Dual-Input Accessory Gearbox for Gas Turbine Engines
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Solution Overview
Problem
Conventional gearboxes in gas turbine engines face inefficiencies when transferring rotational energy to accessories, particularly due to the need for larger or slower high-speed spools to accommodate accessory loads, which increases drag and reduces thermodynamic efficiency.
Innovation Solution
A dual-input accessory gearbox with first and second differentials, allowing rotational energy to be communicated from both low and high-speed spools to accessories, reducing the load on the high-speed spool and enabling efficient power distribution through a selective clutch or brake mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional single-input gearboxes are used to transfer rotational energy from the high-speed spool to accessories, then the gearbox can provide mechanical power to accessories, but the high-speed spool must operate at reduced rotational speed or increased size to accommodate accessory loads, which increases drag and reduces thermodynamic efficiency
Solution Approach 1:
The accessory gearbox is divided into two independent differential inputs: a high-speed input and a low-speed input. Each differential can independently receive rotational energy from its respective spool and distribute it to accessory loads. This segmentation allows the high-speed spool to operate at optimal speeds without being burdened by accessory loads, thereby reducing parasitic losses and improving thermodynamic efficiency.
2Power
If the high-speed spool is increased in size or reduced in speed to accommodate accessory loads, then power transfer to accessories is ensured, but the thermodynamic efficiency of the gas turbine engine decreases
Solution Approach 1:
The power transfer system is segmented into two independent pathways through the dual differential inputs. The high-speed differential handles high-speed power transfer while the low-speed differential handles low-speed power transfer. This allows each spool to operate at its optimal speed range, maintaining thermodynamic efficiency while ensuring adequate power transfer capability to accessories under all operating conditions.
Solution Approach 2:
The gearbox employs dynamic load distribution where the two differentials can independently adjust their power output based on real-time operating conditions. During high-power demands, both differentials contribute; during normal operation, the high-speed differential can operate independently at optimal speeds. This dynamic adaptability ensures power availability while maintaining thermodynamic efficiency.
3Power
If reduction gearing is used to match the rotational speed of the high-speed spool to accessory speeds, then the gearbox can power accessories, but the size of the reduction gearing increases with rotational speed mismatch
Solution Approach 1:
The reduction gearing is segmented into two separate systems: a high-speed reduction gearing connected to the high-speed spool and a low-speed reduction gearing connected to the low-speed spool. Each reduction gearing is sized appropriately for its specific speed range, avoiding the need for oversized gearing that would be required if a single system tried to handle the entire rotational speed mismatch range.
Solution Approach 2:
The system transitions from a single-dimensional speed matching approach to a two-dimensional approach by introducing both high-speed and low-speed pathways. This allows the system to handle rotational speed mismatches more efficiently by distributing the reduction gearing requirements across two dimensions (speed ranges), thereby reducing the overall size and complexity of each individual gearing system.
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 reduces parasitic losses, allows the high-speed spool to operate at higher rotational speeds, and improves overall thermodynamic efficiency by sharing the generator load between spools, while also providing reliable power to accessories during various operational conditions.
Implementation Method 1
The first differential is connected to a first input and couples therethrough the first input to an accessory gear train
Implementation Method 2
The second differential is connected to a second input and couples therethrough the second input to the accessory gear train
Implementation Method 3
The accessory gear train is configured to combine rotational energy received from the spools for powering one or more accessories mounted to the accessory gearbox
Data Source
Figure 1
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AI summary
An accessory gearbox for a gas turbine engine has an accessory gear train (102), a first input (104) and a second input (106). The first input and the second input are coupled to the accessory gear train. The accessory gear train operably couples the first input and the second input for communicating rotational energy between one or more accessories mounted to the accessory gearbox and the first and second inputs.