# US 11,077,953 B2 · Electric ducted fan

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- Number: US 11,077,953 B2
- Document ID: US11077953B2
- Status: Granted
- Kind: B2
- Application number: 16/390,555
- 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/US11077953B2

## CPC

- F02K 5/00: Plants including an engine, other than a gas turbine, driving a compressor or a ducted fan
- B64D 27/34: All-electric aircraft
- F05D 2260/4031: as in toothed gearing
- F05D 2260/40311: of the epicyclical, planetary or differential type
- 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
- F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- 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 speed reduction device is located between the electric machine and the fan, and has a reduction ratio of at least 3:1. A ratio of the electromagnetically active diameter DA to the fan diameter DF (DA/DF) is from 0.3 to 0.5.

## 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;
a speed reduction device between the electric machine and the fan, having a reduction ratio of at least 3:1;
and wherein a ratio of the electromagnetically active diameter DA to the fan diameter DF (DA/DF) is from 0.3 to 0.5.

### 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 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 0.35 to 0.45.

### 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 from 0.37 to 0.43, for example 0.4.

### 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 0.25 to 0.31.

### Claim 10 (depends on 9)

The electric ducted fan of claim 9, in which the fan has a hub-tip ratio of from 0.27 to 0.29, for example 0.28.

### Claim 11 (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 12 (depends on 11)

The electric ducted fan of claim 11, in which the propulsive fan has a tip pressure ratio of from 1.3 to 1.5 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 1.38 at an altitude of 35,000 feet and a true airspeed of Mach 0.85.

### Claim 14 (depends on 1)

The electric ducted fan of claim 1, in which the speed reduction device is a star gearbox with a reduction ratio of at most 3.7:1.

### Claim 15 (depends on 1)

The electric ducted fan of claim 1, in which the speed reduction device is a planetary gearbox with a reduction ratio of at most 4.7:1.