Double-Wall Turbomachine Heat Exchanger Header for Thermal Fatigue
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Solution Overview
Problem
Existing heat exchangers in aircraft turbomachines suffer from thermal fatigue and mechanical stress issues at the junctions between headers and the heat exchanger body, leading to cracks and reduced service life due to substantial thermal loads and thermal transients.
Innovation Solution
A heat exchanger device with a double wall configuration in the upstream hot-fluid header, incorporating a peripheral cavity for a secondary flow of a colder fluid to cool the header walls, reducing thermal gradients and mechanical stress, and optionally using flexible sections to absorb thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single wall header configuration is used, then the device complexity is low, but thermal fatigue and mechanical stress cause cracks and reduced service life
Solution Approach 1:
The header wall is segmented into an inner wall and an outer wall, creating a double-wall structure with a peripheral cavity between them. This segmentation allows the cold fluid to flow through the cavity and cool the outer wall, reducing thermal gradients and preventing thermal fatigue cracks while extending service life.
2Strength
If headers are made thicker to resist thermal stress, then mechanical strength improves, but weight and volume increase
Solution Approach 1:
A cold fluid flow is introduced as an intermediary cooling medium in the peripheral cavity between the inner and outer walls. This mediator actively removes heat from the outer wall, reducing thermal stress and allowing the use of thinner, lighter wall sections while maintaining adequate mechanical strength.
3Stability of the object's composition
If thermal gradients in headers are reduced, then thermal fatigue decreases, but additional cooling structures are required
Solution Approach 1:
The cooling function is merged into the header structure itself by creating a double-wall configuration where the peripheral cavity serves dual purposes: structural support and thermal management. The cold fluid flow path is integrated with the header geometry, combining structural and thermal functions in a unified design.
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 double wall configuration effectively reduces thermal fatigue and mechanical stress, minimizing crack formation and extending the service life of the heat exchanger by maintaining lower temperature variations and improving mechanical strength.
Implementation Method 1
at least the upstream hot-fluid header comprising a double wall forming a peripheral cavity surrounding a main cavity configured to receive a main flow of the first fluid, the peripheral cavity being configured to receive a secondary flow of the first fluid or of the second fluid
Data Source
AI summary
A device including a heat exchanger body, an upstream hot-fluid header attached to the heat exchanger body and configured to collect a first fluid at a first temperature and to feed it to the heat exchanger body, an upstream cold-fluid header attached to the heat exchanger body and configured to collect a second fluid at a second temperature lower than the first temperature and to feed it to the heat exchanger body, at least the upstream hot-fluid header including a double wall forming a peripheral cavity surrounding a main cavity configured to receive a main flow of the first fluid, the peripheral cavity being configured to receive a secondary flow of the first fluid or of the second fluid.