Patent ID: 12234022

DETAILED DESCRIPTION

The present disclosure is directed to gas-turbine engine systems, e.g., for gas-turbine engine powered vehicles such an aircraft, and techniques for operating the same. For ease of description, examples of the disclosure will be primarily described in the context of aircraft as a gas-turbine engine powered vehicle. However, examples of the disclosure are not limited to aircraft. For instance, aspects of this disclosure may be applicable to gas-turbine powered ground vehicles, watercraft, and the like.

Aircraft increasingly require significant amounts of additional electrical power. For instance, in bleedless aircraft, various systems traditionally operated using bleed air (e.g., de-icing, cabin pressurization, engine start) may be replaced with electrically operated versions. Those electrical systems may increase the electrical load requirements for the vehicle.

Electrical machines that function as electric generators may be employed by gas-turbine combustion engine power aircraft to satisfy the transient and/or continuous electrical loads associated with the electrical system(s). For example, a gas-turbine engine having a low-pressure spool assembly (e.g., including a low-pressure (LP) compressor and/or propulsor and a low-pressure turbine connected by a low-pressure shaft) and high-pressure (HP) spool assembly (e.g., including a HP pressure compressor and a HP turbine connected by a HP shaft) may include an electric generator that generates electricity from the rotation of the LP spool shaft and/or the HP spool shaft. The electrical power extracted from the LP spool shaft and/or the HP spool shaft may be used to supply power to various aircraft systems (e.g., electrical systems of the vehicle system that require electrical energy to operate, such as aircraft anti-ice heating, weapon systems, navigation systems including radar, environmental cooling systems (ECS)).

Examples of the gas-turbine engine systems may include a high-pressure (HP) spool assembly and at least one other lower pressure (LP) spool assembly (e.g., a low-pressure spool assembly and/or an intermediate pressure spool assembly). The gas-turbine engine may include a generator coupled to the LP shaft of the LP spool assembly so that the generator generates power from the rotation of the LP shaft.

In some examples of the gas-turbine engine system, a gas-turbine engine may not include a center sump (e.g., in an effort to increase efficiency, improve secondary flow and reduce weight of the gas-turbine engine system). However, when the gas-turbine engine is shut off, the heat produced by the gas-turbine engine may warp a rotor of the gas-turbine engine such that the rotor may contact a compressor of the engine and/or lock-up inside a compressor of the engine. In addition, uneven heating may cause the tight clearances between shafts and top clearances on airfoils to close. When a rotor becomes locked-up, it may take prolonged time at rest to cool the rotor sufficiently to allow for clearance to be restored.

In some cases, rotor warping may be mitigated by removing heat from the gas-turbine engine after shut-off. For instance, large volumes of air may be forced through the engine to remove the heat. However, forcing large volumes of air through the engine may require a substantial amount of energy, which may not be desirable.

In accordance with one or more aspects of this disclosure, one or more components of a gas-turbine engine may be rotated after the gas-turbine engine is shut off. For instance, an energy storage system, such as one or more battery cells, may provide electrical energy to an electrical motor that provides rotational mechanical energy to rotate a rotor. In some examples, the rotation of the rotor upon the engine being shut off may be called “barring”. In some examples, the function of rotating the rotor upon the engine being shut off may be called a “barring function”.

In some examples, starting a gas-turbine engine is typically performed by an air turbine starter with air provided by either a ground cart, an Auxiliary Power Unit (APU), or cross bleeding from an operating engine. Additionally, on a twin-engine aircraft, the Federal Aviation Administration (FAA) requires the ability to perform an inflight restart with both engines off. An APU may be non-essential, meaning that the aircraft can fly without the APU being functional. With a disabled or inactive APU, there may be external assistance available from other equipment to support an inflight restart. With low compression gas-turbine engines, this assistance may come from the windmilling effect whereby the forward flight of the aircraft provides energy to spin the gas-turbine engine shaft(s).

As engines become more fuel-efficient, overall pressure ratio on the compressor may be increased, with most or all of this compression being on a single shaft. This may lead to higher required starting torques. Accordingly, windmilling energy (e.g., at reasonable airspeeds) may no longer be sufficient to restart the engine inflight. Accordingly, supplemental assistance may be required.

In some examples, the present disclosure is directed to using supplemental energy from an energy storage system to provide power for an electrical start system to start one or more engines, such as during an inflight restart. In some examples, the electrical start system in the present disclosure may combine the ability to use supplemental energy from an energy storage system with power provided by the propulsion system to perform an inflight restart.

As noted above, some examples of the present disclosure relate to gas-turbine engine that include an HP spool assembly and one or more lower-pressure spool assemblies (e.g., such as a low-pressure spool assembly or intermediate spool assembly). For ease of illustration, examples of the disclosure are described primarily with regard to dual spool gas-turbine engines including a HP spool assembly, a low-pressure spool assembly (e.g., including a low-pressure propulsor and/or a low-pressure compressor), and a generator that generates power from rotation of the low-pressure shaft. However, the techniques described herein may also be applied to intermediate-pressure spool assemblies with such a generator in addition to, or as an alternative to, the low-pressure spool assemblies. In some examples, an alternative generator or an additional generator may generate power from rotation of the high-pressure shaft. In some examples, a generator may generate power from rotation of the low-pressure shaft and/or rotation of the high-pressure shaft.

FIG.1is a conceptual diagram illustrating an example vehicle in accordance with an example of the present disclosure. In the example ofFIG.1, the vehicle includes an aircraft10. In other examples, the vehicle may include any type of gas-turbine engine-powered vehicle, including one or more types of air vehicles; land vehicles, including but not limited to, tracked and/or wheeled vehicles; marine vehicles, including but not limited to surface vessels, submarines, and/or semi-submersibles; amphibious vehicles; or any combination of one or more types of air, land, and marine vehicles. The vehicle may be manned, semiautonomous, or autonomous.

Aircraft10includes a fuselage12, wings14, an empennage16, two gas-turbine engine systems18A and18B (collectively, “gas-turbine engines18”) as main propulsion engines. In other examples, aircraft10may include a single gas-turbine engine18or a plurality of propulsion systems18. As illustrated inFIG.1, aircraft10is a twin-engine turbofan aircraft. In some examples, aircraft10may be any fixed-wing aircraft, including turbofan aircraft, turbojet aircraft, and turboprop aircraft. In some examples, aircraft10may be a rotary-wing aircraft or a combination rotary-wing/fixed-wing aircraft (e.g., VTOL, STOL, etc.). Aircraft10may employ any number of wings14. Empennage16may employ a single or multiple flight control surfaces. Gas-turbine engines18may be the main propulsion systems of aircraft10. Aircraft may also have more than two engines such as three or four engines or may have a single engine.

