Aircraft Fan Blisk Discharge Slit Bird Impact
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Solution Overview
Problem
Aircraft turbojet fan blisks face challenges in resisting bird impacts without increasing mass, as existing designs often require additional parts to manage stress, leading to overdesign and higher weight.
Innovation Solution
Incorporating a mechanical discharge slit on the annular platform of the fan blisk, which redirects stress from the trailing edge to its ends, reducing the risk of blade breakage and mass by adding flexibility without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan blisk is designed to resist bird impact without breaking, then blade strength and reliability are improved, but the mass of the fan case increases due to overdesign
Solution Approach 1:
The annular platform is segmented by introducing discharge slits that divide the continuous structure into sections. These slits allow controlled stress discharge paths, enabling the platform to flex and absorb impact energy without requiring the entire structure to be overdesigned for strength, thus reducing unnecessary mass while maintaining reliability.
2Strength
If a flow stream reformation part is added to reduce stresses in the trailing edge area, then stress resistance is improved, but the global mass and fabrication complexity increase
Solution Approach 1:
Instead of adding a separate flow stream reformation part, the invention extracts the stress management function by incorporating discharge slits directly into the annular platform. This integrates the stress relief mechanism into the existing structure, eliminating the need for additional components and reducing global mass while maintaining stress resistance.
Solution Approach 2:
The stress relief function is merged with the annular platform structure itself through the discharge slits. The platform simultaneously serves as a structural support and a stress discharge pathway, combining multiple functions into a single integrated component, thereby reducing the need for additional parts.
3Stress or pressure
If the fillet radius between the trailing edge and annular platform is increased to reduce stresses, then stress concentration is reduced, but the device complexity and mass increase
Solution Approach 1:
The discharge slits are pre-positioned in the annular platform to establish predetermined stress discharge pathways before impact occurs. This preliminary configuration of stress paths allows the structure to naturally manage stress concentrations during bird impact without requiring complex geometric modifications like increased fillet radii.
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 slit effectively reduces the risk of blade breakage and minimizes mass increase by distributing stress and enhancing flexibility, while maintaining aerodynamic integrity.
Implementation Method 1
the partial discharge slit can transfer stresses related to the impact to a distance from the sensitive zone at the trailing edge
Implementation Method 2
maximum stresses are shifted to the ends of the slit, and reduced due to the flexibility added due to the presence of this slit
Data Source
AI summary
The invention relates to a fan blink (28) for an aircraft turbomachine, comprising a hub, an annular platform (42) and fan blades (44) arranged projecting from the annual platform. It also comprises a mechanical discharge slit (52) from a trailing edge (49) of the fan blade, associated with at least one of the fan blades (44), for the case of ingestion of a bird, the slit being made on the annular platform (42) going around the trailing edge (49).