Aircraft Hydrogen Casing Inerting with Recirculated Nitrogen
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Solution Overview
Problem
Existing aircraft inerting systems for hydrogen-based systems are inefficient in space and weight usage, and rely on halon for fire suppression, which is environmentally problematic and unsuitable for smaller volumes.
Innovation Solution
An inerting system that recirculates inert gas within the hydrogen system casing, using sensors to monitor oxygen and hydrogen concentrations and control the flow of pure inert gas and recirculated fluid to maintain safe levels, reducing the need for external inert gas storage and eliminating the need for halon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen bottles or nitrogen generation system are used to supply inert gas, then the inerting function is ensured, but the space occupation and on-board weight increase
Solution Approach 1:
The system recirculates and reuses the inert gas atmosphere after it has performed its inerting function. The atmosphere is extracted from the casing, recirculated through the hydrogen system, and reused to maintain inert conditions, thereby eliminating the need for continuous fresh nitrogen supply and reducing the size of nitrogen storage bottles or generation systems.
Solution Approach 2:
The system uses its own exhaust atmosphere to perform the inerting function again. By recirculating the gas that has already been inside the casing, the system makes the atmosphere serve dual purposes: initial inerting and continuous maintenance of inert conditions, reducing dependency on external nitrogen sources.
2Reliability
If nitrogen bottles or nitrogen generation system are used to supply inert gas, then the inerting function is ensured, but the space occupation increases
Solution Approach 1:
The system recirculates and reuses the inert gas atmosphere after it has performed its inerting function. The atmosphere is extracted from the casing, recirculated through the hydrogen system, and reused to maintain inert conditions, thereby eliminating the need for continuous fresh nitrogen supply and reducing the size of nitrogen storage bottles or generation systems.
3Reliability
If halon is used as fire extinguishing agent, then fire suppression capability is provided, but environmental harm occurs and the solution is unsuitable for small volumes
Solution Approach 1:
The system converts the potentially harmful recirculated atmosphere (which could contain leaked hydrogen) into a beneficial fire suppression mechanism. By monitoring and controlling the recirculated gas composition, the system ensures that hydrogen concentrations remain below flammable limits, thereby using the atmosphere itself to prevent combustion rather than requiring separate fire suppression agents.
Solution Approach 2:
The system maintains a permanently inert atmosphere through continuous recirculation and monitoring. By keeping hydrogen concentrations below 4% (the lower flammable limit) through controlled recirculation, the system creates an inherently fire-safe environment that eliminates the need for halon or other fire suppressants.
4Reliability
If nominal rate of nitrogen circulation is used based on worst case scenario, then safety limits are ensured, but the system efficiency decreases
Solution Approach 1:
The system transitions from static nominal circulation to dynamic adaptive recirculation. The recirculation rate is continuously adjusted based on real-time hydrogen concentration measurements and leak detection, allowing the system to operate at minimum necessary rates during normal conditions and increase recirculation only when needed, thereby optimizing efficiency while maintaining safety.
Solution Approach 2:
The system implements continuous feedback control by monitoring hydrogen concentrations and adjusting recirculation rates accordingly. Sensors detect hydrogen levels, and the control system modulates the recirculation pump speed to maintain safe concentrations, avoiding unnecessary high-rate circulation during low-risk periods and ensuring rapid response when leaks are detected.
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 system reduces the amount of inert gas required, minimizing space and weight while effectively preventing fires by maintaining safe oxygen and hydrogen concentrations, and quickly detecting and extinguishing flammable mixtures.
Implementation Method 1
a fluid recirculation system configured to recirculate part of the fluid located inside the casing to the inlet conduct for supplying the recirculated fluid mixed with the pure inert gas to the inside of the casing
Implementation Method 2
sensing means configured to measure the concentration of oxygen and the concentration of hydrogen of a fluid located inside the casing
Implementation Method 3
The present invention provides a solution for the aforementioned problems, with an inerting system according to one or more embodiments described herein... configured to independently control at least the outlet valve and the fluid recirculation system based on the concentration of oxygen and the concentration of hydrogen inside the casing
Data Source
AI summary
An inerting system for an aircraft and a method of inerting a hydrogen system in an aircraft. Also an aircraft with such an inert system. In the inerting system, a part of an inerting gas that has already been supplied to the casing of the hydrogen system is mixed with pure inerting gas through a fluid recirculation system.