Dual Membrane Nitrogen System for Aircraft Fuel Blanketing
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Solution Overview
Problem
Existing membrane separation systems for generating nitrogen-enriched air face challenges in achieving a balance between selectivity and permeance, leading to either slow production rates with highly selective membranes or low enrichment with higher permeance membranes, which are not suitable for space- and weight-constrained applications like aircraft fuel tanks.
Innovation Solution
A multiple-module system using two gas separation membranes with specific selectivity and permeance characteristics, where the first membrane has lower selectivity but higher oxygen permeance than the second, allowing for efficient nitrogen enrichment in a compact, energy-efficient manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a very selective membrane is used to obtain highly N2-enriched air at a specified volumetric rate, then the enrichment quality is improved, but the permeance of the fast-migrating component is relatively low such that production rate is slower than desired
Solution Approach 1:
The single membrane separation process is segmented into multiple stages with different membrane types. The first stage uses a membrane with high selectivity and low permeance for high enrichment, while the second stage uses a membrane with lower selectivity but high permeance for high production rate. This segmentation allows each membrane to be optimized for its specific function, resolving the contradiction between enrichment quality and production rate.
2Productivity
If the working area of the membrane is increased to overcome low permeance, then the production rate is improved, but the size and weight of the system increase which is unacceptable for mobile end use applications
Solution Approach 1:
Instead of using one large membrane area, the system segments the separation function across two smaller membrane units with different characteristics. This reduces the total system size and weight while maintaining high production rate through the high-permeance membrane in the second stage.
Solution Approach 2:
The invention changes the parameters (selectivity and permeance) of the membrane material to achieve high production rate without increasing size. By selecting a membrane with optimized parameters for the second stage, high permeance is achieved, allowing compact system design.
3Volume of moving object
If smaller membranes with higher permeance are used, then the system size is reduced, but the enrichment per separation step is relatively low requiring multiple steps which increases equipment weight and complexity
Solution Approach 1:
The separation process is segmented into two stages with complementary membrane characteristics. The first stage membrane provides high enrichment with moderate size, while the second stage membrane provides high permeance with small size. The segmentation allows each component to be compact while achieving both high enrichment and high production rate overall.
4Manufacturing precision
If a train of separator steps or stages is utilized to increase enrichment in successive steps, then the enrichment quality is improved, but many steps or stages and auxiliary equipment such as compressors with associated power supplies are needed which increases weight and space
Solution Approach 1:
The system uses exactly two membrane separation stages with different membrane characteristics, providing a simple segmented approach that achieves high enrichment without requiring multiple complex stages. Each stage is self-contained and can operate independently, reducing auxiliary equipment needs.
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 system effectively generates nitrogen-enriched air with high concentration and flow rate, suitable for mobile and remote applications like aircraft fuel tank blanketing, while minimizing equipment weight and size.
Implementation Method 1
selectively gas permeable membranes are useful for separating components of gas mixtures
Implementation Method 2
the permeability of the faster permeating component
Data Source
AI summary
A system for providing nitrogen enriched air (NEA) from ambient air uses at least two gas separation membranes that are selectively gas permeable for oxygen and nitrogen. The oxygen/nitrogen selectivity and oxygen permeance of two of the membranes are different such that (1) the selectivity of first membrane is less than the second membrane and the oxygen permeance of first membrane is greater than the second membrane, or (2) the selectivity of first membrane is greater than the second membrane and the oxygen permeance of first membrane is less than the second membrane. The system is very compact, is energy efficient, and highly effective for generating NEA. It is ideally suited for mobile, remote and specialized end use applications, such as automotive vehicles, marine vessels, off-shore platform fuel storage and especially for supplying NEA to blanket ullage of onboard aircraft fuel storage tanks.