Variable Pitch Blade Holder Stress Distribution
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Solution Overview
Problem
Variable pitch fan blades in gas turbine engines face design challenges due to independent operation, leading to uneven stress distribution and potential failure from centrifugal forces, which can cause radial movement and edge loading issues.
Innovation Solution
A fan blade assembly with a dovetail-shaped root and airfoil, featuring a blade holder with deformable posts that create relief slots to distribute contact pressure uniformly, preventing radial movement and reducing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable pitch fan blades are designed with independent operation, then pitch adjustment flexibility is improved, but stress distribution becomes uneven leading to potential failure
Solution Approach 1:
The patent combines multiple posts into a single integrated blade holder structure that collectively supports the fan blade. This merging approach distributes prying forces across multiple contact points and the overall structure, preventing localized stress concentrations while preserving independent pitch adjustment capability of each blade.
Solution Approach 2:
The blade holder is designed with dynamic load distribution capabilities, allowing the structure to adaptively respond to centrifugal forces and prying moments during operation. The holder's geometry and material properties enable it to distribute varying loads uniformly across the blade root interface, maintaining reliability under changing operational conditions.
2Stability of the object's composition
If fan blades are retained with rigid blade holders, then radial movement is prevented, but stress concentrations occur at contact points
Solution Approach 1:
The blade holder features locally optimized contact surfaces and geometry at each post-blade interface. The contact areas are designed with specific curvature and compliance characteristics that distribute pressure uniformly across the blade root, preventing stress concentrations while maintaining effective radial constraint during rotation.
3Strength
If dovetail roots are constrained by adjacent blades, then bending of disc lug posts is prevented, but prying forces create edge loading issues
Solution Approach 1:
The blade holder design transitions from a two-dimensional post structure to a three-dimensional integrated support system. This dimensional enhancement allows the holder to resist prying forces through distributed volumetric support and optimized stress flow paths, eliminating edge loading at the dovetail interface while maintaining bending resistance.
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 solution effectively limits fan blade movement and reduces stress concentrations, enhancing the structural integrity and reliability of the fan blade assembly by uniformly distributing centrifugal forces, thereby minimizing the risk of failure.
Implementation Method 1
allow the first post and the second post to deform and distribute contact pressure along the dovetail shaped root of the fan blade in response to the fan blade being urged radially outward relative to the center axis by centrifugal forces acting on the fan blade during operation of the gas turbine engine
Data Source
AI summary
A variable pitch blade holder for use with a gas turbine engine. The variable pitch blade holder is configured to retain a blade and to rotate about a center axis with the blade during operation of the gas turbine engine. The blade holder is adapted to rotate about a pitch change axis to vary a pitch of the blade.