In accordance with some examples of the disclosure, one or both of gas-turbine engine systems18A and18B may include an HP spool, one or more lower pressure (LP) spools (e.g., a single low-pressure spool or a low-pressure spool and one or more intermediate pressure (IP) spools), and a generator coupled to a rotating shaft of a lower pressure (LP) spool. The systems may be configured such that the generator generates power from the rotation of the LP shaft, which results in a torque applied to the LP shaft. In some examples, when a gas-turbine engine18A,18B is shut off, various components of the gas-turbine engine18A,18B may retain heat that resulted from operation of the gas-turbine engine18A,18B. As the components cool, the components may slightly change size. For certain components, such as rotors or other components with tight clearances, uneven cooling may be undesirable. For instance, uneven cooling may result in the components seizing, which may frustrate re-start of the gas-turbine engine18A,18B until additional cooling has occurred. In accordance with some examples of this disclosure, an electric motor may rotate one or more components of a gas-turbine engine18A,18B after the gas-turbine engine18A,18B has been shut off.

FIG.2Ais a conceptual and schematic diagram illustrating gas-turbine engine system18A in accordance with an example of the present disclosure. Although described herein as with respect to an aircraft propulsion system, in other examples, gas-turbine engine18A may be a propulsion system for providing propulsive thrust to any type of gas-turbine engine powered vehicle, as discussed above, or configured to provide power any suitable nonvehicle system including gas-turbine engine18A. Engine18B may be the same or similar to engine18A inFIG.1.

Engine18A may be a primary propulsion engine that provides thrust for flight operations of aircraft10. In the example ofFIG.2A, engine18A is a two-spool engine having a high-pressure (HP) spool (rotor)24and a low-pressure spool (rotor)26. In other embodiments, engine18A may include three or more spools, e.g., may include an IP spool and/or other spools and/or partial spools, e.g., on-axis or off-axis compressor and/or turbine stages (i.e., stages that rotate about an axis that is the same or different than that of the primary spool(s)). In one form, engine18A is a turbofan engine. In other embodiments, engine18A may be any other type of gas-turbine engine, such as a turboprop engine, a turboshaft engine, a propfan engine, a turbojet engine or a hybrid or combined cycle engine. As a turbofan engine, low-pressure spool26is operative to drive a propulsor28in the form of a fan, which may be referred to as a fan system. As a turboprop engine, low-pressure spool26powers a propulsor28in the form of a propeller system (not shown), e.g., via a reduction gearbox (not shown). In other embodiments, propulsor28may take other forms, such as one or more helicopter rotors or tilt-wing aircraft rotors, for example, powered by one or more engines18A in the form of one or more turboshaft engines.

In some examples, engine18A includes, in addition to propulsor28, a bypass duct30, a high-pressure (HP) compressor32, a diffuser34, a combustor36, a high-pressure (HP) turbine38, a low-pressure turbine40, a nozzle42A, a nozzle42B, and a tailcone46, which are generally disposed about and/or rotate about an engine centerline49. In other embodiments, there may be, for example, an intermediate pressure spool having an intermediate pressure turbine or other turbomachinery components, such as those mentioned above. In some examples, engine centerline49is the axis of rotation of propulsor28, HP compressor32, HP turbine38and turbine40. In other embodiments, one or more of propulsor28, HP compressor32, HP turbine38and turbine40may rotate about a different axis of rotation.

In the depicted example, engine18A core flow is discharged through nozzle42A, and the bypass flow from propulsor28is discharged through nozzle42B. In other embodiments, other nozzle arrangements may be employed, e.g., a common nozzle for core and bypass flow; a nozzle for core flow, but no nozzle for bypass flow; or another nozzle arrangement. Bypass duct30and HP compressor32are in fluid communication with propulsor28. Nozzle42B is in fluid communication with bypass duct30. Diffuser34is in fluid communication with HP compressor32. Combustor36is fluidly disposed between HP compressor32and HP turbine38. Turbine40is fluidly disposed between HP turbine38and nozzle42A. In one form, combustor36includes a combustion liner (not shown) that contains a continuous combustion process. In other embodiments, combustor36may take other forms, and may be, for example, a wave rotor combustion system, a rotary valve combustion system, a pulse detonation combustion system, a continuous detonation combustion system and/or a slinger combustion system, and may employ deflagration and/or detonation combustion processes.

Propulsor28may include a fan rotor system48driven by low-pressure spool26. In various examples, fan rotor system48may include one or more rotors that are powered by turbine40. In various embodiments, propulsor28may include one or more fan vane stages (not shown inFIG.2A) that cooperate with fan blades (not shown) of fan rotor system48to compress air and to generate a thrust-producing flow. Bypass duct30is operative to transmit a bypass flow generated by propulsor28around the core of engine18A. HP compressor32includes a compressor rotor system50. In various examples, compressor rotor system50includes one or more rotors (not shown) that are powered by HP turbine38. HP compressor32also includes a plurality of compressor vane stages (not shown inFIG.2A) that cooperate with compressor blades (not shown) of compressor rotor system50to compress air. In various embodiments, the compressor vane stages may include a compressor discharge vane stage and/or one or more diffuser vane stages. In one form, the compressor vane stages are stationary. In other embodiments, one or more vane stages may be replaced with one or more counter-rotating blade stages.

HP turbine38includes a turbine rotor system52. In various embodiments, turbine rotor system52includes one or more rotors having turbine blades (not shown) operative to extract power from the hot gases flowing through HP turbine38(not shown), to drive compressor rotor system50. HP turbine38also includes a plurality of turbine vane stages (not shown) that cooperate with the turbine blades of turbine rotor system52to extract power from the hot gases discharged by combustor36. In one form, the turbine vane stages are stationary. In other embodiments, one or more vane stages may be replaced with one or more counter-rotating blade stages. Turbine rotor system52is drivingly coupled to compressor rotor system50via a shafting system54(also referred to as high-pressure (HP) shaft54). Turbine40includes a turbine rotor system56. In various embodiments, turbine rotor system56includes one or more rotors having turbine blades (not shown) operative to drive fan rotor system48. Turbine40may also include a plurality of turbine vane stages (not shown inFIG.2A) that cooperate with the turbine blades of turbine rotor system56to extract power from the hot gases discharged by HP turbine38. In one form, the turbine vane stages are stationary. In other embodiments, one or more vane stages may be replaced with one or more counter-rotating blade stages. Turbine rotor system56is drivingly coupled to fan rotor system48via shafting system58(also referred to as low-pressure shaft58). In various embodiments, shafting systems54and58include a plurality of shafts that may rotate at the same or different speeds and directions for driving fan rotor system48rotor(s) and compressor rotor system50rotor(s). For ease of description, shafting system54of HP spool24is described primarily as HP shaft54but is it recognized that system54is not limited to a single shaft. Likewise, shafting system58of low-pressure spool26is described primarily as low-pressure shaft58but is it recognized that system58is not limited to a single shaft. Turbine40is operative to discharge the engine18A core flow to nozzle42A.

