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US-20260125149-A1 - Ultra-Wide-Chord Propeller Including Varying Blade Angle

US20260125149A1US 20260125149 A1US20260125149 A1US 20260125149A1US-20260125149-A1

Abstract

The propeller described herein may increase the pressure differential to be generated at/near a blade tip and, at least in some embodiments, to allow for the greatest pressure differential to be generated at/near the blade tip. Increasing the pressure differential in the blade tip region may promote formation of blade tip vortices when the propeller is in use. The propeller may utilize these blade tip vortices as effective mass flow, which can contribute to the thrust force generated by the propeller. That is, by designing the propeller to form and utilize blade tip vortices, the mass flow of air over the blades may be increased, thereby increasing the amount of thrust generated by the propeller.

Inventors

  • Michael S. Deloyer

Assignees

  • Skydio, Inc.

Dates

Publication Date
20260507
Application Date
20251125

Claims (20)

  1. 1 - 20 . (canceled)
  2. 21 . A blade for a propeller, wherein the blade comprises: a proximal attachment end; a tip region including a free blade tip opposite to the proximal attachment end; and leading and trailing edges extending between the proximal attachment end and the free blade tip, wherein the blade defines chord lengths extending between the leading and trailing edges and includes a maximum chord length spaced proximally from the free blade tip.
  3. 22 . The blade of claim 21 , wherein the blade defines a varying blade angle that increases towards the free blade tip.
  4. 23 . The blade of claim 22 , wherein the varying blade angle is between 13 degrees and 25 degrees.
  5. 24 . The blade of claim 22 , wherein the varying blade angle is measured between a plane orthogonal to an axis of rotation of the propeller and a chord line extending between the leading and trailing edges.
  6. 25 . The blade of claim 21 , wherein the chord lengths vary between the proximal attachment end and the free blade tip.
  7. 26 . The blade of claim 25 , wherein the chord lengths increase from the proximal attachment end to the free blade tip.
  8. 27 . The blade of claim 21 , wherein the tip region extends from the free blade tip to a proximal border.
  9. 28 . The blade of claim 27 , wherein the proximal border is spaced from the proximal attachment end by a distance equal to at least 75% of an overall length of the blade.
  10. 29 . A blade for a propeller, wherein the blade comprises: a proximal attachment end; a blade tip opposite to the proximal attachment end; and leading and trailing edges extending between the proximal attachment end and the blade tip, wherein a chord length of the blade extending between the leading and trailing edges increases from the proximal attachment end to a maximum chord length located in a tip region of the blade and decreases from the maximum chord length to the blade tip.
  11. 30 . The blade of claim 29 , wherein the blade defines a blade angle that increases from the proximal attachment end to the blade tip.
  12. 31 . The blade of claim 29 , wherein the maximum chord length is spaced proximally from the blade tip.
  13. 32 . The blade of claim 31 , wherein the tip region extends from the blade tip to a proximal border spaced from the proximal attachment end.
  14. 33 . The blade of claim 32 , wherein the proximal border is spaced from the proximal attachment end by a distance equal to at least 75% of an overall length of the blade.
  15. 34 . A propeller comprising: a hub; and a blade extending from the hub, wherein the blade includes: a proximal attachment end; a blade tip opposite the proximal attachment end; leading and trailing edges extending between the proximal attachment end and the blade tip; and front and back surfaces extending between the leading and trailing edges and between the proximal attachment end and the blade tip, wherein the blade defines: chord lines extending between the leading and trailing edges; and a maximum chord length in a tip region of the blade.
  16. 35 . The propeller of claim 34 , wherein the proximal attachment end includes a folding hub attachment profile.
  17. 36 . The propeller of claim 34 , wherein the tip region extends from the blade tip to a proximal border spaced from the proximal attachment end.
  18. 37 . The propeller of claim 34 , wherein the blade includes a first pitch in the proximal attachment end that increases towards the hub.
  19. 38 . The propeller of claim 37 , wherein the blade includes a second pitch that increases from the proximal attachment end to the blade tip.
