Aircraft Fuel Recirculating Valve Pressure Actuation
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Solution Overview
Problem
Conventional aircraft engine fuel circuits fail to effectively control the motive flow valve as a function of engine speed, leading to potential malfunctions where the valve remains jammed open, causing fuel to be sent back to the tank when it should not, which impairs engine performance and requires complex and costly dedicated control systems.
Innovation Solution
A fuel circuit architecture where the motive flow valve is actuated passively by pressure differences generated by the low-pressure pump, eliminating the need for dedicated control paths and using a computer to detect valve failures by measuring fuel temperature changes during engine startup, without requiring a dedicated position sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated control system is used to control the motive flow valve, then the valve can be reliably controlled as a function of engine speed, but the device complexity and cost increase
Solution Approach 1:
The motive flow valve is designed to automatically regulate fuel return based on engine speed without external control. The valve uses the engine's own fuel system pressure and flow characteristics to control its opening, eliminating the need for separate control systems while ensuring reliable operation across different engine speeds
Solution Approach 2:
The valve incorporates a feedback mechanism where the fuel pressure and flow from the engine fuel system directly influence the valve's position. As engine speed changes, the fuel system parameters change, which automatically adjusts the valve opening to maintain proper fuel circulation and prevent jamming
2Device complexity
If the motive flow valve is controlled by pressure difference of the low-pressure pump, then the device complexity is reduced, but the control precision may be affected
Solution Approach 1:
The valve is actuated purely by hydraulic pressure difference generated by the low-pressure pump. The pressure differential across the pump directly controls the valve opening, using the fuel system's own hydraulic characteristics to achieve precise control without mechanical or electronic complexity
Solution Approach 2:
The valve control is achieved by utilizing natural changes in fuel pressure and flow parameters that occur with engine speed. As the engine speed varies, the low-pressure pump generates different pressure differences, which automatically adjust the valve position to match the required control precision for each operating condition
3Device complexity
If temperature measurement is used to detect valve failures, then the detection method is simple and cost-effective, but the detection precision may be limited compared to position sensors
Solution Approach 1:
Temperature serves as an intermediary parameter to indirectly detect valve failures. Instead of directly measuring valve position, the system monitors fuel temperature changes that result from improper valve operation, providing a reliable failure detection method that avoids complex position sensing while maintaining adequate precision
Solution Approach 2:
The mechanical position sensing system is replaced with a thermal detection method. Temperature measurements substitute for direct mechanical or electronic position sensors, simplifying the detection system while providing sufficient precision to identify valve malfunctions through characteristic temperature patterns
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 fuel circuit by eliminating the need for additional control paths, reduces complexity and cost, and allows for reliable detection of motive flow valve failures through temperature measurements, ensuring proper engine operation by preventing unnecessary fuel return to the tank.
Implementation Method 1
a low-pressure pump connected to the fuel tank, the low-pressure pump being capable of raising the pressure of a low-pressure stream of fuel from the fuel tank by a variable pressure difference
Implementation Method 2
a high-pressure pump connected to the low-pressure pump capable of converting the low-pressure stream of fuel into a high-pressure stream of fuel
Implementation Method 3
a computer to detect valve failures by measuring fuel temperature changes during engine startup
Data Source
AI summary
A fuel circuit of an aircraft engine including a fuel tank; an engine fuel system including a low-pressure pump and a high-pressure pump, and a fuel recirculating pipeline connected to the engine fuel system; and a fuel recirculating valve arranged so as to switch between an open position and a closed position according to the pressure differential of the low-pressure pump, the valve being able to obstruct the fuel recirculating pipeline in the closed position, and to bring the fuel recirculating pipeline into communication with the fuel tank in the open position.