Variable Delivery Fuel Pump Surplus Flow Control
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Solution Overview
Problem
Fuel control systems for gas turbine engines with fixed positive displacement fuel pumps recirculate excess fuel, generating excess heat and consuming power, while variable delivery pumps face issues with surplus fuel flow variations affecting heat generation at different system back pressures.
Innovation Solution
A variable delivery, positive displacement fuel pump system with a proportional bypass valve and pump control maintains a substantially constant surplus fuel flow by adjusting delivery rates and pressure drops across a metering valve, ensuring efficient fuel distribution and minimizing excess heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed positive displacement fuel pump is used to deliver fuel at maximum demand rate, then adequate burn fuel flow is ensured, but excess fuel is recirculated generating heat and consuming power
Solution Approach 1:
The patent applies a variable delivery fuel pump that dynamically adjusts its delivery rate based on actual system demand. The pump controller modulates the pump output to match the sum of burn fuel demand and servo flow demand, eliminating the need for fixed high-rate delivery and subsequent recirculation. This dynamic adjustment resolves the contradiction by maintaining reliable fuel supply while minimizing excess fuel circulation and associated heat generation.
Solution Approach 2:
The patent changes the delivery rate parameter of the fuel pump from a fixed value to a variable value that responds to system conditions. By continuously adjusting the pump delivery rate parameter based on feedback from fuel flow sensors and system pressure sensors, the system ensures adequate burn fuel flow while minimizing excess delivery that would require recirculation and generate heat.
2Loss of energy
If variable delivery fuel pump is used to reduce excess fuel recirculation, then heat generation and power consumption are reduced, but surplus fuel flow varies with system back pressure affecting heat generation
Solution Approach 1:
The patent implements a feedback control system that uses sensors to monitor system back pressure, burn fuel flow, and servo flow. The pump controller continuously adjusts the variable delivery pump output based on this feedback to maintain optimal surplus fuel flow. This feedback mechanism resolves the contradiction by automatically compensating for back pressure variations, ensuring consistent heat generation characteristics and ease of operation across different system conditions.
Solution Approach 2:
The control system automatically regulates the fuel pump delivery without requiring manual intervention. The system self-adjusts the pump output based on real-time sensor data, maintaining optimal surplus fuel flow that results in consistent, manageable heat generation. This self-service capability simplifies operation while resolving the heat generation control issue.
3Reliability
If minimum surplus flow is maintained at low system back pressures, then adequate fuel capacity is provided, but excess surplus flow is generated at high system back pressures causing heat generation
Solution Approach 1:
The patent uses a dynamically controllable fuel pump that adjusts its delivery rate based on real-time system back pressure conditions. At low back pressures, the pump maintains minimum surplus flow for adequate fuel capacity. At high back pressures, the pump automatically reduces surplus flow to minimize heat generation. This dynamic response resolves the contradiction by adapting fuel capacity provision to actual system conditions.
Solution Approach 2:
The system changes the pump delivery rate parameter in response to system back pressure variations. The controller modifies this parameter to maintain appropriate surplus flow that provides adequate fuel capacity while preventing excessive heat generation at high back pressures.
Data Source
AI summary
A fuel control system (100) for supplying metered fuel flow to a gas turbine engine is disclosed that includes a variable delivery fuel pump (116) for outputting a fuel flow that includes a burn fuel flow for the gas turbine engine and a surplus fuel flow recirculated back to an inlet (124) of the variable delivery fuel pump (116) and a pump control (148, 158, 122) for controlling the output of the variable delivery fuel pump to maintain the surplus fuel flow at a substantially constant rate. A method of controlling a fuel system (100) is also disclosed.