Dual Fuel Pump Flow Control for Lower Cruise Parasitic Draw
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Solution Overview
Problem
Conventional single positive displacement fuel pump systems are inefficient as they are sized to meet high-power conditions, which results in excessive parasitic draw and reduced efficiency during longer cruise conditions with lower flow demands, affecting Thrust Specific Fuel Consumption (TSFC) in modern turbine engines.
Innovation Solution
A dual pump fuel system with a main fuel pump and a support fuel pump, where the support pump is sized to provide additional flow on demand, utilizing a valve assembly with pressure regulating and electro-hydraulic servo valves to manage the flow between the pumps, allowing the support pump to be placed in an idle state during cruise conditions, reducing power draw and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single positive displacement pump is sized to provide flow for high-power conditions, then sufficient fuel flow is ensured for take-off and short-term high-power conditions, but excessive parasitic draw and reduced efficiency occur during cruise conditions with lower flow demands
Solution Approach 1:
The fuel pump system is divided into two separate positive displacement pumps: a main fuel pump sized for cruise conditions and a support fuel pump sized for high-power conditions. This segmentation allows each pump to be optimally sized for its specific operating regime, eliminating the need for a single oversized pump that causes excessive parasitic draw during cruise.
Solution Approach 2:
The system dynamically switches between operating modes by controlling the support fuel pump through a valve assembly. During cruise conditions, the support pump is isolated or operated at minimal flow. During high-power conditions, the support pump is activated to supplement the main pump. This dynamic operation allows the system to adapt fuel flow capacity to actual demand, reducing parasitic draw during extended cruise operations.
2Reliability
If a single positive displacement pump is oversized to meet peak demand, then adequate fuel supply is guaranteed for transient high-power conditions, but efficiency is compromised during longer duration cruise conditions
Solution Approach 1:
The fuel pump system is divided into two separate positive displacement pumps: a main fuel pump sized for cruise conditions and a support fuel pump sized for high-power conditions. This segmentation allows each pump to be optimally sized for its specific operating regime, eliminating the need for a single oversized pump that causes excessive parasitic draw during cruise.
Solution Approach 2:
The support fuel pump operates periodically or on-demand rather than continuously. The valve assembly controls the support pump to activate during high-power conditions and remain isolated or operate at minimal flow during cruise conditions. This periodic operation ensures reliable fuel supply during peak demand while minimizing energy losses during extended cruise operations.
3Use of energy by moving object
If a dual pump system is implemented with a support pump sized for high-power conditions, then fuel flow demand can be met efficiently during cruise conditions, but system complexity increases with additional valves and control mechanisms
Solution Approach 1:
The valve assembly integrates multiple control functions into a single coordinated system. The solenoid valve, pressure bypass valve, and electro-hydraulic servo valve work together to control the support fuel pump's connection to the fuel flow path. This merging of control functions reduces the number of independent components and simplifies the overall system architecture despite the dual pump configuration.
Solution Approach 2:
The valve assembly acts as an intermediary between the two fuel pumps and the fuel flow path. It provides a controlled interface that allows the support pump to be connected or isolated from the main fuel flow path as needed. This intermediary structure enables efficient parasitic draw reduction while maintaining manageable system complexity through centralized control.
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 dual pump system reduces pump horsepower and heat added to fuel during cruise conditions, enhancing efficiency and reducing parasitic losses, while maintaining sufficient flow for high-power conditions, thus improving TSFC without increasing cost and weight excessively.
Implementation Method 1
The PBV can be configured and adapted to translate between an open position and a closed position. In the open position, fluid flow can be permitted between the support fuel pump and the system fuel outlet.
Implementation Method 2
The system includes an electro-hydraulic servo valve (EHSV) in fluid communication with the fuel flow path between the PRV and the system fuel outlet.
Data Source
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AI summary
A fuel pump system includes a main fuel pump (102) between a system fuel inlet (104) and a system fuel outlet (106), a fuel flow path at least partially defined between the main fuel pump and the system fuel outlet, and a support fuel pump (110) between the system fuel inlet and the system fuel outlet. The support fuel pump is sized to provide more flow to the system fuel outlet, when in an active state, than the main fuel pump. The system includes a valve assembly (101) in fluid communication with the support fuel pump configured and adapted to connect the support fuel pump to the system fuel outlet, and a pressure regulating valve in fluid communication with the fuel flow path between the main fuel pump and the system fuel outlet. The system includes an EHSV (118) in fluid communication with the fuel flow path between the PRV (116) and the system fuel outlet.