Rectifier Air Bleed Ports for Stator Vane Crack Resistance
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Solution Overview
Problem
Aircraft turbomachine compressor rectifiers face issues with premature cracking of stator vane heads due to high static/dynamic loads, leading to aerodynamic disturbances and performance degradation when traditional thickening or mechanical deloading solutions are applied.
Innovation Solution
The introduction of circumferentially oblong air bleed ports on the flange of the compressor rectifier, which provides mechanical unloading of the stator vane heads without disturbing the primary jet flow, maintains existing manufacturing simplicity, and allows for the same bleed area and air flow efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional circular bleed ports are used, then manufacturing is simple, but stator vane heads experience high static/dynamic loads leading to premature cracking
Solution Approach 1:
The bleed ports are designed with different geometries at different locations: circumferentially oblong shape at critical locations where stator vane heads require mechanical unloading, and circular shape at other locations. This local differentiation provides targeted stress relief where needed while maintaining manufacturing simplicity elsewhere.
Solution Approach 2:
The invention changes the geometric parameters of the bleed ports by introducing a circumferential dimension in addition to the radial dimension. This parameter modification creates an oblong shape that provides mechanical unloading functionality for the stator vane heads while maintaining ease of manufacture.
2Reliability
If mechanical deloading slots are added to release dynamic loads, then crack appearance is delayed, but aerodynamic disturbances are generated in the primary flow
Solution Approach 1:
The invention extracts the mechanical unloading function from the primary flow path by placing the circumferentially oblong bleed ports on the outer shell in a location that does not interfere with the primary jet. This separates the stress relief function from the aerodynamic flow path, eliminating aerodynamic disturbances while maintaining crack resistance benefits.
Solution Approach 2:
The circumferentially oblong bleed ports serve as an intermediary mechanism that transfers dynamic loads from the stator vane heads to the outer shell structure without disrupting the primary flow. The oblong geometry provides a stress relief path while the strategic placement ensures no interference with aerodynamic performance.
3Reliability
If the outer shell is thickened to limit deformations, then stresses on trailing edges are reduced, but cost and mass increase significantly
Solution Approach 1:
Instead of uniformly thickening the entire outer shell, the invention applies local geometric modification only at specific locations where bleed ports are positioned. The circumferentially oblong bleed ports provide stress relief functionality without requiring increased shell thickness, thereby avoiding unnecessary mass increase while maintaining stress resistance.
4Reliability
If the stator vanes are thickened to reduce cracking risk, then structural strength improves, but air flow through the vanes is disturbed and overall performance decreases
Solution Approach 1:
The invention extracts the mechanical unloading function from the stator vane structure itself and relocates it to the outer shell via the circumferentially oblong bleed ports. This allows the stator vane thickness to remain optimized for aerodynamic performance while the outer shell provides the necessary stress relief, thereby maintaining air flow efficiency without compromising crack resistance.
Data Source
AI summary
The invention relates to a rectifier (1) for an aircraft turbomachine compressor, the rectifier comprising an inner ferrule (24), an outer ferrule (26), and stator blades (28) secured to the inner and outer ferrules, the rectifier also comprising a flange (34) secured to a downstream end of the outer ferrule (26) and designed to be fixed to a compressor housing (36), the flange being provided with air extraction openings (50) arranged at a distance from each other in a peripheral direction (52). According to the invention, at least one of the air extraction openings (50) has a stretched form in the peripheral direction (52).