CMC Turbine Blade Fuse for Predictable Overspeed Shedding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engines face challenges in managing overspeed conditions due to shaft fractures, leading to rapid rotor acceleration, which can exceed safe operating limits, necessitating a predictable and controlled shedding of blades to prevent disk rupture and reduce disk weight.
Innovation Solution
A ceramic matrix composite (CMC) gas turbine blade design incorporates a unidirectional material layup with a limiting section configured to fracture at a predetermined load, aligning 90-degree fibers to ensure predictable blade shedding above the required transient redline speed but below the unsafe overspeed threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turbine blades are designed with high stress strength to prevent fracture during overspeed, then blade reliability is improved, but disk weight increases due to the need for extra weight to withstand the overspeed event
Solution Approach 1:
The blade is segmented into different functional regions with different material properties. The root section uses a laminate structure with 90-degree fibers oriented to create a limiting section that fractures at a predetermined load, while other sections maintain high strength. This segmentation allows the blade to shed predictably at the root rather than causing catastrophic disk failure, enabling weight reduction.
Solution Approach 2:
The blade employs local quality by creating a limiting section with specific fiber orientation (90-degree fibers) and material composition only in the root region where controlled fracture is desired. The rest of the blade maintains optimized material properties for strength and durability. This localized approach allows predictable blade shedding without compromising overall blade reliability during normal operation.
2Duration of action of stationary object
If turbine blades are designed to withstand high overspeed conditions, then disk weight increases, but if blades are designed for long-term creep/stress rupture requirements, then stress levels must remain below short-term strength capability, preventing blade fracture
Solution Approach 1:
The blade design incorporates a preliminary action by pre-configuring a limiting section with 90-degree fiber orientation that is designed to fracture at a predetermined load before the blade would fail from long-term creep or stress rupture. This preliminary fracture mechanism ensures that if overspeed occurs, the blade will shed predictably at the root rather than accumulating damage over time, allowing the blade to meet both long-term durability requirements and controlled failure characteristics.
3Strength
If the disk is sized to include extra weight to withstand overspeed, then disk strength is improved, but blade shedding cannot occur in a predictable manner at controlled speeds
Solution Approach 1:
The invention changes the parameter of blade root strength by introducing a limiting section with 90-degree fiber orientation that has a predetermined fracture load. This creates a controlled weakness point that allows the blade to shed at a specific speed range (above required transient redline but below unsafe overspeed threshold). The disk can be sized appropriately for this controlled shedding scenario rather than being oversized for unlimited overspeed protection, achieving both predictable blade shedding and adequate disk strength.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A ceramic matrix composite gas turbine blade comprising a root portion coupled to a disk, said root portion having a neck; a platform region is disposed along an upper portion of the neck; an airfoil is located opposite the neck relative to the platform and extends outwardly from the platform; and a limiting section fuse formed in the blade proximate the neck.