HYBRID ELECTRIC TAXI SYSTEM (HETS) OR FULL ELECTRIC TAXI SYSTEM (FETS)

Abstract

For aircraft taxiing, an aircraft is equipped with an electric machine installed in a propulsor gearbox (PGB), in parallel to the gas turbine, working in motor mode during taxi, and in generator mode during flight phases (such as take-off, climb, cruise, descent, approach and landing). Typical current systems which use an electric machine in the PGB do not use the electric machine in motor mode for taxi operations (i.e., it is only an additional generator). An optimized power supply providing a combination of a thermal engine such as an Auxiliary Power Unit (APU) and an electric energy storage system such as a battery provides power to the PGB electric machine even when the gas turbine is off.

Claims

1. An aircraft propulsor system for aircraft taxiing of an aircraft of the type including a gas turbine, the system comprising: an electric machine mechanically connected to the gas turbine, the electric machine being configured to work in a motor mode during taxiing and in a generator mode during flight phases such as take-off, climb, cruise, descent, approach and landing; and a power supply operatively coupled to the electric machine, the power supply supplying electrical power to the electric machine operating in the motor mode during taxiing and receiving electrical power from the electric machine operating in the generator mode during flight phases.

2. The system of claim 1 wherein the power supply is configured to provide a combination of a thermal engine such as an Auxiliary Power Unit (APU) and an electric energy storage system such as a battery to provide power to the electric machine even when the gas turbine is off.

3. The system of claim 1 wherein the electric machine comprises a starter/generator that is also configured to rotate the gas turbine to start it.

4. The system of claim 1 further including a controller that switches the electric machine from the motor mode to the generator mode.

5. The system of claim 1 wherein the electric machine is connected in parallel to a shaft of the gas turbine.

6. The system of claim 1 further including a propulsor gearbox that connects the electrical machine in parallel with the gas turbine.

7. The system of claim 1 further including a controller that selectively charges the power supply with power produced by the electric machine during flight phases.

8. The system of claim 1 wherein the electric machine is selectively mechanically connected to a propulsor when operating in the motor mode.

9. The system of claim 1 wherein the electric machine has an efficiency of 85% or more when operating in the motor mode to power a propulsor to produce thrust for taxiing.

10. The system of claim 1 wherein the electric machine includes the capability of regenerating power obtained from a propeller acting as a wind turbine during descent and/or landing phases.

11. A method for aircraft taxiing of an aircraft of the type including a gas turbine, the method comprising: configuring an electric machine mechanically connected to the gas turbine to work in a motor mode during taxiing and in a generator mode during flight phases such as take-off, climb, cruise, descent, approach and landing; supplying electrical power from a power supply operatively coupled to the electric machine to the electric machine operating in the motor mode during taxiing; and receiving electrical power from the electric machine operating in the generator mode during flight phases.

12. The method of claim 11 including configuring the power supply to provide a combination of a thermal engine such as an Auxiliary Power Unit (APU) and an electric energy storage system such as a battery to provide power to the electric machine even when the gas turbine is off.

13. The method of claim 11 wherein the electric machine comprises a starter/generator and the method includes configuring the starter/generator to rotate the gas turbine to start it.

14. The method of claim 11 further including using a controller to switch the electric machine from the motor mode to the generator mode.

15. The method of claim 11 wherein the electric machine is connected in parallel to a shaft of the gas turbine.

16. The method of claim 11 further including using a propulsor gearbox to connect the electrical machine in parallel with the gas turbine.

17. The method of claim 11 further including using a controller to selectively charge the power supply with power produced by the electric machine during flight phases.

18. The method of claim 11 further including selectively connecting the electric machine to a propulsor when operating in the motor mode.

19. The method of claim 11 wherein the electric machine has an efficiency of 85% or more when operating in the motor mode to power a propulsor to produce thrust for taxiing.

20. The method of claim 11 further including the electric machine regenerating power obtained from a propeller acting as a wind turbine during descent and/or landing phases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following detailed description of exemplary non-limiting illustrative embodiments is to be read in conjunction with the drawings of which:

[0030] FIG. 1 shows an example non-limiting propeller architecture;

[0031] FIG. 2 shows an example non-limiting fan architecture; and

[0032] FIG. 3 shows an example non-limiting process flowchart.

