Constant Speed Accessory Gearbox for Variable Engine Shafts
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Solution Overview
Problem
Turbine engines face challenges in efficiently driving accessory components due to variations in engine shaft speed, requiring compromises in component design that lead to inefficiencies.
Innovation Solution
A constant speed drive system, such as a continuously variable transmission (CVT), is integrated with the accessory gearbox to provide a constant or near-constant speed input to accessory components, independent of the varying engine shaft speed, using a controller to manage the CVT and incorporating a heat exchanger for temperature regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If accessory components are driven directly by the engine shaft through a conventional accessory gearbox, then the system structure is simple, but accessory components must accommodate significant speed variations which reduces efficiency and requires design compromises
Solution Approach 1:
A constant speed drive mechanism is introduced as an intermediary between the variable-speed engine shaft and the accessory components. This mediator converts the variable input speed into a constant output speed, allowing accessory components to operate efficiently at their optimal speed regardless of engine shaft variations.
Solution Approach 2:
The drive system transforms the speed parameter from variable (engine shaft speed) to constant (accessory drive speed). By changing the speed parameter through the constant speed drive mechanism, accessory components can maintain optimal operating conditions across different engine power settings.
2Adaptability or versatility
If accessory components are designed to accommodate extremes in shaft speed variations, then the system is adaptable to all operating conditions, but component structure requires compromises that reduce overall efficiency
Solution Approach 1:
The constant speed drive acts as a buffer that decouples the accessory components from engine shaft speed variations. This intermediary absorbs the speed fluctuations, allowing accessories to maintain constant optimal speed while the engine operates across its full speed range.
Solution Approach 2:
The drive system is segmented into two independent functional sections: the variable-speed engine shaft section and the constant-speed accessory drive section. This segmentation allows each section to operate independently at its optimal conditions, with the constant speed drive translating between the two.
3Productivity
If a constant speed drive system is integrated with the accessory gearbox, then accessory components operate at constant optimal speed, but the system complexity and device structure increase
Solution Approach 1:
The constant speed drive mechanism is merged with the existing accessory gearbox structure. By integrating these functions into a single unified device rather than separate components, the overall system complexity is minimized while achieving constant speed output for accessory components.
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 approach allows accessory components to operate efficiently within a limited speed range, reducing inefficiencies and enabling optimized design and performance across varying engine conditions.
Implementation Method 1
a heat exchanger that transfers heat that is generated within the constant speed drive into a cooling flow
Data Source
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AI summary
An accessory drive system (62) for a turbine engine (20) includes a first input shaft (70) that is coupled to a first engine drive shaft (50), a constant speed drive (64) that is driven at an input speed by the first input shaft (70) that varies, the constant speed drive (64) includes an output (80) that rotates at a constant speed independent of the input speed, an accessory gearbox (66) that includes a first gear system that is driven by the output (80) from the constant speed drive (64), and a first accessory component that is mounted to the accessory gearbox (66) and driven by the gear system.