Tilted-Edge Damping Strips for Aircraft Fan Casing Liquid Discharge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing vibration damping strips in aircraft turbomachine fan casings are prone to degradation and reduced efficiency due to prolonged contact with liquids like oil and kerosene, and previous solutions such as transverse grooves compromise their damping ability and stiffness.
Innovation Solution
The damping strips are designed with tilted edges to allow liquids to flow by gravity towards their ends, preventing prolonged contact and degradation, while maintaining high damping performance, with edges oriented to ensure liquid discharge towards the casing's drain, and are made of elastomeric material for effective vibration damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vibration damping strips are made of elastomeric material to effectively damp vibrations, then damping performance is improved, but the strips are sensitive to contact with liquids like oil and kerosene, causing material degradation and efficiency loss
Solution Approach 1:
The edge of the damping strip is segmented into multiple inclined surfaces (first inclined surface, second inclined surface, etc.) that guide liquid flow. This segmentation allows the edge to simultaneously maintain contact with the casing for damping while directing liquids away from the strip body through gravity-driven flow paths along the inclined surfaces.
Solution Approach 2:
Instead of trying to prevent liquid contact through barriers or repelling surfaces, the invention inverts the approach by using gravity and inclined surfaces to actively channel liquids away from the strip. The liquid flow direction is reversed from what would naturally pool on a flat surface, ensuring liquids are diverted before they can penetrate or degrade the elastomeric material.
2Object-affected harmful factors
If transverse grooves are made in the strips to discharge liquids, then liquid discharge is improved, but the grooves embrittle the strips and decrease contact area with the casing, reducing damping efficiency
Solution Approach 1:
The harmful function of liquid retention is extracted from the damping strip by adding a dedicated liquid discharge feature (inclined surfaces) that separates the liquid management function from the damping function. The inclined surfaces act as a separate mechanism that removes liquids without compromising the strip's structural integrity or contact area.
Solution Approach 2:
The liquid discharge mechanism is implemented by modifying the edge geometry in a new dimension - adding inclined surfaces that create a three-dimensional flow path. This dimensional change allows liquids to be directed away from the strip without requiring transverse grooves that would reduce contact area or embrittle the material.
3Object-affected harmful factors
If transverse grooves are made in the strips to discharge liquids, then liquid discharge is improved, but the grooves decrease the stiffness of the strips when compressed, impacting damping ability
Solution Approach 1:
The edge is segmented into multiple inclined surfaces that collectively provide liquid discharge functionality. This segmentation allows the discharge function to be distributed along the edge without requiring deep transverse grooves that would compromise the strip's cross-sectional integrity and stiffness.
Solution Approach 2:
The liquid discharge feature is localized to the edge region of the strip, where it does not affect the overall structural stiffness. The inclined surfaces are confined to a small portion of the strip, preserving the bulk material's mechanical properties and damping capability while providing effective liquid management at the critical edge location.
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 solution effectively prevents liquid retention on the strips, maintaining high damping performance over time and ensuring efficient vibration reduction without compromising the strips' stiffness or contact area.
Implementation Method 1
at least one of the two opposite edges of at least one of the damping strips is shaped such that liquid present in this edge can flow by gravity towards either or both of its upstream and downstream ends
Implementation Method 2
These strips, usually made of elastomeric material, have the advantage of significantly damping the vibratory levels measured in panel testing, when these strips are compressed
Data Source
AI summary
An acoustic protection device for a fan casing of an aircraft turbomachine, including an acoustic protection panel forming a ferrule sector centered on a center axis, and one or more vibration damping strips pressed on a first side to an external surface of the panel and on a second side to an internal surface of the casing, each damping strip including two opposite edges each including an upstream end and a downstream end spaced from each other along a direction of the center axis. At least one of both opposite edges of at least one of the damping strips is shaped such that liquid present on this edge can flow by gravity towards either or both of its upstream and downstream ends.