Aircraft Fuel Recirculation Control for Heated Combustor Fuel
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Solution Overview
Problem
The aviation industry seeks to manage heat and fuel within gas turbine engines effectively when using fuels different from traditional kerosene-based jet fuels, leveraging the unique properties of alternative fuels.
Innovation Solution
A gas turbine engine design incorporating a fuel-oil heat exchanger, a fuel return line, and a modulator valve to regulate the temperature ratio of fuel in the tank to fuel delivered to the combustor, utilizing a modulator valve to control the flow of fuel along the return line to maintain optimal temperature ratios and prevent excessive fuel temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat is transferred from oil to fuel using a fuel-oil heat exchanger, then fuel temperature is increased for efficient combustion, but fuel in the tank may overheat and cause thermal degradation
Solution Approach 1:
The fuel system is segmented into two pathways: a main flow through the heat exchanger for temperature control, and a recirculation loop that returns heated fuel to the tank. This segmentation allows differential temperature management - the combustor receives heated fuel while the tank fuel remains cooler through continuous circulation and mixing
Solution Approach 2:
The recirculation line creates a feedback mechanism where temperature information from the heat exchanger outlet is fed back to the tank. The modulator valve adjusts the recirculation flow rate based on temperature differential, ensuring that when combustor fuel is heated to optimal combustion temperature, an equivalent amount of fuel is returned to the tank to maintain thermal equilibrium and prevent overheating
2Reliability
If modulator valve recirculates heated fuel back to the tank, then tank fuel temperature is controlled to prevent overheating, but energy is wasted by re-heating the same fuel
Solution Approach 1:
The recirculation system maintains continuous useful action by keeping fuel in constant motion through the heat exchanger and back to the tank. This continuous circulation prevents thermal stratification and hot spots in the tank while ensuring the combustor always receives fuel at the optimal temperature. The modulator valve optimizes the recirculation rate to maintain this continuous action with minimal energy waste
Solution Approach 2:
The system uses the fuel itself as the cooling medium for the tank. Heated fuel from the heat exchanger is returned to the tank, where it naturally mixes with and cools the bulk fuel storage. This self-service cooling mechanism eliminates the need for separate cooling systems or energy input to maintain tank fuel temperature
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 design ensures efficient temperature management of alternative fuels, preventing overheating and enhancing engine performance by maintaining a controlled temperature ratio, thereby optimizing engine operation with non-traditional fuels.
Implementation Method 1
a fuel-oil heat exchanger arranged to receive fuel from a fuel tank on board the aircraft and transfer heat from the oil to the fuel
Data Source
AI summary
A gas turbine engine for an aircraft, comprising: a combustor; a fuel-oil heat exchanger arranged to receive fuel and transfer heat from the oil to the fuel so as to raise the fuel temperature to at least 120° C. on entry to the combustor; a fuel recirculation line arranged to recirculate at least some fuel on a fuel flow path from a first point on the fuel flow path to a second point on the fuel flow path, the second point upstream of the first point; and a modulator valve arranged to modulate the flow of fuel along the fuel recirculation line. A method of operating a gas turbine engine is also disclosed.