Servoed Variable Displacement Pump for Gas Turbine Fuel Temperature Control
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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 actuated by an electromechanical actuator, a servo valve, and a gas turbine engine controller, which controls fuel flow rate and pressure to minimize heat input, eliminating the need for additional heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous fuel flow through bypass valve and fuel pump is maintained, then fuel supply reliability is improved, but fuel temperature increases to undesirable levels
Solution Approach 1:
The bypass valve is closed during certain operating conditions (e.g., high altitude, low temperature) to periodically interrupt the continuous fuel flow through the bypass line. This periodic closure prevents excessive fuel heating while maintaining reliable fuel supply when needed, resolving the contradiction between supply reliability and temperature control
Solution Approach 2:
The system changes the flow parameters by dynamically adjusting the bypass valve position based on operating conditions. By varying the bypass flow rate from continuous to intermittent or reduced flow, the system maintains reliable fuel supply while preventing temperature from rising to undesirable levels
2Temperature
If additional heat exchanger is added to cool fuel, then fuel temperature is reduced to acceptable levels, but system weight increases
Solution Approach 1:
The patent extracts the heat exchanger component from the fuel cooling system, eliminating the need for additional cooling equipment. Instead of adding a heat exchanger to remove heat, the system uses bypass flow control to prevent heat accumulation in the first place, thereby reducing system weight while maintaining acceptable fuel temperature
Solution Approach 2:
The bypass line, which originally caused harmful fuel heating, is converted into a beneficial temperature control mechanism. By strategically closing or modulating the bypass valve, the system uses the bypass flow path itself to regulate fuel temperature without requiring additional cooling components, thus eliminating weight penalty
3Temperature
If additional heat exchanger is added to cool fuel, then fuel temperature control is improved, but system noise increases
Solution Approach 1:
The heat exchanger is removed from the system, eliminating the noise source associated with additional cooling equipment. The patent achieves temperature control through bypass valve modulation alone, thereby improving the noise environment without sacrificing fuel temperature management capability
4Temperature
If additional heat exchanger is added to cool fuel, then fuel temperature is reduced to acceptable levels, but net engine thrust is reduced
Solution Approach 1:
The heat exchanger is extracted from the engine system, eliminating the parasitic power losses associated with operating additional cooling equipment. The bypass valve control strategy achieves fuel temperature management without the energy penalty of a heat exchanger, thereby preserving net engine thrust
Solution Approach 2:
The fuel system uses its own bypass line and valve to self-regulate fuel temperature without requiring external cooling equipment. This self-service approach eliminates the need for heat exchangers that would consume engine power, thereby maintaining optimal net thrust
5Temperature
If bypass valve is closed to prevent fuel heating, then fuel temperature is controlled, but fuel flow rate may be insufficient
Solution Approach 1:
The system dynamically changes the bypass valve opening parameter based on real-time operating conditions. When fuel heating is not excessive, the bypass valve remains open to maintain adequate flow rate. When temperature approaches undesirable levels, the valve closes partially or temporarily. This dynamic parameter adjustment ensures both sufficient fuel flow and acceptable temperature control
Solution Approach 2:
The bypass valve employs periodic closure rather than continuous closure to prevent fuel heating. This periodic action allows fuel flow to be maintained during open periods while preventing excessive temperature rise during closed periods, thereby balancing temperature control with sufficient fuel delivery
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 system effectively maintains fuel temperature within acceptable limits without relying on additional heat exchangers, reducing weight, noise, and maintaining engine efficiency.
Implementation Method 1
The servo valve is coupled to receive a spring force and is configured, upon receipt thereof, to control the first force that is supplied to the first piston
Implementation Method 2
The bias spring is coupled between the actuator and the servo valve and is configured to supply the spring force to the servo valve
Implementation Method 3
The electromechanical actuator includes an electric motor, an actuator, and a bias spring. The electric motor is configured to be selectively energized and, upon being selectively energized, supply an actuation drive torque
Data Source
AI summary
A fuel metering system for supplying fuel to load 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.