Aircraft Fuel Vent Line Architecture for Cross-Flow Prevention
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Solution Overview
Problem
Aircraft fuel tank venting systems face challenges in minimizing the introduction of atmospheric air into the ullage space, particularly in center fuel tanks, which increases oxygen concentration and combustion risk due to pressure differences and cross-venting conditions, leading to potential contamination and flammability issues.
Innovation Solution
A fuel tank venting system with a main vent line providing linear flow and branch vent lines extending from it to the center fuel tank, designed to minimize atmospheric air flow through the center tank ullage, using a symmetrical architecture that limits pressure loss and prevents cross-contamination without adding moving parts or complexity, ensuring dual redundancy and maintaining ullage inertness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If cross-venting is used to accommodate pressure changes during flight, then pressure equilibrium is maintained, but atmospheric air enters the ullage space and increases oxygen concentration
Solution Approach 1:
The venting system is segmented into separate pathways: a main vent line that provides a direct linear flow path bypassing the center tank ullage, and branch vent lines that connect to the center tank. This segmentation allows pressure equalization to occur through the main vent line without forcing air through the center tank ullage, thereby maintaining pressure equilibrium while preventing oxygen enrichment
Solution Approach 2:
The main vent line acts as an intermediary pathway between the center tank and the atmosphere. Instead of allowing air to flow directly through the center tank ullage (which would increase oxygen concentration), the main vent line provides a alternative route that mediates the pressure equalization process, allowing air to bypass the ullage space entirely
2Object-affected harmful factors
If a mixing chamber with partition is used to prevent cross-flow, then continuous flow between sides is minimized, but system complexity increases
Solution Approach 1:
The invention extracts the problematic mixing chamber with partition from the system and replaces it with a simpler main vent line that provides a direct linear flow path. By taking out the complex mixing chamber design and using instead a straightforward vent line configuration with branches, the system achieves cross-flow prevention without the added complexity of partitions and mixing chambers
3Shape
If vent openings are provided at opposite ends of main vent line, then linear flow path is established, but pressure differential between sides must be managed
Solution Approach 1:
The venting system is designed to dynamically respond to pressure differentials between the two sides of the aircraft. The main vent line with vent openings at opposite ends creates a balanced configuration where air flow automatically adjusts based on the pressure differential, flowing from the higher pressure side to the lower pressure side through the linear path, thereby managing pressure differences without requiring active control
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 system effectively reduces the risk of flammability and explosion by minimizing atmospheric air flow through the center tank ullage, maintaining ullage inertness, and allowing for pressure differential relief without increasing weight or complexity, thus enhancing safety and efficiency.
Implementation Method 1
The main vent line forms a linear flow path for fluid, generally air, flowing between opposite ends of the vent line
Implementation Method 2
The fuel tanks generally are vented to the atmosphere to accommodate pressure changes with altitude during flight, thereby reducing the required strength, and thus weight, of the fuel tanks
Data Source
AI summary
A venting system (10) in an aircraft (12), where the aircraft (12) is substantially symmetrical about a midline (14), has a pair of wings (16 and 18) extending outwardly on respective sides of the midline (14), a center fuel tank (20), a surge tank (22 and 24) at outer ends of each wing (16 and 18), and optionally one or more wing fuel tanks (26 and 28) interposed between the center fuel tank (20) and the respective surge tank (22 or 24). The venting system (10) for the center fuel tank (20) includes a main vent line (30) that extends across the midline (14) to vent openings (32 and 34) communicating with respective surge tanks (22 and 24). The main vent line (30) forms a linear flow path for fluid, generally air, flowing between opposite ends of the vent line (30). The venting system (10) also includes a branch vent line (36 and 38) extending from the main vent line (30) and opening on the center fuel tank (20). The branch line has at least one fuel tank opening (40 and 42) on each side of the midline (14).