Geared Turbofan Engine Planet Gear Speed Reduction
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Solution Overview
Problem
Conventional gas turbine engines face inefficiencies and size limitations due to the common speed operation of the fan and low-pressure compressor, which hinders the achievement of more efficient and compact turbine designs.
Innovation Solution
A geared turbofan gas turbine engine with a gear reduction mechanism, utilizing a planet gear arrangement that allows the low-pressure spool to rotate at least 2.3 times faster than the fan, maintaining the same direction of rotation, thereby enabling different speed operation and reducing turbine volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a gear reduction mechanism is introduced to allow different speed operation between the fan and low-pressure spool, then fuel efficiency and power density are improved, but device complexity increases
Solution Approach 1:
A planet gear arrangement is introduced as an intermediary mechanism between the low-pressure spool and the fan. The planet gear set includes a pinion gear connected to the low-pressure spool, planet gears meshing with the pinion, and a ring gear connected to the fan. This intermediary gear system enables different speed operation (low-pressure spool rotates faster than the fan) while maintaining a compact configuration, thereby improving fuel efficiency without excessive complexity increase.
2Volume of moving object
If the low-pressure spool rotates at a higher speed relative to the fan through gear reduction, then turbine volume is reduced and power density increases, but device complexity increases
Solution Approach 1:
The planet gear arrangement employs a nested configuration where planet gears are positioned within the annular space between the pinion gear and the ring gear. The planet gears rotate on carriers that are themselves rotated by the pinion, creating a compact nested structure. This nesting principle allows the gear reduction mechanism to fit within a small volume, reducing overall turbine volume while maintaining the speed differential between the low-pressure spool and the fan.
3Productivity
If a planet gear arrangement with gear ratio above 2.3:1 is used to maintain the same direction of rotation, then compactness and efficiency are improved, but manufacturing precision requirements increase
Solution Approach 1:
The planet gear arrangement is designed with a specific gear ratio greater than 2.3:1, which is achieved by carefully selecting the number of teeth on the pinion gear, planet gears, and ring gear. This parameter optimization allows the low-pressure spool to rotate at least 2.3 times faster than the fan while maintaining the same direction of rotation. The high gear ratio enables compact turbine design and high power density, though it does require precise manufacturing to ensure proper meshing and minimize backlash.
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 configuration results in a more compact and efficient engine with increased power density and fuel efficiency, achieving thrust per unit volume significantly higher than prior art engines, while allowing for the use of various materials to further minimize turbine size.
Implementation Method 1
a gear reduction mechanism, utilizing a planet gear arrangement that allows the low-pressure spool to rotate at least 2.3 times faster than the fan
Implementation Method 2
The planet gear arrangement has a gear ratio above 2.3:1, meaning that the low pressure spool turns at least or equal to about 2.3 times as fast as the fan
Data Source
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AI summary
A gas turbine engine turbine has a high pressure turbine configured to rotate with a high pressure compressor as a high pressure spool in a first direction about a central axis and a low pressure turbine configured to rotate with a low pressure compressor as a low pressure spool in the first direction about the central axis. A power density is greater than or equal to about 1.5 and less than or equal to about 5.5 lbf/cubic inches. A fan is connected to the low pressure spool via a speed changing mechanism and rotates in the first direction.