Patent Description:
There is always a need in the art for improvements to electric propulsion in the aerospace industry.

A prior art method having the features of the preamble of claim <NUM> is disclosed in <CIT>.

In accordance with an aspect of the present invention, there is provided a method of accelerating a gas turbine engine in accordance with claim <NUM>.

In certain embodiments, controlling fuel flow to the plurality of fuel injectors includes maintaining engine core acceleration below a predetermined limit for compressor acceleration for a compressor section of the gas turbine engine.

In certain embodiments, controlling fuel flow to the plurality of fuel injectors includes maintaining an acceleration of the core below a predetermined limit for P3/P1 ratio, where P3 is compressor discharge pressure for the gas turbine engine and P1 is ambient pressure for the gas turbine engine.

In accordance with yet another aspect of the present invention, there is provided an electrical assist system for an aircraft gas turbine engine in accordance with claim <NUM>.

In certain embodiments, controlling fuel flow to the plurality of fuel injectors includes maintaining an engine core acceleration below a predetermined limit for compressor acceleration for the compressor section. In certain embodiments, controlling fuel flow to the plurality of fuel injectors includes maintaining an acceleration of the engine core below a predetermined limit for a P3/P1 ratio, where P3 is compressor discharge pressure for the gas turbine engine and P1 is ambient pressure for the gas turbine engine.

In embodiments, the engine core further includes a high pressure core operatively connecting a high pressure turbine of the turbine section to drive a high pressure compressor of the compressor section. A low pressure core connects a low pressure turbine of the turbine section to drive a low pressure compressor of the compressor section. In certain such embodiments, the electric machine can be operatively connected to at least one of the high pressure core and/or the low pressure core. In certain embodiments, the electric machine includes a plurality of electric machines and the plurality of electric machines can be operatively connected to both the high pressure core and the low pressure core.

According to the invention, a feedback control loop is used to control fuel flow to the plurality of fuel injectors based on torque feedback and rotational speed feedback from the electric machine. In certain embodiments, the feedback control loop includes a power sensor electrically connected to the electric machine to sense voltage and current of power supplied to the electric machine so that the control module is operable to control fuel flow based on feedback from the power sensor.

In certain embodiments, the feedback control loop includes a speed sensor operatively connected to a rotatable component of the electric machine to sense rotation speed of the electric machine so that the control module is operable to control fuel flow based on feedback from the speed sensor. In certain embodiments, the feedback control loop includes, at least one of: a rotational speed sensor operatively connected to the engine core, an ambient pressure sensor, and/or a compressor discharge pressure sensor so that the control module is operable to control fuel flow based on feedback from the at least one of the rotational speed sensor, the ambient pressure sensor, and/or the compressor discharge pressure sensor.

In embodiments, a fuel pump connects a fuel source in fluid communication with the plurality of fuel injectors, and the control module is operatively connected to control the fuel pump to control fuel flow to the plurality of fuel injectors. In certain embodiments, controlling fuel flow includes adding fuel flow until the electric machine reaches a torque target.

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a system in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. Other embodiments and/or aspects of this disclosure are shown in <FIG>. Certain embodiments described herein can be used to provide electric assist for turbine engines.

This disclosure relates generally to gas turbine engines, and more particularly to gas turbine engines with electrical motor assistance. In general, there is a limit to how fast a gas turbine engine core can accelerate by just increasing fuel flow to the fuel injectors. This limit can be increased by adding power to the engine core from an electrical motor. In order to control correctly control the electric motor assist, certain control algorithms are required. However, there is a need in the art for more reliable and robust control methods for electrically-assisted acceleration in the aerospace industry. For example, previous systems did not consider adjusting fuel supplied to the engine based on a known condition of the electric motor. This disclosure provides a solution for this need for example, by including both an electric motor control loop and an engine core fuel flow control loop to achieve the target engine speed.

In certain embodiments, referring to <FIG>, an aircraft <NUM> can include an engine <NUM>, where the engine <NUM> can be a propulsive energy engine (e.g. creating thrust for the aircraft <NUM>), or a non-propulsive energy engine, and a fuel system. As described herein, the engine <NUM> is a turbofan engine, although the present disclosure may likewise be used with other engine types. The engine <NUM> includes a compressor section <NUM> having a compressor <NUM> in a primary gas path <NUM> to supply compressed air to a combustor <NUM> of the aircraft engine <NUM>. The primary gas path <NUM> includes a nozzle manifold <NUM> for issuing fluid to the combustor <NUM>.

