Reversed-flow turbofan core spool arrangement
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Solution Overview
Problem
In multi-spool gas turbine engines, reducing the core size while maintaining efficient performance is challenging due to limitations in the low pressure spool's rotational speed and shaft diameter, which necessitates compromises in the high pressure spool's size and weight.
Innovation Solution
The implementation of a two-and-a-half spool turbofan engine architecture with a reversed-flow high pressure spool and a cross-flow low pressure spool, eliminating the need for the low pressure shaft to pass through the high pressure spool, allowing for reduced shaft lengths and diameters without sacrificing critical speed, and incorporating ductwork for efficient air routing and thrust production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the core size is reduced to improve efficiency, then fuel efficiency improves, but the low pressure shaft diameter cannot be reduced due to critical speed limitations
Solution Approach 1:
The patent inverts the traditional nested core arrangement by positioning the high pressure spool outside the low pressure spool. This reversal allows the low pressure shaft to be shortened and thinned without compromising structural integrity, as it no longer needs to extend through the entire combustor section. The high pressure shaft now extends through the combustor while the low pressure shaft is shortened, resolving the contradiction between core size reduction and shaft diameter requirements.
Solution Approach 2:
The patent reconfigures the spatial arrangement of spools from a concentric nested structure to an alternative dimensional layout where the high pressure spool is positioned externally. This dimensional change allows independent optimization of shaft lengths and diameters for each spool, enabling the low pressure shaft to be reduced in diameter while maintaining critical speed requirements, and allowing the core to be reduced in size for improved fuel efficiency.
2Volume of moving object
If the core size is reduced, then engine size decreases, but the high pressure spool size and weight must be increased to accommodate larger low pressure shaft openings
Solution Approach 1:
By inverting the spool arrangement so the high pressure spool is external to the low pressure spool, the patent eliminates the need for large openings in the high pressure spool to accommodate the low pressure shaft. The high pressure shaft extends through the combustor section instead, allowing the high pressure spool to be reduced in size and weight while the core is downsized for improved efficiency.
3Speed
If the low pressure shaft length is reduced, then critical speed requirements are met, but the high pressure spool must accommodate larger openings
Solution Approach 1:
The inverted spool configuration allows the high pressure shaft to extend through the combustor section while the low pressure shaft is shortened. This eliminates the conflict between reducing low pressure shaft length for critical speed and maintaining high pressure spool integrity, as the high pressure shaft now serves as the primary structural element extending through the combustor.
Data Source
Figure 1
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AI summary
A gas turbine engine (10) comprises a fan drive gear system (12), a low spool (14) connected to the fan drive gear system, and a high spool (16) disposed aft of the low spool. The low spool comprises a rearward-flow low pressure compressor (26) disposed aft of the fan drive gear system, and a forward-flow low pressure turbine (30) disposed aft of the low pressure compressor. The high spool comprises a forward-flow high pressure turbine (32) disposed aft of the low pressure turbine, a combustor (18) disposed aft of the high pressure turbine, and a forward-flow high pressure compressor (36) disposed aft of the combustor.