Aircraft Fuel-Line Nitrogen Inerting for Hydrogen Refuelling
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Solution Overview
Problem
Traditional refuelling technologies for kerosene are not suitable for hydrogen refuelling due to the need for cryogenic storage and the highly flammable nature of hydrogen, which poses a risk of ignition during leaks.
Innovation Solution
An apparatus and method that utilize an inert gas supply, such as nitrogen, generated on the aircraft to inert areas around the refuelling/defuelling process, reducing the risk of hydrogen ignition by flushing out combustible elements and maintaining a nitrogen-rich environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional kerosene refuelling technology is used for hydrogen refuelling, then the existing infrastructure can be utilized, but the system cannot withstand the low temperature and high flammability of hydrogen
Solution Approach 1:
The system is divided into separate functional components: a dedicated hydrogen fuel line with insulation for cryogenic transport, and a separate inert gas supply system. This segmentation allows each component to be optimized for its specific function - the fuel line for low-temperature transport and the inert gas system for ignition prevention - rather than requiring the entire existing kerosene infrastructure to handle both temperature and flammability risks simultaneously.
Solution Approach 2:
An inert gas (such as nitrogen) is introduced as an intermediary substance between the hydrogen fuel and the atmospheric oxygen. This intermediary creates a protective atmosphere that prevents ignition of hydrogen leaks while allowing the refuelling operation to proceed using existing infrastructure. The inert gas acts as a buffer that mediates between the flammable hydrogen and the oxidizing atmosphere.
2Quantity of substance
If hydrogen is stored as liquid at atmospheric pressure, then storage efficiency is improved, but the temperature must be maintained at 20K or less which existing fuel lines cannot withstand
Solution Approach 1:
The hydrogen fuel line is provided with specialized insulation along its length to maintain cryogenic temperatures only in the regions where liquid hydrogen is present and being transported. This localized temperature maintenance allows the fuel line to deliver liquid hydrogen at 20K or less without requiring the entire fuel line system to be designed for continuous cryogenic service, making the solution more practical and cost-effective.
Solution Approach 2:
The system changes the temperature parameter of hydrogen from ambient to cryogenic (20K or less) only when necessary for liquid storage and transport. The inert gas supply system is activated during refuelling operations to compensate for the temperature-related risks, allowing the system to dynamically adjust parameters (temperature and atmosphere composition) to maintain safety while achieving high storage density.
3Ease of operation
If current safety measures for kerosene refuelling are used, then the existing safety protocols can be maintained, but they are inadequate for preventing ignition of hydrogen
Solution Approach 1:
The inert gas supply system is activated before hydrogen refuelling begins to pre-establish a protective atmosphere around the refuelling point and fuel line. This preliminary action ensures that when hydrogen is present, the ignitable atmosphere has already been displaced by inert gas, preventing ignition even if leaks occur during the refuelling operation. The system performs the safety preparation in advance rather than reacting to potential hazards.
Solution Approach 2:
The system replaces the ordinary atmospheric environment with an inert atmosphere composed primarily of nitrogen or other inert gases during hydrogen refuelling operations. This inert environment eliminates oxygen from the vicinity of hydrogen, making ignition impossible regardless of the presence of ignition sources. The inert atmosphere serves as a fundamental safety mechanism that goes beyond traditional kerosene safety measures.
4Reliability
If redundant safety provisions are implemented for hydrogen refuelling, then safety against ignition is improved, but the system complexity and availability requirements increase
Solution Approach 1:
The inert gas supply system is designed to serve multiple functions: it prevents ignition of hydrogen leaks during refuelling, flushes out residual hydrogen from the fuel line after refuelling, and can be used to inert the fuel storage area. By making the inert gas system multi-functional, the patent achieves high safety redundancy without proportionally increasing system complexity, as a single system performs multiple safety-critical tasks.
Solution Approach 2:
The inert gas supply operates continuously throughout the refuelling process and beyond, maintaining a protective atmosphere at all times when hydrogen is present or could be present. This continuous operation ensures that safety protection is never interrupted, providing redundant protection without requiring multiple separate safety systems that would need to be coordinated. The single continuous system is simpler than multiple intermittent systems.
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 mitigates the risk of hydrogen ignition during refuelling/defuelling operations by ensuring a nitrogen-rich environment, thereby enhancing safety and reliability of hydrogen refuelling processes.
Implementation Method 1
inert gas is pumped from the aircraft through the fuel line to flush out any combustible elements which may be present
Implementation Method 2
A kerosene fuel line does not have sufficient insulation to carry liquid hydrogen at this temperature
Data Source
AI summary
A fuel line terminating in a refuel connector is used to fuel or defuel an aircraft, for example with liquid hydrogen. A supply of nitrogen housed on an aircraft, for example a Nitrogen Generating System, is used in conjunction with a gas line to supply nitrogen into the fuel line, to flush out potentially combustible materials before liquid hydrogen is supplied through the fuel line. The aircraft supply of nitrogen is also used to supply inert gas, via a gas line, to the Ground Support Equipment refuelling or defuelling the aircraft. This can provide redundancy for the Ground Support Equipment's systems, and may allow the aircraft to operate at less well-equipped airports.