Variable-Pitch Propeller Blade Root Axial Clamping Mechanism
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Solution Overview
Problem
Current attachment methods for propeller blades with variable pitch, especially those with wide chord and large span, fail to adequately limit blade rotation during phases of flight that excite vibration modes, leading to friction damage due to intense aerodynamic forces and vibrational excitations.
Innovation Solution
An angular setting system for propeller blades featuring a bulb-shaped root with an annular retention ring and a movable seat, allowing axial tightening to prevent axial movement and ensure secure fixation within a bowl, thereby reducing rotational freedom and minimizing friction damage.
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 blade can be easily installed and removed, but the blade experiences rigid body movements within its housing during feathered start and windmilling, causing friction damage
Solution Approach 1:
The patent transitions from a static pinned connection to a dynamic clamping system where the blade root is securely retained within the bowl through axial clamping forces. The retention ring and clamping mechanism allow the blade to be firmly held during operation while still permitting installation and removal through controlled axial movement, thus resolving the contradiction between ease of manufacture and operational stability.
Solution Approach 2:
The patent changes the retention parameter from a fixed pin position to a variable clamping force that can be adjusted during installation and maintenance. The clamping mechanism allows the retention force to be applied axially, securing the blade root against the retention ring during operation, while still allowing the blade to be installed or removed by reversing the axial clamping force, thereby resolving the contradiction between ease of installation and operational stability.
2Productivity
If the blade span is increased to improve aerodynamic performance, then the BPR and efficiency increase, but the aerodynamic forces and vibrational excitations become more intense, causing friction damage at the blade root
Solution Approach 1:
The patent applies beforehand cushioning by providing a clamping mechanism that pre-loads the blade root against the retention ring before intense aerodynamic forces act on the blade. This pre-applied retention force creates a friction interface that prevents relative movement between the blade root and bowl during operation, cushioning against the harmful effects of intense aerodynamic forces and vibrations that increase with larger blade spans.
Solution Approach 2:
The patent introduces an intermediary clamping mechanism and retention ring system between the blade root and the bowl. This intermediary system transfers and distributes the intense aerodynamic forces and vibrational excitations more evenly, preventing direct contact and friction damage between the blade root and bowl while allowing the blade to maintain its large span for improved aerodynamic performance.
3Reliability
If axial clamping force is applied to secure the blade root, then blade retention improves, but the complexity of the attachment system increases due to additional clamping mechanisms
Solution Approach 1:
The patent applies universality by designing the retention ring and clamping mechanism to serve multiple functions: securing the blade root axially, providing a friction interface to prevent relative movement, distributing vibrational forces, and allowing for easy installation and removal. This multi-functional design achieves reliable blade retention without proportionally increasing system complexity, as a single integrated mechanism performs multiple retention and security functions.
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 system effectively limits blade rotation and prevents friction damage by ensuring secure axial and radial retention, even under high aerodynamic and centrifugal forces, enhancing the durability and performance of propeller blades.
Implementation Method 1
The friction between the seat and the bulb, and between the retention ring and the bulb, prevents axial displacement of the blade root within the bowl
Implementation Method 2
at least one clamping mechanism allowing axial clamping of the bulb between the seat and the bearing face of the retention ring
Implementation Method 3
the reduced fan speed does not generate sufficient centrifugal force to prevent these movements induced by the aerodynamic force
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to an assembly comprising a propeller blade (10) and a pitch adjustment system (34) for setting the pitch of the blade (10), wherein a root (14) of the blade (10) has a bulb (32) and the pitch adjustment system (34) for setting the pitch of the blade (10) comprises: - a cup (58) having an upper opening (58c); - a retaining ring (82), which extends around the bulb (32), is restricted at least in terms of axial movement towards the opening (58c) relative to the cup (58) and has a bearing face (84) to inhibit axial movement of the root (14) towards the opening (58c); the pitch adjustment system (34) being characterized in that it further comprises a lower seat (88) by means of which the root (14) engages the cup (58), the seat (88) and/or the retaining ring (82) being mounted so as to be capable of axial translation relative to the cup (58) by means of at least one clamping mechanism (90).