Patent Description:
Variable geometry in a gas turbine engine can provide a faster thrust response as one or more components of the gas turbine engine are adjusted in position or orientation as compared to only modifying a fuel flow rate to accelerate or decelerate a rate of engine spool rotation within the gas turbine engine. Engine thrust response changes are typically slower to adjust relative to the rate at which variable geometry of the engine can change.

<CIT> discloses a propulsion system comprising a gas turbine engine and an acceleration schedule which determines the rate of acceleration of the gas turbine engine from an idle condition in response to a demand for increased thrust off-idle.

<CIT> discloses a method and apparatus for controlling power distribution in an electrical aircraft propulsive system.

<CIT> discloses a power extraction system for a gas turbine engine.

According to a first aspect, there is provided a gas turbine engine as claimed in claim <NUM>.

Optionally, the controller is further operable to receive a control input, determine a plurality of current operating conditions of the gas turbine engine, calculate a plurality of commands to a plurality of power production and absorption subsystems for adjusting the variable cycle based on the current operation condition of the gas turbine engine using a plurality of models of the subsystems that describe relationships between the commands and respective impacts on engine power production and absorption, and communicate the commands to the power production, power absorption, and one or more other actuation subsystems based on the control input and the current operating conditions.

The electric component is a motor-generator.

Optionally, the electric component absorbs power as the electric generator to produce electrical power for an aircraft use or recharging of a battery system.

Optionally, the actuation system includes a variable area turbine.

Optionally, the electric component adds power as the electric motor.

Optionally, the actuation system includes one or more of: a variable area nozzle, a variable fan blade angle, an adaptive fan system, and a rotating fan inlet guide vane.

According to a second aspect, there is provided a propulsion system as claimed in claim <NUM>.

Optionally, the variable cycle system compensation means performs control operations based on one or more of: a thrust command, a throttle lever angle, a clearance, a compressor parameter, and a turbine parameter.

Optionally, the electric component is operable as the electric generator to charge a battery system and as the electric motor to provide supplemental rotation force to the gas turbine engine based on electric current from the battery system or an auxiliary power unit.

Optionally, the battery system is used during flight to power one or more electrical systems.

According to a third aspect, there is provided a method of variable cycle compensation in a gas turbine engine as claimed in claim <NUM>.

Optionally, determining the plurality of current operating conditions of the gas turbine engine is performed using a control model and a plurality of actuator parameters, sensor values, and limits.

A technical effect of the apparatus, systems and methods is achieved by providing variable cycle compensation in a gas turbine engine as described herein.

The following descriptions are exemplary only and should not be considered limiting in any way.

In one disclosed embodiment, the engine <NUM> bypass ratio is greater than about ten (<NUM>:<NUM>), 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 about five (<NUM>:<NUM>). The geared architecture <NUM> may be an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans.

The fan section <NUM> of the engine <NUM> is designed for a particular flight condition--typically cruise at about <NUM> Mach and about <NUM>,<NUM> feet (<NUM>,<NUM> meters). The flight condition of <NUM> Mach and <NUM>,<NUM> ft (<NUM>,<NUM> meters), with the engine at its best fuel consumption--also known as "bucket cruise Thrust Specific Fuel Consumption ("TSFC")"--is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. "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>.

While the example of <FIG> illustrates one example of the gas turbine engine <NUM>, it will be understood that any number of spools, inclusion or omission of the gear system <NUM>, and/or other elements and subsystems are contemplated. Further, rotor systems described herein can be used in a variety of applications and need not be limited to gas turbine engines for aircraft applications. For example, rotor systems can be included in power generation systems, which may be ground-based as a fixed position or mobile system, and other such applications.

<FIG> illustrates turbomachinery <NUM> that includes at least one compressor section <NUM> and at least one turbine section <NUM> operably coupled to a shaft <NUM> as part of an aircraft <NUM>. The turbomachinery <NUM> can be a spool of the gas turbine engine <NUM> of <FIG>, such as the low speed spool <NUM> or the high speed spool <NUM>. For example, when embodied as the low speed spool <NUM>, the at least one compressor section <NUM> can be equivalent to the low pressure compressor <NUM>, the shaft <NUM> can be equivalent to the inner shaft <NUM>, and the at least one turbine section <NUM> can be equivalent to the low pressure turbine <NUM> of <FIG>. When embodied as the high speed spool <NUM>, the at least one compressor section <NUM> can be equivalent to the high pressure compressor <NUM>, the shaft <NUM> can be equivalent to the outer shaft <NUM>, and the at least one turbine section <NUM> can be equivalent to the high pressure turbine <NUM> of <FIG>. The at least one compressor section <NUM> can include a fan, such as an adaptive fan system or a fan that supports a variable fan blade angle.

