Close Coupled Gearbox for Tip Turbine Engine Length Reduction
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Solution Overview
Problem
Conventional turbofan engines have a complex elongated structure due to their axial flow relationship, which complicates packaging and integration of the fan-turbine rotor assembly and axial compressor, necessitating a gearbox assembly that minimizes engine length and reduces the number of bearings for increased reliability.
Innovation Solution
A gearbox assembly with a sun gear shaft rotating with the axial compressor and a planet carrier rotating with the fan-turbine rotor assembly provides a speed differential, allowing direct attachment of the fan-turbine rotor flange to the gearbox, reducing engine length and minimizing bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional axial flow turbofan engine structure is used, then the engine can achieve efficient operation, but the engine structure becomes elongated and complicated, increasing packaging difficulty
Solution Approach 1:
The patent transitions from a conventional axial-flow arrangement to a tip turbine configuration where the turbine is positioned at the tip of the fan blade rather than in the axial path. This dimensional repositioning allows the engine to maintain efficient gas path operation while significantly reducing the longitudinal length of the engine structure, enabling more compact packaging.
Solution Approach 2:
The tip turbine is integrated into the fan blade structure itself, with the turbine housed within the hollow fan blade. This nesting arrangement eliminates the need for separate axial turbine housings and reduces the overall engine length while maintaining functional efficiency.
2Speed
If the fan-turbine rotor assembly and axial compressor are integrated with a gearbox, then speed differential is achieved, but the number of bearings increases and complexity increases
Solution Approach 1:
The gearbox assembly is merged with the fan-turbine rotor assembly by directly coupling the rotor flange to the gearbox. This integration eliminates intermediate bearing supports and reduces the number of separate components, thereby reducing overall complexity while maintaining the required speed differential between the fan-turbine rotor and axial compressor.
3Speed
If the fan-turbine rotor assembly and axial compressor are integrated with a gearbox, then speed differential is achieved, but the overall engine length increases
Solution Approach 1:
The gearbox assembly is merged with the fan-turbine rotor assembly by directly coupling the rotor flange to the gearbox. This integration eliminates intermediate bearing supports and reduces the number of separate components, thereby reducing overall complexity while maintaining the required speed differential between the fan-turbine rotor and axial compressor.
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 reduces engine complexity and increases reliability by closely coupling the fan-turbine rotor assembly with the gearbox, minimizing the number of bearings and maintaining a compact engine design.
Implementation Method 1
A planetary gear system is integrated onto the tips of the hollow bypass fan blades
Data Source
AI summary
A gearbox assembly (90) closely couples a fan-turbine rotor assembly (25) and an axial compressor rotor (46) to reduce the overall engine length and minimizes the number of engine bearings.