Variable-Transmission Accessory Gearbox for Compact Turbine Packaging
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Solution Overview
Problem
As gas turbine engines become smaller, packaging for the gearboxes that transmit drive from the tower shafts to various auxiliary systems becomes a challenge due to the need for efficient and compact transmission of power from multiple spools with different speed and pressure characteristics.
Innovation Solution
A compact accessory gearbox design featuring concentric low speed and high speed input shafts, with a variable speed transmission that adjusts input speed to achieve a desired output speed, driving accessories with rotational axes arranged in a V configuration to optimize packaging and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional separate shaft designs are used for low speed and high speed spools, then each accessory can be driven independently, but the gearbox volume increases and packaging becomes difficult in smaller engines
Solution Approach 1:
The patent combines two separate input shafts (low speed and high speed) into a single integrated shaft structure. The low speed input shaft and high speed input shaft are merged into one common shaft that receives power from both spools, eliminating the need for separate shafts and reducing overall gearbox volume while maintaining independent accessory drive capabilities
Solution Approach 2:
The patent employs a nested arrangement where the high speed input shaft is positioned within or alongside the low speed input shaft in a compact configuration. This nesting allows both shafts to occupy overlapping or adjacent spatial volumes, significantly reducing the overall footprint of the gearbox and enabling packaging in smaller engine applications
2Volume of moving object
If accessories are arranged in a V configuration with rotational axes perpendicular to respective planes, then packaging efficiency improves, but the gear transmission path becomes more complex
Solution Approach 1:
The patent transitions from a conventional single-plane accessory arrangement to a three-dimensional V configuration. Accessories are distributed across two different planes with their rotational axes perpendicular to each plane, effectively utilizing vertical and lateral space to improve packaging efficiency while managing transmission complexity through strategic gear placement
3Adaptability or versatility
If a variable speed transmission is added to accommodate wide speed excursions, then accessory speed control improves, but the device complexity and packaging difficulty increase
Solution Approach 1:
The variable speed transmission is designed to serve multiple functions simultaneously: it accommodates the wide speed excursions from both low speed and high speed spools, provides adjustable output speeds for different accessories, and integrates into the existing shaft and gear structure without requiring a completely separate transmission system. This multi-functionality reduces the overall volume impact while maintaining adaptability
Data Source
AI summary
An auxiliary gearbox has a low speed input shaft driving a first plurality of accessories. A high speed input shaft drives a second plurality of accessories. The first plurality of accessories rotating about a first set of rotational axes, which are parallel to each other and perpendicular to a first plane. The second plurality of accessories rotating about a second set of rotational axes, which are parallel to each other and perpendicular to a second plane. The first and second planes extending in opposed directions away from a drive input axis of the high speed input shaft and the low speed input shaft. The low speed input shaft drives a variable speed transmission. A gas turbine engine is also disclosed.