Float-Actuated Shut-Off Valve for Fuel Return Systems
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Solution Overview
Problem
Traditional ecology fuel return systems in gas turbine engines experience instability, particularly during negative G events, leading to air leakage and potential engine operation disruptions due to air entrainment in the fuel system.
Innovation Solution
A shut-off valve system with a float that occludes and unoccludes the tank outlet based on fluid levels, combined with a flow restricting orifice or hydraulic fuse to control fluid communication between the tank and ejector pump, ensuring fluid flow direction aligns with positive G forces and restricting flow during negative G events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional ecology fuel return system is used, then fuel can be recovered and returned to the engine, but air leakage and air entrainment occur during negative G events causing system instability
Solution Approach 1:
A float valve is introduced as an intermediary component between the fuel tank and the ejector pump. The float valve responds to changes in fluid level and G-forces by occluding or unoccluding the tank outlet, thereby mediating the flow of fuel and preventing air from entering the system during negative G events. This intermediary mechanism resolves the contradiction by selectively controlling fluid communication based on operational conditions.
Solution Approach 2:
The float valve operates autonomously based on the fluid level and G-forces without requiring external control. When negative G forces occur, the float automatically occludes the outlet to prevent air leakage. When positive G forces occur, the float automatically unoccludes to allow fuel flow. This self-service mechanism eliminates air leakage while maintaining system stability during normal operation.
2Productivity
If the tank outlet remains open to allow fuel flow, then fuel can be pumped to the engine, but air can be drawn into the fuel system during negative G events
Solution Approach 1:
The tank outlet is made dynamic through the float valve mechanism that can occlude or unocclude based on real-time conditions. During negative G events, the float valve dynamically occludes the outlet to prevent air entrainment. During normal operation, it dynamically unoccludes to maintain fuel flow. This dynamic control resolves the contradiction by adapting the outlet state to operational requirements.
Solution Approach 2:
The system changes the flow parameter (open/closed state) based on G-forces and fluid level. The float valve detects changes in these parameters and accordingly occludes or unoccludes the tank outlet. This parameter-based control allows the system to maintain high productivity during normal operation while preventing air entrainment during negative G events.
3Object-affected harmful factors
If a flow restricting orifice is added to restrict fluid communication, then air flow is reduced during negative G events, but flow restriction occurs during normal operation
Solution Approach 1:
The flow restriction is made dynamic through the float valve that occludes or unoccludes the tank outlet based on conditions. During negative G events, the float valve dynamically occludes to restrict air flow. During normal operation, it dynamically unoccludes to maintain full fuel flow. This dynamic approach resolves the contradiction by applying restriction only when necessary.
Solution Approach 2:
The float valve performs periodic occlusion and unocclusion actions based on the oscillating G-forces during aircraft maneuvers. During negative G phases, it occludes to restrict air flow. During positive G phases, it unoccludes to maintain fuel flow. This periodic action resolves the contradiction by alternating between restriction and full flow based on operational phases.
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 solution effectively reduces air ingestion into the fuel system during negative G events, minimizing fuel coking, plugging of fuel injectors, and ensuring stable engine operation by maintaining a sufficient fluid level and preventing air entrainment.
Implementation Method 1
A float within the tank occludes the tank outlet at a first fluid level under positive G forces and unoccludes the tank outlet at a second fluid level under positive G forces
Implementation Method 2
A flow restricting orifice downstream of the float and the tank outlet to restrict fluid communication between the tank outlet and an ejector pump
Implementation Method 3
A hydraulic fuse can be in an ejector flow path defined between the tank outlet and an inlet of the ejector pump
Implementation Method 4
An ejector pump can be in fluid communication with the outlet of the tank to pump fuel from the tank to a fuel pump inlet of an engine
Data Source
AI summary
A shut-off valve system includes a tank having an inlet and an outlet with a flow path defined therebetween. A float within the tank occludes the tank outlet at a first fluid level under positive G forces and unoccludes the tank outlet at a second fluid level under positive G forces. A flow restricting orifice and/or a hydraulic fuse is downstream of float and tank outlet to restrict fluid communication between tank outlet and an ejector pump. A method for restricting flow in an ecology fuel return system includes recovering fuel from engine components, communicating the fuel to an inlet of a fuel tank, pumping the fuel from an outlet of fuel tank to an inlet of an engine when a float within tank unoccludes the outlet of the fuel tank, and restricting fluid flow from tank outlet to an ejector pump with a flow restricting orifice and/or a hydraulic fuse.