Differential Gear Power Offtake for Double-Shaft Turbine Engines
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Solution Overview
Problem
Current systems for taking mechanical power from multi-shaft gas turbine engines, particularly double-shaft engines, face challenges in accommodating the different operating ranges of high-pressure (HP) and low-pressure (LP) shafts, as existing solutions are not compatible with the varying speed ratios between idling and full gas speeds, which affects the operation of auxiliary machines installed on the accessory gearbox.
Innovation Solution
A device with a differential gear system featuring a selective coupling mechanism, where a common drive shaft is connected to either the LP or HP shaft based on engine speed, using a dog clutch for efficient power transfer, ensuring the accessory gearbox operates within compatible speed ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If power is taken off from the HP shaft only, then the auxiliary machines can operate within compatible speed ranges, but the engine performance deteriorates at low rotation speeds due to increased power demand
Solution Approach 1:
The patent implements a dynamic power offtake system that automatically switches between LP and HP shaft power sources based on engine operating conditions. A selective coupling mechanism engages the LP shaft power transmission path when engine speed is below a threshold value, and engages the HP shaft power transmission path when engine speed exceeds the threshold, allowing the system to adapt to varying operational requirements and maintain optimal engine performance across different speed ranges
2Power
If power is taken off from the LP shaft, then engine performance is maintained at low rotation speeds, but the speed ratio variation between idling and full gas speeds creates incompatibility with auxiliary machine operating ranges
Solution Approach 1:
The system dynamically selects which shaft (LP or HP) to couple to the differential gear based on engine speed thresholds. At low speeds, the LP shaft is engaged providing power while keeping the gearbox speed within acceptable ranges for auxiliary machines. At higher speeds, the HP shaft is engaged to provide power. This dynamic switching resolves the contradiction by adapting the power source to match both engine performance requirements and auxiliary machine operating constraints
Solution Approach 2:
The patent changes the operating parameter of power source selection based on engine speed. By monitoring engine speed and switching between LP and HP shaft power transmissions accordingly, the system maintains gearbox output speed within the operational range of auxiliary machines while preserving engine performance characteristics across different operating conditions
3Device complexity
If a fixed power offtake system is used, then the structure is simple, but it cannot adapt to the wide speed variations between LP and HP shafts
Solution Approach 1:
The patent introduces a dynamic selective coupling system that can switch between different power transmission paths (LP shaft and HP shaft) based on engine operating conditions. This dynamic capability allows the system to adapt to wide speed variations while maintaining a relatively compact structure. The selective coupling mechanism engages the appropriate shaft through a differential gear, providing adaptability without requiring completely separate power transmission systems for each shaft
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
Enables efficient mechanical power extraction from both LP and HP shafts, maintaining engine performance and compatible rotation speeds for auxiliary machines, thereby addressing the limitations of previous systems that could not adapt to the wide speed variations.
Implementation Method 1
a differential gear with a first input shaft and a second input shaft and an output shaft, the first input shaft being connected via a selective coupling either to the LP shaft or to the HP shaft, the second input shaft being connected to the HP shaft, and the output shaft being connected to the drive shaft of the said gearbox
Implementation Method 2
the selective coupling is of the dog clutch type
Data Source
AI summary
A device for driving auxiliary machines of a double-shaft turbine engine with an LP shaft and an HP shaft is disclosed. The machines are installed in an accessory gearbox which includes a common drive shaft. The device includes a differential gear with a first input shaft and a second input shaft and an output shaft. The first shaft being connected via a selective coupling either to the LP shaft or to the HP shaft, the second input shaft is connected to the HP shaft, and the output shaft being connected to the drive shaft of the gearbox.