Dual Pump Fuel Flow System for Gas Turbine Heat Management
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Solution Overview
Problem
In gas turbine engines, the excess fuel flow and pump inefficiencies lead to increased fuel temperature, limiting the amount of heat that can be rejected from circulating oil, which affects engine performance, especially during cruise conditions.
Innovation Solution
A fuel flow system with a dual window valve and bypass mechanism that adjusts fuel flow between a cruise pump and an idling pump to minimize heat rejection into the fuel, optimizing pressure and flow to reduce horsepower consumption and increase heat transfer from the oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single main fuel pump is used to meet high power conditions, then sufficient fuel flow capacity is achieved, but excess fuel flow and pump inefficiencies increase fuel temperature during cruise conditions
Solution Approach 1:
The fuel pump system is segmented into two separate positive displacement pumps: a first pump sized for high power conditions and a second pump sized for cruise conditions. This segmentation allows each pump to operate at optimal efficiency in its designated regime, eliminating the need for a single oversized pump that operates inefficiently during cruise conditions and reduces fuel temperature rise.
Solution Approach 2:
The system dynamically switches between the first and second pumps based on engine operating conditions. A controller monitors engine speed and fuel flow requirements, activating the appropriate pump for each condition. This dynamic operation ensures optimal pump efficiency across the entire operating range, preventing excessive fuel temperature increase during cruise while maintaining sufficient capacity during high power conditions.
2Ease of operation
If fuel is recycled through a bypass loop to meet low fuel requirements at high engine speed, then fuel flow control is achieved, but fuel temperature increases due to repeated circulation and pump inefficiencies
Solution Approach 1:
The system dynamically selects between two pumps based on operating conditions. During cruise conditions, the second pump (sized for cruise) replaces the need for bypass recycling, directly delivering the required fuel flow without excessive circulation. This dynamic operation eliminates the temperature increase caused by repeated bypass recycling while maintaining precise fuel flow control.
3Power
If the main fuel pump is sized for high power conditions, then sufficient fuel flow is provided during start and high power, but excess flow capacity and heat rejection occur during cruise conditions
Solution Approach 1:
The fuel pump system is divided into two specialized pumps: the first pump handles high power conditions with appropriate power capacity, while the second pump handles cruise conditions with lower power consumption. This segmentation eliminates the energy waste and heat rejection that would occur if a single high-power pump operated during cruise conditions.
Solution Approach 2:
The system changes the operating parameters by switching between two pumps with different displacement volumes and power characteristics. The first pump operates at high displacement for high power conditions, while the second pump operates at lower displacement for cruise conditions. This parameter change optimizes power consumption and minimizes heat rejection during each operating regime.
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 reduces the amount of heat rejected into the fuel, enhancing engine performance by allowing more heat to be transferred from the oil while maintaining fuel temperature within tolerable limits, particularly during cruise conditions.
Implementation Method 1
The fuel system of a gas turbine engine includes a fuel pump for pressurizing and transporting the fuel through the system to the combustion chamber. The fuel pump is generally a boost stage and single positive displacement main stage
Implementation Method 2
The oil can be cooled by cooling air or fuel flowing to the combustion chamber. Fuel flowing to the combustion chamber can also be used to cool the hot circulating oil. Rejecting heat from the oil into the fuel incurs few of the penalties of air cooling.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A fuel flow system (10) for a gas turbine includes a first pump (20), a main fuel flow path (12c) and a second pump (20). The first pump (20) is connected to an actuator and a metering valve (26). The main fuel flow path (12c) is formed between the first pump (20) and the metering valve (26). The second pump (30) is connected to the main fuel flow path (12c) and supplements the fuel flow from the first pump (20) under certain conditions. The second pump (30) and first pump (20) are in parallel.