Abradable Fan Case Rub Strips for Blade Rub and Vibration
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Solution Overview
Problem
The challenge of maintaining a close fit between fan blades and the surrounding housing in gas turbine engines while avoiding material damage, resonant frequencies, and high temperatures due to blade rub interactions, particularly under varying operational conditions.
Innovation Solution
The use of an abradable material formed into panels, which are cured and installed in the fan case to create a rubstrip, designed to wear away during contact with the blades, thereby maintaining a close fit and reducing the risk of resonant frequencies through vibration dampening properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fan blades are positioned close to the fan case housing, then airflow sealing efficiency is improved, but material damage and resonant frequencies occur due to blade rub interactions
Solution Approach 1:
An abradable rub strip material is introduced as an intermediary layer between the fan blade and the fan case housing. This rub strip absorbs the rub interaction damage through controlled abrasion rather than allowing direct contact between the fan blade and the rigid housing, thereby preventing material damage and resonant frequencies while maintaining the close fit necessary for airflow sealing efficiency
Solution Approach 2:
The rub strip material is designed with specific parameter changes including compression spring rate profiling (varying stiffness along the thickness), controlled abrasion characteristics, and vibration dampening properties. These parameter changes allow the material to transition from a rigid barrier to a compliant, damage-absorbing layer that maintains sealing while preventing harmful interactions
2Reliability
If abradable material is used to protect fan blades, then material damage is reduced, but resonant frequencies can still be incited creating unstable vibratory conditions
Solution Approach 1:
The rub strip material incorporates vibration dampening properties through its composition and structure, including viscoelastic characteristics and internal friction mechanisms that dissipate vibratory energy. This transforms the material from a simple protective layer to an active vibration control element that reduces resonant frequencies while maintaining protection from material damage
Solution Approach 2:
The abradable rub strip is formulated as a composite material combining abradable properties with vibration dampening characteristics. This composite structure integrates multiple functional properties including controlled abrasion, compression spring rate profiling, and vibration dampening in a single material system, simultaneously addressing both protection and stability requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The abradable material effectively maintains a close fit between fan blades and the housing, enhancing airflow sealing and reducing the risk of resonant frequencies and high temperatures, ensuring efficient engine operation.
Implementation Method 1
The abradable material is designed to rub and wear away when contacted by the fan blades
Implementation Method 2
maintaining a close fit and reducing the risk of resonant frequencies through vibration dampening properties
Data Source
AI summary
A method for preparing an abradable panel for a rub strip of a fan case of a gas turbine engine includes forming an abradable material into a plurality of panels each comprising an abradable structure; curing the abradable material in the plurality of panels; and installing the plurality of panels into the fan case. The panels can be cured and assembled into a fully assembled rubstrip, and then the assembled rubstrip can be installed into the fan case.