Patent Description:
The fan section typically provides a majority of propulsive thrust for the engine. Adjusting a speed of the fan to provide more efficient operation requires adjustment of a speed of the drive turbine. A geared architecture between the fan and the drive turbine enables both to operate closer to optimal speeds. However, the drive turbine and fan are still mechanically linked and therefore any changes in speed to adjust fan speed also changes the speed of the drive turbine. Moreover, the drive turbine typically drives a low pressure compressor. Changing speeds of the low pressure compressor can complicate operation and place constraints on the speed of the fan.

Although improved technology and materials have improved engine efficiency, turbine engine manufacturers continue to seek further improvements to engine performance including improvements to thermal, transfer and propulsive efficiencies.

<CIT> discloses a prior art differential geared turbine engine with torque modulation capability.

<CIT> discloses a prior art Fan drive gear system mechanical controller.

<CIT> discloses a prior art gas turbine engine having a differential transmission.

In accordance with a first aspect of the invention, there is provided a gas turbine engine as claimed in claim <NUM>.

In an embodiment of the foregoing gas turbine engine, a first clutch assembly is disposed between the first electric motor and the geared architecture and a second clutch assembly disposed between the second electric motor and the geared architecture, wherein the first clutch assembly enables input from the first electric motor in only the first direction and the second clutch assembly enables input from the second electric motor in only the second direction.

In another embodiment of any of the foregoing gas turbine engines, the driven gear is coupled to the carrier.

In another embodiment of any of the foregoing gas turbine engines, the driven gear is coupled to the ring gear.

In another embodiment of any of the foregoing gas turbine engines, the fan section includes a fan shaft coupled to the ring gear.

In another embodiment of any of the foregoing gas turbine engines, the fan section includes a fan shaft coupled to the carrier.

In another embodiment of any of the foregoing gas turbine engines, a compressor includes a section with a low pressure compressor and the turbine section includes a low pressure turbine that drives both the low pressure compressor and the geared architecture.

In another embodiment of any of the foregoing gas turbine engines, the low pressure compressor is driven by the low pressure turbine at a speed different then the fan section.

In another embodiment of any of the foregoing gas turbine engines, the first electric motor assembly drives the fan in the first direction to increase fan speed.

In another embodiment of any of the foregoing gas turbine engines, the second electric motor assembly is configured such that rotation of the geared architecture enables a speed of the fan to remain constant with a change in speed of the second driving input provided by the turbine section.

In accordance with a second aspect of the invention, there is provided a method of operating a gas turbine engine as claimed in claim <NUM>.

In a further embodiment of the foregoing method of operating a gas turbine engine, coupling a first clutch assembly between the first electric motor and the drive gear and coupling a second clutch assembly between the second electric motor and the drive gear. The first electric motor and the second electric motor only drive the geared architecture in a single direction.

In a further embodiment of the foregoing method of operating a gas turbine engine, the first electric motor assembly and the second electric motor assembly operate to maintain a rotational speed of the fan blades while decreasing a speed of a low pressure compressor driven by the turbine section.

In a further embodiment of the foregoing method of operating a gas turbine engine, the first electric motor assembly is mounted to drive a fan shaft.

Although the different examples have the specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations.

The exemplary engine <NUM> generally includes a low speed spool <NUM> and a high speed spool <NUM> mounted for rotation about an engine central longitudinal axis A relative to an engine static structure (or 'fixed structure') <NUM> via several bearing systems <NUM>.

The inner shaft <NUM> is connected to the fan section <NUM> through a speed change mechanism, which in the exemplary gas turbine engine <NUM> is illustrated as a geared architecture <NUM> to drive fan blades <NUM> at a lower speed than the low speed spool <NUM>.

The core airflow is compressed by the low pressure compressor <NUM> then the high pressure compressor <NUM>, mixed and burned with fuel in the combustor <NUM> to generate a high energy flow that is expanded over the high pressure turbine <NUM> and low pressure turbine <NUM>. For example, gear system <NUM> may be located aft of the low pressure compressor <NUM>, and fan blades <NUM> may be positioned forward or aft of the location of the geared architecture <NUM> or even aft of turbine section <NUM>.

In a further example, the engine <NUM> bypass ratio is greater than six, with an example embodiment being greater than ten, the geared architecture <NUM> is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than <NUM> and the low pressure turbine <NUM> has a pressure ratio that is greater than five. In one disclosed embodiment, the engine <NUM> bypass ratio is greater than ten, the fan diameter is significantly larger than that of the low pressure compressor <NUM>, and the low pressure turbine <NUM> has a pressure ratio that is greater than five. The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than <NUM>:<NUM> and less than <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine.

