Fan Blade Root Trench for Impact Strain Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine fan blades are susceptible to damage during bird impact events due to elevated strain in the transition zone on the leading edge, particularly in stiff blades, which existing attachment root designs fail to adequately address.
Innovation Solution
The attachment root features a trench with a cylindrical trough and spherical end surface, providing increased flexibility by distributing impact strain and reducing stress concentrations, with the trench's dimensions optimized to enhance flexibility and absorb impact forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fan blades are made stiff to maintain structural strength, then strength is improved, but susceptibility to damage during impact events increases
Solution Approach 1:
The attachment root is designed with a trench that creates local geometric variation, making the root more flexible at the trench location while maintaining overall blade strength. This local modification allows the blade to better absorb impact forces without compromising the global structural integrity of the blade assembly.
Solution Approach 2:
The trench geometry parameters (depth, width, length, curvature radius) are specifically optimized to change the flexibility characteristics of the attachment root. By adjusting these parameters, the blade achieves improved flexibility for impact absorption while maintaining sufficient strength for normal operation.
2Strength
If the attachment root is made rigid to ensure secure mounting, then mounting security is improved, but strain concentration during impact increases
Solution Approach 1:
The trench incorporates curved surfaces with specific radius of curvature at its ends and along its length. This curvature eliminates sharp corners and stress concentration points, allowing the attachment root to flex during impact events without creating localized strain peaks that would compromise mounting security.
Solution Approach 2:
The trench divides the attachment root structure into distinct regions with different flexibility characteristics. The root section with the trench has modified stiffness compared to the rest of the blade, creating a controlled flexibility zone that manages strain distribution during impact while maintaining secure mounting.
3Productivity
If the transition zone on the leading edge is made stiffer to maintain aerodynamic performance, then aerodynamic performance is improved, but damage susceptibility during bird impact increases
Solution Approach 1:
The trench creates a localized region of modified flexibility in the attachment root, allowing the blade to have different mechanical properties in different zones. The aerodynamic portions of the blade maintain their stiffness for performance, while the attachment root zone with the trench provides flexibility for impact absorption.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A fan blade (42) is provided and comprises a leading edge, an attachment root (100;130;150;170) extending aft of the leading edge, and a trench (104;124;134;154;174) formed in a surface of the attachment root (100;130;150;170). An attachment root (100;130;150;170) is also provided. The attachment root (100;130;150;170) comprises a leading edge (106;160;178), a dovetail (122) extending aft of the leading edge (106;160;178), and a trench (104;124;134;154;174) formed in a surface of the dovetail (122). A gas turbine engine (20) is also provided. The gas turbine engine (20) comprises a compressor section (24) configured to rotate about an axis (A-A'), a combustor (56) aft of the compressor section (24), and a turbine section (28) aft of the compressor section (24) and configured to rotate about the axis (A-A'). A fan (22) may be disposed forward of the turbine section (28) and include a blade (42). The blade (42) may have a trench (104;124;134;154;174) formed in an attachment root (100; 130;150;170).