During normal operation of gas-turbine engine18A, air is drawn into the inlet of propulsor28and pressurized. Some of the air pressurized by propulsor28is directed into HP compressor32as core flow, and some of the pressurized air is directed into bypass duct30as bypass flow. HP compressor32further pressurizes the portion of the air received therein from propulsor28, which is then discharged into diffuser34. Diffuser34reduces the velocity of the pressurized air, and directs the diffused core airflow into combustor36. Fuel is mixed with the pressurized air in combustor36, which is then combusted. The hot gases exiting combustor36are directed into turbines38and40, which extract energy in the form of mechanical shaft power to drive HP compressor32and propulsor28via respective HP shaft54and low-pressure shaft58. The hot gases exiting turbine40are discharged through nozzle system42A, and provide a component of the thrust output by engine18A.

As shown inFIG.2A, engine18A includes generator60. In the illustrated example, generator60is positioned between fan system48and HP compressor32along centerline49. Generator60may include any suitable type and/or arrangement of an electrical machine such as an electro-mechanical generator that operates in the manner described herein, e.g., by generating power from the rotation of low-pressure shaft58, with the amount of power being generated being adjusted in some circumstances based on the operation of engine18A. For example, the amount of power being generated by generator60may be increased in combination with a decrease in thrust by engine18A, e.g., to temporarily increase the torque applied on low-pressure shaft58when the thrust generated by engine18A is initially reduced.

In some examples, generator60may be positioned in front of the nose cone or spinner of engine18A. In other examples, rather than being embedded and positioned coaxially with low-pressure shaft58, generator60may be mounted on an externally mounted gearbox which is powered by a shaft driven from the LP rotor (or by either LP rotor or IP rotor in a three-spool engine).

In some examples, generator60may be an electrical machine that is configured to be selectively operated as an electric generator or an electric motor. Example of suitable motor-generators60may include one or more of the examples of the motor-generator and motor generator assemblies disclosed within U.S. patent application Ser. Nos. 15/590,623; 15/590,606; 15/590,581; and 15/590,554, filed May 9, 2017 and the example electrical machines describes in U.S. patent application Ser. No. 15/135,167 filed Dec. 19, 2013. The entire content of these applications are incorporated by reference herein. In some examples, generator60may be selectively operated to extract and/or provide power to the low-pressure shaft58. For example, generator60may be configured for selective operation between a generation mode to generate electrical power from rotation of the low-pressure turbine40and in a drive or motor mode to receive electrical power for applying rotational force to the low-pressure shaft58. In some examples, generator60may be a permanent magnet alternator. However, in some examples of the disclosure, generator60is an electrical machine that operates in a generator mode but not a motor mode.

In the example ofFIG.2Aas well as the other examples turbine engine systems described herein, generator60may be an embedded electrical machine in that the stator and rotor of electrical machine core are positioned coaxially with low-pressure shaft58. The stator of generator60may be fixed against rotation relative to the low-pressure shaft58and a rotor may be coupled to the low-pressure shaft58for rotation therewith. The rotor may be attached to a mount of the low-pressure shaft58positioned axially between shaft bearings of the low-pressure shaft58. The stator may include a number of stator windings positioned radially outward of the rotor, such that each stator winding is arranged in electromagnetic communication with the rotor44. In other examples, generator60may include a stator and rotor positioned non-coaxially, e.g., where the rotor of generator60is rotationally coupled to low-pressure shaft58via one or more other shafts and suitable gearing.

FIG.2Bis another example of a schematic functional diagram illustrating an additional configuration and components of engine system18A ofFIGS.1and2A, and like features are similarly numbered. As noted above, engine system18A may be a gas turbofan system. Engine18A may include propulsor rotor system28that is rotationally coupled to low-pressure turbine40by low-pressure shaft58, and HP compressor32rotationally coupled to HP turbine38by HP shaft54. The speed of HP shaft54driving the HP compressor32may be different from that of the speed of shaft58driving the propulsor rotor system28. The combination of HP compressor32, HP turbine38and HP shaft54may be referred to as the HP spool assembly24or HP spool24.

Engine18A ofFIG.2Bincludes low-pressure compressor29. Low-pressure compressor29is coupled to rotationally coupled to low-pressure turbine40by low-pressure shaft58. In some examples, low-pressure compressor29may be referred to as a booster. In some examples, low-pressure compressor29may be similar to that of HP compressor32and may include a compressor rotor system (not shown in detail inFIG.2B). In various examples, the compressor rotor system includes one or more rotors (not shown) that are powered by low-pressure turbine40. Low-pressure compressor29may also include a plurality of compressor vane stages (not shown inFIG.2B) that cooperate with compressor blades (not shown) of the compressor rotor system to compress air. In various embodiments, the compressor vane stages may include a compressor discharge vane stage and/or one or more diffuser vane stages. In one form, the compressor vane stages are stationary. In other embodiments, one or more vane stages may be replaced with one or more counter-rotating blade stages. In operation, low-pressure compressor29may operate to increase the pressure of the intake air, which is then further increase in pressure by HP compressor32.

The combination of propulsor system28, low-pressure compressor29, low-pressure turbine40and low-pressure shaft58may be referred to as the low-pressure spool assembly26or low-pressure spool26. In some examples, as shown inFIG.2B, engine18A ofFIG.2Bmay include generator60, which is operably coupled to one or more of HP shaft54or LP shaft58, e.g., in an embedded (co-axial) with HP shaft54and/or LP shaft58or non-co-axial.

Engine system18A may also include a rectifier/inverter62. In some examples, electrical systems65and power storage device66may be part of the aircraft system10. In some examples, system10may also include controller64. In some examples, controller64may include control circuitry for the control of the engine systems and may control the rectifier62. In some examples, controller64may include one or a combination of controllers as part of a control system that controls the operation of engine18A and/or other components of system10. For example, controller64may represent more than one controller, wherein the more than one controller includes one or more electronic engine controllers. The electronic engine controllers may be part of the engine but may be physically located on the aircraft. In some examples, one of the individual controllers of controller64may control the electrical loads and battery in aircraft10as part of system10. As illustrated, all or a portion of controller64may be located on aircraft10. However, there may be some configuration where an engine controller may be mounted on engine18A.

In some examples, electrical system65and power storage system66, which are devices that can absorb relatively large amounts of power, use power supplied by generator60. As described herein, the amount of electrical load applied by electrical system65and/or power storage system66on generator60may be varied to vary the amount of torque load applied by generator60on low-pressure shaft58, e.g., to decrease the rotational speed of low-pressure shaft58over a shorter period of time in combination with the reduction in thrust by engine18A. The generator output voltage may be controlled by the rectifier62that may control the power input to power storage66on a DC bus. If the rectifier62is powering a DC bus with multiple power sources (not shown) then it may also control the generator power to the electrical system65.