DETAILED DESCRIPTION OF EXAMPLE NON-LIMITING EMBODIMENTS

[0033] A schematic layout of an example non-limiting propeller architecture based system is shown in FIG. 1. The main components are listed from 1 to 11. A core engine (1), comprising a compressor, combustion chamber and a turbine (mechanically coupled to the compressor), is defined as the engine core. A free power turbine (PT) (2), mechanically de-coupled but aerodynamically coupled to the core engine, is connected to a propulsor gearbox (PGB) (4). Other core engine arrangements may be considered, including two or more shaft architectures, often found in gas turbine engines. The referred propulsor may be a Propeller (ducted or unducted, single plane or multi-planes, co-rotating or contrarotating) or a Fan (see FIG. 2).

[0034] During flight operations (e.g., take-off, climb, cruise, descent, approach and landing), fuel is provided to the core engine 1, which produces a hot, compressed gas output, which powers the power turbine 2, providing torque to the PGB 4 and to the propulsor (5), generating propulsive thrust to propel the aircraft.

[0035] An electric starter/generator (3) is coupled to the PGB 4, in parallel to the gas turbine 1. During the quoted flight operations, the electric machine 3 is working in generator mode, providing electric power to the aircraft electric bus (6). The electric bus 6 feeds the aircraft loads (7), which may be of very different nature (such as, but not limited tolightning, communications, navigations, hydraulics, ice protections, environmental control systems (ECS) providing air conditioning, etc.). The electric bus 6 may also recharge electric energy storage devices (8) during flight, such as batteries or capacitors, via dedicated electric switches (11). This recharge strategy may be interesting from an energy standpoint since the gas turbine 1 thermal efficiency in high power settings is considerably higher, as previously mentioned, reaching the 40-55% range.

[0036] During ground operations (e.g., taxi-in, taxi-out, push-backs, etc.), the core engine (1) fuel supply is turned off. An electric power supply source (12) is activated and coupled to the Electric bus (6) via adequate electric switches (11). The electric power supply (12) may be a combination of electric energy storage devices (8) (such as batteries and capacitors) with other power generation systems, such as an APU (9) or other thermal engines coupled to an electric starter/generator (S/G) (10). The energized electric bus 6 provides electric power to the PGB starter/generator (3), which operating in motor mode provides power to the PGB 4, which turns the PT 2 and the propulsor 5. The propulsor 5 provides propulsive thrust to propel the aircraft during ground operations.

[0037] The method described above is summarized in Table 1 and in the FIG. 3 process flowchart.

TABLE-US-00001 TABLE 1 System operation - summary AC Electrical # Ref Mission Phase Battery 8 APU 9 Bus 6 Starter/Gen 3 Main Engines 1 01 Power-on Initiate Turn on Turn on Start motor OFF mode 02 Taxi-out Powers AC Powers AC ON Motor mode OFF El. BUS 6 El Bus 6 + ECS Air conditioner 03 Take-off Depleted OFF ON Generator ON mode 04 Climb/Cruise/ In-flight OFF ON Generator ON Descent/LDG Recharge mode 05 Taxi-in Power AC Powers AC ON Motor mode OFF El. Bus 6 El Bus 6 + ECS Air conditioner

[0038] In an example non-limiting embodiment, one or more electronic controllers 20 control the operating modes of the various described components. Such controller(s) 20 may execute program instructions stored in non-transitory memory, or they may be implemented as programmable gate arrays or other programmed logic circuitry. In one example non-limiting embodiment, controller 20 detects that power has been turned on and controls starter/generator 3 to start in the motor mode.

[0039] During taxi-out, controller 20 operates switch 11 so that battery 8 and/or APU 9 and S/G 10 powers electric machine 3 operating in the motor mode. The power supply 12 may also also power aircraft electrical loads 7 such as the ECS via the electrical bus 6. The starter/generator 3 powered by the electrical power from the power supply 12 supplies mechanical power to PGB 4, which turns the power turbine 2 and the propulsor 5. The gas turbine engine 1 remains off during this time, but the the electric machine 3 powers propulsor 5 to supply forward thrust to move the aircraft forward on the taxiway. In some embodiments, controller 20 controls gearbox 4 to couple mechanical power the electric machine 3 produces to power the propulsor 5.

