Compact Accessory Gearbox for Gas Turbine Engine
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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
The design incorporates a compact accessory gearbox with concentric low speed and high speed input shafts, utilizing bevel gears and an intercooled cooling air boost compressor, where the boost axis is parallel or concentric with the drive input axis, allowing for efficient drive transmission to multiple accessories within a single, compact gearbox.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional separate gearboxes are used for low speed and high speed accessories, then each accessory system can be independently driven, but the overall packaging volume increases and space constraints are not met
Solution Approach 1:
The patent combines two separate accessory drive systems (low speed and high speed) into a single integrated gearbox assembly. The low speed input shaft and high speed input shaft are merged into one housing, with both shafts driving their respective accessories through shared bearing support and a common oil lubrication system. This merging reduces the total packaging volume while maintaining the functional independence of each accessory system.
Solution Approach 2:
The patent implements a nested configuration where the low speed input shaft is positioned concentrically within the high speed input shaft. The low speed shaft rotates within the hollow interior of the high speed shaft, allowing both shafts to occupy the same radial space. This nesting arrangement significantly reduces the overall gearbox diameter and packaging volume while enabling independent rotation and drive transmission for each shaft to their respective accessories.
2Volume of moving object
If tower shafts drive accessories at angled orientations, then drive transmission to multiple accessories is achieved, but the gearbox packaging volume increases
Solution Approach 1:
The patent transitions from traditional angled tower shaft drives to a concentric dimensional arrangement where both low speed and high speed input shafts rotate about the same central axis. This dimensional change from angular to concentric configuration allows drive transmission to multiple accessories while minimizing the radial packaging volume, as both shafts occupy the same axial space rather than requiring angular separation.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~5
AI summary
A gas turbine engine (20) has a low speed input shaft (110) which drives a first plurality of accessories. A high speed input shaft (114) drives a second plurality of accessories. The first plurality of accessories rotate about a first set of rotational axes (128) perpendicular to a first plane (L). The second plurality of accessories rotate about a second set rotational axes (130) perpendicular to a second plane (H). The first and second planes (L, H) extending in opposed directions away from a drive input axis (102X). Compressed air is tapped and passes through a heat exchanger (96), then to a boost compressor (122), and then to at least one rotatable components in a main compressor section (90) and a main turbine section (92). The boost compressor (122) driven on a boost axis (122x), which is non-parallel to the first set of rotational axes (128) and the second set of rotational axes (130).