Nested Expansion Tank in Helicopter Fuel System
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Solution Overview
Problem
Rotary-wing aircraft face challenges in designing a fuel storage system that meets certification regulations for expansion volume without complicating the aircraft architecture or increasing maintenance complexity, as existing solutions either require complex venting systems or ancillary safety measures that are not compatible with the unique structural constraints of helicopters.
Innovation Solution
A fuel storage system where the expansion tank is integrated inside the main tank, connected by a single hose to the vent pipe, allowing fuel to flow by gravity into the tank only, thus avoiding inadvertent filling during normal operations and minimizing the center of gravity shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an expansion vessel is used as a separate component, then the expansion volume can be positioned above the filling orifice, but it becomes difficult to free space for the expansion tank and increases device complexity
Solution Approach 1:
The expansion tank is integrated inside the fuel tank, with the expansion tank forming an internal cavity within the main fuel tank structure. This nested arrangement allows the expansion volume to be positioned above the filling orifice while utilizing the existing tank space, avoiding the need for separate external expansion tank mounting space and reducing overall system complexity
Solution Approach 2:
The expansion tank and fuel tank are merged into a single integrated structure where the expansion tank is positioned inside the fuel tank. The bottom wall of the expansion tank forms the ceiling of the fuel tank, creating a unified structure that combines both functions (fuel storage and expansion accommodation) while reducing the number of separate components and simplifying the overall system architecture
2Reliability
If the expansion tank is positioned above the filling plane, then it avoids inadvertent filling, but this positioning constraint complicates integration on aircraft with tanks arranged within a boat structure
Solution Approach 1:
The expansion tank is nested inside the fuel tank structure, allowing it to be positioned in the upper region above the filling plane while utilizing the vertical space within the existing tank boundaries. This nested configuration ensures the expansion tank remains above the filling plane to prevent inadvertent filling during refueling operations
Solution Approach 2:
The filling orifice is positioned on the side wall of the fuel tank at a specific height, creating a localized filling zone. The expansion tank is positioned in the upper region above this filling zone, ensuring that during normal refueling operations, fuel enters only the fuel tank and does not reach the expansion tank, thereby preventing inadvertent filling
3Volume of moving object
If a separate expansion vessel is used, then the expansion volume is available, but ancillary safety means must be arranged to prevent fire risk, increasing device complexity
Solution Approach 1:
The expansion tank is merged with the fuel tank structure, eliminating the need for separate ancillary safety means that would be required for an external expansion vessel. The integrated structure allows for simplified fire safety arrangements since the expansion volume is contained within the protected fuel tank environment, reducing the need for additional fire prevention and containment systems
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 solution simplifies the system architecture, reduces production and installation costs, and ensures compliance with certification regulations by preventing the expansion tank from being filled during filling, while maintaining low fuel pressure and minimizing tank deformation risks.
Implementation Method 1
The expansion volume has the function of accommodating part of the fuel stored in the tanks in the event of expansion of this fuel
Implementation Method 2
the expansion tank being provided with emptying means for evacuating fuel from the expansion tank to the interior of the tank by gravity when the vehicle is in a normal position
Data Source
Figure 1~2
AI summary
The system (10) has a container (15) connected to a filling pipe (20). A surge tank (30) and a conduit i.e. drain (40), are arranged for communication with open air. The surge tank is arranged inside the container. The surge tank is connected to a hose (50) that is opened into the conduit perpendicularly to a filling orifice (21). The surge tank comprises a draining unit (35) for allowing passage of fuel by gravity to interior (INT) of the container.