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US 5,190,441 AGranted
Noise reduction in aircraft propellers
AssigneeGeneral Electric Company
InventorsGuy C. Murphy, Bruce J. Gordon, Leroy H. Smith, Jr., Jan C. Schilling, Alan R. Stuart
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Abstract
The invention concerns reduction of tip vortices in aircraft propellers, wherein a fence having anhedral or dihedral is attached to the blades of the propeller. Another form of the invention is applicable to counterrotating propeller systems, wherein a fence is attached to the blades of the forward propeller of the system, and no fences are attached to the aft propeller.
Claims9
An aircraft propeller system, comprising:
- a) forward and aft counterrotating propellers, each including a plurality of blades having curved leading edges, wherein said forward propeller blade leading edges are approximately mirror images of said aft propeller blade leading edges, except in the tip regions;
- b) a tip region on each of said forward propeller blades which has cahedral.
An aircraft propulsion system, comprising:
- a) a forward propeller which
- i) includes a plurality of blades, wherein
- A) part of each forward propeller blade produces a wake along its length which is generally crescent-shaped in cross-section;
- and
- B) each forward propeller blade includes a cahedral tip and a body section;
- b) an aft propeller which
- i) rotates opposite to the forward propeller;
- ii) includes a plurality of blades, wherein
- A) each aft propeller blade includes a root;
- B) each aft propeller blade has a leading edge which is approximately crescent-shaped, but in mirror image to the wake's crescent cross-section;
- and
- C) each aft propeller blade leading edge cuts each crescent-shaped wake encountered by the leading edge in a scissoring action beginning at the root of the blade and ending at the tip of the blade, wherein the scissoring action produces a sequence of noise pulses spread over time and smaller in magnitude than a corresponding noise pulse which would be created if the leading edge cut the wake at one time with no scissoring action;
- and
- c) wherein each of said forward propeller blade cahedral tips adds a wakelet to each of the crescent-shaped wakes, the wakelets having the same sense of curvature as the crescent-shaped wakes, thereby producing less wake-chopping noise than an aircraft propulsion system having wakelets with curvature opposite to those of respective wakes.
11 more elements
Dependencies are inferred from the claim text.