Fuel Viscosity Control via Oil-Fuel Heat Exchange in Gas Turbines
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Solution Overview
Problem
The use of fuels different from traditional kerosene-based jet fuels, such as sustainable aviation fuels, necessitates adjustments in gas turbine engine operations to manage their differing fuel properties, particularly to improve combustion efficiency and oil cooling.
Innovation Solution
A heat exchange system with parallel air-oil and fuel-oil heat exchangers and a modulation valve is used to control the heat transfer between oil and fuel, raising the fuel temperature to specific ranges (135° C. to 200° C.) and adjusting viscosity (0.2 mm²/s to 0.58 mm²/s) on entry to the combustor, optimizing fuel delivery and combustion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fuel temperature is increased to improve combustion efficiency, then fuel viscosity decreases and atomization improves, but fuel may degrade or coke formation increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling fuel temperature within a specific range (135°C to 200°C) to optimize combustion efficiency while preventing fuel degradation. The modulation valve dynamically adjusts the proportion of oil flowing through each heat exchanger branch, enabling real-time temperature regulation that balances improved atomization with fuel stability maintenance.
Solution Approach 2:
The system implements dynamics through the modulation valve that can vary the oil flow distribution between parallel heat exchanger branches in real-time. This dynamic control allows the fuel temperature to be adjusted according to operating conditions, maintaining optimal combustion efficiency while preventing excessive temperature effects that would cause fuel degradation or coking.
2Productivity
If more heat is transferred from oil to fuel, then fuel temperature increases and combustion efficiency improves, but oil cooling effectiveness decreases
Solution Approach 1:
The patent applies segmentation by dividing the oil cooling system into two parallel heat exchanger branches. One branch transfers heat to fuel for combustion efficiency, while the other branch removes excess heat from oil to maintain proper oil temperature. The modulation valve controls the distribution of oil flow between these segmented paths, balancing fuel heating needs with oil cooling requirements.
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 approach enhances combustion efficiency, improves oil cooling, and extends the life of engine components by controlling fuel temperature and viscosity, resulting in a more thermally efficient and performance-enhanced gas turbine engine.
Implementation Method 1
a fuel-oil heat exchanger through which the oil in the primary oil loop system and the fuel flow such that heat is transferred between the oil and the fuel
Implementation Method 2
an air-oil heat exchanger through which oil in the primary oil loop system flows
Data Source
AI summary
A method of operating a gas turbine engine including an engine core including a turbine, compressor, combustor to combust a fuel, and core shaft connecting the turbine and compressor; a fan upstream of the engine core; a fan shaft; a gearbox that receives an input from the core shaft and outputs drive to the fan via the fan shaft; a primary oil loop system to supply oil to the gearbox; and a heat exchange system. The method includes controlling the heat exchange system to adjust fuel viscosity to be lower than or equal to 0.58 mm2/s on entry to the combustor at cruise conditions.