Fuel Recirculation Thermal Management for Gas Turbine Engines
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Solution Overview
Problem
The heat sink capacity of thermal management systems in gas turbine engines is limited by temperature constraints on engine oil and fuel, leading to issues like coking and lacquering, which restrict the effective transfer of excess heat.
Innovation Solution
A thermal management system utilizing a fuel recirculation circuit with a recirculation fuel-oil cooler, air-fuel cooler, and a fuel throttle valve, along with sensors and controllers, to manage heat transfer by circulating fuel and oil, adjusting flow rates, and maintaining temperatures within limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fuel and oil are used to cool the engine by transferring excess heat, then heat transfer capability is improved, but temperature limits (coking and lacquering) restrict the heat sink capacity
Solution Approach 1:
The fuel system is segmented into a burn line and a recirculation line, allowing different portions of fuel to serve different functions. The recirculation line specifically handles heat transfer from oil without requiring high flow rates, while the burn line maintains combustion function. This segmentation enables the system to achieve effective heat transfer while maintaining fuel temperatures below coking and lacquering thresholds.
Solution Approach 2:
A recirculation fuel-oil cooler is introduced as an intermediary device between the oil system and fuel system. This cooler acts as a mediator that transfers heat from oil to fuel in a controlled manner, enabling heat transfer without directly exposing large volumes of fuel to high temperatures. The cooler facilitates thermal energy transfer while maintaining both oil and fuel temperatures within safe operating limits.
2Temperature
If fuel recirculation volume and flow rate are increased to improve cooling, then heat sink capacity is improved, but system complexity and fuel consumption increase
Solution Approach 1:
A fuel throttle valve is incorporated in the recirculation line to dynamically control the flow rate of fuel through the recirculation cooler. This dynamic control mechanism allows the system to adjust fuel recirculation based on actual thermal demands, achieving effective heat transfer with minimized fuel flow rates. The throttle valve enables precise flow regulation without requiring complex pump systems or large reservoirs.
3Temperature
If fuel recirculation volume is increased to maintain temperature limits, then temperature control is improved, but heat transfer efficiency decreases
Solution Approach 1:
The system changes the temperature parameter of fuel by the time it returns to the tank. Fuel is drawn from the tank, cooled in the recirculation cooler by absorbing heat from oil, and returned to the tank at a lower temperature. This parameter change creates a temperature gradient that enhances heat transfer efficiency while maintaining fuel temperatures below degradation thresholds throughout the system.
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 solution increases the heat sink capacity, reduces fuel recirculation volume and flow rate, and prevents engine fluids from exceeding critical temperature thresholds, thereby enhancing the thermal management efficiency of gas turbine engines.
Implementation Method 1
a recirculation fuel-oil cooler coupled to the recirculation line and the oil circuit
Implementation Method 2
an air-fuel cooler coupled to the recirculation line
Implementation Method 3
transferring heat from the second portion of fuel to air
Implementation Method 4
The heat generated by a gas turbine engine may be managed by a thermal management system. Thermal management systems may utilize engine fluids such as fuel and oil to cool the engine by transferring excess engine heat overboard.
Data Source
AI summary
The present disclosure provides systems and methods related to thermal management systems for gas turbine engines. For example, a thermal management system comprises a fuel circuit, comprising a burn line and a recirculation line, and a burn line fuel-oil cooler, coupled to the burn line and an oil circuit. The oil circuit comprises a sending portion, configured to carry oil from the burn line fuel-oil cooler to an engine lube system, and a returning portion, configured to carry oil from the engine lube system to the burn line fuel-oil cooler. The thermal management system further comprises a recirculation fuel-oil cooler, coupled to the recirculation line and the returning portion, and an air-fuel cooler coupled to the recirculation line.