Jet Engine Vane Conduction Structure for Lightning Protection
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Solution Overview
Problem
The outlet guide vanes in turbofan engines, made of carbon fiber reinforced plastics (CFRP), exhibit electric resistance that could lead to spark generation and Joule heat, posing a risk to the matrix resin during lightning strikes, as the resistance between the fan case and the core portion is several ohms, potentially causing damage.
Innovation Solution
An electric conduction structure is introduced, featuring a metal sheath covering the leading edge of the vane main body, an electrically conductive pad with a contact portion overlapping the sheath, and a washer portion for bolt insertion, connected via welds, spot-welds, solder, conductive paste, or crimping, establishing a low-resistance path between the fan case and the core portion, bypassing the CFRP vane main body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If outlet guide vanes are made of CFRP to reduce weight, then weight is reduced, but electric resistance increases to several ohms causing spark generation risk
Solution Approach 1:
The outlet guide vane is constructed as a composite structure combining CFRP for the vane body (weight reduction) with aluminum alloy sheaths and pads for electric conduction (reliability enhancement). This composite approach allows each material to perform its optimal function: CFRP provides lightweight structural integrity while aluminum components provide low-resistance electrical pathways for lightning protection.
2Reliability
If outlet guide vanes are made of aluminum alloys for low electric resistance, then electric conduction reliability is improved, but weight increases
Solution Approach 1:
Instead of making the entire outlet guide vane from aluminum alloy, the invention applies aluminum alloy sheaths and pads only at specific locations where electrical conduction is critical (leading edge and support structure connection points). This localized application of high-conductivity material minimizes weight increase while ensuring low-resistance pathways for lightning current dissipation.
3Strength
If electric current flows through CFRP outlet guide vanes, then structural support function is maintained, but Joule heat deteriorates the matrix resin
Solution Approach 1:
Aluminum alloy sheaths and pads serve as intermediary elements between the CFRP vane body and the support structure. These aluminum components create dedicated low-resistance electrical pathways that bypass the CFRP material, allowing lightning current to flow through the aluminum intermediaries rather than through the CFRP matrix resin, thereby preventing Joule heat generation and resin deterioration.
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
This configuration reduces electric resistance to several tens or hundreds of milliohms, minimizing the risk of spark generation and preventing deterioration of the CFRP matrix resin, while also preventing current flow through liners, thus ensuring safe and efficient electric current diversion.
Implementation Method 1
an electrically conductive pad of the metal comprising a contact portion so dimensioned as to have an overlap with an end of the sheath, and a washer portion into which a bolt for being tightened into the support structure is insertable
Implementation Method 2
one or more joints selected from the group of a weld, a spot-weld, a solder, a bond by an electrically conductive paste and a crimp establish connection between the end of the sheath and the contact portion
Implementation Method 3
In combination with the electric resistance up to several ohms, generated Joule heat could not be disregarded and might rather cause a risk of deteriorating the matrix resin of the CFRP
Data Source
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AI summary
An electric conduction structure for conducting and diverting electric current from a vane main body of an outlet guide vane into an exterior support structure is comprised of: a sheath of a metal covering a leading edge of the vane main body; and an electrically conductive pad of the metal comprising a contact portion so dimensioned as to have an overlap with an end of the sheath, and a washer portion into which a bolt for being tightened into the support structure is insertable, wherein one or more joints selected from the group of a weld, a spot-weld, a solder, a bond by an electrically conductive paste and a crimp establish connection between the end of the sheath and the contact portion.