Geared Core Compressor Layout to Limit Rotor Bow in Turbofans
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Solution Overview
Problem
Modern gas turbine engines face challenges in optimizing overall efficiency without compromising engine operability and maintenance requirements, particularly due to issues like rotor bow and inefficient compression systems.
Innovation Solution
The design incorporates a gearbox to drive the fan at a lower rotational speed than the core shaft, with specific ratios for core compressor pressure, aspect ratio, and compression system parameters, including 12-14 rotor stages, to achieve high thermal efficiency and reduce rotor bow, while optimizing installation and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the core compressor pressure ratio is increased to achieve high thermal efficiency, then thermal efficiency is improved, but the compressor length increases excessively
Solution Approach 1:
The patent applies parameter changes by optimizing the core compressor pressure ratio to fall within a specific range (34-60) and controlling the aspect ratio within defined limits. This allows achieving high thermal efficiency while preventing excessive compressor length, resolving the contradiction between efficiency and compactness.
Solution Approach 2:
The patent introduces a gearbox that allows the fan to rotate at a lower speed than the core shaft, enabling dynamic speed adjustment. This dynamic configuration enables the system to achieve high compressor pressure ratio without proportionally increasing compressor length, as the gearbox can accommodate the speed differential while maintaining compact dimensions.
2Productivity
If the number of rotor stages is increased to achieve higher compression ratio, then compression efficiency is improved, but the compressor becomes excessively long
Solution Approach 1:
The patent specifies that the core compressor should have between 12-14 rotor stages, which is an optimized number that achieves high compression efficiency without requiring an excessively long compressor. This parameter optimization resolves the contradiction between compression efficiency and compact length.
3Adaptability or versatility
If the core compressor aspect ratio is reduced to shorten the compressor, then installation flexibility is improved, but compression efficiency deteriorates
Solution Approach 1:
The patent defines the core compressor aspect ratio within a specific range that balances compression efficiency and installation flexibility. By controlling the aspect ratio parameter, the design achieves high compression efficiency while maintaining sufficient compactness for various installation configurations, resolving the contradiction between efficiency and adaptability.
4Loss of energy
If the fan is driven at higher rotational speed to improve propulsive efficiency, then propulsive efficiency is improved, but rotor bow risk increases
Solution Approach 1:
The patent introduces a gearbox that allows the fan to rotate at a lower speed than the core shaft, creating a dynamic speed relationship. This configuration reduces the rotational speed differential that causes rotor bow while maintaining acceptable propulsive efficiency, resolving the contradiction between efficiency and reliability.
Solution Approach 2:
The patent optimizes the fan rotational speed parameter to be lower than the core shaft speed, which directly reduces rotor bow risk. This parameter change is achieved through the gearbox configuration, balancing propulsive efficiency with reliability by preventing excessive speed differentials.
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
The design achieves high thermal and propulsive efficiency with reduced rotor bow risk, improved installation flexibility, and lower maintenance requirements, enhancing overall engine performance when integrated with an airframe.
Implementation Method 1
a gearbox that receives an input from a core shaft that is connected to at least a part of the turbine, the gearbox outputting drive to the fan so as to drive the fan at a lower rotational speed than the core shaft
Implementation Method 2
The flow that does pass into the core of the gas turbine engine is compressed in a compressor before being combusted
Implementation Method 3
compressed in a compressor before being combusted
Implementation Method 4
then expanded through a turbine
Data Source
AI summary
A gas turbine engine that has improved fuel burn provides operability and/or maintenance requirements when installed on an aircraft. The gas turbine engine is provided with a core compressor that includes twelve, thirteen or fourteen rotor stages. The gas turbine engine has a ratio of a core compressor aspect ratio divided by a core compressor pressure ratio is in the range of from 0.03 to 0.09. This results in an optimum balance between installation benefits, operability, maintenance requirements and engine efficiency when the gas turbine engine is installed on an aircraft.