Controller64may be configured to control the components of engine18A and/or aircraft10individually and selectively such that engine18A and system10more generally implement the techniques described herein. Controller64may comprise any suitable arrangement of hardware, software, firmware, or any combination thereof, to perform the techniques attributed to controller64herein. Examples of controller64include any of one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), processing circuitry, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. When controller64includes software or firmware, controller64further includes any necessary hardware for storing and executing the software or firmware, such as one or more processors or processing units. In some examples, all or portions of controller64may be embodied in a full authority digital engine control (FADEC) including an electronic engine controller (EEC) or engine control unit (ECU) and related accessories that control one or more aspects of the operation of engine system18A.

In general, a processing unit may include one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. Although not shown inFIG.2B, controller64may include a memory configured to store data. The memory may include any volatile or non-volatile media, such as a random access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and the like. In some examples, the memory may be external to controller64(e.g., may be external to a package in which controller64is housed).

Although controller64is generally described as being the primary unit for controlling each of the engine components of system18A for performing the techniques described herein, in some examples, the individual components of system18A may include additional functionality for performing some or all the operations described below with respect to controller64. For example, a combination of one or more of HP compressor32, turbines38,40, propulsor28, low-pressure compressor29, generator60, rectifier/inverter62, and the like may include components for controlling the operation of system18A in the manner described herein. As described herein, generator60, is configured to generate power from the rotation of shaft58, e.g., as driven by turbine40. The electrical energy generated by generator60in a generator mode may be used to provide operational power to one or more electrically operated systems65of vehicle10(FIG.1). In some examples, generator60may be configured to generate continuous aircraft or transient system power also defined by the desired end user application. Example electrical systems65that may be powered by generator60include hydraulic and/or pneumatic drive systems, environmental control systems, communications systems, directed energy systems, radar systems and component cooling systems. Electrical systems65may be any system having electrical components requiring power to operate. When operation power is supplied by a generator such as generator60, electrical system65may apply an electrical load on the generator in order for electrical system65to operate in the desired manner.

Additionally, or alternatively, all or some of the power generated by generator60may be stored by power storage device66. In such an example, rectifier/inverter62, under the control of controller64may increase its output voltage to input all or a portion of the power generated by generator60as direct current to power storage device66for storage of the power. Power storage device66may be any suitable device such as one or more suitable batteries or capacitors. Engine18A may utilize the power stored in power storage device at times when the power generated by generator60is relatively low. Power storage device66may apply (e.g., selectively) an electrical load on generator60to recharge the power storage device (e.g., battery). The electrical load applied by power storage device66on generator60may increase the torque on LP shaft58.

In some examples, an engine system may include two generators, one generator operatively coupled to the HP rotor/HP shaft54and the other generator to the lower-pressure rotor/shaft58.

In some examples of the gas-turbine engine system, one or more gas-turbine engines may not include a center sump to increase efficiency, improve secondary flow and reduce weight of the gas-turbine engine system. However, when one or more of the gas-turbine engines are shut off, heat produced by the gas-turbine engine(s) may warp a rotor of the gas-turbine engine(s) such that the rotor may contact a compressor of the engine(s) and/or lock-up inside a compressor of the engine. In addition, uneven heating may cause the tight clearances between shafts and top clearances on airfoils to close. When a rotor is becomes locked-up, it may take prolonged time at rest to cool the rotor sufficiently to allow for clearance to be restored. Such a delay may be undesirable as it may delay subsequent operation of the gas-turbine engine and associated vehicle.

In accordance with one or more aspects of this disclosure, an electrical machine may rotate a shaft of a gas-turbine engine responsive to the gas-turbine engine being shut off. For instance, an energy storage system, such as one or more batteries, may provide electrical energy to the electrical machine, which converts the electrical energy into rotational mechanical energy that in turn rotates the shaft of the gas-turbine engine. In some examples, the rotation of the rotor upon the engine being shut off may be called barring.

In some examples, the electrical machine that rotates the shaft (e.g., that performs the barring) may perform one or more other functions of the gas-turbine engine. For instance, during normal operation of the gas-turbine engine, the electrical machine may generate electrical power that is used to operate one or more ignitors of the gas-turbine engine. In some examples, the electrical machine may be a permanent magnet alternator (PMA). Windings on the electrical machine that perform the barring operation may be the same windings that generate the ignitor energy or may be different windings. When the windings are different, the windings for the barring function and the windings for the ignitors may be on a common shaft (e.g., a same shaft). Using the same windings for both operations may provide advantages, such as weight savings. Using different windings may also provide advantages, such as manufacturing simplicity (e.g., reduction in slot count).

FIG.3Ais a schematic functional diagram illustrating an example system100for powering a shaft to cause a rotor to rotate to bar the rotor using the energy received from the energy storage system, in accordance with examples of the disclosure. In some examples, electrical machine78may be similar to generator60, power electronics system75may be similar to electrical system65, and controller64may be similar to electronic engine controllers74A,74B. In some examples, energy storage system76may be in addition to power storage device66. In some examples, electrical machine78may include two electrical machines78A,78B that are distinct from each other. In some examples, electrical machine78A may provide electrical energy to ignitor modules70A,70B, and engine controllers74A,74B while electrical machine78B may be separately electrically coupled to energy storage system76and power electronics system75. While electrical machine78while be reference in the singular below, electrical machine78may include two electrical machines78A,78B, such as in the examples discussed above.

In some examples, system100may include one or more ignitor modules70A,70B configured to ignite/maintain ignition of one or more gas-turbine engines (not shown inFIG.3A). In some examples, an ignitor module70A may include an ignitor71A and an exciter box72A. In some examples, the system may include one or more electronic engine controllers74A,74B, to control one or more gas-turbine engines (e.g., in a redundant/fault-tolerant arrangement). In some examples, the system may further include an electrical machine78electrically connected to the one or more ignitor modules70A,70B, and electrically connected to the one or more electronic engine controllers74A,74B (e.g., configured to supply electrical energy to). In some examples, electrical machine78may be a permanent magnet alternator. In some examples, electrical machine78may be configured to provide electrical energy to the one or more ignitor modules70A,70B, to ignite/maintain ignition the one or more engines. In some examples, electrical machine78may be configured to generate electrical energy used by the one or more electronic engine controllers74A,74B. In some examples, electrical machine78may be configured to provide electrical energy to the one or more ignitor modules70A,70B and the one or more ignitor modules70A,70B, simultaneously. In some examples, the electronic engine controllers74A,74B may use the electrical energy received from the electrical machine78to control the one or more gas-turbine engines. In some examples, one or more electric engine controllers74A,74B may be configured to shut off each of the one or more gas-turbine engines (e.g., responsive to pilot commands).

In some examples, electrical machine78may be configured to selectively operate as a motor, such as a permanent magnet alternator (PMA). For example, electrical machine78may be configured to receive energy from energy storage system76via the power electronics system75and cause the rotor (e.g., HP spool) to rotate to bar the rotor using the energy received from the energy storage system76.

In some examples, the system100may further include an energy storage system76and a power electronics system75electrically connected to the energy storage system76and configured to receive electrical energy from the energy storage system76. In some examples, the energy storage system76may comprise one or more battery cells.

