Turbofan Fan Case Composite Containment Design
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Solution Overview
Problem
Existing fan case designs for turbofan gas turbine engines face inefficiencies due to the need for larger tip clearance to prevent fan blade tip rubs, which increases engine weight and reduces efficiency, as containment fabrics can be compromised by blade tip contact.
Innovation Solution
A structurally integrated fan case design featuring a strong inner shell, a lightweight honeycomb material, and a stiffening ring, with a high-strength fibrous containment fabric, minimizing the risk of blade tip contact and reducing the fan case diameter and weight while maintaining containment capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger tip clearance is provided between blade tips and fan case to prevent blade tip rubs, then the containment fabric strength is preserved, but the fan case envelope size increases and engine weight increases
Solution Approach 1:
The fan case employs a composite structure combining a thin-walled metal or composite support case with a containment fabric layer (such as Kevlar®). This composite design allows the support case to be thinner and lighter while the fabric layer provides the necessary containment strength, eliminating the need for increased tip clearance to protect the fabric from blade tip rubs.
Solution Approach 2:
The invention changes the material parameters of the containment structure by using high-strength composite materials and advanced fabric layers that can withstand blade tip contact without compromising integrity. This allows reduced tip clearance while maintaining fabric strength, thereby reducing engine weight.
2Reliability
If a larger tip clearance is provided between blade tips and fan case to prevent blade tip rubs, then the containment fabric is protected from damage, but the fan case envelope size increases
Solution Approach 1:
The composite structure of the support case and containment fabric allows the fan case envelope to be minimized. The thin-walled support case combined with the high-strength fabric layer provides sufficient protection against blade tip rubs without requiring increased clearance, thus maintaining a compact fan case envelope size.
Solution Approach 2:
The thin-walled support case acts as a flexible structure that can accommodate blade tip proximity without requiring large clearance. The containment fabric layer wraps around this thin support structure, providing protection while maintaining a compact overall envelope size.
3Weight of stationary object
If a thin-walled support case is used to reduce weight, then the fan case weight is reduced, but the structural strength may be compromised
Solution Approach 1:
The support case is constructed as a composite structure combining thin-walled metal or composite materials with a containment fabric layer. This composite design maintains structural strength despite the thin-walled configuration, as the fabric layer reinforces the support case and provides additional containment capability.
Solution Approach 2:
The support case employs variable wall thickness design with localized reinforcement at critical areas. The wall thickness is optimized to provide sufficient strength where needed while maintaining overall thin-walled configuration for weight reduction. Local reinforcement is provided at areas subject to blade tip contact or high stress.
Data Source
AI summary
A gas turbine engine rotor containment structure comprises an inner structurally supporting case having an inner surface positioned adjacent to a gas turbine engine rotor component to be contained. A layer of acoustic material is wrapped around and bounded to a radially outer surface of the inner case. A thin walled outer ring is bounded to a radially outer surface the layer of acoustic material. A layer of fibrous containment material surrounds a radially outer surface of the outer ring.