Star Gear Turbofan Architecture for Fan Speed Decoupling
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Solution Overview
Problem
Traditional gas turbine engines with a single-speed fan drive turbine face inefficiencies due to the fixed speed relationship between the fan and the turbine, limiting flexibility and efficiency, especially in high-bypass geared aircraft engines.
Innovation Solution
The implementation of a geared architecture in a turbofan engine, which includes a speed change mechanism such as a planetary gear system, allows the fan to rotate at a lower speed than the low-speed spool, optimizing efficiency and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-speed fan drive turbine is used, then the structure is simple, but the efficiency and flexibility are limited
Solution Approach 1:
The patent applies a geared architecture with a planetary gear system that enables variable speed operation between the fan and the low-speed spool. The gear reduction mechanism allows the fan to rotate at a lower speed than the low-speed spool, creating a dynamic speed relationship that optimizes efficiency across different operating conditions while maintaining structural integrity.
Solution Approach 2:
The planetary gear system acts as an intermediary mechanism between the fan drive turbine and the low-speed spool. This gear reduction system mediates the speed difference, allowing the fan to operate at optimized speeds while transmitting power from the turbine, thereby improving flexibility without directly complicating the turbine structure itself.
2Force
If the fan rotates at higher speed, then thrust is increased, but stress on components increases
Solution Approach 1:
The geared architecture dynamically adjusts the speed relationship between the fan and turbine through gear reduction. The fan can rotate at lower speeds while the low-speed spool rotates at higher speeds, maintaining necessary thrust while reducing mechanical stress on fan components and bearings through the speed differentiation enabled by the planetary gear system.
Data Source
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AI summary
A turbofan engine includes a fan section. A turbine section is in driving engagement with the fan section through a star gear system (48). The star gear system (48) includes a plurality of star gears (82) surrounding a sun gear (74). A carrier (90) supports the plurality of star gears (82) and includes a first carrier bearing flange (128). A ring gear (108) surrounds the plurality of star gears (82) and includes a ring gear bearing flange (124). At least one ring gear carrier bearing (130) engages the carrier bearing flange (128) and the ring gear bearing flange (124). A speed change mechanism (48) for a gas turbine engine is also disclosed.