Multilayer Bleed Duct Structure for Lightweight High-Temperature Exhaust
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Solution Overview
Problem
Existing metal bleed air ducts for aircraft engines face issues with excessive weight, deformability, and weak points due to welding, and composite materials lose chemical and physical properties at high temperatures, making them unsuitable for high-temperature applications.
Innovation Solution
A multilayer tubular duct composed of an inner thermal insulating layer with carbon fiber fabric and ceramic-based matrix, an outer structural layer with carbon or glass fiber reinforcement, and an intermediate adhesive layer, manufactured using pre-impregnated materials to ensure structural integrity and thermal insulation without welds, reducing weight and maintaining performance at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal material is used for bleed air ducts, then structural strength and high temperature resistance are achieved, but weight becomes excessive
Solution Approach 1:
The patent applies composite materials consisting of carbon fiber fabric and ceramic-based matrix (such as cyanate ester, phenolic, or epoxy resin) to manufacture the bleed air duct. This composite structure provides both high structural strength and high temperature resistance while significantly reducing weight compared to traditional metal ducts. The carbon fiber reinforcement provides tensile strength while the ceramic matrix maintains dimensional stability at elevated temperatures.
Solution Approach 2:
The duct is manufactured as an integrated composite structure that segments the functional requirements into different material layers: the carbon fiber fabric provides structural strength, the ceramic-based matrix provides high temperature resistance, and the overall composite structure eliminates the need for separate insulation layers and welding joints, thereby reducing weight while maintaining structural integrity.
2Stability of the object's composition
If metal ducts are assembled by welding, then structural continuity is achieved, but welding points become weak points and starting points of fracture cracks
Solution Approach 1:
The composite material structure allows the duct to be manufactured as a seamless integrated component through resin transfer molding or similar processes. The ceramic-based matrix acts as a continuous binder that bonds the carbon fiber reinforcement continuously throughout the structure, eliminating discrete welding joints. This continuous composite structure maintains both structural continuity and high reliability by removing stress concentration points at weld interfaces.
3Weight of moving object
If pre-impregnated composite material is used, then weight is reduced, but chemical properties are lost at high temperature values
Solution Approach 1:
The patent changes the chemical parameters of the matrix material by selecting ceramic-based matrices (cyanate ester, phenolic, or epoxy resin) that are specifically formulated to maintain their chemical properties at high temperatures. These materials have been engineered to resist thermal degradation and maintain structural integrity at temperatures exceeding 200°C, thereby preserving both weight reduction benefits and high temperature resistance.
Solution Approach 2:
The specific combination of carbon fiber fabric with ceramic-based composite matrix creates a material system where the inorganic ceramic matrix provides high temperature stability while the organic resin system provides structural bonding. This composite formulation maintains chemical resistance at elevated temperatures while achieving significant weight reduction compared to metal alternatives.
4Weight of moving object
If composite material ducts are manufactured, then weight is reduced, but manufacturing complexity increases due to multiple layers and materials
Solution Approach 1:
The patent merges multiple functional requirements into a single integrated composite manufacturing process. The resin transfer molding process simultaneously cures the ceramic-based matrix and impregnates the carbon fiber fabric in one operation, creating the structural layer and thermal insulation layer as an integrated component. This eliminates the need for separate manufacturing steps for different layers, reducing overall manufacturing complexity despite the advanced material system.
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 provides a lightweight, structurally robust, and thermally insulated duct that maintains chemical and physical resistance at high temperatures, increasing the duct's useful life cycle and reducing weight compared to metallic ducts, while ensuring mechanical and thermal stability.
Implementation Method 1
an intermediate layer, positioned between the inner layer and the outer layer, to ensure a chemical/physical insulation between the two above-mentioned layers
Implementation Method 2
an intermediate layer, positioned between the inner layer and the outer layer, to ensure a chemical/physical insulation between the two above-mentioned layers
Implementation Method 3
the characteristic of having an inner thermal insulating layer resistant to the high operating temperature values of a Bleed Air Duct guarantees that the chemical/physical resistance of the surfaces in contact with the air coming out of the engines
Implementation Method 4
The presence of an outer layer configured to structurally resist the external mechanical stresses allows the tubular shape of the duct to be maintained even when it is subjected to considerable stress due to the high pressure of the fluids passing through the duct itself
Data Source
Figure 1~2
Figure 3a~5b
Figure 6~7a
AI summary
The invention relates to a multilayer bleed duct 100; 200 and its manufacturing method. The duct, configured to direct a flow of exhaust gases from an aircraft, comprises an inner thermal insulating layer 10 having a tubular surface which defines a passageway for the exhaust gases, comprises at least two edges 10a and 10b, substantially parallel to each other, superposing or at least partially superposing along a longitudinal direction of the tubular surface, an outer layer 30 made of fiber-reinforced composite material, an intermediate adhesive layer 20 positioned between the inner layer 10 and the outer layer 30.