In the example of <FIG>, a variable cycle system <NUM> is operably coupled to the turbomachinery <NUM>. The variable cycle system <NUM> includes an electric component <NUM> operably coupled to the shaft <NUM>. In the example of <FIG>, a geared interface <NUM> operably couples the electric component <NUM> to the shaft <NUM>. The geared interface <NUM> can include, for instance, an auxiliary gear <NUM> coupled to an auxiliary shaft <NUM> driven by the electric component <NUM>. The geared interface <NUM> can also include a rotor gear <NUM> coupled to the shaft <NUM>. The auxiliary gear <NUM> and the rotor gear <NUM> can each be beveled gears. The auxiliary shaft <NUM> can be a tower shaft that enables the electric component <NUM> to be separated at a greater distance from the turbomachinery <NUM> than direct coupling to the shaft <NUM> would provide. Further separation of the electric component <NUM> from the turbomachinery <NUM> can improve accessibility to the electric component <NUM> for servicing and may reduce heating effects of the turbomachinery <NUM> on the electric component <NUM> (e.g., due to fuel combustion). A disconnect <NUM>, such as a clutch, can be positioned between the electric component <NUM> and a portion of the shaft <NUM> such that the electric component <NUM> can be selectively engaged and disengaged to rotate with rotation of the shaft <NUM>.

In alternate embodiments, the electric component <NUM> is operably coupled to the shaft <NUM> absent the geared interface <NUM> (e.g., direct coupling).

The variable cycle system <NUM> also includes converter electronics <NUM> operable to condition current to/from the electric component <NUM>. In some embodiments, the electric component <NUM> is a motor-generator configurable in a generator mode to charge a battery system <NUM> and in a motor mode to provide supplemental rotation force to the turbomachinery <NUM> of gas turbine engine <NUM> of <FIG>. The electric component <NUM> can include conventional generator/motor components, such as a rotor and stator, including a plurality of windings and/or permanent magnets. The converter electronics <NUM> can also include conventional current control electronics, such as filters, switching components, rectifiers, inverters, voltage converters, and the like. The electric component <NUM> can perform as a variable frequency generator in a generator mode due to speed fluctuations of rotation of the shaft <NUM>, which may be primarily driven by the at least one turbine section <NUM>. Alternatively, a frequency normalizing component can interface with the electric component <NUM> to produce a constant frequency output (e.g., through the converter electronics <NUM> or as a mechanical interface between the electric component <NUM> and the shaft <NUM>). In some embodiments, the electric component <NUM> may be operable as a starter motor to partially or completely power rotation of the shaft <NUM> in a starting mode of operation (e.g., to start the gas turbine engine <NUM> of <FIG>) and/or can provide supplemental power to the shaft <NUM> during various flight phases of the aircraft <NUM>. Other uses and functions for the electric component <NUM> are contemplated.

The converter electronics <NUM> can control charging of the battery system <NUM> responsive to a controller <NUM>. The controller <NUM> can enable a flow of a charging current from the electric component <NUM> or a power input <NUM> to charge the battery system <NUM> as regulated and conditioned through the converter electronics <NUM>. The power input <NUM> can be an external input, such as power received through a plug interface while the aircraft <NUM> is on the ground at a ground-based power source, e.g., at a gate or service location. In some embodiments, the converter electronics <NUM> may receive electric current from an auxiliary power input <NUM> to provide a supplemental or alternative power source for charging the battery system <NUM>. For instance, the auxiliary power input <NUM> may receive electric current from an auxiliary power unit (not depicted) or another instance of the gas turbine engine <NUM> on the aircraft <NUM>. The charge stored in the battery system <NUM> can provide an electric current for a propulsion system use <NUM>, which may include powering one or more electric motors of the aircraft <NUM> during various operational states and/or providing power to the electric component <NUM> when operating in a motor mode, for instance, to assist in driving rotation of shaft <NUM>. The propulsion system use <NUM> can be part of the gas turbine engine <NUM> that includes the turbomachinery <NUM> or another aircraft system, such as another instance of the gas turbine engine <NUM> on the aircraft <NUM>. The battery system <NUM> can be used on the ground or during flight to power one or more electrical systems.

