Propulsion system for electric aircraft
In a first aspect, described herein is a direct drive electric aircraft propulsion wherein the propulsion rotor torque is decoupled from the primary proprotor mast moment forces. A hub shaft locates the propulsion proprotor assembly in space relative to the aircraft nacelle, while a motor torque coupler transfers torque from the electric motor to the propulsion rotor while resolving a negligible amount of mast moment through the electric motor.
1 . An aircraft propulsion system comprising:
a rotor hub;
an electric motor; and
a flexible motor torque coupler mechanically coupled between the hub and the electric motor, the motor torque coupler comprising a stiffness in a mast moment bending direction less than a stiffness in a motor shaft torsion direction.
2 . The aircraft propulsion system of claim 1 additionally comprising a nacelle comprising an inner member, a webbing, and an outer member, wherein the webbing is located between the inner member and the outer member.
3 . The aircraft propulsion system of claim 1 wherein the motor torque coupler comprises a composite material.
4 . The aircraft propulsion system of claim 3 wherein the motor torque coupler comprises a composite flexure plate arranged such that that the motor torque coupler is rigid to torsional loads but compliant to mast moment loads.
5 . The aircraft propulsion system of claim 1 wherein the motor torque coupler comprises an articulated linkage.
6 . The aircraft propulsion system of claim 5 wherein the articulated linkage is metallic.
7 . The aircraft propulsion system of claim 1 wherein the motor torque coupler comprises a flexure plate.
8 . The aircraft propulsion system of claim 1 wherein the propulsion system comprises a slip ring.
9 . The aircraft propulsion system of claim 1 further comprising a composite web configured to connect a first nacelle structural layer and a second nacelle structural layer.
10 . The aircraft propulsion system of claim 1 additionally comprising a second motor.
11 . The aircraft propulsion system of claim 1 additionally comprising a first and a second hub bearing wherein the first and second hub bearings are separated along an axis of rotation of the hub.
12 . The aircraft propulsion system of claim 1 wherein the aircraft propulsion system is configured for a tiltrotor aircraft.
13 . The aircraft propulsion system of claim 1 wherein a radial distance, from a hub center of rotation, of the torque coupler to the hub connection point is larger than a radial distance of the hub to nacelle connection point, from a hub center of rotation.
14 . The aircraft propulsion system of claim 1 wherein an rpm of a motor rotor housing of the motor is equal to an rpm of a propulsion rotor.
15 . The aircraft propulsion system of claim 1 wherein the torque coupler comprises a torsion stiffness to mast moment stiffness ratio of at least 200:1.
16 . The aircraft propulsion system of claim 1 wherein the mast moment bending direction extends in a direction perpendicular to an axis of rotation of the rotor hub and the motor shaft torsion direction comprises a torsional force vector defined by the relative rotation between the rotor hub and the motor torque coupler.
17 . The aircraft propulsion system of claim 2 wherein the webbing comprises a composite webbing.
18 . An aircraft comprising:
a propulsion rotor hub;
a drive motor;
a flexible torque coupler mechanically coupled between the drive motor and the propulsion rotor hub; and
the motor torque coupler comprising a stiffness in a mast moment bending direction less than a stiffness in a motor shaft torsion direction.