Pump Authority Switching for Jet Engine Fuel Thermal Management
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Solution Overview
Problem
Conventional fuel systems for jet engines face limited operability due to thermal loads at high turndown conditions, with high-speed centrifugal pumps contributing significantly to heat loads and lacking sufficient heat capacity, leading to inefficiencies and reduced performance.
Innovation Solution
A Fuel Thermal Management System that switches pump authority between a high-speed centrifugal main fuel pump and a variable or fixed positive displacement actuation pump, shutting off the main fuel pump at high turndown conditions to eliminate its heat load and using the actuation pump to supply fuel, while maintaining stable fluid flow through controlled valve transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high-speed centrifugal main fuel pump is used to supply fuel at high flow conditions, then fuel delivery capacity is improved, but heat load and thermal capacity are worsened at high turndown conditions
Solution Approach 1:
The system dynamically switches between two pump configurations based on operating conditions: using the centrifugal main fuel pump at high flow conditions for maximum delivery capacity, and switching to the positive displacement actuation pump at high turndown conditions to minimize heat load. This dynamic reconfiguration allows the system to adapt its thermal and flow characteristics to match instantaneous demands.
Solution Approach 2:
The fuel delivery function is segmented into two separate pump systems with complementary characteristics: the centrifugal main fuel pump handles high-flow, low-pressure-rise requirements, while the positive displacement actuation pump handles low-flow, high-pressure-rise requirements. This segmentation allows each pump to operate in its optimal efficiency range and minimizes overall system heat load across the full operating envelope.
2Temperature
If the main fuel pump is shut off to reduce heat load at high turndown conditions, then thermal capacity is improved, but fuel supply stability is worsened during pump transitions
Solution Approach 1:
The control system initiates preliminary actions during pump transitions by first opening the actuation pump discharge valve before closing the main fuel pump discharge valve. This ensures that the actuation pump is already pressurized and ready to immediately assume full fuel delivery responsibility when the main pump shuts off, preventing any supply instability or pressure drops during the transition.
Solution Approach 2:
The actuation pump serves as an intermediary system that bridges the gap between the main fuel pump and the fuel metering system during transitions. By maintaining continuous fuel supply capability through the actuation pump, the system ensures uninterrupted and stable fuel delivery even as authority transfers between pumps.
3Temperature
If pump authority is switched between main fuel pump and actuation pump, then thermal management is improved, but pressure change at metering system inlet is worsened
Solution Approach 1:
The valve system dynamically adjusts valve positions and opening areas during transitions to maintain relatively stable pressure at the metering system inlet. By controlling the rate of valve movement and coordinating the opening/closing sequences, the system minimizes pressure transients and ensures smooth authority transfer without challenging the metering system's ability to maintain stable flow.
Data Source
AI summary
A fluid distribution system includes a boost supply providing a fluid flow, and a fluid metering system downstream of the boost supply. The fluid metering system supplies fluid to a downstream device. A main fluid pump supplies at least a portion of the fluid flow to the fluid metering system. A shut-off valve is positioned upstream of a main fluid pump inlet. An actuation system is positioned downstream of the boost supply. The actuation system supplies fluid to one or more hydraulically-operated devices. An actuation pump supplies at least a portion of the fluid flow to the fluid metering system and to the actuation system. A first valve is positioned between the actuation pump and the fluid metering system. The first valve and the shut-off valve are operable to switch between the main fluid pump and the actuation pump as a source of fluid supply to the fluid metering system.