Variable Displacement Fuel Pump for Minimal Heat Input
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Solution Overview
Problem
Gas turbine engine fuel supply systems often experience undesirable fuel heating due to continuous fuel flow, which can exceed temperature limits and require additional heat exchangers, increasing weight and noise while reducing net engine thrust.
Innovation Solution
A fuel metering system incorporating a variable displacement piston pump with an adjustable hanger and actuator, controlled by a gas turbine engine controller, which adjusts fuel flow rate based on drive speed and hanger position to maintain a constant differential pressure across the metering valve, minimizing fuel temperature increase and eliminating the need for additional heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous fuel flow is maintained through the bypass valve and pump, then fuel supply reliability is improved, but fuel temperature increases to undesirable levels
Solution Approach 1:
The bypass valve operates periodically rather than continuously, opening only when fuel temperature reaches a predetermined threshold. This periodic operation allows the system to maintain reliability through continuous fuel circulation capability while preventing excessive temperature buildup by interrupting the heating process at appropriate intervals.
Solution Approach 2:
A temperature sensor continuously monitors fuel temperature and provides feedback to the control system. This feedback mechanism enables the bypass valve to operate based on actual temperature conditions, opening when temperature exceeds the threshold and closing when it returns to acceptable levels, thus dynamically balancing reliability and temperature control.
2Temperature
If additional heat exchangers are added to cool waste heat, then fuel temperature control is improved, but system weight and noise increase
Solution Approach 1:
The fuel system utilizes its own circulation capability to manage temperature by diverting fuel through the bypass valve back to the pump inlet. This self-service approach allows the system to control fuel temperature using existing components (pump, valves, and temperature sensor) without requiring additional heat exchangers or external cooling systems, thereby avoiding increased weight.
3Loss of energy
If additional heat exchangers are installed in the engine fan ducts, then waste heat removal is improved, but net engine thrust is reduced
Solution Approach 1:
The system extracts only the necessary amount of waste heat removal capability by using periodic bypass valve operation rather than continuously extracting heat through additional exchangers. This selective extraction approach removes sufficient heat to maintain fuel temperature within limits while minimizing the impact on engine thrust by avoiding continuous energy extraction that would otherwise be available for propulsion.
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 ensures efficient fuel delivery with minimal heat input, improving thermal efficiency, reducing power requirements, and enhancing specific fuel consumption by delivering only the necessary fuel flow at optimal pressure, thus maintaining engine performance without excessive heating.
Implementation Method 1
a variable displacement piston pump configured to receive a drive torque and, upon receipt of the drive torque, to supply fuel to a plurality of loads
Implementation Method 2
a head sensor configured to sense differential pressure across the metering valve and supply the hanger position commands based on the sensed differential pressure
Data Source
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AI summary
A fuel metering system for supplying fuel to a plurality of loads includes a variable displacement piston pump having an adjustable hanger that is movable to a plurality of positions. The variable displacement piston pump is configured to receive a drive torque and, upon receipt of the drive torque, to supply fuel to the plurality of loads at a flow rate dependent on the position of the adjustable hanger. A hanger actuator is coupled to receive hanger position commands and is operable, in response thereto, to move the adjustable hanger to the commanded position. A pump control mechanism is coupled to receive the fuel flow commands supplied by the gas turbine engine controller and is operable, in response thereto, to supply the hanger position commands.