Gas Turbine Fan Blade Transition Section Stress Reduction
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Solution Overview
Problem
Large fan blades in gas turbine engines experience high stress concentrations at the leading edges, which can lead to structural failures and increased weight, making it challenging to achieve weight reduction while maintaining strength and efficiency.
Innovation Solution
The design incorporates a transition section that extends axially or widens as it moves from the single tooth attachment to the airfoil, creating a longer first chord compared to a shorter second chord, reducing stress concentrations by distributing loads more effectively, and may be covered with a titanium or titanium alloy sheath for added strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If larger fan blades are used to increase thrust, then engine propulsion capability is improved, but weight and stress on fan blades increase
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the fan blade, specifically increasing the fan diameter and blade chord length to enhance thrust generation capability while managing the associated weight and stress increases through design optimization
2Strength
If high strength materials are used to counteract stresses, then blade strength is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by implementing a titanium sheath only at the leading edge of the fan blade where stress concentrations are highest, rather than making the entire blade from titanium. This provides localized strength enhancement at the critical stress area while using lighter, less expensive materials for the remainder of the blade structure
Solution Approach 2:
The patent applies composite materials by combining a titanium sheath with a lighter core material (such as aluminum or composite) to create a hybrid structure. The titanium sheath provides the necessary strength and stress resistance at the leading edge, while the lighter core material reduces overall blade weight and manufacturing cost compared to solid titanium construction
3Weight of moving object
If hollow titanium fan blades are used to reduce weight, then weight is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies local quality by applying a titanium sheath only to the leading edge portion of the fan blade where strength requirements are most critical, rather than constructing the entire blade from titanium. This localized approach reduces material cost and manufacturing complexity while maintaining necessary strength properties at the stress-critical leading edge area
4Productivity
If wider chord blades are used to increase efficiency, then aerodynamic efficiency is improved, but stress concentration at leading edge increases
Solution Approach 1:
The patent applies local quality by reinforcing only the leading edge area with a titanium sheath, which is the specific location experiencing high stress concentrations due to the wider chord design. This localized reinforcement addresses the stress concentration problem without requiring a reduction in overall blade chord length, thereby maintaining aerodynamic efficiency
Data Source
AI summary
A light weight fan blade for a gas turbine engine is disclosed. The disclosed fan blade has an increased chord length at a transition section between the inner edge or single tooth attachment portion of the fan blade that connects to the rotor disk and the airfoil. Increasing the chord length at the transition section substantially reduces the stress concentration when the fan blade is operated under normal operating conditions. Reducing the stress concentration enables engineers to design lighter fan blades and larger fan blades for larger gas turbine engines. By increasing the size of gas turbine engines, additional thrust can be provided without adding additional engines to the aircraft.