Integral Thermally Insulated Fuel Bladder for Aircraft
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Solution Overview
Problem
Conventional fuel tank designs require rigid structures for thermal insulation, increasing aircraft weight and complexity due to the need for external insulation and accommodation of thermally induced stresses, which limits fuel capacity and efficiency.
Innovation Solution
An integral thermally insulated fuel bladder with a bladder wall composed of stratified refractory fabric and refractory metal, internally coated with a sealant, which thermally decouples cold fuel from the hot airframe structure, reducing thermal gradients and allowing for a smaller, lighter airframe structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a rigid fuel tank structure is used with external thermal insulation, then thermal insulation performance is improved, but structural weight and device complexity increase
Solution Approach 1:
The patent merges the fuel tank structure with the thermal insulation system into a single integrated bladder assembly. The bladder wall itself is constructed with insulating layers, eliminating the need for separate external insulation components and their supporting structures. This integration directly reduces device complexity while maintaining thermal insulation performance.
Solution Approach 2:
The bladder wall is constructed as a composite structure with multiple layers including refractory fabric, refractory metal, and sealant coating. This composite construction provides inherent thermal insulation properties within the bladder wall itself, eliminating the need for external insulation layers and reducing overall structural complexity.
2Temperature
If a rigid fuel tank structure is used with external thermal insulation, then thermal insulation performance is improved, but structural weight increases
Solution Approach 1:
By combining the fuel containment function with the thermal insulation function in a single integrated bladder assembly, the patent eliminates the need for separate rigid tank structures and external insulation layers. This merging reduces the total material volume and structural weight while maintaining effective thermal insulation.
Solution Approach 2:
The patent employs a flexible bladder wall construction that can conform to the airframe structure without requiring rigid supporting frameworks. This flexibility allows the use of thinner, lighter materials while maintaining structural integrity and thermal insulation performance, thereby reducing overall weight.
3Device complexity
If cold fuel is disposed in a hot airframe structure without thermal decoupling, then structural simplicity is maintained, but thermally induced stresses increase requiring larger airframe structure
Solution Approach 1:
The bladder assembly serves as a thermal intermediary between the hot airframe structure and the cold fuel. The bladder wall with its insulating layers and thermal barrier properties decouples the thermal interaction, protecting the fuel from excessive heat while allowing the airframe to maintain its structural simplicity without requiring oversized dimensions to accommodate thermal stresses.
4Strength
If conventional rigid fuel tanks are used, then structural strength is maintained, but ability to withstand thermal loads and stresses is reduced
Solution Approach 1:
The bladder wall is constructed from composite materials including refractory fabric and refractory metal layers that are specifically selected for their high-temperature resistance and thermal stability. These materials maintain their structural integrity and strength properties under extreme thermal loading conditions, making the bladder more reliable than conventional rigid tanks in withstanding thermal stresses.
Solution Approach 2:
The patent changes the material parameters of the bladder wall to include high-temperature resistant refractory materials with stable mechanical properties at elevated temperatures. This parameter change enables the bladder to maintain both strength and reliability under thermal loads that would cause conventional materials to fail or deform.
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 effectively reduces thermally induced stresses in the airframe, enabling a lighter and more volumetrically efficient aircraft by maintaining an internal surface temperature that prevents fuel boiling even at external temperatures exceeding 500° F, while withstanding thermal loads and stresses better than conventional rigid fuel tanks.
Implementation Method 1
The fuel bladder comprises a bladder wall having stratified refractory fabric and refractory metal... configured to maintain an internal surface temperature sufficient to prevent boiling of a fuel when exposed to an external surface temperature of at least 500° F
Data Source
AI summary
A method and apparatus for thermally decoupling fuel from an airframe structure is provided. In some aspects, an apparatus may include a bladder wall having stratified refractory fabric and refractory metal, and a sealant coating an internal surface of the bladder wall. The bladder wall may be configured to maintain an internal surface temperature of 300° F. or less when exposed to an external surface temperature of at least 500° F.