Dual Input Drive Accessory Gearbox for Gas Turbine Speed Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional aircraft gas turbine engines require an accessory drive gearbox that can provide both increased and decreased output speeds for the starter/generator and other accessories, respectively, which is challenging due to the need for a higher starter/generator speed and lower speeds for other components.
Innovation Solution
A mechanical drive system featuring a tower shaft at a non-zero angle with bevel gears on the tower and accessory drive gearbox shafts, allowing for dual input drives with specific speed ratios to accommodate the varying requirements, including bevel gears that provide increased speed for the starter/generator and reduced speed for other accessories through spur gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional accessory drive gearbox is used with a single input shaft, then the structure is simple, but it cannot provide both increased speed for starter/generator and decreased speed for other accessories simultaneously
Solution Approach 1:
The single input shaft is segmented into two separate input shafts, each capable of receiving power from different sources (tower shaft and accessory shaft). This segmentation allows independent speed control for different accessory groups, enabling the starter/generator to receive increased speed while other accessories receive decreased speed simultaneously.
Solution Approach 2:
The accessory drive gearbox is designed with multi-functionality to serve dual purposes: it can provide speed reduction for traditional accessories (fuel pump, hydraulic pump, oil pump) while simultaneously providing speed increase for the starter/generator. The gearbox incorporates multiple gear trains that can operate independently to achieve different speed ratios for different outputs.
2Productivity
If the starter/generator runs at higher speed than the tower shaft, then the starter/generator efficiency is improved, but the other accessories require additional speed reduction
Solution Approach 1:
The patent merges the speed increase function for the starter/generator with the speed reduction function for other accessories into a single integrated gearbox system. By combining multiple gear trains within one gearbox, the system achieves both speed increase and speed reduction simultaneously without requiring separate drive systems, thereby improving starter/generator productivity while managing the complexity through integration.
Solution Approach 2:
The gearbox employs dynamic gear train configurations that can selectively engage different gear paths based on the required output. The system dynamically adjusts the speed ratios by engaging different gear combinations, allowing the starter/generator to receive amplified speed when needed while other accessories receive appropriate speed reduction, optimizing productivity across all components.
3Adaptability or versatility
If multiple gear trains are used to provide different speed ratios, then the speed distribution requirements are met, but the device complexity increases
Solution Approach 1:
Multiple gear trains are nested within a single gearbox housing, with gears and shafts arranged in a compact, space-efficient configuration. The nested arrangement allows multiple gear trains to coexist in a confined space, providing different speed ratios without proportionally increasing the overall device volume or complexity. This nesting strategy enables versatile speed distribution while containing the structural complexity within a unified gearbox assembly.
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 enables the starter/generator to operate at a higher speed while other accessories receive reduced speeds, optimizing power distribution and efficiency within the aircraft gas turbine engine.
Implementation Method 1
first and second bevel gears mounted on the tower shaft... a third bevel gear mounted on the first shaft and meshing with the first bevel gear on the tower shaft and a fourth bevel gear mounted on the second shaft and meshing with the second bevel gear on the tower shaft
Data Source
AI summary
A mechanical drive system of an aircraft gas turbine engine includes a tower shaft operatively connected to first and second shafts in an accessory drive gearbox. The first shaft rotates at a rotational speed lower than the rotational speed of the tower shaft and the second shaft rotates at a rotational speed equal to or higher than the rotational speed of the tower shaft.