Electric propulsion system for an aircraft

• US 10,137,981 B2
• Filed: 03/31/2017
• Issued: 11/27/2018
• Est. Priority Date: 03/31/2017
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Miller, Brandon Wayne, Vondrell, Randy M., Marrinan, Patrick Michael, Gemin, Paul Robert, Moore, Nicholas Taylor
• Primary Examiner(s): Nguyen, Viet
• Application Number:
  US15/475,401
• Publication Number:
  US 20180281931A1
• Time in Patent Office: 606 Days
• CPC Class Codes: B64C 21/01 Boundary layer ingestion [BLI] propulsion
• CPC Class Codes: B64C 2230/04 by actively generating fluid flow
• CPC Class Codes: B64D 2221/00 Electric power distribution systems onboard aircraft
• CPC Class Codes: B64D 27/026 comprising different types of power plants, e.g. combination of a piston engine and a gas-turbine Hybrid electric aircraft B64D27/33
• CPC Class Codes: B64D 27/18 within, or attached to, wings
• CPC Class Codes: B64D 27/24 using steam or spring force jet aircraft B64D27/16
• CPC Class Codes: F01D 15/10 Adaptations for driving, or combinations with, electric generators
• CPC Class Codes: F02K 5/00 Plants including an engine, other than a gas turbine, driving a compressor or a ducted fan
• CPC Class Codes: F05D 2220/36 specially adapted for the fan of turbofan engines
• CPC Class Codes: Y02T 50/10 Drag reduction
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

An aeronautical propulsion system includes a fan having a plurality of fan blades rotatable about a central axis and defining a fan pressure ratio, FPR. The propulsion system also includes an electric motor mechanically coupled to the fan for driving the fan, the electric motor including a number of poles, n_poles, and defining a maximum power, P. The relationship between the fan pressure ratio, FPR, of the fan, the number of poles, n_poles, of the electric motor, and the maximum power, P, of the electric motor is defined by an equation:

$\frac{n_{\mathrm{pole}}}{\sqrt{p}}=C_1·e^{-9.062·\mathrm{FPR}}+C_2·e^{-1.2604·\mathrm{FPR}};$
wherein C₁ is a constant having a value between 22,000 and 52,000, wherein C₂ is a constant having a value between 4.0 and 9.8, and wherein e is Euler'"'"'s number.

Claims

1. An aeronautical propulsion system defining a central axis and comprising:

a fan having a plurality of fan blades rotatable about the central axis and defining a fan pressure ratio, FPR, wherein the FPR is a ratio of a discharge pressure of a fan to an inlet pressure of the fan; and

an electric motor mechanically coupled to the fan for driving the fan, the electric motor comprising a number of poles, n_poles, and defining a maximum power, P;

wherein the relationship between the fan pressure ratio, FPR, of the fan, the number of poles, n_poles, of the electric motor, and the maximum power, P, of the electric motor is defined by an equation;

2. The aeronautical propulsion system of claim 1, wherein the number of poles, n_poles, is between 4 and 180, wherein the maximum power, P, is between 650 horsepower and 6,000 horsepower, and wherein the fan pressure ratio, FPR, is between 1 and 2.

3. The aeronautical propulsion system of claim 1, wherein the electric motor operates at a maximum pole passing frequency between about 1,500 Hertz (“

Hz”

) and about 3,500 Hz.

4. The aeronautical propulsion system of claim 1, wherein the electric motor is connected directly to the fan without use of a gearbox.

5. The aeronautical propulsion system of claim 1, wherein the fan and the electric motor are together configured as a boundary layer ingestion fan.

6. The aeronautical propulsion system of claim 1, wherein the fan and the electric motor are together configured as an aft fan configured to be mounted at the aft end of the aircraft.

7. The aeronautical propulsion system of claim 1, wherein the fan defines a hub radius, wherein the plurality of fan blades define a fan radius, wherein a ratio of the hub radius to the fan radius is between about 0.2 and about 0.4.

8. The aeronautical propulsion system of claim 7, wherein the ratio of the hub radius to the fan radius is between about 0.25 and about 0.3.

9. The aeronautical propulsion system of claim 1, further comprising:

a combustion engine;

an electric generator mechanically coupled to the combustion engine for producing electrical power; and

a power bus electrically connecting the electric generator to the electric motor, wherein the power bus includes power electronics.

10. The aeronautical propulsion system of claim 9, wherein the power electronics utilize one or more Silicon Carbide components.

11. The aeronautical propulsion system of claim 9, wherein the power electronics are configured to operate at a switching frequency between about 5 kilohertz (kHz) and about 30 kHz.

12. The aeronautical propulsion system of claim 1, wherein the fan defines a maximum fan tip speed, and wherein the maximum fan tip speed is between about 200 feet per second and about 1,350 feet per second.

13. An electric fan assembly of an aeronautical propulsion system, the electric fan assembly comprising:

a fan defining a fan pressure ratio, FPR, a hub radius, and a fan radius, wherein the FPR is a ratio of a discharge pressure of a fan to an inlet pressure of the fan, and a ratio of the hub radius to the fan radius being between about 0.2 and about 0.4;

an electric motor directly mechanically coupled to the fan for driving the fan, the electric motor comprising a number of poles, n_poles, defining a maximum power, P, and operating at a maximum pole passing frequency between about 1,500 Hertz (“

Hz”

) and about 2,500 Hz;

wherein the relationship between the fan pressure ratio, FPR, of the fan, the number of poles, n_poles, of the electric motor, and the maximum power, P, of the electric motor is defined by an equation;

14. The electric fan assembly of claim 13, wherein the fan further defines a maximum fan tip speed, and wherein the maximum fan tip speed is between about 200 feet per second and about 1,350 feet per second.

15. The electric fan assembly of claim 13, wherein the ratio of the hub radius to the fan radius is between about 0.25 and about 0.3.

16. A method for operating a propulsion system for an aircraft, the propulsion system comprising a fan having a plurality of fan blades and an electric motor mechanically coupled to the fan, the method comprising:

driving the fan using the electric motor, wherein the relationship between a fan pressure ratio, FPR, of the fan, wherein the FPR is a ratio of a discharge pressure of a fan to an inlet pressure of the fan, a number of the poles, maximum power, P, of the electric motor is defined by an equation;

17. The method of claim 16, wherein driving the fan using the electric motor comprises operating the electric motor at a maximum pole passing frequency between about 1,500 Hertz (“

Hz”

) and about 3,500 Hz.

18. The method of claim 16, wherein driving the fan using the electric motor comprises rotating the fan at a rotational speed equal to a rotational speed of a rotor of the electric motor.

19. The method of claim 16, wherein the propulsion system further comprises a combustion engine, an electric generator mechanically coupled to the combustion engine, and a power bus electrically connecting the electric generator to the electric motor, and wherein the method further comprises:

generating electrical power with the electric generator; and

providing the electrical power generated to the electric motor through the power bus.

20. The method of claim 19, wherein providing the electrical power generated to the electric motor through the power bus comprises passing the electrical power through power electronics operating at a switching frequency between about 5 kilohertz (kHz) and about 30 kHz.