In some examples, energy storage system76may generate direct current (DC) electricity to output to power electronics system75. In some examples, power electronics system75may include a DC/alternating current (AC) converter to convert DC electricity received from the energy storage system to AC electricity. In some examples, power electronics system75may be configured to output the converted AC electricity to cause the electrical machine78to rotate the rotor.

In some examples, energy storage system76and power electronics system75may configured to have electrical energy flow bi-directionally between energy storage system76and power electronics system75. In some examples, power electronics system75may be configured to provide electrical energy to energy storage system76when the one or more gas-turbine engines are operating and/or electrical machine78is turned on. In some examples, energy storage system76may be configured to store electrical energy received from power electronics system75when the one or more gas-turbine engines are operating and/or electrical machine78is turned on. In some examples, since the power electronics system75uses energy from the energy storage system76to cause the electrical machine78to rotate the rotor and the energy storage system76is charged when the one or more gas-turbine engines are operating, the power used to rotate the rotor may be at least partially obtained from electrical energy generated by the one or more gas-turbine engines. This may help improve energy efficiency of system100.

In some examples, the electrical machine78may further include a shaft, such as an HP shaft54as shown inFIG.2A, coupled to the one or more electronic engine controllers74A,74B via first windings77a. In some examples, as shown inFIG.3B, the shaft54may be coupled to the power electronics system75via second windings77b, which may be electrically isolated from the first windings. In this example, while the functions of the electrical machine78, such as a permanent magnet alternator, and the functions of the power electronics system75may be on the same shaft54, they may be electrically isolated from each other.

In some examples, such as shown inFIGS.4A and4B, the one or more electronic engine controllers74A,74B, and the power electronics system75may be coupled to shaft54(not shown inFIG.4A) via the same windings77c. In this example, the functions of the electrical machine78, such as a permanent magnet alternator, and the functions of the power electronics system75may be integrated into the same machine.

In some examples, in response to each of the one or more gas-turbine engines being shut off, the power electronics system75may cause the electrical machine78to rotate a rotor, such as rotor32, using the energy received from the energy storage system76. In some examples, the rotation of the rotor upon the engine being shut off may be called barring.

Power electronics system75may cause the electrical machine78to rotate at a speed that is fast enough to prevent seizing of the rotor, but low enough to avoid expending unnecessary energy. In some examples, power electronics system75may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 1000 revolutions per minute. In some examples, power electronics system75may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 500 revolutions per minute. In some examples, power electronics system75may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 200 revolutions per minute. In some examples, power electronics system75may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 100 revolutions per minute. In some examples, power electronics system75may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 50 revolutions per minute. In some examples, power electronics system65may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 25 revolutions per minute. In some examples, power electronics system75may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 10 revolutions per minute. In some examples, power electronics system75may be configured to cause the electrical machine78to rotate the rotor at a speed of less than 5 revolutions per minute.

In some examples, power electronics system75may be configured to stop/cease causing the electrical machine78to rotate the rotor based on one or more criterion. For instance, power electronics system75may cease causing the electrical machine78to rotate the rotor in response to one or more of determining an amount of time after the one or more gas-turbine engines being shut off is above a time threshold, determining an engine maintenance switch is activated, and/or determining the power stored in energy storage system76falls below an energy threshold. In some examples, power electronics system75may be configured to include a time threshold in which power electronics system75stops causing the electrical machine78to rotate the rotor. The time threshold may be preset. In some examples, the time threshold may be based on one or more of temperature of a rotor, an outside temperature, speed the rotor rotates during operation of the barring function, and/or other various features. In other examples, the point at which power electronics75ceases causing the electrical machine78to rotate the rotor may not be based on a temperature (e.g., a temperature of the rotor).

In some examples, a switch, such as an engine maintenance switch, when turned on, may instruct power electronics system75to stop powering shaft to rotate the rotor. In some examples, a user, such as a pilot or maintenance person, may turn on the engine maintenance switch. In some examples, an engine maintenance switch may be used when maintenance needs to be done on the engine and a person needs to access one or more engines. In some examples, electrical energy may flow to rotate the rotor regardless of one or more other switches (e.g., regardless of a battery master switch or other such switch that controls a ship's main battery).

In some examples, power electronics system75may cause the electrical machine78to stop causing the rotor to rotate when determining power stored in energy storage system76is below an energy threshold. In some examples, an energy threshold may be an amount in which energy storage system76no longer has enough remaining power to power a rotor to rotate. In some examples, an energy threshold may be an amount in which energy storage system76needs to maintain to not reduce a lifetime of energy storage system76and/or one or more battery cells in energy storage system76.

In accordance with the system100described above, a barring function may be triggered by a loss of power to the electronic engine controllers74A,74B, such as when the gas-turbine engine(s) are shut off, and the barring function may be powered by the energy storage system76. This enables the rotor to rotate while the gas-turbine engine(s) and/or electrical machine78are shut off. This may improve energy efficiency. In addition, since a barring function may be triggered by one of the gas-turbine engine(s) and/or the electrical machine78being shut off, the system100described above simplifies initiating the barring function and may reduce occurrences when the barring function is not initiated as needed. This may reduce occurrences of a rotor locking-up and/or rotor bow problems in which tight clearances between shafts and tip clearances close. When a rotor locks-up, a prolonged amount of time may be needed to cool the rotor sufficiently to allow for clearance to be restored. This may delay the ability of a plane to be able to fly. Accordingly, the system100described above may reduce occurrences of flight delays caused by rotor lock-up and/or lack of clearance between shafts and tip.

In some examples, in response to the barring function being energized after shutdown of the one or more engines, once a rotor speed slows to below a torque of a barring motor, the speed of the rotor may stabilize.

In some examples, electrical machine78may be a permanent magnet alternator (PMA). In some examples, when a gas-turbine engine is started, one or more ignitor modules70A,70B, may engage and drive a high-pressure spool to light-off and to idle. At this time, PMA78is performing its functions as an electrical machine, such as providing power to one or more of the ignitor modules70A,70B and/or electronic engine controllers74A,74B, and there is no need for barring at this time. In addition, when one or more gas-turbine engines are on, an energy storage system76may either be re-charging or be electrically isolated during this time.

In some examples, upon shutdown of the gas-turbine engine(s), a barring function may be triggered (e.g., by a loss of power to the electronic engine controllers74A,74B from PMA78). In some examples, the barring function may be initiated by a user or other triggers as well. In response to the barring function being triggered, energy storage system76provides power to power electronics system75. In some examples, power electronics system75may provide power, using the energy received from the energy storage system, to cause PMA78to rotate the rotor. For example, power electronics system75may provide power to PMA78using the same windings that PMA78powers electronic engine controllers74A,74B and/or ignitor modules70A,70B. In some examples, power electronics system75may power a barring function causing the electrical machine78to rotate a rotor using different windings than the windings used by PMA78to power electronic engine controllers74A,74B and/or ignitor modules70A,70B. For example, the powering of the barring function may be electrically isolated from electronic engine controllers74A,74B and/or ignitor modules70A,70B.

