Variable-Pitch Propeller Bearing Layout for Compact Hub Design
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Solution Overview
Problem
Existing propeller designs for aircraft turbomachines face challenges in optimizing aerodynamic performance, mechanical strength, and acoustic signature while managing the increased span and reduced fan pressure ratio due to variable pitch blades, leading to issues with bearing dimensions and mass, which affect engine performance and efficiency.
Innovation Solution
The propeller design incorporates a control system with a blade connected to a root, a bowl housing the root, and guide bearings featuring two annular rows of balls with different diameters and oblique contacts, allowing for reduced ball diameter and optimized assembly stroke without increasing system size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the BPR (By Pass Ratio) is increased to improve aerodynamic performance, then the external diameter and blade span increase, but the FPF (Fan Pressure Ratio) decreases
Solution Approach 1:
The patent implements variable pitch blades that can dynamically adjust their angle during operation, allowing the propeller to maintain optimal aerodynamic performance across different flight conditions and phases, thereby resolving the trade-off between BPR and FPF through adaptive configuration
2Strength
If the inner guide bearing is oversized to withstand high centrifugal forces, then the bearing dimensions increase, but the assembly stroke increases and the hub ratio deteriorates
Solution Approach 1:
The patent transitions from a single-row bearing configuration to a double-row bearing configuration, utilizing the radial dimension to arrange two rows of balls around the setting axis. This dimensional change allows the bearing to handle high centrifugal forces without increasing the axial assembly stroke, as the load distribution is achieved through radial arrangement rather than axial extension
3Productivity
If the number of blades is increased to maintain propeller function, then the proximity between inner bearings of adjacent blades decreases, but the bearings must be moved away from the engine axis, increasing centrifugal forces
Solution Approach 1:
By arranging bearing rows in the radial direction rather than axially, the patent allows bearings to remain closer to the engine axis even with multiple blades, thereby reducing the centrifugal forces experienced by the bearings while maintaining proper spacing between adjacent blade bearings
4Strength
If the bowl is extended to accommodate larger bearing dimensions, then the bearing capacity increases, but the system mass and bowl size increase
Solution Approach 1:
The patent achieves increased bearing capacity through radial expansion with two rows of balls rather than axial extension, allowing the bowl to maintain a compact size and mass while providing the necessary load-bearing capacity through the dual-row configuration
Data Source
Figure 1
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AI summary
A propeller for an aircraft turbomachine, said propeller having; - a hub (50) extending around a first axis comprising openings (50a) distributed around the first axis, each of said openings (50a) having a substantially radial orientation relative to the first axis and extending through the hub, - a system (34) for controlling the angular setting of a blade (10) which is mounted in each of the openings (50a), and - bearings (46, 48) for guiding the control system (34), which are mounted in each of the openings (50a), said guide bearings (46, 48) comprising two guide bearings (46, 48), one of which comprises two annular rows of angular contact coaxial balls (70, 72) having different diameters (D2, D3).