  20. 39 . The propeller of claim 34 , wherein the blade further defines: mean camber lines extending between the leading and trailing edges at locations halfway between the front and back surfaces.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) This application is a continuation of U.S. patent application Ser. No. 18/649,249, filed Apr. 29, 2024, which is a continuation of U.S. patent application Ser. No. 17/094,960, filed Nov. 11, 2020, which claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 62/935,333, filed Nov. 14, 2019, the entire disclosures of which are hereby incorporated by reference. FIELD The described embodiments relate to propellers. In particular, the described embodiments relate to propellers used to provide thrust to an aircraft. BACKGROUND It is well known that propellers can be used to convert rotational motion into thrust. For example, U.S. Pat. No. 6,866,482 (“Han”) describes a high-performance propeller that has one hub and a plurality of blades, characterized in that a double-side or a single-side arc brim is provided at the tip of each blade. According to Han, the propeller described therein can provide a small induced drag and can convert the centrifugal force to the effective force so as is to increase the differential pressure near the tip of blades and thereby increase the acting force on blades. Under the condition of same power consumption, Han has tested that for the large propeller in the type of lateral inclination that the amount of flow is increased about 12%˜17%, which is equivalent to save energy 40%˜70%. According to Han, since the fluid dynamic performance presents the aspect ratio approaching infinity, the width of the blades can be increased whereas the induced drag is not increased. According to Han, applying the method of increasing the area of the blades and decreasing the velocity of outflow fluid, the effect on saving of energy can be further improved greatly on the present basis. U.S. Pat. No. 5,292,088 (“Lemont”) describes a low-aspect ratio propeller system with a multiple ring structure formed with a plurality of circular or non-circular, annular, narrow equivalent air foil rings which are held by rails in a predetermined relationship with the propeller blades. The upstream ring is located downstream from the tip vortex of the propeller within the axial span of the propeller. One or more additional downstream-located rings are used so as to provide at least one annular multiple ring-defined pump aperture through which peripheral vortices generated by the propeller blades or fan blades may enhance the mass flow. In one propeller system of Lemont, a low-aspect-ratio propeller is employed with high blade angles of attack and non-stall capability to generate strong vortices which enhance the beneficial effect of the multiple ring structure. According to Lemont, these vortices increase thrust because their induction action on the rings increase beneficial ring flow circulation. Also according to Lemont, augmented ring flow reduces the velocities in the expanding wake by increasing the mass flow and the destruction of tip and root vortices reduces noise. The multiple ring structure also serves as a guard to protect people and animals against the rotating propeller. SUMMARY OF THE INVENTION The following is intended to introduce the reader to the detailed description that follows and not to define or limit the claimed subject matter. In general, disclosed herein are one or more propellers. In a first aspect, some embodiments of the invention provide a propeller including a central hub mountable for drivable rotation about a central axis of rotation and at least one blade extending from the central hub and rotatable about the central axis of rotation by the central hub to generate a backward airflow. Each blade of the at least one blade, (a) extends from a proximal attachment end attached to the central hub to a blade tip, distal from the central hub; (b) comprises a leading edge extending from the proximal attachment end to the blade tip, and a trailing edge extending from the proximal attachment end to the blade tip; and (c) comprises a front surface extending between the leading edge and the trailing edge from the proximal attachment end to the blade tip, and a back surface extending between the leading edge and the trailing edge from the proximal attachment end to the blade tip. At each point along the blade from the proximal attachment end to the blade tip, the blade (a) defines a mean camber line extending between the leading edge and the trailing edge halfway between the front surface and the back surface; and (b) defines a chord line extending straight between the leading edge and the trailing edge, wherein a chord length of the chord line varies along the blade from the proximal attachment end to the blade tip, the chord length is maximized in a blade tip region of the blade, the blade tip region extends from a proximal border to the blade tip, and the proximal border is located toward the blade tip by at least 75% of the distance from the proximal attachment end to the blade tip. At each point along the blade in the blade t