The fan section <NUM> of the engine <NUM> is designed for a particular flight condition -- typically cruise at <NUM> Mach and <NUM>,<NUM> feet (<NUM>,<NUM> meters). The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than <NUM>. "Low corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]^<NUM> (where °R = K x <NUM>/<NUM>). The "Low corrected fan tip speed" as disclosed herein according to one non-limiting embodiment is less than <NUM> ft / second (<NUM> meters/second).

The example gas turbine engine includes the fan section <NUM> that comprises in one non-limiting embodiment less than twenty-six fan blades <NUM>. In another non-limiting embodiment, the fan section <NUM> includes less than twenty fan blades <NUM>. Moreover, in one disclosed embodiment the low pressure turbine <NUM> includes no more than six turbine rotors schematically indicated at <NUM>. In another non-limiting example embodiment the low pressure turbine <NUM> includes three turbine rotors. A ratio between the number of fan blades <NUM> and the number of low pressure turbine rotors is between <NUM> and <NUM>. The example low pressure turbine <NUM> provides the driving power to rotate the fan section <NUM> and therefore the relationship between the number of turbine rotors <NUM> in the low pressure turbine <NUM> and the number of blades <NUM> in the fan section <NUM> disclose an example gas turbine engine <NUM> with increased power transfer efficiency.

The example gas turbine engine <NUM> includes a first electric motor assembly <NUM> that is coupled to drive the fan section <NUM>. A second electric motor assembly <NUM> is coupled to drive the geared architecture <NUM> relative to the static structure <NUM> of the engine <NUM>. The first and second electric motor assemblies <NUM>, <NUM> enable the fan blades <NUM> to rotate about the axis A at a speed different than provided by the geared architecture <NUM>.

Changes to propulsive thrust provided by the fan section <NUM> require a corresponding change of speed of the low pressure turbine <NUM>. The low pressure turbine <NUM> also drives the low pressure compressor <NUM> and results in changes in speed of the low pressure compressor <NUM>. Increasing the speed of the low pressure compressor <NUM> may result in the compressor rotating at speeds that do not provide efficient operation or that provide pressures and flows that are not within desired ranges for efficient operation of the high pressure compressor <NUM>. Performance of the low-pressure compressor <NUM> is matched to the operation of the high-pressure compressor <NUM> to provide the most efficient use of energy and provide optimal engine operating conditions. Inputting additional power by increasing the speed of the low-pressure compressor <NUM> may disrupt the matched performance between the low-pressure compressor <NUM> and the high-pressure compressor <NUM>.

The example gas turbine engine <NUM> includes the first electric motor assembly <NUM> that boosts a speed of rotation of the fan blades <NUM> about the axis A to a speed greater than that provided by the output of the geared architecture <NUM>. The geared architecture <NUM> is driven relative to the static structure <NUM> of the engine by the second electric motor assembly <NUM>. The geared architecture <NUM> is not structurally grounded directly to the static engine structure <NUM> but is instead mechanically grounded to the engine static <NUM> structure through the electric motor assembly <NUM>. The electric motor assembly <NUM> rotates the geared architecture <NUM> to partially decouple fan speed from a speed provided by the low pressure turbine <NUM> through the geared architecture <NUM>.

Referring to <FIG> the example gas turbine engine <NUM> is shown schematically and includes the first electric motor assembly <NUM> that is disposed on a fan shaft <NUM> that supports the plurality of fan blades <NUM>. The first motor assembly <NUM> provides a first drive input for driving the fan blades <NUM> about the axis and is operated by a motor control <NUM> that is a part of a motor controller <NUM>. The example motor controller <NUM> can receive information from an engine control such as in this example a Full Authority Digital Electronic Control (FADEC) <NUM>. The electric motor <NUM> inputs power directly to the fan shaft <NUM> to provide a boost of power directly to the fan section <NUM>. The increased power provided by the electric motor <NUM> enables a boost to the speed of the fan section <NUM> independent of the low pressure turbine <NUM>. The geared architecture <NUM> provides a second drive input to drive the fan blades <NUM> about the axis A.

The second electric motor assembly <NUM> includes a first electric motor <NUM> and a second electric motor <NUM> that are both coupled to drive a driven gear <NUM> that is attached to a carrier <NUM>. The example geared architecture <NUM> includes a sun gear <NUM> driven by the shaft <NUM>. The sun gear <NUM> in turns drives intermediate gears <NUM> that are supported on the carrier <NUM>. The intermediate gears <NUM> are circumscribed by a ring gear <NUM>. The ring gear <NUM> is coupled to drive the fan shaft <NUM>. The driven gear <NUM> is a single gear that is attached to the carrier <NUM> and is coupled to a first drive gear <NUM> and second drive gear <NUM>. The disclosed gear architecture <NUM> is not directly coupled to the engine static structure <NUM> but is instead rotatable about the axis A independent of rotation of the shaft <NUM>.