In embodiments, the controller <NUM> of the variable cycle system <NUM> can monitor one or more rotor system sensors <NUM> while the turbomachinery <NUM> is rotating. The rotor system sensors <NUM> can be any type or combination of sensors operable to measure aspects of the motion of the turbomachinery <NUM>. For example, the rotor system sensors <NUM> can include one or more accelerometers, speed sensors, torque sensors, and the like. The rotor system sensors <NUM> can be existing sensors used for controlling the gas turbine engine <NUM>. The controller <NUM> can control a charging of the battery system <NUM>, for instance, by selecting the source of electric current received through the converter electronics <NUM>. The controller <NUM> can also control operation of the electric component <NUM>. Data collected from the rotor system sensors <NUM> can be used to determine an operational status of a gas turbine engine <NUM> of <FIG>. Alternatively, the operational status of a gas turbine engine <NUM> can be received as a signal or message from an alternate source, such as an engine system or aircraft communication bus. The controller <NUM> may also control other system aspects, such as controlling operation of the gas turbine engine <NUM> of <FIG>. For example, the controller <NUM> can be integrally formed or otherwise in communication with a full authority digital engine control (FADEC) of the gas turbine engine <NUM>. The rotor system sensors <NUM> need not be directly coupled to the controller <NUM>, as sensor data or sensor-derived data can be observed or determined by another control (e.g., a FADEC) and provided to the controller <NUM>. In embodiments, the controller <NUM> can include a processing system <NUM>, a memory system <NUM>, and an input/output interface <NUM>. The processing system <NUM> can include any type or combination of central processing unit (CPU), including one or more of: a microprocessor, a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like. The memory system <NUM> can store data and instructions that are executed by the processing system <NUM>. In embodiments, the memory system <NUM> may include random access memory (RAM), read only memory (ROM), or other electronic, optical, magnetic, or any other computer readable medium onto which is stored data and algorithms in a non-transitory form. The input/output interface <NUM> is configured to collect sensor data from the one or more rotor system sensors <NUM> and interface with the converter electronics <NUM> and/or other systems (not depicted).

The controller <NUM> controls an output of the electric component <NUM> to compensate a shaft power supply and/or loading of the turbomachinery <NUM> in coordination with an output of an actuation system <NUM>. The actuation system <NUM> can be located in a gas path of the gas turbine engine <NUM> <FIG>. Although only a single instance of the actuation system <NUM>, there can be multiple instances of the actuation system <NUM> at various locations on the gas turbine engine <NUM> having different features that modify an engine geometry to impact thrust and/or other parameters of the gas turbine engine <NUM>. The actuation system <NUM> is a means of adjusting power absorption, such as one or more of: a variable area nozzle, a variable fan blade angle, an adaptive fan system, and a rotating fan inlet guide vane. To compensate power absorption, the electric component <NUM> can be implemented as an electric motor or operated in a motor mode. Alternatively, the actuation system <NUM> is a means of adjusting power production, such as a variable area turbine. The actuation system <NUM> can include any system operable to effect a variable cycle in the gas turbine engine <NUM>, and may include components not directly in the gas path, such as, an intercooled cooling air control system with an adjustable flow control. To compensate power production, the electric component <NUM> can be implemented as an electric generator or operated in a generator mode. Thus, the variable cycle feature of the actuation system <NUM> is compensated by the electric component <NUM>. As one feature adjusts the ability of the gas turbine engine <NUM> to absorb power, the other provides the required power without time needed for spool speeds to change.

The electric component <NUM> may be generally referred to as a variable cycle system compensation means and is operable to compensate a power change induced by or in coordination with the actuation system <NUM>, where the variable cycle system compensation means is operable to respond at a second rate that is faster than a first rate of change initiated by the actuation system <NUM>. The actuation system <NUM> is a variable cycle component that may lag in responsiveness, for instance, due to spool inertia and/or other factors. Further, although only a single instance of the electric component <NUM> is depicted, there can be multiple instances of the electric component <NUM> incorporated in variable cycle system <NUM>, such as one or more dedicated instances of an electric motor and an electric generator for one or more spools of the gas turbine engine <NUM>.

<FIG> illustrate a variable cycle compensation example for a variable fan paired with an electric motor with corresponding responses during a snap acceleration. For instance, a variable pitch fan can provide a rapid thrust response without compensation, but power may be drawn from spool inertia, which is counterproductive to increasing power production of the turbine to compensate the increased power absorption of the variable pitch fan. Spool speed can go down, which takes time for the gas turbine engine <NUM> to catch up. By pairing an electric motor as the electric component <NUM> with the variable pitch fan as the actuation system <NUM>, the electric motor can compensate to increase the ability of the variable pitch fan to translate shaft power to thrust. This provides a more rapid thrust response without losing shaft speed. Thus, thrust response can be limited by actuator speed rather than spool speed.

