Secondary Fuel Pumping Using Excess Main Flow at Intermediate Power
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Solution Overview
Problem
Existing gas turbine engines waste energy and reduce efficiency by recirculating excess fuel, which is not needed at intermediate power conditions, leading to increased fuel temperature and reduced heat acceptance capacity.
Innovation Solution
A fuel system with a main pump and a secondary pump, driven by a common shaft, utilizes excess fuel flow to generate a secondary fuel flow, reducing waste heat and improving efficiency by using the excess fuel for intermediate power conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical pump is sized for high power conditions, then sufficient fuel is provided for high power and low power conditions, but excess fuel not needed is recirculated back to the fuel tank, wasting energy and reducing efficiency
Solution Approach 1:
The fuel pump is divided into two separate pumps: a main pump sized for high power conditions and a secondary pump for intermediate power conditions. This segmentation allows each pump to be optimally sized for its specific operating regime, eliminating the need to recirculate excess fuel from an oversized single pump.
Solution Approach 2:
The system dynamically switches between the main pump and secondary pump based on engine power conditions. The secondary pump is activated when the engine operates at intermediate power levels, automatically adjusting the fuel delivery configuration to match current demand and eliminate waste recirculation.
2Quantity of substance
If excess fuel is recirculated to maintain fuel supply capacity, then fuel availability is ensured, but fuel temperature increases and heat acceptance capacity is reduced
Solution Approach 1:
By segmenting the fuel delivery into two pumps, the system eliminates unnecessary recirculation loops that generate heat. Each pump operates only when needed, preventing the continuous circulation of fuel that would otherwise absorb engine heat and increase fuel temperature.
Solution Approach 2:
The system converts what would be wasted fuel flow (excess fuel from an oversized pump) into a useful function by directing it through the secondary pump only when needed for intermediate power conditions, thereby converting potential waste heat into useful fuel delivery while maintaining proper fuel temperature.
3Device complexity
If a single mechanical pump is used for all power conditions, then system complexity is minimized, but efficiency is reduced due to excess fuel recirculation at intermediate power conditions
Solution Approach 1:
The fuel pump system is segmented into two pumps with distinct functions: the main pump handles high power conditions while the secondary pump handles intermediate power conditions. This segmentation, controlled by a relatively simple valve system, achieves significant efficiency improvements with minimal increase in overall system complexity.
Data Source
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AI summary
A fuel system (62) for a gas turbine engine (20) includes a main fuel pump (70) generating a main fuel flow (64) into a main fuel passage (114) and a secondary pump (72) generating a secondary fuel flow (88) into a secondary flow passage (118). A first control valve (76) is disposed in a passage (120) between the main fuel passage (114) and the secondary flow passage (118). The first control valve (76) selectively directs an excess portion of the main fuel flow (64) to the secondary flow passage (118) to provide at least a portion of the secondary fuel flow (88).