Aircraft Fuel System Segmented Pump Architecture
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Solution Overview
Problem
Current fuel systems for aircraft turbomachines suffer from excessive bypass flow, leading to waste heat generation due to the recirculation of excess fuel, which reduces the fuel's effectiveness as a heat sink for cooling purposes.
Innovation Solution
A fuel system incorporating a primary mechanically driven fuel pump and a supplemental fuel pump, with a return loop and boost pump, where the supplemental pump is driven by a turbine or electric motor, allowing for precise control of fuel flow to match engine requirements, reducing bypass flow and waste heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single fuel pump is sized to provide flow for high power conditions, then sufficient fuel flow is guaranteed for takeoff and start/windmill, but excessive bypass flow and waste heat are generated during cruise and descent
Solution Approach 1:
The fuel pump system is segmented into a primary fuel pump (mechanically driven) and a supplemental fuel pump (electrically driven). The primary pump handles high power conditions while the supplemental pump provides additional flow during high power conditions or can operate alone during low power conditions, eliminating the need for a single oversized pump that generates excessive bypass flow.
Solution Approach 2:
The system dynamically switches between different pump configurations: both pumps operating during high power conditions, primary pump alone during transition, or supplemental pump alone during low power conditions. This dynamic operation allows the system to match fuel delivery to actual engine demands, minimizing bypass flow and waste heat generation.
2Reliability
If excess fuel is recirculated to guarantee sufficient fuel flow in all conditions, then fuel availability is ensured, but the fuel's ability to serve as a heat sink is greatly reduced
Solution Approach 1:
The fuel pump system is segmented into a primary fuel pump (mechanically driven) and a supplemental fuel pump (electrically driven). The primary pump handles high power conditions while the supplemental pump provides additional flow during high power conditions or can operate alone during low power conditions, eliminating the need for a single oversized pump that generates excessive bypass flow.
Solution Approach 2:
The system changes operational parameters by switching between different pump configurations based on engine demands. During low power conditions, the supplemental pump operates alone at lower speeds, reducing bypass flow and allowing fuel to maintain its heat sink capacity. This parameter change resolves the contradiction between fuel availability and heat sink capacity.
3Reliability
If a mechanically driven primary fuel pump is used, then fuel flow is reliably provided as a function of engine speed, but parasitic horsepower extraction occurs
Solution Approach 1:
The fuel pump system is segmented into a primary fuel pump (mechanically driven) and a supplemental fuel pump (electrically driven). The primary pump handles high power conditions while the supplemental pump provides additional flow during high power conditions or can operate alone during low power conditions, eliminating the need for a single oversized pump that generates excessive bypass flow.
Solution Approach 2:
The system replaces the traditional single mechanically driven pump with a hybrid configuration where an electrically driven supplemental pump can operate independently during low power conditions. This substitution reduces parasitic horsepower extraction from the engine while maintaining reliable fuel flow, as the electric pump draws power from the aircraft's electrical system rather than mechanically from the engine.
4Device complexity
If a single fuel pump operates across all engine speeds, then system complexity is minimized, but the ability to precisely match fuel flow to engine requirements is reduced
Solution Approach 1:
The fuel pump system is segmented into a primary fuel pump (mechanically driven) and a supplemental fuel pump (electrically driven). The primary pump handles high power conditions while the supplemental pump provides additional flow during high power conditions or can operate alone during low power conditions, eliminating the need for a single oversized pump that generates excessive bypass flow.
Solution Approach 2:
The system dynamically switches between different pump configurations: both pumps operating during high power conditions, primary pump alone during transition, or supplemental pump alone during low power conditions. This dynamic operation allows the system to match fuel delivery to actual engine demands, minimizing bypass flow and waste heat generation.
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 sufficient fuel flow to the engine while minimizing waste heat, enabling the fuel to be used more effectively for cooling and reducing parasitic horsepower extraction, thus enhancing thermal management efficiency.
Implementation Method 1
the supplemental fuel pump can be driven by a turbine or electric motor
Data Source
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AI summary
A fuel system for an engine can include a fuel circuit (101) and a primary fuel pump (103) in fluid communication with the fuel circuit and configured to pump fuel to the engine as a function of engine speed. The primary fuel pump is configured to pump insufficient fuel flow to the engine during at least one engine speed or speed range. The system also includes a supplemental fuel pump (105) in fluid communication with the fuel circuit configured to selectively pump fuel to the engine at least during the at least one engine speed or speed range to supplement fuel flow from the primary fuel pump to provide sufficient total fuel flow to the engine during all engine speeds.