As shown inFIG.5, power electronics system75detects the gas-turbine engine being shut off (80). As one example, power electronics system75may determine that fuel flow to the gas-turbine engine has been cut off. As another example, power electronics system75may monitor voltage from barring windings (e.g., windings of PMA78used to rotate the rotor during barring), and determine that the gas-turbine has been shut off based on the voltage dropping below a threshold.

In response to detecting the gas-turbine engine being shut off, power electronics system75may cause energy storage system76to deliver electrical energy to power electronics system75. Thus, energy storage system76may delver electrical energy to power electronics system75in response to the gas-turbine engine being shut off (82). In some examples, power electronics system75may further selectively initiate barring based on other signals, such as squat switches (e.g., a signal indicating the aircraft is on the ground). In response to the electrical energy being delivered by energy storage system76to power electronics system75, power electronic system75causes the electrical machine78to rotate a rotor using the energy received from energy storage system76(84).

As discussed above, starting a gas-turbine engine is typically performed by an air turbine starter with air provided by either a ground cart, an APU, or cross bleeding from an operating engine. Additionally, there is a requirement by the FAA that a twin-engine aircraft be able to perform an inflight restart with both engines off. An airframer may choose to make the APU non-essential, meaning that the aircraft may fly without the APU being functional (e.g., the APU may not be an on minimum equipment list (MEL)). An air turbine starter is a component in a pneumatic system with the pneumatic system also encompassing a starter air valve, appropriate sensing and control instrumentation, ducting, and a load compressor or bleed system from the APU. With a disabled or inactive APU, there may be no external assistance available from other equipment to support an inflight restart. In some examples, with low compression gas-turbine engines, this assistance may come from the windmilling effect whereby the forward flight of the aircraft provides energy to spin the gas-turbine engine shaft(s).

In some examples, to increase fuel efficiency of gas-turbine engines, overall pressure ratio on the compressor may be increased. In some examples, all of this compression may be on a single shaft (e.g., a gas-turbine engine may include a single high-pressure spool) and which may lead to higher required starting torques. In some examples, windmilling energy may no longer be sufficient to restart the gas-turbine engine inflight and therefore, supplemental assistance is required. In accordance with one or more aspects of this disclosure, an electrical starting system may provide supplemental assistance that may be required to restart the gas-turbine engines inflight. For instance, electrical energy from an energy storage system may be combined with electrical energy from an electrical machine to power one or more starters during an inflight restart to restart one or more of the gas-turbine engines. Accordingly, sufficient power may be provided to restart one or more gas-turbine engines inflight.

FIG.6is a schematic functional diagram illustrating an example system200for starting one or more gas-turbine engines, including starting one or more gas-turbine engines during an inflight restart. In some examples, as described herein, electrical starting system200may use supplemental energy with propulsion system provided power to power one or more starters during an inflight restart to restart one or more of the gas-turbine engines. In some examples, electrical starting system200may power one or more starters during an inflight restart to restart one or more of the gas-turbine engines.

In some examples, an electrical starting system200may include a power electronics system75, one or more starters73A,73B, one or more electronic engine controllers74A,74B, an alternating current (AC) bus79, and an energy storage system76.

In some examples, one or more starters73A,73B may be electrically connected to the power electronics system75and configured to start one or more gas-turbine engines. One or more electronic engine controllers74A,64B may be electrically connected to the power electronics system200and configured to control the one or more gas-turbine engines. AC bus79may be electrically connected to the power electronics system75and configured to provide electrical energy to the power electronics system75. Energy storage system76may be electrically connected to the power electronics system75and configured to provide electrical energy to the power electronics system75. In some examples, power electronics system75may be configured to deliver power to the one or more starters73A,73B to start the one or more gas-turbine engines using electrical energy from the energy storage system76and using electrical energy from the electrical machine78.

In some examples, power electronics system75may include one or more inverters, one or more rectifiers and/or one or more converters. In some examples, the one or more starters73A,73B may be a 3-phase electric starter. In some examples, the one or more rectifiers and the one or more converters may supply an inverter that drives a 3-phase electric starter. The power electronics system75may be configured to convert DC electricity to AC electricity and/or convert AC electricity to DC electricity. In some examples, power electronics system75may supply power to the one or more starters73A,73B one at a time (e.g., during non-overlapping time periods). In some examples, power electronics system75may supply power to the one or more starters73A,73B simultaneously.

In some examples, the power electronics system75may be configured to receive AC power from the AC bus79, receive DC power from the energy storage system76, and convert the received DC power from the energy storage system76to AC power. In some examples, AC power may be put back on the AC bus. In some examples, the power electronics system75may be further configured to rectify the received AC power from the AC bus79to DC power, then combine that rectified DC power with the DC power received from energy storage system76, and then invert the combined DC power to AC power to generate a combined AC power. In some examples, the power electronics system75may be further configured to output the combined AC power to the one or more starters71A,71B to start one or more of the gas-turbine engine(s).

AC bus79may be an AC electrical bus supplied by (e.g., energized by) various power sources. As one example, AC bus79may receive power from electrical machine78(e.g., when a corresponding gas-turbine engine is operating). As another example, AC bus79may receive power from an inverter that sources DC power from a DC electrical energy source that is different than the energy storage system76. In some examples, the DC electrical energy source may be one or both of a main ship's battery of the aircraft; and/or an external power connection. The DC electrical energy source may, in some examples, be a 28 volt DC electrical energy source. An operating voltage level of AC bus79may be between 80 and 150 volts. As one specific example, the operating voltage level of AC bus79may be 115 volts.

In some examples, energy storage system may include one or more battery cells. In some examples, energy storage system76may include a voltage between 12 volts DC and 1080 volts DC. In some examples, energy storage system76may include a voltage between 50 volts DC and 500 volts DC. In some examples, energy storage system76may include a voltage between 150 volts DC and 400 volts DC. In some examples, energy storage system76may include a voltage between 225 volts DC and 378 volts DC. In some examples, energy storage system76may include a voltage between 240 volts DC and 300 volts DC. In some examples, energy storage system76may include a voltage of 270 volts DC.

In some examples, a cold day ground start may require the largest amounts of power and may subsequently dictate a size of the electrical machine (starter), cables, and thermal management system. However, energy storage system76may be sized for in-air restarts if there is supplemental energy available for cold day ground starts, such as that provided by a ground cart or an APU.

In some examples, electrical energy may flow bi-directionally between electrical machine78and power electronics system75. In some examples, the electrical energy that flows between electrical machine78and power electronics system75may be AC power. In some examples, electrical energy may flow between electrical machine78and power electronics system75between 0.01 kilowatt (kW) and 500 kW. In some examples, electrical energy may flow between electrical machine78and power electronics system75between 0.1 kW and 200 kW. In some examples, electrical energy may flow between electrical machine78and power electronics system75between 1 kW and 100 kW. In some examples, electrical energy may flow between electrical machine78and power electronics system75between 5 kW and 75 kW. In some examples, electrical energy may flow between electrical machine60and power electronics system75between 10 kW and 50 kW. In some examples, electrical energy may flow between electrical machine78and power electronics system75between 20 kW and 40 kW. In some examples, electrical energy may flow between electrical machine78and power electronics system75at 28 kW.

