Frangible Airfoil Design for Gas Turbine Impact Mitigation
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Solution Overview
Problem
Airfoils in gas turbine engines face challenges with extreme loading events such as bird strikes and fan blade liberation, leading to unbalanced rotor conditions and increased weight due to existing fan case configurations, which affect engine performance and efficiency.
Innovation Solution
The development of a frangible airfoil design with multiple zones and cavities containing inclusions, allowing for controlled deformation or detachment to mitigate load transfer and reduce rotor unbalance, featuring a functionally graded material and additive manufacturing for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fan cases are configured to withstand impact of fan blades during extreme loading events, then reliability is improved, but weight of the fan case increases
Solution Approach 1:
The fan case is designed with frangible structures that change their mechanical properties under extreme loading conditions. These structures remain rigid during normal operation but are configured to deform or collapse when subjected to impact forces from liberated fan blades, thereby absorbing impact energy without requiring the entire fan case to be overweight.
Solution Approach 2:
The fan case incorporates discrete frangible structures (such as honeycombs or trench-filler material) that are segmented throughout the case. These segmented structures provide localized impact mitigation zones that can deform independently to absorb impact forces, rather than requiring the entire fan case structure to be reinforced and thereby reduced in weight.
2Reliability
If frangible structures are added to fan cases to mitigate load transfer, then reliability is improved, but device complexity increases
Solution Approach 1:
The frangible structures are integrated directly into the fan case structure itself, merging the impact mitigation function with the existing fan case geometry. Rather than adding separate, complex mitigation systems, the frangible features are incorporated as part of the fan case's structural design, thereby providing load transfer mitigation without significantly increasing overall device complexity.
3Strength
If fan blades are made more robust to withstand extreme loading, then strength is improved, but weight of the airfoil increases
Solution Approach 1:
The airfoil is constructed using composite material structures that provide high strength-to-weight ratio. By utilizing composite materials, the airfoil achieves the necessary strength to withstand extreme loading events without requiring a proportional increase in weight, as composite materials offer superior specific strength compared to conventional materials.
Solution Approach 2:
The airfoil design incorporates varying material properties and structural characteristics at different locations along the blade. Critical high-stress regions are reinforced with higher strength materials or thicker sections, while lower-stress regions use lighter materials, thereby achieving overall strength requirements without uniformly increasing the weight of the entire airfoil.
Data Source
AI summary
An airfoil for gas turbine engines is generally provided. The airfoil defines a span extending between a root and a tip, the airfoil further defines a chord at each point along the span extending between a leading edge and a trailing edge. Further, the airfoil includes at least one frangible airfoil portion, a residual airfoil portion adjacent to the at least one frangible airfoil portion, and one or more zones. The one or more zones may include a plurality of cavities, where at least one or more cavities of the plurality of cavities include inclusions, with the inclusions having one or more materials.