The first electric motor <NUM> includes a first clutch <NUM>. The electric motor <NUM> drives the first shaft <NUM> that drives the first drive gear <NUM> that is coupled to the driven gear <NUM>. The driven gear <NUM> is a gear that is disposed about the axis A and rotates the geared architecture <NUM>.

The second electric motor <NUM> drives a second shaft <NUM> and the second drive gear <NUM>. A second clutch <NUM> is provided to enable the electric motor <NUM> to drive the driven gear <NUM> in only one direction. Moreover the first clutch <NUM> driven by the first electric motor <NUM> is able to drive the driven gear <NUM> in only a single direction. In one disclosed embodiment, the first electric motor <NUM> drives the driven gear <NUM> in a clockwise or first direction and the second electric motor <NUM> drives the second driven gear <NUM> in a counterclockwise or second direction. It should be appreciated, that although the first electric motor <NUM> and the second electric motor <NUM> are depicted as a single electric motor, multiple electric motors could be utilized and are within the contemplation of this disclosure.

The example controller <NUM> includes the motor controller <NUM> that commands operation of the first electric motor assembly <NUM>, a power source <NUM> and electronics <NUM> required to drive and command operation of the first electric motor assembly <NUM>. The controller <NUM> further includes motor controllers <NUM> and <NUM> that control operation of the corresponding first and second electric motors <NUM> and <NUM> of the second electric motor assembly <NUM>. The example controller <NUM> may be provided as part of the engine controller or may be a separate controller for the first and second electric motor assemblies <NUM>, <NUM>. Additionally, the controller <NUM> can be implemented as hardware or software. The power source <NUM> maybe a battery or generator powered by the engine <NUM>.

Referring to <FIG> with continued reference to <FIG>, operation of the example gas turbine engine <NUM> to provide a boost to the fan section <NUM> enables the speed of the fan blades <NUM> to be increased or decreased independent of the speed provided by the low pressure turbine <NUM> and geared architecture <NUM>. In one disclosed example operation of the gas turbine engine <NUM>, increase the fan speed <NUM> without increasing the speed of the low pressure turbine <NUM> includes inputting power to drive the first electric motor <NUM> to drive the fan blades <NUM>. The increase boost of power provided by the first electric motor assembly alone is not possible unless the fan shaft <NUM> is decoupled from input from the low pressure turbine <NUM>. In this example the decoupling of the direct input from the fan shaft <NUM> is enabled by rotation of the geared architecture <NUM>. In this example the sun gear <NUM> rotates counterclockwise.

In the embodiment disclosed in <FIG>, the first electric motor <NUM> drives the first drive gear <NUM> to drive the driven gear <NUM> and thereby the geared architecture <NUM> in a first clockwise direction <NUM>. In the clockwise direction <NUM> the fan section <NUM> may rotate at a faster speed than that provided by the low pressure turbine <NUM> and geared architecture <NUM>.

Operation of the first electric motor <NUM> to drive the geared architecture <NUM> in the first direction <NUM> enables an increase speed of the fan section <NUM> independent of speed of the low pressure turbine <NUM> and thereby the sun gear <NUM>.

The first clutch assembly <NUM> is a one way clutch such that the electric motor <NUM> may only drive the first shaft <NUM> in the first direction. The second electric motor <NUM> and the second clutch <NUM> enables the second electric motor <NUM> to drive the shaft <NUM> in a second direction. When the first electric motor <NUM> engages to drive the geared architecture <NUM>, the second clutch <NUM> decouples the second electric motor <NUM> such that no driving input is provided by the second electric motor <NUM>. In this example the sun gear <NUM> rotates counterclockwise.

Referring for <FIG> with continued reference to <FIG> and <FIG>, another example operational condition is illustrated where the second electric motor <NUM> is driving the second gear <NUM> in a second counterclockwise direction <NUM>. In the second direction <NUM> the geared architecture <NUM> is rotated in a counterclockwise direction and provides for a reduction in fan speed relative to the input provided by the low pressure turbine <NUM>. The reduction in the fan speed is independent of the input speed provided by the low pressure turbine <NUM>. Accordingly the fan speed <NUM> is decoupled from the input provided by the low pressure turbine <NUM> and the geared architecture <NUM>.