In some examples, electrical energy may flow bi-directionally between energy storage system76and the power electronics system75. In some examples, electrical energy that flows between energy storage system76and power electronics system75may be DC power. In some examples, when one or more gas-turbine engines are in operation, energy storage system76may be charged from energy received from electrical machine78via power electronics system75. In some examples, electrical energy may flow between energy storage system76and power electronics system75between 0.01 kW and 500 kW. n some examples, electrical energy may flow between energy storage system76and power electronics system75between 0.1 kW and 400 kW. In some examples, electrical energy may flow between energy storage system76and power electronics system75between 1 kW and 300 kW. In some examples, electrical energy may flow between energy storage system76and power electronics system75between 10 kW and 250 kW. In some examples, electrical energy may flow between energy storage system76and power electronics system75between 40 kW and 200 kW. In some examples, electrical energy may flow between energy storage system66and power electronics system75between 50 kW and 100 kW. In some examples, electrical energy may flow between energy storage system76and power electronics system75at 79 kW.

In some examples, electrical energy may flow unidirectionally from power electronics75system to the one or more starters70A,70B. In some examples, the electrical energy that flows from power electronics system75to one or more starters70A,70B may be AC power. In some examples, power electronics system75may convert DC electrical energy received from the energy storage system76to AC energy and combine the converted energy with the AC energy received from the electrical machine78to then be output to the one of starters70A,70B to start one or more gas-turbine engines. In some examples, electrical energy may flow from power electronics system75to one or more starters70A,70B between 1 kW and 400 kW. In some examples, electrical energy may flow from power electronics system75to one or more starters70A,70B between 20 kW and 300 kW. In some examples, electrical energy may flow from power electronics system75to one or more starters70A,70B between 50 kW and 200 kW. In some examples, electrical energy may flow from power electronics system75to one or more starters70A,70B between 75 kW and 150 kW. In some examples, electrical energy may flow from power electronics system75to one or more starters70A,70B at 107 kW.

In some examples, electronic engine controller74A may include one or more controllers (not shown) and may control one particular engine of the gas-turbine engines. In some examples, electronic engine controller74B may include one or more controllers (not shown) and may be control one particular engine of the gas-turbine engines. In some examples, electronic engine controller74A may control a different engine than electronic engine controller74B. In some examples, electronic engine controller74A and engine controller74B may control the same engine.

Due to the weight impact of electric start system200, a thermal management system may be self-contained to minimize any additional burden on the airframe, such as the addition of heat exchangers and their increased drag. In some examples, power electronics system75may include a closed loop liquid coolant system including an integrated electrical pump plus tank. In some examples, energy storage system76may be at least partially coated in at least one of paraffin or phase-change wax. In some examples, one or more starters73A,73B may include features to pump air into the motor and out.

In some examples, electric start system may be thermally isolated, such as not having any heat exchangers to outside air. In some examples, this may simplify operation and integration.

In some examples, in response to each of the one or more gas-turbine engines being shut off for a period of time greater than a time threshold, power electronics system75may be configured to cause electrical machine78to rotate a rotor using energy received from the energy storage system76. In some examples, energy storage system76, as shown inFIG.6, may also be used to bar a rotor, as was discussed in examples above in reference toFIGS.3-4.

As shown inFIG.7, power electronics system75may receive a start request (90). For instance, power electronics system75may receive a start request provided by a pilot of the aircraft. Power electronics system75may receive electrical energy from AC bus79(92). Power electronics system75may receive electrical energy from energy storage system76(94). In response to receiving the start request, power electronics system75may power the starter73A,73B to start the gas-turbine engine using electrical energy received from energy storage system76and using electrical energy received from the electrical machine78(96).

In some examples, power electronics system75may receive AC power from the electrical machine78, receive DC power from the energy storage system76, convert the received DC power from the energy storage system76to AC power, combine the received AC power from the electrical machine78with the converted AC power to generate a combined AC power, and output the combined AC power to the starter70A,70B to start the gas-turbine engine.

In some examples, energy storage system76may receive electrical energy from electrical machine78via power electronics system75to charge energy storage system76when the gas-turbine engine is on.

The following examples may illustrate one or more aspects of the disclosure:

Example 1A: A system includes an electrical machine electrically configured to generate electrical energy used by one or more components of a gas-turbine engine; an energy storage system; and a controller electrically connected to the energy storage system and configured to receive electrical energy from the energy storage system, wherein, in response to the gas-turbine engine being shut off, the controller is configured to cause the electrical machine to rotate a rotor of the gas-turbine engine using the energy received from the energy storage system.

Example 2A: The system of example 1A, wherein the electrical machine is a permanent magnet alternator (PMA).

Example 3A: The system of any of examples 1A and 2A, wherein the electrical machine includes: a shaft mechanically coupled to the rotor; first windings configured to supply, during operation of the gas-turbine engine, electrical energy to the one or more components of the gas-turbine engine; and second windings configured to cause the shaft to rotate the rotor using power sourced from the energy storage system.

Example 4A: The system of any of examples 1A through 3A, wherein the electrical machine includes: a shaft mechanically coupled to the rotor; common windings configured to: supply, during operation of the gas-turbine engine, electrical energy to the one or more components of the gas-turbine engine; and cause the shaft to rotate the rotor using power sourced from the energy storage system.

Example 5A: The system of any of examples 1A through 4A, wherein the energy storage system includes one or more battery cells configured to generate direct current (DC) electricity to output to the power electronics system.

Example 6A: The system of example 5A, wherein the controller includes a DC/alternating current (AC) converter configured to convert DC electricity received from the energy storage system to AC electricity to output to power the rotor to rotate.

Example 7A: The system of any of examples 1A through 6A, wherein the controller is configured to cause the electrical machine to rotate the rotor at a speed of less than 100 revolutions per minute.

Example 8A: The system of example 7A, wherein the controller is configured to cause the electrical machine to rotate the rotor at a speed of less than 10 revolutions per minute.

Example 9A: The system of any of examples 1A through 8A, wherein the controller is configured to cease causing the electrical machine to rotate the rotor in response to one or more of: an amount of time after the gas-turbine engine being shut off crossing a time threshold; an engine maintenance switch being activated; or the power stored in the energy storage system falling below an energy threshold.

Example 10A: The system of any of examples 1A through 9A, wherein the one or more components of the gas-turbine engine include one or more of: one or more ignitor modules; and one or more electronic engine controllers (EECs).

Example 11A: The system of any of examples 1A through 10A, wherein the gas-turbine comprises a low-pressure spool and a high-pressure spool.

Example 12A: The system of example 11A, wherein the rotor is the high-pressure spool.

