induced in a rotor winding <NUM> of the winding circuit <NUM> when a switch <NUM> therein is closed. When the current is induced in the rotor winding <NUM>, the rotor winding <NUM> generates a rotor magnetic field that is pushed or pulled in the direction of rotation of the first spool shaft 160A by the permanent magnetic field associated with the permanent magnet array <NUM>. Accordingly, the rotational energy of the first spool shaft 160A is transferred from via the first magnetic gearbox assembly 210A to the second magnetic gearbox assembly 210B, which is connected to the fan <NUM>, thus causing the fan <NUM> to rotate with the first spool shaft 160A.

At block <NUM>, the fan <NUM> rotates at a second rotational speed based on the first rotational speed of the first spool shaft 160A and the duty cycle for the switch <NUM> selected by the speed controller <NUM>.

At block <NUM>, the speed controller <NUM> measures the second rotational speed of the fan <NUM>. In various examples, a speed sensor <NUM> (such as a Hall-effect sensor, an inductive sensor, an opto-isolator sensor, or the like) measures the speed of the fan <NUM>, and the speed controller <NUM> compares the measured speed against a reference (or target) speed at which the fan <NUM> has been set to rotate at. The speed controller <NUM> determines whether to adjust the duty cycle of the switch <NUM> (and thereby the speed of the fan <NUM>) based on whether a difference between the reference speed for the fan <NUM> and the measured speed for the fan <NUM> falls outside of a threshold range (e.g., Δ(ωreference, ωmeasured) ± x% of Wreference).

At block <NUM>, the speed controller <NUM> adjusts a portion of the rotational energy transferred to the fan <NUM> based on a duty cycle of the switch <NUM> in the winding circuit <NUM> of the electrical gearbox <NUM>. By increasing a relative amount of time that the switch <NUM> is closed, the speed controller <NUM> increases the portion of the rotational energy transferred from the spool shafts <NUM> to the fan <NUM>, thus increasing the speed of the fan <NUM>. Similarly, by decreasing the relative amount of time that the switch <NUM> is open, the speed controller <NUM> decreases the portion of the rotational energy transferred from the spool shafts <NUM> to the fan <NUM>, thus decreasing the speed of the fan <NUM>. When the reference speed is greater than the measured speed and outside of the threshold, method <NUM> returns to block <NUM> with an increased duty cycle for the switch <NUM> to thereby increase the speed of the fan <NUM>. When the reference speed is less than the measured speed and outside of the threshold, method <NUM> returns to block <NUM>, with a decreased the duty cycle for the switch <NUM> to thereby decrease the speed of the fan <NUM>. Method <NUM> may thus continue so as to control the speed of the fan <NUM> with respect to updated reference speeds, changes in environmental conditions, changes in rotational speeds of the spool shafts <NUM>, and combinations thereof.

<FIG> is a flowchart of a method <NUM> for fabricating a turbofan engine <NUM> with an electrical gearbox <NUM>, according to the present disclosure.

At block <NUM>, a fabricator affixes a first magnetic gearbox assembly 210A to a first spool shaft 160A of a turbofan engine <NUM>.

At block <NUM>, the fabricator affixes a second magnetic gearbox assembly 210B to the fan <NUM> of the turbofan engine <NUM>.

The first magnetic gearbox assembly 210A includes a first one of a winding circuit <NUM> and a permanent magnet array <NUM>, while the second magnetic gearbox assembly 210B includes the second one of the winding circuit <NUM> and the permanent magnet array <NUM>, different from the first one included in the first magnetic gearbox assembly 210A. The first magnetic gearbox assembly 210A and the second magnetic gearbox assembly 210B define an air gap <NUM> between one another, such that the first magnetic gearbox assembly 210A and the second magnetic gearbox assembly 210B are not in physical contact with one another. Rather, the first magnetic gearbox assembly 210A and the second magnetic gearbox assembly 210B are configured to be selectively in magnetic contact with one another. In various examples, the first magnetic gearbox assembly 210A is disposed in a first cavity 240A defined by the second magnetic gearbox assembly 210B (as per <FIG>), the second magnetic gearbox assembly 210B is disposed in a second cavity 240B defined by the first magnetic gearbox assembly 210A, or the magnetic gearbox assemblies <NUM> are disposed parallel to one another to define an air gap <NUM> that is perpendicular to the axis of rotation <NUM> for the spool shafts <NUM> (as per <FIG>).

