Cryogenic Pipe Assembly With Composite Outer Tube and Thermal Isolation
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Solution Overview
Problem
The integration of cryogenic fluid pipes into the primary structure of aerospace systems poses challenges due to material-dependent length changes, thermal insulation difficulties at fastening points, and the dual use of pipes for structural support and fluid conduction, which increases heat flow and complicates secure connections.
Innovation Solution
A pipe design comprising a fibre-reinforced polymer outer tube with a gas-proof inner tube and insulation layer, where the outer tube bears structural loads and the inner tube conducts cryogenic fluids, minimizing thermal expansion and heat ingress, with flanges for secure connections and thermal stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If pipes are integrated into the primary structure for structural support, then weight is reduced, but thermal expansion compensation becomes difficult
Solution Approach 1:
The pipe is divided into two separate tubes: an outer tube for structural support and an inner tube for fluid conduction. This segmentation allows each tube to be optimized for its specific function, with the outer tube providing structural integration and the inner tube handling thermal expansion independently through its own insulation and movement capability.
Solution Approach 2:
The inner tube is nested within the outer tube, creating a concentric arrangement where the inner tube can expand and contract independently while remaining constrained by the outer tube. This nested structure enables thermal expansion compensation without compromising the structural integration into the primary system.
2Strength
If pipes are used for structural support, then stiffness and stability are improved, but the number of connection points increases leading to augmented heat flow
Solution Approach 1:
The outer tube is made of fibre-reinforced polymer with different laminate structures in different regions: a first laminate in the centre region and a second laminate in the end region. This local quality variation optimizes structural stiffness where needed while minimizing thermal conductivity at connection points, thereby reducing heat flow into the cryogenic fluid.
Solution Approach 2:
The outer tube uses composite fibre-reinforced polymer materials with tailored laminate structures, combining different fibre orientations and material properties to achieve optimal balance between structural stiffness and thermal insulation performance at different locations along the tube.
3Temperature
If insulation is added to reduce heat flow, then thermal insulation is improved, but insulation at fastening points becomes difficult due to conductive connections
Solution Approach 1:
The pipe system is segmented into an outer structural tube and an inner fluid-conducting tube with insulation between them. This segmentation allows the insulation layer to be effectively placed in the thermal path while fastening points can be attached to the outer tube without compromising insulation, as the inner tube remains thermally isolated.
4Strength
If classical metal pipes are used, then structural integration is achieved, but material-dependent length changes require compensators
Solution Approach 1:
The outer tube uses fibre-reinforced polymer with specifically engineered laminate structures that provide low coefficient of thermal expansion in critical directions. By changing the material parameters and fibre orientation, the tube maintains dimensional stability under cryogenic temperature variations while still providing structural support.
Solution Approach 2:
The use of composite fibre-reinforced polymer materials allows tailoring of thermal expansion properties through laminate design, achieving low thermal expansion in the longitudinal direction while maintaining structural strength and stiffness for primary structure integration.
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 design allows for weight-saving, thermally stable, and structurally efficient integration of cryogenic fluid pipes into aerospace systems, reducing the need for compensators and enhancing durability through minimized thermal expansion and improved connection methods.
Implementation Method 1
an (thermal) insulation layer in-between
Implementation Method 2
a significant cooling of the pipes occurs during operation. This change in temperature between the state of assembling on the one hand and operating states on the other hand leads to large, material-dependent changes in length
Data Source
Figure 1~2b
Figure 3~4
AI summary
Disclosed is a pipe 100, 100', 1002' for conducting a cryogenic fluid. The pipe comprises a rigid outer tube 10, 10', 102' at least partially made of a fibre-reinforced polymer, a gas-proof inner tube 20, 20', 202' running within the outer tube 10, 10', 102', an insulation layer 30, 30', 302' arranged between the inner tube 20, 20', 202' and the outer tube 10, 10', 102', and at least one flange 40, 40', 402' formed at a respective end of the inner tube 20, 20', 202'. The at least one flange 40, 40', 402' connects the inner tube 20, 20', 202' with the outer tube 10, 10', 102' . Further disclosed are a pipe assembly 1000 comprising at least two such pipes 100, 100', 1002' which are connected or configured to be connected at a respective flange 40, 40', 402' thereof, and an aerospace system comprising at least one such pipe 100, 100', 1002'.