Variable Sweep Gas Module for Aircraft Fuel Tank Inerting
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Solution Overview
Problem
Conventional gas-separation membrane modules face inefficiencies due to uneven oxygen concentration gradients along the module length, requiring optimal adjustment of the sweep stream to maintain partial pressure differentials and achieve desired nitrogen purity levels, especially in applications like aircraft fuel tank inerting where pressure and purity requirements change during flight.
Innovation Solution
A gas-separation module with a variable sweep gas system, where the amount and location of sweep gas introduction along the module length can be adjusted using a rotatable slotted sleeve within a perforated conduit, optimizing the sweep gas profile to match changing oxygen concentrations and pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform sweep stream is applied along the entire module length, then the permeate gas removal is improved, but the nitrogen purity and productivity are reduced due to excessive oxygen dilution in regions where oxygen concentration is already low
Solution Approach 1:
The sweep stream distribution is made non-uniform by introducing sweep gas at selected locations along the module length rather than uniformly along the entire length. The number and positioning of sweep gas introduction points are optimized based on the local oxygen concentration profile, applying sweep only where oxygen accumulation occurs (typically the first third to one-half of the module length from the feed end), thereby avoiding excessive dilution in regions where oxygen concentration is already low and maintaining both effective permeate removal and high nitrogen productivity
2Reliability
If the sweep gas flow rate is increased to maintain partial pressure differential, then the oxygen concentration control is improved, but the energy consumption and feed air requirements increase
Solution Approach 1:
Sweep gas is introduced at specific locations along the module length where oxygen concentration exceeds the target level, rather than applying uniform sweep throughout. This localized approach maintains the necessary partial pressure differential for oxygen removal only where needed, avoiding unnecessary energy consumption and feed air requirements in regions where oxygen concentration is already within acceptable limits
Solution Approach 2:
Sweep gas is applied partially along the module length rather than excessively throughout the entire length. The sweep gas introduction is limited to the region where oxygen accumulation occurs (typically the first third to one-half of the module), providing just enough sweep action to maintain oxygen concentration control without the excessive energy penalty of uniform full-length sweeping
3Device complexity
If the module operates at fixed sweep gas configuration, then the device complexity is reduced, but the adaptability to changing flight conditions (pressure and purity requirements) is limited
Solution Approach 1:
The sweep gas distribution system is segmented into multiple discrete introduction points along the module length, each可控 independently through rotatable slotted sleeves. This segmentation allows the system to adapt to different flight conditions by adjusting which segments receive sweep gas and at what rates, providing versatility for different pressure and purity requirements while maintaining relatively simple individual component designs
Solution Approach 2:
The sweep gas distribution configuration is made dynamic through rotatable slotted sleeves that can be adjusted to change the number and positioning of active sweep gas introduction points along the module length. This dynamic adjustment capability allows the system to adapt to varying flight conditions (different altitudes, pressure requirements, and purity specifications) without requiring complex control systems or multiple fixed configurations
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
This design enhances nitrogen product flow and reduces high-pressure feed air requirements, allowing for efficient operation across varying flight conditions by dynamically controlling the sweep gas distribution, thereby optimizing module performance and ensuring safe oxygen levels in aircraft fuel tanks.
Implementation Method 1
A polymer used in air separation, for example, will pass oxygen and nitrogen at different rates. The gas that preferentially flows through the membrane wall is called the 'permeate' gas
Implementation Method 2
Gas permeates through the membrane due to the pressure differential between one side of the membrane and the other
Data Source
AI summary
A gas-separation module allows a sweep gas to be introduced at selectively variable locations, and in selectively varying amounts, along the length of the module. The sweep gas enters the module through a perforated conduit. A slotted sleeve, disposed within the conduit, selectively blocks and unblocks perforations in the conduit. Rotation of the sleeve causes slots to come into, or out of, registration with the perforations. The sleeve permits varying amounts of sweep gas to be introduced at different locations along the length of the module. Rotation of the sleeve changes the profile of introduction of sweep gas, and can be used to optimize the performance of the module for each of a set of different pressure conditions.