Low noise ducted fan
An exemplary ducted fan includes a duct having a central longitudinal axis, a rotor hub and stator hub extending along the central longitudinal axis, rotor blades extending from the rotor hub, each of the rotor blades operable to rotate about its own pitch-change axis, the pitch-change axes lying in a rotor plane that is generally perpendicular to the central longitudinal axis, each of the rotor blades having a rotor trailing edge and a rotor chord length, stators extending from the stator hub to an interior surface of the duct, each of the stators having a stator leading edge and a stator thickness, and a first separation between the rotor plane and the stator leading edge of not less than approximately 1.5 times the stator thickness.
1. A ducted fan comprising:
a duct having a central longitudinal axis;
a rotor hub and a stator hub extending along the central longitudinal axis;
a plurality of rotor blades extending from the rotor hub, each of the plurality of rotor blades operable to rotate about a respective pitch-change axis of the rotor hub, the pitch-change axes lying in a rotor plane that is substantially perpendicular to the central longitudinal axis, each of the rotor blades having a rotor trailing edge and a rotor chord length; and
a plurality of stators extending from the stator hub to an interior surface of the duct, each of the plurality of stators having a stator leading edge and a stator thickness;
wherein a first separation between the rotor plane and the stator leading edge is 1.5-2.7 times the stator thickness;
wherein a second separation between the rotor trailing edge and the stator leading edge is not less than the rotor chord length.
2. The ducted fan of claim 1 , wherein the first separation is substantially 1.5 times the stator thickness.
3. The ducted fan of claim 1 , wherein a number of the rotor blades and the stators is unequal.
4. The ducted fan of claim 1 , wherein a number of the rotor blades is greater than a number of the stators.
5. The ducted fan of claim 1 , wherein the stator leading edge is inclined toward the rotor plane extending from the stator hub to the interior surface of the duct.
6. The ducted fan of claim 1 , wherein the rotor trailing edge is inclined toward the rotor plane extending from the rotor hub toward the interior surface of the duct.
7. The ducted fan of claim 1 , wherein:
the stator leading edge is inclined toward the rotor plane extending from the stator hub to the interior surface of the duct; and
the rotor trailing edge is inclined toward the rotor plane extending from the rotor hub toward the interior surface of the duct.
8. The ducted fan of claim 1 , wherein the stator leading edge is inclined toward the rotor plane extending from the stator hub to the interior surface of the duct; and
the rotor trailing edge is inclined toward the rotor plane from the rotor hub toward the interior surface of the duct.
9. An aircraft comprising:
a fuselage having a forward portion and an aft portion; and
a tiltable ducted fan comprising:
a duct having a central longitudinal axis;
a rotor hub and a stator hub extending along the central longitudinal axis;
a plurality of rotor blades extending from the rotor hub, each of the plurality of rotor blades operable to rotate about a respective pitch-change axis of the rotor hub, the pitch-change axes lying in a rotor plane that is generally perpendicular to the central longitudinal axis, each of the plurality of rotor blades having a rotor trailing edge and a rotor chord length; and
a plurality of stators extending from the stator hub to an interior surface of the duct, each of the a plurality of stators having a stator leading edge and a stator thickness;
wherein a first separation between the rotor plane and the stator leading edge is 1.5-2.7 times the stator thickness;
wherein a second separation between the rotor trailing edge and the stator leading edge is not less than the rotor chord length.
10. The aircraft of claim 9 , wherein the stator leading edge is inclined toward the rotor plane extending from the stator hub to the interior surface of the duct.