Aircraft Fuel Control Bypass Valve for Rapid Overspeed Shutdown
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Solution Overview
Problem
The existing fuel control systems for aircraft engines have a response time that is longer than desirable for reducing fuel delivery during an overspeed protection shutdown request, as the control valves take time to cease fuel delivery to the combustion section.
Innovation Solution
A fuel control system incorporating a shutoff valve and a bypass valve, where the bypass valve is actuated to reduce fuel delivery to the aircraft engine by connecting the fourth bypass valve port to the fuel pump inlet, allowing the bypass valve spool to move from a closed to an open position, facilitating quicker closure of the shutoff valve by increasing the pressure differential and utilizing a damping orifice to stabilize the spool movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control valves are used to regulate fuel delivery in response to an overspeed protection shutdown request, then fuel delivery is reduced to the combustion section, but the response time is longer than desirable
Solution Approach 1:
The fuel control system is segmented into multiple independent valves: a metering valve for normal fuel flow regulation, a bypass valve for alternative fuel path control, and a shutoff valve for complete fuel delivery interruption. This segmentation allows the shutoff valve to rapidly close and stop fuel delivery independently, achieving fast response time for overspeed protection without interfering with normal metering operations
Solution Approach 2:
The bypass valve acts as an intermediary component that redirects fuel flow away from the shutoff valve when normal operation is required. During overspeed shutdown, the bypass valve closes to prevent fuel from bypassing the shutoff mechanism, ensuring complete and rapid fuel delivery cessation. This intermediary mechanism enables the shutoff valve to achieve fast response while maintaining system reliability
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 configuration enables the shutoff valve to close more quickly, thereby inhibiting fuel delivery to the aircraft engine efficiently during an overspeed shutdown, addressing the slow response time issue of existing systems.
Implementation Method 1
The biasing member biases the spool toward the first position
Implementation Method 2
utilizing a damping orifice to stabilize the spool movement
Data Source
AI summary
A bypass valve for a fuel control includes a sleeve, a spool, and a biasing member. The sleeve has a body extending between a first end and a second. The first end defines a first bypass valve port. The body defines a second bypass valve port, a third bypass valve port, and a shutoff port. The second end defines a fourth bypass valve port. The spool is received within the inner bore and is movable between a first position and a second position. The biasing member biases the spool toward the first position.