Coaxial Accessory Gearbox Layout for Compact Gas Turbine Packaging
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Solution Overview
Problem
As gas turbine engines become smaller, the packaging for gearboxes that transmit drive from the tower shafts to various auxiliary systems becomes a challenge due to space constraints.
Innovation Solution
A compact accessory gearbox design is implemented, where a low speed input shaft and a high speed input shaft are connected to their respective tower shafts, which are coaxial and rotate about a common axis, with an angle drive mechanism allowing the low speed and high speed tower shafts to drive accessories through bevel gears, enabling efficient transmission of power to multiple accessories while optimizing space usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional gearbox packaging is used, then power transmission function is achieved, but space requirements increase making it unsuitable for smaller gas turbine engines
Solution Approach 1:
The patent implements a nested configuration where the high-speed input shaft is positioned concentrically within the low-speed input shaft, and the high-speed tower shaft is received within the low-speed tower shaft. This nesting arrangement allows both speed inputs and tower shafts to occupy the same radial space, dramatically reducing the overall gearbox volume while maintaining full power transmission capability to multiple accessories
Solution Approach 2:
The patent transitions from traditional parallel shaft arrangements to a concentric/collinear arrangement where shafts are positioned along the same axis. This dimensional reorganization allows the gearbox to exploit radial space more efficiently, reducing the axial and radial footprint while preserving all power transmission paths to the accessory systems
2Adaptability or versatility
If separate tower shafts for low speed and high speed spools are used, then both spools can drive accessories independently, but packaging space increases
Solution Approach 1:
The patent merges the low-speed and high-speed tower shafts into a single collinear arrangement where both shafts rotate about a common axis. This consolidation allows both speed inputs to drive their respective accessories through shared structural elements and common mounting spaces, reducing the overall packaging area while maintaining independent accessory drive capability
Solution Approach 2:
The collinear tower shaft configuration serves multiple functions simultaneously: it supports both low-speed and high-speed inputs, provides mounting points for multiple accessories, and enables angle drives to both input shafts from a single structural location. This multi-functionality reduces the number of separate components needed, thereby reducing packaging area
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 design allows for efficient power transmission to multiple accessories while minimizing space requirements, enhancing the compactness and efficiency of the gearbox packaging in smaller gas turbine engines.
Implementation Method 1
each of the low speed and high speed tower shafts drive a bevel gear to in turn drive a bevel gear connected to the low speed input shaft and low speed output shaft
Data Source
Figure 1
Figure 2A~2C
Figure 3A~4
AI summary
A gas turbine engine (20) includes a low speed input shaft (114) connected to a low speed tower shaft (97), in turn connected to a lower speed spool (30) and a high speed input shaft (110) connected to a high speed tower shaft (99), in turn connected to a higher speed spool (32). The low speed input shaft (114) is connected to drive a first plurality of accessories. The high speed input shaft (110) is connected to drive a second plurality of accessories. The high speed tower shaft (99) and the low speed tower shaft (97) are coaxial and rotate about a common axis (I). An angle drive is provided into the low speed input shaft (114) and the high speed input shaft (110), respectively.