Annulus filler assembly for gas turbine engine
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Solution Overview
Problem
Conventional annulus fillers in gas turbine engines face challenges such as weight inefficiency, fretting fatigue, and increased risk of damage during blade movement or 'blade-off' events, which affect aerodynamic performance and engine efficiency, and require regular inspection and design considerations for stress management.
Innovation Solution
A lightweight annulus filler assembly using Organic Matrix Composite (OMC) components with a flexible seal configuration, including a brace with a lip and co-operating feature, designed to absorb relative movement and reduce debris in case of extreme blade movement, while maintaining structural stability and aerodynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional annulus fillers are used to bridge the annulus gap between adjacent blades, then the air washed surface is formed ensuring clean flow of air through the stage, but the component mass increases leading to higher internal forces and reduced engine efficiency
Solution Approach 1:
The annulus filler is constructed from composite materials that provide the necessary structural strength and stiffness to maintain the air washed surface while significantly reducing the component mass compared to conventional materials. This allows the filler to bridge the annulus gap effectively without imposing excessive weight penalties on the rotating assembly.
2Ease of manufacture
If engagement features such as hooks, pins or trunnions are provided on the annulus filler, then the filler can be mounted to the rotor disc, but these features are prone to wear and corrosion termed fretting fatigue reducing the life of the rotor disc
Solution Approach 1:
A flexible seal element is introduced between the annulus filler and the blade to accommodate shape variations and movements without relying on rigid engagement features that are susceptible to fretting fatigue. This flexible connection maintains the seal integrity while eliminating the wear and corrosion problems associated with traditional hooks, pins, or trunnions.
3Weight of moving object
If the annulus filler is designed to be lightweight with smaller component mass, then the overall weight of the engine is reduced improving efficiency, but the filler must still meet operational demands of being secure under normal and gust wind loads and reverse air flow during engine surge
Solution Approach 1:
Composite materials are used to achieve a high strength-to-weight ratio, allowing the annulus filler to be significantly lighter than conventional designs while maintaining the structural integrity necessary to withstand normal operating loads, gust wind loads, and reverse air flow conditions during engine surge.
Solution Approach 2:
The annulus filler is designed as a segmented or modular structure that can be assembled from multiple lightweight components. This segmentation allows for optimized material distribution, placing material only where structurally necessary, thereby minimizing overall mass while maintaining strength under various loading conditions.
4Reliability
If dedicated features are provided on the rotor disc for mounting the annulus filler, then the filler can be securely attached, but this gives rise to additional design and manufacturing considerations to control stress in the component
Solution Approach 1:
The rotor disc is designed with multi-functional features that serve both as mounting structures for the annulus filler and as stress-management elements. These features are integrated into the existing rotor disc geometry, eliminating the need for dedicated attachment features and reducing the additional design and manufacturing complexity that would otherwise be required to control stress concentrations.
Data Source
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AI summary
A rotor assembly for a gas turbine engine, the rotor assembly has a disc supporting a plurality of radially extending blades. The blades define passages therebetween and each passage has an annulus filler assembly. The annulus filler assembly includes at least two bodies and a brace, each of the bodies being arranged to abut respective adjacent blades and the brace is arranged to occupy a position centrally of the two bodies. The brace is mounted to the disc and each body and the brace are arranged to engage one another to form an airwash surface. The airwash surface improves aerodynamic flow of air entering the gas turbine engine.