Composite Airfoil Core Design for Stress Reduction
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Solution Overview
Problem
Turbine blades and vanes face challenges in combining high heat resistance, light weight, and strength to withstand high centrifugal and gas loads, particularly in the leading and trailing edge regions, where high tensile stress is a design concern due to radial pull and bending loads.
Innovation Solution
A composite airfoil design featuring a core with a higher Young's Modulus than the outer section, where the core is surrounded by the outer section, allowing the core to carry more radial loads and reduce stress in the leading and trailing edges, thereby increasing the blade's overall load capacity and resistance to impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If CMC or OMC materials are used to reduce weight and increase heat resistance, then weight is reduced and temperature limitation is increased, but tensile stress in leading edge and trailing edge regions increases due to combined radial pull load and gas load bending
Solution Approach 1:
The patent applies local quality by creating a core region with different material properties (higher Young's modulus) than the outer section. The core, formed from unidirectional fibers, provides localized stiffness and strength exactly where the leading and trailing edges experience highest tensile stresses, while the outer section maintains the lightweight composite characteristics.
Solution Approach 2:
The patent uses composite materials by combining two distinct composite structures: a core made from unidirectional fibers with high Young's modulus for strength, and an outer section made from woven fabric with lower Young's modulus for weight savings. This composite approach allows the blade to simultaneously achieve lightweight construction and high stress resistance in critical regions.
2Weight of moving object
If the trailing edge is made very thin to reduce weight, then weight is reduced, but the structure becomes more vulnerable to high tensile stress from radial pull and gas load bending
Solution Approach 1:
The core extends to the trailing edge, providing localized reinforcement with high Young's modulus material exactly where the thin trailing edge structure is most vulnerable to stress. This allows the trailing edge to maintain its thin, lightweight profile while the embedded core provides the necessary strength and reliability.
3Strength
If high strength alloys are used as single pieces, then strength and heat resistance are improved, but weight increases and propulsive efficiency decreases
Solution Approach 1:
The patent employs composite materials (CMC or OMC) throughout the blade structure, replacing traditional high-strength metal alloys. This provides equivalent or superior strength and heat resistance while achieving weight reduction to approximately one-third of metal alloy weight, thereby improving propulsive efficiency.
Solution Approach 2:
Rather than using uniform material throughout, the patent optimizes material distribution by placing high-strength core material strategically in regions requiring maximum stress resistance while using lighter outer section material elsewhere, achieving overall weight reduction while maintaining necessary strength characteristics.
Data Source
Figure 1
Figure 2A
Figure 2B~3
AI summary
An airfoil includes a core with a first Young's Modulus; and an outer section ate least partially surrounding the core with a second Young's Modulus, wherein the first Young's Modulus is higher than the second Young's Modulus.