[0040] Just before takeoff, the pilot starts the gas turbine engine 1. In some embodiments, the controller 20 may assist in this operation by operating starter/generator 3 as a starter motor for the gas turbine 1 (e.g., if the gas turbine has a single shaft arrangement). Once the gas turbine 1 is running, the controller 20 switches the operating mode of starter/generator 3 from motor mode to generator mode. The starter/generator 3 uses magnetic fields and windings to convert the mechanical rotational power supplied by the core engine 1 through the gearbox 4 into electrical energy. In some embodiments, the controller 20 may control PGB 4 to decouple the propulsor 5 from the electric machine 3 and/or change gear ratios and/or gear configurations so mechanical power generated by the gas turbine 1 shaft is coupled to turn starter/generator 3 at an appropropiate rotational speed to generate electrical power.

[0041] During flight phases, the starter/generator 3 supplies electrical power to the aircraft loads 7 via the electrical bus 6. Controller 20 can also act as a charge controller to control switch 11 to selectively close, thereby allowing the starter/generator 3 to supply power to recharge battery 8 while preventing overcharging. Once the controller 20 detects that the battery 8 is fully charged, it can operate switch 11 to disconnect the battery from the starter/generator 3 to prevent overcharging. In some embodiments, the starter/generator 3 has the capability of regenerating power obtained from a propeller acting as a wind turbine during descent or landing phases.

[0042] Upon landing, once the controller 20 detects that the pilot has turned off the gas turbine engine 1, the controller returns the starter/generator 3 and switch 11 to the same generator configuration used during taxiiing before takeoff

[0043] Expected Benefits

[0044] The electric motor installed in the PGB 4 has two main functions: propel the aircraft during ground operations (motor mode), and provide electric power to the aircraft bus 6 (generator mode) during flight operations. Therefore, the same machine is used for several purposesin other words, the system does not require the installation of dedicated electric motors to perform the taxi manoeuvres (as required for example in the wheel-driven electric taxi).

[0045] In one example non-limiting embodiment, the electric motor is installed in the PGB 5 in parallel to the main gas turbine engines, avoiding impacts in the main engine architecture. In other words, the gas turbine architecture can be designed as a conventional engine, without having the need to provision mechanical installation of electric motors in the engine shafts (as required in the systems which employ an electric motor concentric to the gas turbine shafts). Maintainability of the PGB gearbox 4 is also easier when compared to the concentric installation of an electric engine.

[0046] The solution can provide better results for a More Electric Aircraft (MEA) system architecture, which electrifies several systems (ECS, Ice protection, etc.), since it re-uses several electric systems already installed on the aircraft to perform the electric taxi.

[0047] The propulsor driven electric taxi has the potential to decrease the Block Fuel consumption of the aircraft, increasing the aircraft efficiency and competitiveness.

[0048] There is the potential to perform the push-back maneuver using the proposed system; since the tug-driven push-back maneuver has an associated cost, the system has the potential to dismiss the tug and push the aircraft autonomously, potential reducing other operational costs than those associated with fuel consumption.

[0049] If the system employs electric energy storage systems 8 (such as batteries), the batteries' weight can be reduced over time with the development of batteries with higher power densities, as shown in Table 2.

TABLE-US-00002 TABLE 1 Battery energy density forecast (*All estimated data). EIS Battery energy density 2025 250 Wh/kg (*) 2030 300 Wh/kg (*) 2035 500 Wh/kg (*) 2040 800 Wh/kg (*)

[0050] Example Features and Advantages of the Example Non-Limiting Technology Include:

[0051] System architecture and method: system with the electric machine 3 installed in the PGB 4, in parallel to the gas turbine 1, working in motor mode during taxi, and in generator mode during flight phases (such as take-off, climb, cruise, descent, approach and landing). Typical current systems which use an electric machine in the PGB 4 do not use the electric machine in motor mode for taxi operations (i.e., it is only an additional generator).

[0052] Optimized power supply: combination of a thermal engine such as an APU and an electric energy storage system such as a battery to provide power to the PGB electric machine.

[0053] The electric machine may have an efficiency on the order of 85%-95% when operating as a motor for the propulsor 5

[0054] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.