The primary gas path <NUM> includes, in fluid communication in a series: the compressor <NUM> having an inlet <NUM>, the combustor <NUM> fluidly connected to an outlet <NUM> of the compressor <NUM>, and a turbine section <NUM> fluidly connected to an outlet <NUM> of the combustor <NUM>. The turbine section <NUM> is operatively connected to the compressor <NUM> to drive the compressor <NUM>.

The combustor <NUM> includes a plurality of fuel nozzles <NUM> each fluidly connected via a fuel feed conduit <NUM>, which feeds the nozzle manifold <NUM>, which feeds the plurality of fuel nozzles <NUM> of the combustor <NUM> with a gaseous fuel supply <NUM>. The feed conduit <NUM> includes an inlet end <NUM> and an outlet end <NUM> to fluidly connect a fuel supply <NUM> to the combustor <NUM> through the plurality of fuel nozzles <NUM>. In embodiments, the fuel supply <NUM> can be any suitable fuel, such as a gaseous pressure and/or temperature regulated fuel supply, which may be or include hydrogen gas.

Certain additional components may also be included in fluid communication between the combustor and the gaseous fuel supply in any suitable order or combination, such as a fuel shut off valve <NUM>, a fuel pump <NUM>, a liquid/gaseous fuel evaporator <NUM>, a turbine air cooling heat exchanger <NUM>, a gaseous fuel accumulator <NUM>, a gaseous fuel metering unit <NUM>, and/or a fuel manifold shut off valve <NUM>.

Referring now to <FIG>, in accordance with at least one aspect of this disclosure, there is provided an electrical assist system <NUM> for an aircraft gas turbine engine (e.g. engine <NUM>). An engine core <NUM> extends through and operatively connects the compressor section <NUM> and the turbine section <NUM> so the turbine section <NUM> can drive the compressor section <NUM>. In embodiments, the engine <NUM> is a dual-spool engine, and the engine core includes a high pressure core 144a operatively connecting a high pressure turbine 116a of the turbine section to drive a high pressure compressor 104a of the compressor section <NUM>. A low pressure core 144b connects a low pressure turbine 116b of the turbine section <NUM> to drive a low pressure compressor 104b of the compressor section <NUM>. It is contemplated the engine <NUM> can have any number of spools and engine cores for a given application, without departing from the scope of this disclosure. An electric machine <NUM> (e.g. an electric motor) is operatively connected to the engine core <NUM>, for example to at least one of the high pressure core 144a, and/or the low pressure core 144b.

A fuel control mechanism <NUM> is disposed in the fuel feed conduit <NUM> to selectively control fuel flow from the fuel source <NUM> to the plurality of fuel nozzles <NUM>. The fuel control mechanism <NUM> can be any suitable controllable fuel flow valve, or in certain embodiments, the fuel control mechanism <NUM> can be the fuel pump <NUM> itself where the control module <NUM> is operatively connected to control the fuel pump <NUM>. The control module <NUM> is operatively connected the electric machine <NUM> and the fuel control mechanism <NUM> to control fuel flow to the plurality of fuel injectors <NUM> and to control the electric machine <NUM> based on feedback from a plurality of inputs using a feedback control loop.

For example, the fuel flow mechanism <NUM> can be controlled based on feedback from at least a power sensor <NUM> electrically connected to the electric machine <NUM> to sense voltage and current of power supplied to the electric machine <NUM> (e.g. via a generator) so that the control module <NUM> is operable to control fuel flow based on feedback from the power sensor <NUM>. In certain embodiments, a speed sensor <NUM> is operatively connected to a rotatable component (e.g. a shaft or a rotor) of the electric machine <NUM> to sense the rotational speed of the electric machine <NUM> so that the control module <NUM> is operable to control fuel flow based on feedback from the speed sensor <NUM>.

In certain embodiments, the electric machine <NUM> can have an individual electric machine controller, separate from the control module <NUM>. In such embodiments, the fuel flow mechanism <NUM> can be controlled based on feedback from a torque estimate (derived from a torque sensor on the shaft of the electric machine) that is calculated by the electric machine controller and shared with the control module <NUM> through a data bus (e.g. a CANbus).

With continued reference to <FIG>, in certain embodiments the electric machine <NUM> can be controlled based on feedback from at least one of a rotational speed sensor <NUM> that is operatively connected to the engine core <NUM> (e.g. either the high pressure core 144a or low pressure core 144b in a dual-spool engine, or the single core in a single spool engine), an ambient pressure sensor <NUM>, and/or a compressor discharge pressure sensor <NUM>. The sensors <NUM>, <NUM>, <NUM> can be operatively connected to the engine <NUM> and to the control module <NUM> so that the control module <NUM> is operable to control fuel flow based on feedback from the rotational speed sensor <NUM>, the ambient pressure sensor <NUM>, and/or the compressor discharge pressure sensor <NUM>.