In another operational phase of the example gas turbine engine <NUM>, neither the first electric motor <NUM> nor the second electric motor <NUM> is operational thereby locking the geared architecture in a fixed position. In the fixed position, the low pressure turbine <NUM> drives the geared architecture <NUM> and thereby the fan section <NUM> at a constant speed dictated by the structure and gear ratio of the geared architecture <NUM>. The first electric motor assembly <NUM> is not operated and the engine operates with the fan blades <NUM> turning at a speed that corresponds with the low pressure turbine <NUM> and the gear ratio provided by the gear architecture <NUM>. In another operational phase of the example gas turbine engine <NUM> the first electric motor assembly <NUM> provides a boost to fan shaft <NUM> speed of rotation of the fan blades <NUM> about the axis A to a speed greater than that provided by the output of the geared architecture <NUM>.

In the disclosed embodiment shown in <FIG>, the first electric motor assembly <NUM> that is coupled to drive the fan section <NUM> is a motor. However the assembly <NUM> may comprise of a motor-generator that provides a load to fan shaft <NUM> speed of rotation of the fan blades <NUM> about the axis A to a speed smaller than that provided by the output of the geared architecture <NUM>.

In the disclosed embodiment shown in <FIG>, the first electric motor <NUM> and the second electric motor <NUM> are each illustrated as a single electric motor. However, each of the first electric motor and second electric motor <NUM>, <NUM> may comprise several electric motors that are each engaged to the driven gear <NUM> to provide rotation of the geared architecture relative of the engine static structure in either the first direction <NUM> or the second direction <NUM>.

Moreover the first electric motor assembly <NUM> is illustrated as a motor including a first static part fixed to a static structure and a second rotor part that is attached to a portion of the fan shaft <NUM>. It should be appreciated that although the first electric motor assembly <NUM> is schematically shown as a single electric motor mounted to and coupled as part of the fan shaft <NUM> that other configurations and separate electric motors could be utilized including an electric motor that drives the fan shafts <NUM> through a gear system or other drive configuration.

Additionally in the disclosed example the driven gear <NUM> is coupled to rotate the carrier <NUM> relative to the engine static structure <NUM>. The ring gear <NUM> is fixed to and is coupled to drive the fan shaft <NUM>. However, other configurations of a geared architecture could be utilized and are within the contemplation of this invention.

Referring to <FIG> another gas turbine engine <NUM> is schematically shown and includes another geared architecture <NUM>. The geared architecture <NUM> includes the ring gear <NUM> that is coupled to the driven gear <NUM>. The carrier <NUM> is coupled to drive the fan shaft <NUM>. Operation of the engine illustrated in <FIG> would proceed as is described above with regard to the disclosed engine <NUM> and in this example the sun gear <NUM> rotates clockwise. The application or mounting of the driven gear <NUM> to the ring gear <NUM> instead of the carrier <NUM> enables other gear ratios and operational structures that may be utilized within the contemplation of this disclosure.

Accordingly, the example disclosed engines <NUM>, <NUM> provided a boost of power to the fan section <NUM> independent of power provided by the low pressure turbine <NUM> and geared architecture <NUM> to enable an increase in thrust produced by the fan section <NUM> independent of the low speed spool <NUM>.

Claim 1:
A gas turbine engine (<NUM>, <NUM>) comprising:
a fan section (<NUM>) including a plurality of fan blades (<NUM>), a first electric motor assembly (<NUM>) coupled to a fan shaft (<NUM>) and providing a first drive input for driving the fan blades (<NUM>) about an axis (A);
a controller (<NUM>) commanding operation of the first electric motor assembly (<NUM>);
a turbine section (<NUM>);
a geared architecture (<NUM>) driven by the turbine section (<NUM>) and coupled to the fan section (<NUM>) to provide a second drive input for driving the fan blades (<NUM>), the geared architecture (<NUM>) including a sun gear (<NUM>) driving a plurality of intermediate gears (<NUM>) circumscribed by a ring gear (<NUM>) with a carrier (<NUM>) supporting the plurality of intermediate gears (<NUM>);
a driven gear (<NUM>) coupled to the geared architecture (<NUM>); and
a second electric motor assembly (<NUM>) coupled to the driven gear (<NUM>) for rotating the geared architecture (<NUM>) relative to a fixed structure (<NUM>) as commanded by the controller (<NUM>) to control a speed of the fan blades (<NUM>) provided by a combination of the first drive input and the second drive input, wherein the second electric motor assembly (<NUM>) includes a first electric motor (<NUM>) for rotating the geared architecture (<NUM>) in a first direction and a second electric motor (<NUM>) for rotating the geared architecture (<NUM>) in a second direction, wherein rotation of the geared architecture (<NUM>) in the first direction enables an increase of a speed of the fan section (<NUM>) and rotation in the second direction enables a decrease of a speed of the fan section (<NUM>) without a change in speed of the second driving input provided by the turbine section (<NUM>).