Concentric Power Takeoff Transmission for Gas Turbine Engines
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Solution Overview
Problem
Gas turbine engines face challenges in providing higher power extraction for future aircraft systems without compromising engine performance and increasing weight, length, and cost due to the addition of low rotor gears, which affect the critical speed margin.
Innovation Solution
A power takeoff and gearbox system with concentric high and low rotor towershafts extending to a common gearbox housing, where the low rotor towershaft is driven by the low pressure compressor and the high rotor towershaft by the high pressure compressor, with bevel gears for power transmission, allowing for co- or counter-rotation and axial disposition between thrust bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If low rotor gears are added to accommodate higher power extraction demand, then power extraction capability is improved, but engine weight, overall length, and cost increase
Solution Approach 1:
The patent combines the low rotor power takeoff and high rotor power takeoff into a single integrated gearbox housing. The low rotor towershaft and high rotor towershaft are concentric and extend to the common gearbox housing, merging two separate power transmission paths into one unified structure. This eliminates the need for separate gearboxes and reduces overall engine weight while maintaining high power extraction capability.
Solution Approach 2:
The patent implements a nested configuration where the low rotor towershaft is positioned concentrically within the high rotor towershaft path, and both shafts extend to the common gearbox housing. The bevel gears are arranged in a nested manner with the low rotor bevel gear meshed with the low rotor towershaft, and the high rotor bevel gear meshed with the high rotor towershaft. This nesting approach minimizes axial length and reduces engine overall dimensions.
2Power
If low rotor gears are added to accommodate higher power extraction demand, then power extraction capability is improved, but engine overall length increases
Solution Approach 1:
The patent implements a nested configuration where the low rotor towershaft is positioned concentrically within the high rotor towershaft path, and both shafts extend to the common gearbox housing. The bevel gears are arranged in a nested manner with the low rotor bevel gear meshed with the low rotor towershaft, and the high rotor bevel gear meshed with the high rotor towershaft. This nesting approach minimizes axial length and reduces engine overall dimensions.
Solution Approach 2:
The patent transitions from a traditional axial arrangement to a concentric radial arrangement. Instead of placing low rotor gears and high rotor gears in series along the axial direction, the patent positions both towershafts concentrically, with the low rotor towershaft inside the high rotor towershaft path. This dimensional change from axial to radial/concentric arrangement significantly reduces the axial length requirement while maintaining both power extraction functions.
3Power
If low rotor gears are added to accommodate higher power extraction demand, then power extraction capability is improved, but low rotor critical speed margin is reduced
Solution Approach 1:
The patent combines the low rotor power takeoff and high rotor power takeoff into a single integrated gearbox housing. The low rotor towershaft and high rotor towershaft are concentric and extend to the common gearbox housing, merging two separate power transmission paths into one unified structure. This eliminates the need for separate gearboxes and reduces overall engine weight while maintaining high power extraction capability.
4Power
If traditional separate power takeoff configurations are used, then power extraction is provided, but device complexity and mounting difficulty increase
Solution Approach 1:
The patent combines the low rotor power takeoff and high rotor power takeoff into a single integrated gearbox housing. The low rotor towershaft and high rotor towershaft are concentric and extend to the common gearbox housing, merging two separate power transmission paths into one unified structure. This eliminates the need for separate gearboxes and reduces overall engine weight while maintaining high power extraction capability.
Solution Approach 2:
The common gearbox housing serves multiple functions: it houses both the low rotor bevel gear and high rotor bevel gear, provides mounting locations for both power takeoff shafts, and contains the lubrication system for both gear sets. This multi-functional design simplifies the overall structure and reduces the number of separate components required.
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 minimizes axial length and weight, simplifies mounting and lubrication, and maintains a low rotor critical speed margin while providing efficient power distribution to aircraft subsystems.
Implementation Method 1
a low rotor bevel gear is fixed for rotation with the first spool and a low rotor bevel gear is fixed to the low rotor towershaft and meshed with the low rotor bevel gear such that rotation of the first spool drives rotation of the low rotor towershaft
Data Source
AI summary
A power takeoff and gearbox system of a multi-spool gas turbine engine includes a low rotor towershaft operably connected to and driven by a first spool of the gas turbine engine, and a high rotor towershaft operably connected to and driven by a second spool of the gas turbine engine. The high rotor towershaft and the low rotor towershaft are concentric and extend to a common gearbox housing.