Fuel Pump Thermal Bypass for Actuation Pump Cooling
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Solution Overview
Problem
Modern aircraft require more efficient pumping systems and higher running fuel temperatures to improve thrust specific fuel consumption, necessitating a lighter, more efficient actuation pump isolated from high temperature main fuel flow, which requires a cooling loop to prevent thermal runaway.
Innovation Solution
A fuel delivery system with an actuation pump positioned upstream of the main fuel filter, incorporating a thermal bypass valve and high pressure relief valve to manage temperature and pressure thresholds, ensuring efficient operation and preventing thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the actuation pump is isolated from the high temperature main fuel flow to reduce weight and improve efficiency, then the actuation pump weight and power extraction requirements are reduced, but a cooling loop is required to prevent thermal runaway
Solution Approach 1:
The cooling loop for the actuation pump is merged with the existing main fuel flow system. The actuation pump draws fuel from the main fuel line upstream of the main fuel filter, and excess fuel returns to the main fuel line downstream of the main fuel pump, utilizing the existing fuel circulation infrastructure for cooling purposes without requiring a completely separate cooling system.
Solution Approach 2:
The main fuel flow acts as an intermediary cooling medium for the actuation pump. By positioning the actuation pump to draw from and return to the main fuel line, the main fuel flow serves as a thermal mediator that absorbs excess heat from the actuation pump, preventing thermal runaway while avoiding the need for dedicated cooling components.
2Productivity
If the actuation pump is isolated from the high temperature main fuel flow, then the actuation pump can be lighter and more efficient, but thermal runaway of the actuation pump may occur
Solution Approach 1:
The actuation pump operates continuously within the main fuel flow circulation system, ensuring constant thermal management. The fuel continuously flows through the actuation pump housing, providing ongoing cooling to prevent thermal buildup while maintaining the pump's isolation benefits for efficiency and weight reduction.
Solution Approach 2:
The actuation pump utilizes the main fuel flow system's own circulation to provide its own cooling. By drawing fuel from upstream and returning excess fuel downstream, the system uses the existing fuel circulation to self-regulate the actuation pump's temperature, eliminating the need for external cooling mechanisms.
3Reliability
If a thermal bypass valve is added to decrease fuel temperature across the actuation pump, then thermal runaway is prevented, but device complexity increases
Solution Approach 1:
The thermal bypass valve is designed to operate automatically based on temperature conditions without requiring external control systems. When the fuel temperature exceeds a predetermined threshold, the valve automatically opens to divert fuel flow and reduce temperature, then closes when the temperature returns to normal, providing self-regulating thermal protection.
Solution Approach 2:
The thermal bypass valve responds to temperature parameter changes by automatically adjusting its opening state. When fuel temperature rises above a threshold, the valve changes its flow resistance parameter to divert excess fuel through the bypass, thereby reducing the temperature parameter back to acceptable levels without manual intervention.
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 system allows for the use of a lighter, more efficient actuation pump, reducing fuel temperature to actuation devices and extending their service life while maintaining operational efficiency.
Implementation Method 1
a thermal bypass valve located downstream of the actuation pump and configured when activated to increase fuel flow of the second flow of fuel across the actuation pump when a temperature of the second flow of fuel exceeds a predetermined threshold, thereby decreasing the temperature of the second flow of fuel
Data Source
AI summary
A fuel delivery system for a gas turbine engine includes a fuel source, a main fuel pump configured to deliver a first flow of fuel to a combustor assembly of the gas turbine engine, a main fuel filter positioned upstream of the main fuel pump, and an actuation pump disposed upstream of the main fuel filter and configured to deliver a second flow of fuel from the fuel source to one or more actuation devices of the gas turbine engine.