Variable-Pitch Propeller Vane Root to Limit Swivelling Wear
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Solution Overview
Problem
Existing broached attachments for variable pitch propeller vanes in aircraft turbine engines suffer from premature wear and swivelling due to intense aerodynamic and vibratory forces, particularly during feathered starts and high rotational speeds, leading to frictional damage and reduced mechanical integrity.
Innovation Solution
A variable pitch propeller vane design featuring a root with a bulbous cross-section and a stilt, combined with an annular barrel and guide bearings, which provides enhanced retention and reduces aerodynamic disturbances, using a system with guide bearings and an immobilization ring to stabilize the vane against swivelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a broached attachment is used to attach the vane to its support, then the vane can be connected to the support in a form-fitting manner, but the intense aerodynamic forces cause rigid solid movements of the vane root in its pocket leading to swivelling and frictional damage
Solution Approach 1:
The attachment system is divided into multiple functional components: the broached pocket for form-fitting connection, guide bearings for preventing radial movements, and an immobilization ring for eliminating swivelling. This segmentation allows each component to address specific aspects of the attachment problem, with guide bearings handling radial constraints and the immobilization ring handling rotational constraints.
Solution Approach 2:
Guide bearings are introduced as intermediary elements between the vane root and the broached pocket. These bearings act as mediators that prevent direct contact and frictional damage between the vane root and pocket walls during aerodynamic loading, while still maintaining the form-fitting connection through the broached attachment.
2Power
If the pitch angle of the vanes is increased to maximize torque during engine start, then the power consumption increases and machine safety is guaranteed, but the aerodynamic force becomes so intense that it causes swivelling and frictional damage to the blade
Solution Approach 1:
The guide bearings and immobilization ring are pre-installed in the attachment system before operation. These components provide protective constraints against swivelling and excessive movements before the intense aerodynamic forces act on the blade during high-pitch operation, preventing frictional damage from occurring in the first place.
Solution Approach 2:
The intense aerodynamic forces that would normally cause harmful swivelling and friction are converted into beneficial controlled forces by the guide bearings. The bearings transform the potentially damaging radial movements into controlled loading conditions that the attachment system can withstand without frictional damage.
3Productivity
If the span of the vanes is increased to improve aerodynamic performance and increase the BPR, then the thrust generation is improved, but the aerodynamic forces and vibratory excitations increase leading to stronger swivelling and frictional damage
Solution Approach 1:
The attachment system combines different functional elements (broached metal-to-metal connection, rolling element guide bearings, and immobilization ring) into a composite structure. This composite approach allows the system to handle both the aerodynamic loading from large-span blades and the constraint requirements for preventing swivelling and frictional damage.
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 design effectively limits swivelling and premature wear, enhances mechanical strength, and reduces aerodynamic disturbances, improving the overall performance and durability of the propeller vanes.
Implementation Method 1
the reduced speed of the fan does not allow a sufficient centrifugal force to be generated to prevent these movements induced by the aerodynamical force
Implementation Method 2
The vane comprises a root which has a general dovetail shape and which is intended to be engaged in a form-fitting manner in a pocket of the support, this pocket being conventionally produced by broaching
Data Source
AI summary
Disclosed is a variable pitch propeller blade for an aircraft turbine engine. The blade includes an airfoil connected to a root, the root having a body housed in an annular barrel that extends around a pitch axis of the blade, the body including a free end opposite the airfoil; a shoulder towards the airfoil; and a bulb located between the free end and the shoulder. The bulb can have a cross-section, referred to as the middle section, that has a maximum value Sm, and the barrel can be affixed to the body and covers and matches at least a portion of the bulb and the shoulder.