Aircraft Fuel Vent System Dilution Mechanism
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Solution Overview
Problem
Aircraft fuel systems face challenges in safely venting flammable gases from fuel tanks during fuelling, as direct venting can pose safety risks due to the potential for ignition when vented gases mix with atmospheric oxygen.
Innovation Solution
A vent system that incorporates a conduit with a mixer fluid, such as air, which is introduced upstream of the conduit outlet to dilute the tank fluid, reducing its flammability before expulsion into the atmosphere. This system includes a fluid mover to ensure adequate mixing and can optionally include features like thermally insulating materials and multiple openings for enhanced mixing and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tank fluid is vented directly to atmosphere, then pressure relief is achieved quickly, but flammability risk increases
Solution Approach 1:
A mixer fluid (inert gas or air) is introduced as an intermediary substance in the conduit to mix with the flammable tank fluid before discharge. This intermediary dilutes the fuel concentration and reduces flammability while allowing continuous pressure relief operation.
Solution Approach 2:
The concentration parameter of the flammable component in the vented gas is changed by mixing with mixer fluid. The fuel concentration in the conduit is reduced from high (flammable) to low (non-flammable or less flammable) levels before discharge to atmosphere.
2Object-affected harmful factors
If mixer fluid is introduced to dilute tank fluid, then flammability risk is reduced, but device complexity increases
Solution Approach 1:
The conduit serves multiple functions: it transports tank fluid, introduces and mixes mixer fluid, and discharges the diluted mixture. The fluid mover handles both mixing and flow control, reducing the need for separate components and minimizing overall system complexity.
Solution Approach 2:
The fluid mover utilizes the pressure differential created by fuel injection to drive the mixer fluid flow and mixing process. The system self-regulates the mixing ratio and flow rates without requiring external control mechanisms, simplifying the overall device structure.
3Ease of operation
If vent stack is located closer to personnel, then operational convenience improves, but safety risk increases
Solution Approach 1:
The mixer fluid acts as a protective intermediary between the vent stack and the personnel. By diluting the flammable tank fluid with inert mixer fluid in the conduit, the hazard level at the discharge point is reduced, allowing safer operation near personnel.
Solution Approach 2:
The potential harm of flammable gas discharge is converted into a benefit by using the mixer fluid introduction point as a controlled mixing zone. The harmful flammable gas is safely diluted and transformed into a low-hazard discharge, turning a safety risk into a controlled process.
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 vent system effectively reduces the flammability of vented gases by diluting them with a mixer fluid, thereby enhancing safety by minimizing the risk of ignition and allowing the vent stack to be located closer to personnel. Additionally, the system provides improved mixing and reduced operating noise.
Implementation Method 1
a fluid mover operable to cause a mixer fluid receivable in the conduit inlet to flow through the conduit towards the conduit outlet, thereby to mix the mixer fluid with the tank fluid in the conduit, upstream of the conduit outlet
Implementation Method 2
mixing of the mixer fluid and the tank fluid upstream of the conduit outlet dilutes the component of the tank fluid in the mixer fluid before it is expelled into the atmosphere
Implementation Method 3
a fluid mover operable to cause a mixer fluid receivable in the conduit inlet to flow through the conduit towards the conduit outlet
Data Source
AI summary
A vent system includes a vent stack for venting a tank fluid from a fuel tank that is external to the vent stack, during fuelling of the fuel tank. The vent stack includes a conduit including a conduit inlet and a conduit outlet, the conduit outlet opening to atmosphere external to the conduit. The vent stack also includes an opening into the conduit between the conduit inlet and the conduit outlet. The opening is fluidically connected, or connectable, to the fuel tank so the tank fluid from the fuel tank flows through the opening to the conduit outlet, in use. The vent stack also includes a fluid mover operable to cause a mixer fluid receivable in the conduit inlet to flow through the conduit towards the conduit outlet, thereby to mix the mixer fluid with the tank fluid in the conduit, upstream of the conduit outlet.