Gas Turbine Blade Root Retention Wedging System
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Solution Overview
Problem
Current methods for retaining dovetail roots of gas turbine engine blades in dovetail slots are inefficient, leading to increased disc weight, machining time, and costs, and do not effectively manage vibrational damping, especially when dealing with composite blades.
Innovation Solution
The use of angled wedging bodies that insert into dovetail slots to radially expand the blade roots, providing axial retention without extending the disc, and featuring key portions and angled surfaces to match the dovetail geometry, allowing for shear and compressive force dissipation under extreme loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid block or plate of metal is inserted into machined grooves in the disc to retain blades axially, then blade axial retention is achieved, but disc weight increases and machining time increases
Solution Approach 1:
The retention system is segmented into multiple small wedging bodies distributed around the dovetail slot, replacing a single large solid plate. Each wedging body is a discrete element that can be independently positioned and sized, reducing the total material required while maintaining retention functionality through distributed load bearing.
Solution Approach 2:
The invention changes the geometric parameters of the retention elements from thick plates to thin wedging bodies with specific angled surfaces. The angled surfaces (e.g., 10-45 degrees) transform the retention mechanism from direct shear loading to wedge-driven radial expansion, allowing thinner elements that reduce weight while maintaining strength.
2Reliability
If a solid block or plate of metal is inserted into machined grooves in the disc to retain blades axially, then blade axial retention is achieved, but disc machining time increases
Solution Approach 1:
The retention system is segmented into multiple small wedging bodies distributed around the dovetail slot, replacing a single large solid plate. Each wedging body is a discrete element that can be independently positioned and sized, reducing the total material required while maintaining retention functionality through distributed load bearing.
Solution Approach 2:
The invention changes the geometric parameters of the retention elements from thick plates to thin wedging bodies with specific angled surfaces. The angled surfaces (e.g., 10-45 degrees) transform the retention mechanism from direct shear loading to wedge-driven radial expansion, allowing thinner elements that reduce weight while maintaining strength.
3Strength
If the disc is extended to accommodate thicker retention plates, then blade axial retention strength is improved, but disc forging cost increases and engine space is reduced
Solution Approach 1:
The invention changes the geometric parameters of the retention elements from thick plates to thin wedging bodies with specific angled surfaces. The angled surfaces (e.g., 10-45 degrees) transform the retention mechanism from direct shear loading to wedge-driven radial expansion, allowing thinner elements that reduce weight while maintaining strength.
Solution Approach 2:
The wedging bodies utilize angled surfaces that create a wedge geometry, transforming linear axial forces into radial expansion forces. This geometric transformation allows the retention function to be achieved with shorter axial dimensions while maintaining or improving strength through the mechanical advantage of the wedge angle.
4Reliability
If retention plates are used to retain blades axially, then blade retention is achieved, but vibrational damping is insufficient
Solution Approach 1:
The invention changes the geometric parameters of the retention elements from thick plates to thin wedging bodies with specific angled surfaces. The angled surfaces (e.g., 10-45 degrees) transform the retention mechanism from direct shear loading to wedge-driven radial expansion, allowing thinner elements that reduce weight while maintaining strength.
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
This solution reduces disc weight and machining costs, maintains compatibility with composite blades, and enhances vibrational damping by redistributing axial loads through compressive forces, improving the overall efficiency and reliability of blade retention.
Implementation Method 1
a first wedging body having a key portion receivable in a keyway formed at the distal end of the slot, the keyway restraining the first wedging body against movement in the axial direction, and the first wedging body further having a first angled surface over which a correspondingly angled leading end surface of the root slides when the root is inserted in the slot to urge the leading end of the root radially outwardly
Implementation Method 2
the angled surfaces of the wedging bodies cause the flanks of the root to mate with flanks of the slot while also retaining the root axially in the slot
Data Source
AI summary
A device for chocking and retaining a dovetail root of a blade of a gas turbine engine in a corresponding axially-extending slot in the rim of a disc, the root being mounted in the slot by insertion of a leading end of the root into a proximal end of the slot and then sliding the root towards a distal end of the slot. The device includes a first wedging body having a key portion receivable in a keyway formed at the distal end of the slot. The keyway restrains the first wedging body against movement in the axial direction. The first wedging body further has a first angled surface over which a correspondingly angled leading end surface of the root slides when the root is inserted in the slot to urge the leading end of the root radially outwardly.