Variable-Displacement Pump Control for Accurate Aircraft Fuel Metering
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Solution Overview
Problem
Existing variable displacement pumps (VDPs) face challenges in reducing fuel system weight and heat rejection, improving reliability, and increasing fuel flow accuracy for aircraft applications.
Innovation Solution
A system incorporating a variable displacement pump with an electromechanical actuator, flow sensing valve, and minimum pressure shutoff valve, controlled by a controller that uses sensors for feedback to manage flow and pressure, enabling direct electrical actuation and precise control of fuel delivery to downstream systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional variable displacement pump control techniques are used, then the system maintains basic flow support capability, but fuel system weight and heat rejection remain high, and flow accuracy is limited
Solution Approach 1:
The patent replaces conventional mechanical pump control mechanisms with an electromechanical actuator that directly controls the variable displacement mechanism. This substitution enables more precise electronic control of fuel flow while reducing the mechanical complexity and weight of the overall fuel system, thereby improving flow accuracy without significantly increasing system weight.
Solution Approach 2:
The patent implements a feedback control system using a flow sensing valve with a position sensor that monitors actual fuel flow and provides feedback to the controller. The controller adjusts the electromechanical actuator based on this feedback to maintain accurate flow control, directly addressing the measurement precision requirement while using efficient electronic control rather than heavier mechanical systems.
2Loss of energy
If conventional pump control systems are used, then basic flow support is provided, but heat rejection from the fuel system remains high
Solution Approach 1:
By replacing conventional mechanical control systems with an electromechanical actuator and electronic control, the patent reduces unnecessary mechanical friction and energy loss. The direct electrical actuation of the variable displacement mechanism eliminates intermediate mechanical transmission losses, thereby reducing heat generation while maintaining effective fuel delivery to the combustor.
Solution Approach 2:
The patent utilizes the variable displacement mechanism to dynamically change pump operating parameters based on actual fuel flow demands. By adjusting the displacement volume in real-time based on feedback from the flow sensing valve, the system avoids unnecessary pumping of excess fuel that would generate heat, thereby reducing heat rejection while maintaining optimal fuel delivery efficiency.
3Reliability
If simple pump control is used, then system complexity is low, but reliability and flow accuracy are insufficient
Solution Approach 1:
The patent integrates multiple functions into a unified control architecture where the controller manages both the electromechanical actuator for flow control and the minimum pressure shutoff valve for pressure protection. The flow sensing valve serves both as a flow measurement device and as part of the control feedback loop. This multi-functional integration improves reliability through coordinated control while avoiding the complexity of separate independent systems.
Solution Approach 2:
The patent implements feedback control using the position sensor on the flow sensing valve that continuously monitors actual fuel flow and provides feedback to the controller. This closed-loop control automatically compensates for variations and maintains accurate flow control, significantly improving reliability. The feedback mechanism adds computational complexity but reduces mechanical complexity by eliminating the need for overly robust mechanical tolerances and manual adjustment mechanisms.
4Speed
If fast response control is implemented, then fuel metering speed improves, but system complexity and heat generation increase
Solution Approach 1:
The patent uses an electromechanical actuator with direct electrical actuation to control the variable displacement mechanism, replacing slower mechanical linkage systems. Electrical signals can be changed instantaneously by the controller based on feedback, enabling very fast response in fuel metering adjustments. This electronic control approach achieves high speed response while actually reducing mechanical complexity compared to traditional mechanical control linkages.
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 reduces valve count, enhances fuel metering speed, and ensures accurate flow control, thereby improving reliability and reducing weight and heat rejection in aircraft fuel systems.
Implementation Method 1
Pressure of flow through the FSV from the FSV inlet to the FSV outlet can bias the valve member in a second direction opposite the first direction
Implementation Method 2
A biasing member can bias the valve member in a first direction
Implementation Method 3
The sensor can include a position sensor operatively connected to monitor position of the valve member in the FSV to generate the sensor data as feedback for the controller
Implementation Method 4
An electromechanical actuator (EMA) is operatively connected to actuate the variable displacement mechanism
Implementation Method 5
A solenoid valve (SOL) can be connected in fluid communication with the outlet line and with the MPSOV control line for actuating the MPSOV between first and second states
Data Source
AI summary
A system includes a variable displacement pump (VDP) in fluid communication with an inlet line and with an outlet line. The VDP includes a variable displacement mechanism configured to vary pressure to the outlet line. An electromechanical actuator (EMA) is operatively connected to actuate the variable displacement mechanism. A flow sensing valve (FSV) connected in the outlet line. The FSV includes a sensor configured to generate sensor data indicative of flow out of the outlet line. A controller is operatively connected to the EMA to control the variable displacement mechanism based on the sensor data to support flow demands from one or more downstream systems.