At block <NUM>, the fabricator affixes a speed sensor <NUM> in the turbofan engine <NUM> for the fan <NUM>, to monitor a rotational speed of the fan <NUM>. The speed sensor <NUM> can include various types of speed sensing or measuring devices including, but not limited to: Hall-effect sensors, inductive sensors, and opto-isolator sensors. In various examples, the speed sensor may include components affixed to one or more of the fan <NUM>, the first spool shaft 160A, the turbine enclosure <NUM>, the nacelle <NUM>, or other components of the turbofan engine <NUM>.

At block <NUM>, the fabricator couples the speed controller <NUM> to the speed sensor <NUM> and to the winding circuit <NUM>. The speed controller <NUM> is configured to adjust a duty cycle of a switch <NUM> included in the winding circuit <NUM> based on a difference between the rotational speed of the fan <NUM> as measured by the speed sensor <NUM> and a desired speed for the fan <NUM>, as indicated by an engine thrust controller <NUM> in contactless communication with the speed controller <NUM>. The speed controller <NUM> is located on the fan <NUM> when the first magnetic gearbox assembly 210A includes the winding circuit <NUM>, or is located on the first spool shaft 160A when the second magnetic gearbox assembly 210B includes the winding circuit <NUM>.

<FIG> illustrates a first component arrangement 800A for an electrical generator <NUM>, according to the present disclosure. A first rotor assembly 810A is connected to a second (higher-pressure) compressor 170B and a second rotor assembly 810B is connected to a first (lower-pressure) compressor 170A at an interface between the two compressors 170A-B. In various examples, the rotor assemblies 810A-B are connected to one or more blades of the associated compressor <NUM>, to a ring/connection point of the blades to an associated spool shaft <NUM>, or to the associated spool shaft <NUM>. The rotor assemblies 810A-B position various electromagnetic components of the electrical generator <NUM> at known distances and orientations relative to one another, the shafts <NUM>, and the compressors <NUM>.

In <FIG>, the first rotor assembly 810A includes a permanent magnet <NUM>, which produces a generator magnetic field <NUM>. The permanent magnet <NUM> emits the generator magnetic field <NUM> radially through an air gap defined coaxially to the shafts <NUM> to magnetically link the permanent magnet <NUM> with a generator armature winding <NUM> included in the second rotor assembly 810B. In various examples, the permanent magnet <NUM> may include a plurality of magnets arranged circumferentially around the shaft <NUM> to emit a plurality of generator magnetic fields <NUM>.

The second rotor assembly 810B includes the generator armature winding <NUM> arranged concentrically and radially, but not in physical contact with, the permanent magnet <NUM> or the shafts <NUM>, and positions the generator armature winding <NUM> within a predefined field strength of the generator magnetic field <NUM>. Accordingly, the generator magnetic field <NUM> radially links the permanent magnet <NUM> and the generator armature winding <NUM>.

<FIG> illustrates a second component arrangement 800B for an electrical generator <NUM>, according to the present disclosure. A first rotor assembly 810A is connected to a higher-pressure second compressor 170B and a second rotor assembly 810B is connected to a lower-pressure first compressor 170A at an interface between the two compressors <NUM>. In various examples, the rotor assemblies 810A-B are connected to one or more blades of the associated compressor <NUM>, to a ring/connection point of the blades to an associated spool shaft <NUM>, or to the associated spool shaft <NUM>. The rotor assemblies 810A-B position various electromagnetic components of the electrical generator <NUM> at known distances and orientations relative to one another, the shafts <NUM>, and the compressors <NUM>.

In <FIG>, the first rotor assembly 810A includes a permanent magnet <NUM>, which produces a generator magnetic field <NUM>. The permanent magnet <NUM> emits the generator magnetic field <NUM> through an air gap defined in a plane intersecting the axis of rotation for the shafts <NUM> to magnetically link the permanent magnet <NUM> with a generator armature winding <NUM> included in the second rotor assembly 810B. Although illustrated as defining an air gap in a plane orthogonal to the axis of rotation (e.g., for a coaxial magnetic linkage between the permanent magnet <NUM> and the generator armature winding <NUM>), in other examples, the air gap may be defined at other angles relative to the shafts <NUM>. In examples, the permanent magnet <NUM> may include a plurality of magnets arranged radially around the shaft <NUM> to emit a plurality of generator magnetic fields <NUM>.

