Rotor Blade Root Locking Wedge and Ring Sector Design
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Solution Overview
Problem
Conventional methods for attaching rotor blades to turbomachine rotors using composite materials face challenges in forming concave zones and ensuring axial retention, leading to unsatisfactory radial retention and differential expansions during engine operation.
Innovation Solution
A device comprising a circular ring sector with orthogonal blocking wedges and radially extending locking teeth, which allows for axial and radial blocking of rotor blades without the need for a fir tree foot or downstream hook, and includes ventilation means for air flow and reduced mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If composite material is used for blade root to reduce mass, then weight is reduced, but forming concave zones and ensuring axial retention becomes difficult
Solution Approach 1:
The blade root is segmented into multiple teeth (fir-tree structure) that engage with corresponding grooves in the rotor disc, allowing composite material to be used while maintaining retention capability through distributed mechanical interlocking rather than monolithic concave zones
Solution Approach 2:
A retention ring is introduced as an intermediary component between the composite blade root and the rotor disc, providing the necessary mechanical interlocking feature (downstream hook) without requiring complex shaping of the composite material itself
2Reliability
If traditional metal foot attachment methods are used, then axial retention is ensured, but radial retention becomes unsatisfactory due to differential expansions
Solution Approach 1:
The retention system is designed to accommodate thermal expansion parameters by allowing controlled movement in the radial direction while maintaining axial retention, with the retention ring and groove geometry optimized for thermal cycle conditions
Solution Approach 2:
The blade root-retention ring-rotor disc assembly is designed with dynamic clearance and interference fit characteristics that adapt to thermal expansion, allowing radial movement while maintaining secure axial retention during operation
3Reliability
If a downstream hook is added to the blade root for axial retention, then axial displacement is blocked, but device complexity increases
Solution Approach 1:
The retention ring serves multiple functions simultaneously: it provides axial retention through the downstream hook, enables radial retention through groove engagement, and facilitates ventilation by creating clearance space, eliminating the need for separate components for each function
Solution Approach 2:
The retention ring combines the downstream hook feature with the ventilation clearance function into a single integrated component, reducing overall device complexity compared to having separate elements for axial retention and ventilation
4Use of energy by moving object
If ventilation space is created between blade root and groove bottom, then air circulation is improved, but radial retention may be compromised
Solution Approach 1:
The retention ring is designed with localized features: the downstream hook provides axial retention at one location, while the groove engagement provides radial retention at another, and the spacing creates ventilation clearance in a third area, with each local region optimized for its specific function
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 enables secure positioning and retention of rotor blades made of composite materials, preventing axial displacement and ensuring correct radial positioning, while allowing for efficient air ventilation and reduced mass, thus addressing the limitations of traditional metal foot attachment methods.
Implementation Method 1
ventilation means, arranged in said ring sector, arranged to allow evacuation of a flow of air circulating between the bottom of the groove and the blocking wedge
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A device (8) for locking a root of a rotor blade in a groove in a rotor disc of a turbomachine, comprising: - a circular ring sector (81) designed to be mounted, transversely to the axis of the turbomachine, in a groove in the rotor disc; - at least one locking wedge (82), which is rigidly secured and perpendicular to the ring sector (81), and extends parallel to the axis (S) of the ring sector (81) so as to hold the root of the blade radially in the groove; and - at least one locking tooth (83) extending from the ring sector (81) radially with respect to the axis (S) of the ring sector (81), so as to prevent the root of the blade from moving axially in the groove.