Aircraft Turbine Stator Shroud Mechanical Unloading Slots
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Solution Overview
Problem
Aircraft turbine engine stator blades experience cracks at the trailing edge and root due to high static charges, leading to reduced dynamic margin and service life, with existing solutions like thickening shrouds or blades either costly or detrimental to engine performance.
Innovation Solution
Incorporating mechanical unloading slots in the shell with a U or V shape, positioned opposite the trailing edge, to reduce static loads and offset heavily loaded zones, allowing for dynamic margin and crack delay without penalizing mass, cost, or performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shroud is thickened to reduce deformations and stresses on blade trailing edges, then the strength and reliability improve, but the mass and cost increase significantly
Solution Approach 1:
The patent applies local quality by introducing mechanical unloading slots specifically at the trailing edge region where high static charges occur, rather than uniformly thickening the entire shroud. This localized structural modification reduces stress concentration at the critical area while maintaining the original shroud mass and overall strength characteristics.
Solution Approach 2:
The patent segments the continuous shroud structure by introducing discrete mechanical unloading slots at specific locations (trailing edges of blades). This segmentation allows stress relief at critical points without compromising the overall structural integrity of the shroud, thereby avoiding the need for global thickening.
2Strength
If the blades are thickened to reduce stresses on trailing edges, then the strength improves, but the air flow through the blades is disturbed and engine performance decreases
Solution Approach 1:
The patent applies local quality by modifying only the shroud structure at the blade trailing edge region with mechanical unloading slots, rather than thickening the entire blade. This localized approach relieves stress at the critical trailing edge area while preserving the original blade aerodynamic profile and air flow characteristics, thus maintaining engine performance.
3Reliability
If mechanical unloading slots are introduced to reduce static loads on blade trailing edges, then the reliability and service life improve, but the manufacturing complexity increases slightly
Solution Approach 1:
The patent applies preliminary action by incorporating mechanical unloading slots into the shroud design during the manufacturing stage, before the blades are installed and before any cracks can develop. This preventive measure proactively reduces static loads and stress concentrations at the trailing edges, thereby preventing crack initiation and extending service life.
Data Source
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AI summary
The invention relates to a housing (16a) for a stator of a module of an aircraft turbine engine provided with a plurality of through-openings (22) respectively receiving a stator blade (4) and defining a skeleton (32) extending between a first end (25) for housing the trailing edge of the blade and a second end (27) for housing the leading edge (28) of the blade. According to the invention, a mechanical offloading slit formed through the housing is associated with one of the openings (22), facing, and at a distance from, the first end (25) of the opening according to the direction of the skeleton (32).