Aircraft Fuel Tank Tie Assemblies for Hydrodynamic Ram Resistance
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Solution Overview
Problem
High-speed projectile impacts on liquid storage tanks cause hydrodynamic ram, leading to intense pressure pulses and potential catastrophic failure due to the inability of existing tank structures to sustain such impacts without damage.
Innovation Solution
The implementation of tie assemblies within the tank, comprising elongate members and attachment devices fixed to the tank walls, which exert inward forces to resist outward deformation and reduce hydrodynamic ram pressure, with the elongate members potentially made of wires or poly-paraphenylene terephthalamide, and strategically spaced to minimize volume occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tie assemblies are added to resist hydrodynamic ram pressure, then the tank's ability to withstand projectile impact is improved, but the device complexity increases
Solution Approach 1:
The tank is divided into multiple sections with tie assemblies strategically positioned at intervals along the tank length and circumference. This segmentation approach provides distributed reinforcement without requiring a completely complex structural redesign, as each tie assembly acts as an independent reinforcement element
Solution Approach 2:
Tie assemblies are pre-installed within the tank before liquid loading, positioned and tensioned to exert preliminary inward force on the tank wall. This preliminary action ensures the tank is already in a reinforced state before hydrodynamic ram pressure occurs, eliminating the need for complex active response systems
2Strength
If tie assemblies are installed within the tank, then structural integrity is improved, but the volume available for liquid storage is reduced
Solution Approach 1:
Tie assemblies utilize thin wire or cable elements that provide substantial structural reinforcement while occupying minimal volume. The flexible nature of these thin-film-like elements allows them to be positioned within the tank without significantly reducing the liquid storage volume, as they can conform to the tank geometry with minimal space requirement
Solution Approach 2:
The tie assemblies are designed to provide sufficient reinforcement with minimal volume occupancy (less than 5% of tank volume). This partial action approach uses just enough material to achieve the required structural integrity improvement without excessive volume consumption that would reduce liquid storage capacity
3Strength
If tie assemblies are closely spaced at tank edges, then resistance to hydrodynamic ram pressure is improved, but the number of components increases
Solution Approach 1:
Tie assemblies are closely spaced specifically at tank edges and ends where hydrodynamic ram pressure causes maximum stress and where the tank wall experiences greatest outward deformation. In these critical local regions, higher component density provides targeted reinforcement. In less critical central regions, spacing can be reduced, optimizing the balance between protection and component count
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 tie assemblies effectively reduce the likelihood of catastrophic failure by resisting outward deformation and hydrodynamic ram pressure, enhancing the tank's ability to withstand projectile impacts while occupying less than 5% of the tank's volume, thus improving the tank's structural integrity and reducing the risk of damage.
Implementation Method 1
A high speed projectile on impact with and penetration into a liquid containing tank generates very high pressure in the liquid. This phenomenon, known as hydrodynamic ram, typically includes the generation of shock waves and subsequent pressure pulses in the liquid.
Implementation Method 2
These pressures, combined with the penetration damage from the projectile, can cause damage to the tank structure and frequently are the cause of catastrophic failure of the tank. The hydrodynamic ram pressure pulses are intense but of short duration which propagate through the liquid in the tank.
Data Source
AI summary
A liquid storage tank, for example an aircraft fuel tank, having a tank wall enclosing a liquid storage space, and a tie assembly located at least partially within the liquid storage space. The tie assembly includes an elongate member, for example a wire or cable, and a plurality of attachment devices fixed to an inner surface of the tank wall. The elongate member includes a plurality of spaced part points along its length, each of the spaced apart points being fixed to a respective attachment device such that the tie assembly resists outward deformation of the tank wall.