Example 13A: The system of any of examples 1A through 12A, wherein the gas-turbine engine comprises a turbo-prop engine configured to propel an aircraft.

Example 14A: The system of example 13A, wherein the gas-turbine engine does not include a center sump.

Example 15A: The system of any of examples 1A through 14A, wherein the controller is configured to charge the energy storage system using power generated by the electric machine during operation of the gas-turbine operation.

Example 16A: A method includes detecting, by a controller, shut down of a gas-turbine engine of an aircraft; and responsive to detecting the shut down of the gas-turbine engine, causing, by the controller, an electrical machine to rotate a rotor of the gas-turbine engine using electrical energy sourced from an electrical energy storage system of the aircraft.

Example 17A: The method of example 16A, wherein causing the electrical machine to rotate the rotor comprises: causing the electrical machine to rotate the rotor at a speed of less than 100 revolutions per minute.

Example 18A: The method of any of examples 16A and 17A, wherein detecting shut down of the gas-turbine engine comprises: determining that fuel flow to the gas-turbine engine has been shut off.

Example 19A: The method of any of examples 16A through 18A, wherein the method further comprises: stopping, by power electronics system, the electrical machine causing the rotor to rotate in response to one or more of: determining an amount of time after the gas-turbine engine being shut off is above a time threshold; determining an engine maintenance switch is activated; or determining the power stored in the energy storage system falls below an energy threshold.

Example 20A: The method of any of examples 14A through 19A, wherein the electrical machine is a permanent magnet alternator (PMA), the method further includes supplying, during operation of the gas-turbine engine, electrical energy generated by the PMA to one or more ignitors of the gas-turbine engine.

Example 1B: A system includes a power electronics system; a starter electrically connected to the power electronics system and configured to start a gas-turbine engine of an aircraft; and an energy storage system electrically connected to the power electronics system and configured to provide direct current (DC) electrical energy to the power electronics system, wherein the power electronics system is configured to deliver alternating current (AC) electrical energy to the starter to start the gas-turbine engine using the DC electrical energy from the energy storage system and AC electrical energy sourced from an AC electrical bus of the aircraft.

Example 2B: The system of example 1B, further includes a DC electrical energy source that is different than the energy storage system; and an inverter configured to energize the AC electrical bus using electrical energy sourced from the DC electrical energy source.

Example 3B: The system of any of examples 1B and 2B, wherein the DC electrical energy source comprises one or more of: a main ship's battery of the aircraft; and an external power connection.

Example 4B: The system of any of examples 1B through 3B, wherein more the power electronics system is configured to source more than half of the AC electrical energy delivered to the starter from the energy storage system.

Example 5B: The system of any of examples 1B through 4B, wherein the starter is a first starter configured to start a first gas-turbine engine of a plurality of gas-turbine engines of the aircraft, the system further includes a second starter electrically connected to the power electronics system and configured to start a second gas-turbine engine of the plurality of gas-turbine engines of the aircraft, wherein the power electronics system is configured to deliver AC electrical energy to the second starter to start the second gas-turbine engine using the DC electrical energy from the energy storage system and the AC electrical bus of the aircraft.

Example 6B: The system of example 5B, wherein the power electronics system is configured to deliver, during flight of the aircraft and when the plurality of gas-turbine engines are shut down, AC electrical energy to the second starter to start the second gas-turbine engine using the DC electrical energy from the energy storage system.

Example 7B: The system of any of examples 1B through 6B, further includes a self-contained thermal management system configured to absorb heat generated by one or more of the energy storage system and the power electronics system.

Example 8B: The system of example 7B, wherein the self-contained thermal management system comprises a closed loop glycol system configured to absorb heat generated by the power electronics system.

Example 9B: The system of any of examples 7B and 8B, wherein the self-contained thermal management system comprises at least one of paraffin or phase-change wax configured to absorb heat generated by the energy storage system.

Example 10B: The system of any of examples 1B through 9B, wherein the DC electrical energy received from the energy storage system has a voltage between 225 volts and 378 volts, and wherein the AC electrical energy received from the AC electrical bus has a voltage between 60 volts and 180 volts.

Example 11B: The system of any of examples 1B through 10B, wherein the gas-turbine engine comprises a turbo-prop engine configured to propel the aircraft.

Example 12B: The system of example 11B, wherein the gas-turbine engine comprises a single high-pressure spool.

Example 13B: The system of example 12B, further includes an electrical machine electrically configured to generate electrical energy used by one or more components of the gas-turbine engine, wherein the power electronics system is configured to, responsive to shut down of the gas-turbine engine, to cause the electrical machine to rotate a rotor of the gas-turbine engine using the energy received from the energy storage system.

Example 14B: A method includes receiving, by a power electronics system of an aircraft; direct current (DC) electrical energy from an energy storage system of the aircraft; receiving, by the power electronics system, alternating current (AC) electrical energy from an AC electrical bus of the aircraft; generating, by the power electronics system and from the DC electrical energy received from the energy storage system and the AC electrical energy received from the AC electrical bus, combined AC electrical energy; outputting, by the power electronics system and to a starter of a gas-turbine engine of the aircraft, the combined AC electrical energy; and starting, by the starter and using the combined AC electrical energy, the gas-turbine engine.

Example 15B: The method of example 14B, wherein the starter is a first starter configured to start a first gas-turbine engine of a plurality of gas-turbine engines of the aircraft, the method further includes outputting, by the power electronics system and to a second starter of a second gas-turbine engine of the aircraft, the combined AC electrical energy; and starting, by the second starter and using the combined AC electrical energy, the second gas-turbine engine.

Example 16B: The method of any of examples 14B and 15B, further includes generating, by the power electronics system and during flight of the aircraft when the plurality of gas-turbine engines are shut down, mid-air restart AC electrical energy from the DC electrical energy received from the energy storage system; outputting, by the power electronics system and to the starter of the first gas-turbine engine of, the mid-air restart AC electrical energy; and mid-air restarting, by the first starter and using the mid-air restart AC electrical energy, the first gas-turbine engine.

Example 17B: The method of example 16B, wherein the mid-air restart AC electrical energy includes a lesser amount of power than the combined AC electrical energy.

Example 18B: The method of example 17B, wherein the gas-turbine engine comprises a turbo-prop engine configured to propel the aircraft, and wherein the gas-turbine engine comprises a single high-pressure spool.

Example 19B: The method of any of examples 14B through 18B, wherein the gas-turbine engine comprises a turbo-prop engine configured to propel the aircraft, and wherein the gas-turbine engine comprises a single high-pressure spool.

Example 20B: The method of any of examples 14B through 19B, wherein the DC electrical energy includes a first amount of power, wherein the AC electrical energy includes a second amount of power, wherein the combined AC electrical energy includes a combined amount of power that is substantially a sum of the first amount of power and the second amount of power, and wherein the first amount of power is greater than the second amount of power.

Various examples have been described. These and other examples are within the scope of the following examples and claims.