Aircraft Fuel Thermal Recirculation System
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Solution Overview
Problem
Traditional fuel systems for aircraft require the main fuel pump to handle all loads, including cooling, which can lead to inefficiencies and increased weight, as cooling components are downstream and driven by the main fuel pump, necessitating oversized pumps and inefficient thermal management.
Innovation Solution
A fuel system with a main pump assembly that includes a recirculation pump and a fuel recirculation system capable of selecting between recirculation, backup, and bypass modes, allowing fuel to be recirculated through coolers or provided directly to the main fuel control, reducing pressure and flow demands on the main fuel pump and enabling thermal cooling upstream of the main fuel control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the main fuel pump is sized to drive all loads including cooling components downstream, then all fuel loads can be supplied, but the pump becomes oversized and inefficient
Solution Approach 1:
The fuel pump system is segmented into a main fuel pump for supplying fuel to the main fuel control and a separate recirculation pump for thermal management. This segmentation allows each pump to be sized appropriately for its specific function, eliminating the need for the main pump to be oversized to handle both fuel supply and cooling loads simultaneously.
Solution Approach 2:
The thermal recirculation function is extracted from the main fuel pump system and implemented as a separate recirculation pump. This extraction allows the main fuel pump to focus solely on fuel supply while the recirculation pump handles thermal management, improving overall system efficiency and eliminating pump oversizing.
2Temperature
If cooling components are placed downstream of main fuel control and driven by main fuel pump, then thermal cooling is provided, but system complexity and weight increase
Solution Approach 1:
The system is segmented into separate functional loops: a main fuel pump loop for fuel supply and a recirculation pump loop for thermal management. The recirculation pump draws fuel from the main fuel control outlet, cools it through heat exchangers, and returns it to the main fuel control inlet. This segmentation simplifies the overall system architecture by allowing independent optimization of fuel supply and thermal management functions.
Solution Approach 2:
A recirculation pump acts as an intermediary between the main fuel pump and the thermal management system. This intermediary component enables thermal cooling to be provided without directly coupling the cooling load to the main fuel pump, thereby reducing system complexity and allowing for more flexible thermal management architecture.
3Reliability
If the main fuel pump handles all loads, then fuel supply is ensured, but pump weight increases
Solution Approach 1:
The pump system is segmented into a main fuel pump dedicated to fuel supply and a recirculation pump dedicated to thermal management. This segmentation allows the main fuel pump to be sized for fuel supply requirements only, significantly reducing its weight compared to a single pump that must handle both fuel supply and cooling loads.
Solution Approach 2:
The thermal management function is extracted from the main fuel pump system, allowing the main fuel pump to be lighter and optimized solely for fuel supply. The recirculation pump assumes the thermal management function with its own dedicated sizing, eliminating the need for the main pump to be oversized for combined functions.
4Use of energy by moving object
If thermal recirculation is implemented with separate recirculation pump, then thermal management efficiency improves, but system complexity increases
Solution Approach 1:
The recirculation pump is designed with multi-functionality, serving both as a thermal management device and as a backup fuel supply source. The recirculation control system includes selector valves that can direct recirculation pump output to either the heat exchangers for cooling or to the main fuel control as a backup supply, eliminating the need for a separate backup pump and reducing overall system complexity.
Solution Approach 2:
The recirculation pump system incorporates self-service features where the recirculation control uses pressure differential and flow sensors to automatically manage its own operation. The system can autonomously switch between recirculation mode and backup mode based on system conditions, reducing the need for complex external control systems and minimizing operational complexity.
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 reduces power usage, weight, and pump heat rejection, allowing for more efficient thermal management, increased fuel capacity, and provides a backup pumping stage for failure immunity, improving overall system efficiency and reliability.
Implementation Method 1
The fuel recirculation system is configured to recirculate fuel from the recirculation pump to a tank through one or more coolers in the recirculation mode
Implementation Method 2
A check valve can be included in the backup line, configured to open to provide backup fuel flow to the main fuel control from the recirculation pump in the backup mode and to prevent back flow in the backup line otherwise
Implementation Method 3
The cooler recirculation line can include a pressure regulating valve configured to only allow flow through the cooler recirculation line above a predetermined pressure
Data Source
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AI summary
A fuel system includes a main pump assembly (101). The main pump assembly (101) has a main fuel pump (103) connected to an input line (105), a recirculation pump (111) connected to the input line (105), and a fuel recirculation system (113). A recirculation control (121) includes a first selector valve (135) in fluid communication with an outlet line of the recirculation pump (111), with a recirculation return line (137) connected to return fuel to the input line (105), and with an inter-valve line (139). The recirculation control (121) includes a second selector valve (141) in fluid communication with the inter-valve line (139), with a backup line connecting the second selector valve (141) to a main fuel control (107), and with a cooler recirculation line (125) connected to supply the one or more coolers.