Reticulated Polyurethane Foam Ignition Mitigation in Aircraft Fuel Tanks
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Solution Overview
Problem
Current methods for preventing fuel ignition and explosion in aircraft fuel tanks are either expensive or prone to system failures, and there is a need for a passive, reliable solution that can effectively mitigate ignition sources in compliance with regulatory requirements such as SFAR No. 88.
Innovation Solution
The use of reticulated polyurethane foam (RPF) is proposed to fill the internal space of fuel tanks, providing a passive means to mitigate ignition by acting as a heat sink, mechanically interfering with combustion waves, and entrapping flammable vapors, thus reducing the risk of explosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active inerting systems (Halon 1301 or nitrogen) are used to prevent fuel ignition, then fuel tank safety is improved, but system complexity and cost increase
Solution Approach 1:
The patent removes the complex active inerting system (gas delivery mechanisms, sensors, control systems) and extracts only the essential safety function by filling the fuel tank with inert granular material. This eliminates the need for active components while maintaining fuel ignition prevention through passive inerting.
Solution Approach 2:
The inert granular material performs the safety function autonomously without requiring external control systems, power sources, or active intervention. The material naturally absorbs fuel vapors and prevents ignition through its physical and chemical properties, making the system self-regulating and fail-safe.
2Reliability
If reactive explosion suppression systems are used to mitigate fuel ignition, then fuel tank safety is improved, but system complexity and potential failure points increase
Solution Approach 1:
The patent applies preliminary action by pre-filling the fuel tank with inert granular material before any ignition event can occur. This proactive measure ensures that when fuel vapors are generated, they are immediately absorbed and neutralized by the inert material, preventing explosion propagation without requiring any reactive response systems.
3Reliability
If electronic ignition suppression systems are used, then fuel tank safety is improved, but cost and system failure risk increase
Solution Approach 1:
The patent replaces expensive electronic systems with inexpensive inert granular material that can be easily replenished if needed. The material serves its safety function throughout the system's operational life and can be replaced as a simple maintenance task, eliminating the need for costly electronic components and their associated failure risks.
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
RPF effectively prevents hazardous ignition in aircraft fuel tanks, meeting all three phases of compliance requirements, is less likely to experience system failures, and is more cost-effective than electronic solutions, while also offering additional benefits like slosh attenuation and foreign object debris filtration.
Implementation Method 1
acting as a heat sink
Implementation Method 2
mechanically interfering with combustion waves
Implementation Method 3
entrapping flammable vapors
Data Source
AI summary
The use of flexible foam material to provide ignition mitigation in fuel tanks is described. In one example, a system for ignition mitigation includes a number of foam blocks, wherein each foam block is pre-cut from a flexible foam material. Each foam block can have a unique profile corresponding to inner surfaces of a fuel tank at a particular sector within a compartment of the fuel tank. In other aspects, one or more of the foam blocks can include one or more upper cutouts to provide clearance for upper stiffeners in the fuel tank, one or more lower cutouts to provide clearance for lower stiffeners in the fuel tank, and one or more arcuate cutouts to provide clearance for a tank fuel pump. The foam blocks can be arranged in a stack corresponding to a sequential installation at respective sectors within the compartment of the fuel tank.