Fan-Tied Inducer Section for Gas Turbine Engine Swirl Control
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Solution Overview
Problem
The low energy air exiting the fan in a typical jet engine creates a swirling effect that makes it difficult to efficiently feed air into the low pressure compressor, leading to inefficiencies in the engine's operation.
Innovation Solution
The implementation of a fan-tied inducer section with a gearbox having a gear reduction ratio greater than 2.3, which includes a plurality of inducer stages coupled to the fan rotor and a core inlet stator with vanes, helps to stabilize and control the air flow, reducing swirl and improving air diffusion into the compressor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a typical jet engine uses a low speed spool to drive the low pressure compressor, then the fan can be connected to the low shaft, but the low energy air exiting the fan creates a swirling effect that makes it difficult to efficiently feed air into the low pressure compressor
Solution Approach 1:
An inducer section is introduced as an intermediary component between the fan and the low pressure compressor. This inducer section includes inducer blades that are directly driven by the fan rotor through a gear system, creating a controlled induced flow that eliminates the harmful swirling effect while efficiently feeding air to the low pressure compressor.
Solution Approach 2:
The patent replaces the conventional direct mechanical connection between the low speed spool and low pressure compressor with a gear-driven inducer system. The gear system reduces the fan rotor speed and drives the inducer blades, which mechanically control the air flow to eliminate swirl and improve feeding efficiency to the compressor.
2Device complexity
If the fan rotor is directly connected to the low pressure compressor, then the structure is simpler, but the low energy air creates swirl that reduces efficiency
Solution Approach 1:
The inducer section serves as a mediating structure between the fan rotor and low pressure compressor. While it adds some structural complexity, it dramatically improves air flow efficiency by controlling the induced flow and eliminating harmful swirl, thus resolving the trade-off between structural simplicity and operational efficiency.
3Object-generated harmful factors
If the gear reduction ratio is increased to improve air flow control, then the swirl reduction is enhanced, but the device complexity increases
Solution Approach 1:
The patent optimizes the gear reduction ratio as a key parameter, specifying a ratio greater than 2.3:1 between the fan rotor and inducer blades. This parameter change achieves effective swirl reduction and improved air flow control while maintaining reasonable device complexity through careful selection of the reduction ratio.
Data Source
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Figure 4~5B
AI summary
A gas turbine engine includes a shaft (40), a speed reduction device (48) driven by the shaft, and a fan including a fan rotor driven by the speed reduction device. A compressor section (44) has a plurality of compressor stages driven by the shaft. At least one inducer stage (114) is positioned aft of the fan and coupled for rotation with the fan rotor. The at least one inducer stage is positioned upstream of the compressor section.