<FIG> is a thrust plot <NUM> of a snap acceleration, in accordance with an embodiment. In thrust plot <NUM>, a conventional engine with variable pitch fan response <NUM> is illustrated relative to an ideal response <NUM> and a conventional engine acceleration response <NUM>.

<FIG> is a low spool speed plot <NUM> of a snap acceleration, in accordance with an embodiment. In low spool speed plot <NUM>, a conventional engine with variable pitch fan response <NUM> is illustrated relative to a variable pitch fan with electric motor response <NUM>, and a conventional engine response <NUM>.

<FIG> is a fan pitch plot <NUM> of a snap acceleration, in accordance with an embodiment. In fan pitch plot <NUM>, a conventional engine with variable pitch fan response <NUM> is illustrated relative to a variable pitch fan with electric motor response <NUM> and a conventional engine response <NUM> that does not support a variable fan pitch.

<FIG> is a motor power plot <NUM> of a snap acceleration, in accordance with an embodiment. In motor power plot <NUM>, a conventional engine with variable pitch fan response <NUM> is illustrated relative to a variable pitch fan with electric motor response <NUM> and a conventional engine response <NUM> that does not support a variable fan pitch. Collectively, the motor power depicted in the variable pitch fan with electric motor response <NUM> combines with the fan pitch in the variable pitch fan with electric motor response <NUM> of <FIG> to enhance snap acceleration performance as illustrated, for example, in <FIG>.

<FIG> illustrate a variable cycle compensation example for a variable fan paired with an electric motor with corresponding responses during an auto-throttle or other high frequency oscillation event. A conventional engine with variable pitch fan can see a rapid thrust response but dependence upon spool speed limits the ability to replicate a commanded high frequency thrust response. A pairing of an electric motor as the electric component <NUM> with the variable pitch fan as the actuation system <NUM> can more accurately reproduce a commanded thrust profile without affecting the cycle match. The electric motor can be a motor-generator and absorb excess power into energy storage and reduce total energy use when the stored energy is harvested.

<FIG> is a thrust plot <NUM> of an auto-throttle, in accordance with an embodiment. In thrust plot <NUM>, a conventional engine with variable pitch fan response <NUM> is illustrated relative to a variable pitch fan with electric motor response <NUM>. Notably, due to inertia effects, for example, not only does the conventional engine with variable pitch fan response <NUM> fail to track the oscillation magnitude, but the delayed responsiveness can result in a cumulative effect with each cycle of oscillation. For instance, since the first peak value is not reached in the conventional engine with variable pitch fan response <NUM>, a subsequent cycle starts at a lower level which reduces the amplitude response for the conventional engine with variable pitch fan response <NUM>.

<FIG> is a low spool speed plot <NUM> of an auto-throttle, in accordance with an embodiment. In low spool speed plot <NUM>, a conventional engine with variable pitch fan response <NUM> is illustrated relative to a variable pitch fan with electric motor response <NUM>. As can be seen in comparison to <FIG>, the imbalanced thrust response of the conventional engine with variable pitch fan response <NUM> can result in an imbalance in the conventional engine with variable pitch fan response <NUM>, with the speed not held substantially constant. In contrast, the more rapid responsiveness of the variable pitch fan with electric motor response <NUM> can enable the variable pitch fan with electric motor response <NUM> to remain substantially constant during the thrust oscillations of <FIG>.

<FIG> is a fan pitch plot <NUM> of an auto-throttle, in accordance with an embodiment, and <FIG> is a motor power plot <NUM> of an auto-throttle, in accordance with an embodiment. In fan pitch plot <NUM>, a variable pitch fan with electric motor response <NUM> is depicted. In motor power plot <NUM>, a variable pitch fan with electric motor response <NUM> is depicted. Collectively, the fan pitch in the variable pitch fan with electric motor response <NUM> combines with the motor power depicted in the variable pitch fan with electric motor response <NUM> to high frequency oscillation performance as illustrated, for example, in <FIG>.

Referring to <FIG>, a block diagram of a propulsion system <NUM> is depicted in accordance with an embodiment. In the example of <FIG>, an engine control <NUM>, such as controller <NUM> of <FIG>, receives a control input <NUM>. The control input <NUM> can be, for instance, one or more of: a thrust command, a throttle lever angle, a clearance, a compressor parameter, and a turbine parameter. The control input <NUM> may be a pilot input or otherwise received on an aircraft bus. The engine control <NUM> may interface with multiple subsystems <NUM>, <NUM>, <NUM> to control an engine <NUM>, such as the gas turbine engine <NUM> of <FIG>. Power production subsystems <NUM> can include either or both of the actuation system <NUM> and the electric component <NUM> of <FIG> when operating in a power production mode. Power absorption subsystems <NUM> can include either or both of the actuation system <NUM> and the electric component <NUM> of <FIG> when operating in a power absorption mode. Primary actuation subsystems <NUM> can include other non-cyclic actuation systems, such as fuel system control, compressor vane control, and the like. A control example for the engine control <NUM> is depicted in <FIG>.