The second rotor assembly 810B includes the generator armature winding <NUM> arranged radially around, but not in physical contact with, the shafts <NUM> and arranged planetary to the permanent magnet <NUM>. The relative positions and lengths of the rotor assemblies 810A-B position the generator armature winding <NUM> within a predefined field strength of the generator magnetic field <NUM>. Accordingly, the generator magnetic field <NUM> axially links the permanent magnet <NUM> and the generator armature winding <NUM>.

During operation of the turbofan engine <NUM> in which the components are disposed, the rotational forces imparted by turbines <NUM> cause the compressors <NUM> and attached EM components to rotate relative to one another and the stationary turbine enclosure <NUM>. Due to the differential in the rotational speeds of the higher-pressure compressor 170B and the lower-pressure compressor 170A, the generator magnetic field <NUM> rotates relative to the generator armature winding <NUM>. Accordingly, electrical energy is extracted from the rotational forces of the shafts <NUM> and is transferred to power the speed controller <NUM> of the electrical gearbox <NUM>, among other components (e.g., as a power supply <NUM>).

The relative sizes and positions of the electromagnetically coupled components in <FIG> and <FIG> have been illustrated for easy identification and differentiation. However, in various examples, the relative sizes, shapes, and orientations of these components may be altered based on the physical properties of the turbofan engine <NUM> in which the components are installed (e.g., length, thickness, circumference, gap distance, rotational torque, and speed, operating temperature), the desired power characteristics for the extracted power (e.g., number of power phases, voltage/current levels), and the like. The lengths of the components along the axis of the shafts <NUM> are determined by the torque and/or power rating requirements of the vehicle from the turbofan engine <NUM>, and the relative sizes and distances of individual components are sized to optimize torque production and speed from the turbofan engine <NUM> and power transfer efficiency in the electrical generator <NUM> within the physical confines of the turbofan engine <NUM>. Thus, <FIG> and <FIG> are intended to demonstrate the concepts of operation, and not necessarily a specific implementation, which may be modified based on the power requirements, thrust requirements, turbofan engine <NUM> specific fuel consumption, and material properties of various components. For example, a fabricator can design the permanent magnet <NUM> and the generator armature winding <NUM> according to <FIG> when radial space along the length of blades of the compressors <NUM> is more readily available or according to <FIG> when axial space between the compressors <NUM> is more readily available.

In the current disclosure, reference is made to various examples. However, it should be understood that the present disclosure is not limited to specific described examples. Instead, any combination of the following features and elements, whether related to different examples or not, is contemplated to implement and practice the teachings provided herein. Additionally, when elements of the examples are described in the form of "at least one of A and B," it will be understood that examples including element A exclusively, including element B exclusively, and including element A and B are each contemplated. Furthermore, although some examples may achieve advantages over other possible solutions and/or over the prior art, whether or not a particular advantage is achieved by a given example is not limiting of the present disclosure. Thus, the examples, features, and advantages disclosed herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s).

As will be appreciated by one skilled in the art, examples described herein may be embodied as a system, method or computer program product. Accordingly, examples may take the form of an entirely hardware example, an entirely software example (including firmware, resident software, micro-code, etc.) or an example combining software and hardware examples that may all generally be referred to herein as a "circuit," "module" or "system. " Furthermore, examples described herein may take the form of a computer program product embodied in one or more computer readable storage medium(s) having computer readable program code embodied thereon.

Program code embodied on a computer readable storage medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations of the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages.

Examples of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatuses (systems), and computer program products according to the present disclosure.

Claim 1:
A turbofan engine (<NUM>), comprising:
a first magnetic gearbox assembly (210A) connected to a fan (<NUM>) of the turbofan engine (<NUM>);
a second magnetic gearbox assembly (210B) connected to a spool shaft (<NUM>) of the turbofan engine (<NUM>);
a switch (<NUM>) in a winding circuit (<NUM>) in one of the gearbox assemblies (210A, 210B) for coupling and decoupling the first magnetic gearbox assembly (210A) with the second magnetic gearbox assembly (210B); and
a speed controller (<NUM>) configured to adjust a portion of the rotational energy transferred to the fan (<NUM>) based on a duty cycle of the switch to thereby control a rotational speed of the fan (<NUM>) based on a rotational speed of the spool shaft (<NUM>) by selectively coupling and decoupling the first magnetic gearbox assembly (210A) with the second magnetic gearbox assembly (210B).