Aluminium Gearbox Coating for Thermal Protection
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Solution Overview
Problem
Turbine engine accessory gearboxes face challenges in reducing weight while maintaining resistance to high thermal stress and fire exposure, as traditional lightweight materials and thin boxes struggle to meet stringent thermal resistance standards.
Innovation Solution
A multi-layer coating system comprising an epoxy curing polyamides primer layer, an intumescent material layer, and a polyurethane enamel hardened isocyanate top coat is applied to an aluminium alloy wall, providing thermal protection and corrosion resistance, allowing for a lightweight yet robust gearbox design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the box is made with low thickness and/or aluminium alloy to reduce weight, then weight is reduced, but thermal resistance capability deteriorates
Solution Approach 1:
The patent applies a multi-layer composite coating system on the aluminium alloy box wall. The coating comprises: (i) a primer layer for adhesion and corrosion protection, (ii) an intermediate intumescent layer for thermal insulation that expands when exposed to fire, and (iii) a top protective layer for enhanced durability. This composite structure provides sufficient thermal resistance at 1,100°C for 15 minutes while maintaining the lightweight aluminium alloy substrate, thus resolving the contradiction between weight reduction and thermal resistance.
2Weight of moving object
If the box thickness is reduced to reduce weight, then weight is reduced, but structural strength deteriorates
Solution Approach 1:
The multi-layer coating system acts as a protective composite structure on the thin aluminium alloy wall. The primer layer ensures strong adhesion to the substrate, the intumescent intermediate layer provides thermal insulation and structural support during fire exposure, and the top layer enhances overall durability. This composite approach compensates for the reduced structural strength of the thin-walled box, maintaining integrity under thermal and mechanical loads.
3Temperature
If a multi-layer coating system is applied to protect against thermal stress, then thermal resistance is improved, but device complexity increases
Solution Approach 1:
The protective coating is segmented into three distinct functional layers: a primer layer for adhesion and corrosion protection, an intermediate intumescent layer for thermal insulation, and a top protective layer for enhanced durability. Each layer performs a specific function, allowing the system to achieve comprehensive thermal protection while maintaining a structured and manageable complexity through clear functional segmentation.
4Weight of moving object
If aluminium alloy is used to reduce weight, then weight is reduced, but resistance to fire exposition deteriorates
Solution Approach 1:
The patent combines lightweight aluminium alloy substrate with a tri-layer protective coating system. The coating includes a primer layer for adhesion, an intumescent intermediate layer that expands to form an insulating barrier when exposed to fire, and a top protective layer for enhanced durability. This composite structure enables the aluminium alloy box to withstand fire exposure at 1,100°C for 15 minutes while maintaining its weight advantage.
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 coating system effectively protects the gearbox from thermal stress and corrosion, enabling it to withstand extended fire exposure up to 1,100°C for 15 minutes while maintaining a low weight and ensuring proper adhesion during operational vibrations.
Implementation Method 1
a second layer of an intumescent material, covering the first layer
Data Source
Figure 1
AI summary
The invention relates to a turbine engine member, such as an accessory gearbox for example, comprising at least one wall (1) made of an aluminium alloy, characterised in that said wall (1) is coated with a set of layers comprising: - a first layer (3) of a primer layer covering said wall, - a second layer (4) of an intumescent layer covering the first layer, - a third top coat (5), covering the second layer.