In certain embodiments, the control module <NUM> includes machine readable instructions operative to accelerate the engine core <NUM> based on the sensor inputs described above. According to the invention the control module <NUM> is operative to perform a method of accelerating the engine core <NUM>, including adding torque to the engine core <NUM> to accelerate rotation of the engine core <NUM> by controlling fuel flow to the fuel injectors <NUM> based on feedback from the electric machine <NUM>, and simultaneously adding torque to the engine core <NUM> by powering the electric machine <NUM>.

Controlling fuel flow based on feedback from the electric machine <NUM> includes controlling fuel flow to achieve a target torque from the electric machine <NUM>. As used herein a target torque can be any suitable torque for a given application, for example, a target value such as zero torque, or a target value that can be a positive value or a negative value. A slightly negative target torque can be a constant extract of a small amount of electrical power, and a slightly positive value can be a constant add of a small amount of electrical power. In certain embodiments, constant addition or extraction of power could be useful to tune engine performance for peak efficiency (e.g. transferring power between high spool and low spool), or in certain embodiments, the steady extraction of power could be used to recharge batteries gradually and/or provide electrical power to other power consuming electric devices.

In embodiments, the method includes maintaining an engine core acceleration below a predetermined limit for compressor acceleration for the compressor section <NUM>, and/or maintaining an acceleration of the engine core <NUM> below a predetermined limit for a P3/P1 ratio (where P3 is compressor discharge pressure for the gas turbine engine and P1 is ambient pressure for the gas turbine engine as sensed by sensors <NUM> and <NUM> respectively). In embodiments, controlling fuel flow can include controlling the fuel flow mechanism <NUM> to allow fuel flow to continue to be added to the plurality of fuel nozzles <NUM> until the electric machine <NUM> reaches a torque target, whereby power to the electric machine <NUM> can be reduced or stopped all together.

Powering the electric machine <NUM> includes controlling the electric machine <NUM> based on the engine core speed feedback from the engine core <NUM> to reach a target core speed. Once the increased target speed is reached, the electric motor torque will be positive until the fuel flow is increased so that the turbine takes more of the compressor load and reduces the load on the electric machine <NUM>. At that time, power to the electric machine <NUM> can be reduced or stopped all together and fuel flow to the plurality of fuel injectors <NUM> can be maintained.

In embodiments, the electric motor can be used to accelerate the engine core without being limited by surge limits because the motor does not rely on over-fueling to accelerate. In certain instances, this can allow the compressor run line to be set closer to the surge limit where its performance is better. Knowing the condition of the electric motor thus allows the control module to know if fuel flow should increase or decrease to off-load the electric motor. However, in embodiments, it is possible that the control module does not need to change fuel flow rapidly, though rapid fuel flow change may occur because the electric motor acceleration would have put the core into an under-fueled state temporarily. Accordingly, as long as electric motor torque is positive, the fuel flow can be increased more rapidly than may otherwise be the case. The rate of change in fuel flow will therefore depend on how quickly the electric motor can accelerate the core and knowing the torque can indicate whether the fuel flow can be further increased without surge.

Aspects of this disclosure may be described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of this disclosure. It will be understood that each block of any flowchart illustrations and/or block diagrams, and combinations of blocks in any flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in any flowchart and/or block diagram block or blocks.

Claim 1:
A method of accelerating a gas turbine engine (<NUM>) of an aircraft (<NUM>), comprising:
adding torque to a core (<NUM>) of the gas turbine engine (<NUM>) to accelerate rotation of the core (<NUM>) by controlling fuel flow to a plurality of fuel injectors (<NUM>) of the gas turbine engine (<NUM>); and
adding torque to the core (<NUM>) by powering an electric machine (<NUM>) that is operatively connected to the core (<NUM>) to drive the core (<NUM>),
characterized in that:
the controlling fuel flow to the plurality of fuel injectors is based on feedback from the electric machine (<NUM>) including a torque feedback and a rotational speed feedback;
powering the electric machine (<NUM>) includes controlling the electric machine (<NUM>) based on an engine core speed feedback from the core (<NUM>) to reach a target core speed of the core (<NUM>); and
the controlling fuel flow based on feedback from the electric machine (<NUM>) includes controlling fuel flow to achieve a target torque generated by the electric machine (<NUM>).