Variable-Pitch Propeller Blade Attachment for Wear and Vibration
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Solution Overview
Problem
Existing pinned connections for variable-pitch propeller blades in aircraft turbomachinery are prone to friction damage and vibration issues, particularly in wide-chord, large-span blades, leading to premature wear and inefficient operation.
Innovation Solution
A bulb-type attachment with a recess in the blade foot and a protrusion on the bowl, reversing the traditional configuration to reduce mass and size, allowing for a more direct force path and reduced radial space requirements, enhancing operational behavior under centrifugal forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pinned connection is used to attach the blade to its support, then the attachment is simple and allows for easy assembly, but the blade root experiences rigid movement and friction damage leading to premature wear
Solution Approach 1:
The patent inverts the traditional pinned connection configuration by using a bulb-type attachment where the blade foot is retained within a recess in the support, rather than pinning the blade to the support. This inversion eliminates the rigid movement and friction damage at the blade root while maintaining assembly simplicity through complementary shapes that enable easy insertion and rotational fixing.
2Power
If the blade pitch is increased to generate thrust, then the aerodynamic performance improves, but the drag increases and the blade experiences turbulent flow and vibration
Solution Approach 1:
The patent enables dynamic adjustment of the blade pitch angle through a mechanism that allows the blade to be rotated relative to the support around an adjustment axis. This dynamic capability allows the blade to operate at optimal pitch angles during normal flight to maximize thrust, while being able to feather (reduce pitch) during takeoff and landing to minimize drag and vibration, thus resolving the contradiction between thrust generation and aerodynamic efficiency.
3Productivity
If the blade span is increased to improve aerodynamic performance, then the thrust efficiency improves, but the blade mass and centrifugal forces increase
Solution Approach 1:
The patent employs a bulb-type attachment with a swollen section that provides optimal retention of the blade along its axis. This attachment design allows for reduced blade mass while maintaining structural integrity and aerodynamic performance. The bulbous section distributes centrifugal forces more effectively along the blade root, enabling longer blade spans for improved aerodynamic efficiency without proportionally increasing mass.
4Reliability
If a bulb-type attachment is used to limit ball jointing, then the blade wear is reduced, but the attachment size and mass increase
Solution Approach 1:
The patent applies local quality by concentrating the retention function in a localized bulbous section of the blade foot, rather than distributing mass throughout the entire attachment. The swollen section provides optimal retention along the blade axis through its complementary shape engagement with the support recess, limiting ball jointing and wear while minimizing overall attachment mass. The bulbous geometry efficiently distributes contact stresses locally at the retention interface.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The revised attachment design reduces blade mass and friction, improving mechanical strength and aerodynamic efficiency while minimizing vibration and wear, contributing to a more compact and efficient engine performance.
Implementation Method 1
The blade is equipped with a foot designed to limit the risk of ball jointing. The distinctive feature of this blade foot is the presence of a bulbous section, which provides optimal retention of the blade along its axis.
Implementation Method 2
The bottom wall is configured to cooperate by complementary shapes with the free end of the foot so that the bowl is rotationally fixed to the foot around the axis.
Implementation Method 3
This is particularly advantageous because it reduces the foot's size and, above all, its mass. The blade's mass is therefore reduced, which has a positive effect on its operating behavior, particularly under the effect of centrifugal forces.
Data Source
Figure 1
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AI summary
The invention relates to an assembly comprising a propeller blade (10) and a system (34) for angularly setting the pitch of the blade (10) for an aircraft turbomachine, the blade (10) having a root (14) extending from an upper end connected to an airfoil (12) of the blade (10) to a free lower end (28), the root (14) having a bulging segment, which bulging segment is referred to as the "bulb" (32), the system (34) for angularly setting the pitch of the blade (10) comprising a cup (58) which is radially defined by an annular wall (58a) and which comprises a lower bottom closed by a bottom wall (58b) and an upper opening (58c) through which the bulb (32) is intended to be axially inserted into the cup (58), the bottom wall (58b) comprising a protrusion (200) which engages with a cavity (202) having a complementary shape in the free end (28) of the root (14).