# US 11,077,952 B2 · Electric ducted fan

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- Number: US 11,077,952 B2
- Document ID: US11077952B2
- Status: Granted
- Kind: B2
- Application number: 16/390,553
- Filed: 2019-04-22
- Published: 2019-11-14
- Granted: 2021-08-03
- Earliest claimed: 2018-05-14
- Assignees: ROLLS-ROYCE plc
- Applicants: ROLLS-ROYCE plc
- Inventors: Giles E. Harvey
- Web page: https://patentgrep.com/patent/US11077952B2

## CPC

- F02K 5/00: Plants including an engine, other than a gas turbine, driving a compressor or a ducted fan
- B64D 27/31: within, or attached to, wings
- B64D 27/34: All-electric aircraft
- Y02T 50/40: Weight reduction
- Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft
- F02K: JET-PROPULSION PLANTS (features of jet-propulsion plants common to gas-turbine plants, air intakes or fuel supply control of air-breathing jet-propulsion plants F02C7/00, F02C9/00)
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

An electric ducted fan for an aircraft is shown. A nacelle defines a duct that houses a propulsive fan having a fan diameter DF. An electric machine is configured to drive the fan, and has an electromagnetically active length LA and an electromagnetically active diameter DA defining an aspect ratio (LA/DA) of from 0.8 to 2. A ratio of the electromagnetically active diameter DA to the fan diameter DF (DA/DF) is from 0.45 to 0.60.

## Claims

### Claim 1

An electric ducted fan for an aircraft, comprising:
a nacelle defining a duct;
a propulsive fan in the duct having a fan diameter DF;
an electric machine configured to drive the fan, the electric machine having an electromagnetically active length LA and an electromagnetically active diameter DA defining an aspect ratio (LA/DA) of from 0.8 to 2;
and wherein a ratio of the electromagnetically active diameter DA to the fan diameter DF (DA/DF) is from 0.45 to 0.60.

### Claim 2 (depends on 1)

The electric ducted fan of claim 1, in which the aspect ratio (LA/DA) is from 1.1 to 1.7.

### Claim 3 (depends on 2)

The electric ducted fan of claim 2, in which the aspect ratio (LA/DA) is from 1.3 to 1.5, for example 1.4.

### Claim 4 (depends on 1)

The electric ducted fan of claim 1, in which the ratio of the electromagnetically active diameter DA to the fan diameter DF (DA/DF) is from 0.50 to 0.55.

### Claim 5 (depends on 4)

The electric ducted fan of claim 4, in which the ratio of the electromagnetically active diameter DA to the fan diameter DF (DA/DF) is 0.525.

### Claim 6 (depends on 1)

The electric ducted fan of claim 1, in which the electric machine is a radial flux electric machine.

### Claim 7 (depends on 6)

The electric ducted fan of claim 6, in which the stator is exterior to the rotor, the electromagnetically active diameter DA is the diameter of a stator stack, and the electromagnetically active length LA is the length of the stator stack.

### Claim 8 (depends on 6)

The electric ducted fan of claim 6, in which the stator is interior to the rotor, the electromagnetically active diameter DA is the diameter of the rotor, and the electromagnetically active length LA is the length of the stator stack.

### Claim 9 (depends on 1)

The electric ducted fan of claim 1, in which the fan has a hub-tip ratio of from 0.24 to 0.32.

### Claim 10 (depends on 9)

The electric ducted fan of claim 9, in which the fan has a hub-tip ratio of from 0.26 to 0.3.

### Claim 11 (depends on 10)

The electric ducted fan of claim 10, in which the fan has a hub-tip ratio of 0.28.

### Claim 12 (depends on 1)

The electric ducted fan of claim 1, in which the propulsive fan has a tip pressure ratio of from 1.3 to 1.7 at an altitude of 35,000 feet and a true airspeed of Mach 0.85.

### Claim 13 (depends on 12)

The electric ducted fan of claim 12, in which the propulsive fan has a tip pressure ratio of from 1.3 to 1.5, for example 1.38, at an altitude of 35,000 feet and a true airspeed of Mach 0.85.

### Claim 14 (depends on 13)

The electric ducted fan of claim 13, in which the electric machine has a maximum continuous power rating of from 100 kilowatts to 100 megawatts.

### Claim 15 (depends on 14)

The electric ducted fan of claim 14, in which the electric machine has a maximum continuous power rating of from 1 megawatt to 10 megawatts, for example 2 megawatts.