In <FIG>, a method <NUM> may be executed by the engine control <NUM> of <FIG> at each control time step in a loop. At block <NUM>, a control input <NUM> of <FIG>, such as a thrust command, can be communicated to and received at the engine control <NUM>.

At block <NUM>, the engine control <NUM> can determine a plurality of current operating conditions of the engine <NUM> of <FIG>. Determining the plurality of current operating conditions of the engine <NUM> can be performed using a control model and a plurality of actuator parameters, sensor values, and limits.

At block <NUM>, a control problem solution can be generated. Examples of control system implementations can include constrained model-based control, multivariable system control, adaptive control, constrained dynamic inversion control, and other such techniques known in the art. Models can be incorporated for the power production subsystems <NUM>, power absorption subsystems <NUM>, and/or primary actuation subsystems <NUM> with associated limits and rate limits. For example, fan flow can depend on shaft speed and fan blade variable angle, which can be modeled based on an actuator time response. Torque is added or subtracted by the electric component <NUM> of <FIG> from dynamical equations associated with spool dynamics, which can account for spool inertia. Models can be added for electrical power generation and may include battery system and/or auxiliary power unit effects. Rather than controlling to low shaft speed, control objectives can be shifted to other parameters, such as thrust, clearance, and/or other compressor or turbine parameters beyond speed control. Compensation effects can be added and diminished as balancing of power contributions or reductions shift between the power production subsystems <NUM> and the power absorption subsystems <NUM>. Thus, the engine control <NUM> can calculate a plurality of commands to a plurality of power production and absorption subsystems <NUM>, <NUM> for adjusting a variable cycle based on the current operation condition of the gas turbine engine <NUM> using a plurality of models of the subsystems that describe relationships between the commands and respective impacts on engine power production and absorption.

At block <NUM>, the engine control <NUM> can communicate commands to power production subsystems <NUM>, power absorption subsystems <NUM>, and/or primary actuation subsystems <NUM>.

Referring now to <FIG> with continued reference to <FIG>, <FIG> is a flow chart illustrating a method <NUM> of variable cycle compensation in a gas turbine engine, in accordance with an embodiment. The method <NUM> may be performed, for example, by the variable cycle system <NUM> of <FIG> and propulsion system <NUM> of <FIG>. For purposes of explanation, the method <NUM> is described primarily with respect to the variable cycle system <NUM> of <FIG> and the propulsion system <NUM> of <FIG>; however, it will be understood that the method <NUM> can be performed on other configurations (not depicted).

At block <NUM>, a control input <NUM> can be received at a controller <NUM> (e.g., engine control <NUM>) of a gas turbine engine <NUM> (e.g., engine <NUM>). At block <NUM>, the controller <NUM> can determine a plurality of current operating conditions of the gas turbine engine <NUM>. At block <NUM>, the controller <NUM> can adjust an output of either or both of an actuation system <NUM> and an electric component <NUM> for separate control of thrust and cycle responses based on the control input <NUM> and the current operating conditions. The actuation system <NUM> is configured to adjust a variable cycle of turbomachinery <NUM> of the gas turbine engine <NUM> (e.g., as the power production subsystems <NUM> or the power absorption subsystems <NUM>). The electric component <NUM> can be operable to provide a shaft power supply or a load corresponding respectively to an adjustment of the turbomachinery <NUM>.

Claim 1:
A gas turbine engine (<NUM>) comprising a variable cycle system (<NUM>) and a turbomachinery (<NUM>) comprising at least one compressor section (<NUM>) and at least one turbine section (<NUM>) operably coupled to a shaft (<NUM>) of the gas turbine engine (<NUM>); the variable cycle system comprising:
an actuation system (<NUM>) configured to adjust a variable cycle of the turbomachinery (<NUM>) of the gas turbine engine by adjusting power absorption or power production;
characterised in that the variable cycle system further comprises:
an electric component (<NUM>) mechanically interfaced to the shaft, the electric component configured to add or subtract torque to the shaft; and
a controller (<NUM>) operable to adjust an output of the electric component to compensate for a power change induced by the actuation system by operating the electric component as an electric motor to compensate for power absorption of the turbomachinery and operating the electric component as an electric generator to compensate for power production of the turbomachinery, wherein the controller provides separate control of thrust and cycle responses.