Turbomachine Uncoupling Means for Torsional Torque Management
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Solution Overview
Problem
Dual flow turbomachines face issues with torsional torque buildup in the reduction device and turbine shaft due to fan blade loss or ingestion of foreign objects, leading to potential shaft breakages and increased aerodynamic drag, which can render an airplane impossible to pilot.
Innovation Solution
Incorporating an uncoupling means, such as a fuse connecting element, between the reduction device and the turbine shaft that breaks when a predetermined resistant torque is exceeded, allowing the system to uncouple and prevent further damage, along with additional uncoupling means between the reduction device and the fan shaft to manage excessive torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the fan is driven directly by the LP turbine shaft without a reduction device, then the structure is simpler and more reliable, but the fan cannot rotate at an optimized lower speed for better aerodynamic adaptation
Solution Approach 1:
A reduction device is introduced as an intermediary component between the LP turbine shaft and the fan. This device includes a first reduction gear connected to the LP turbine shaft and a second reduction gear connected to the fan shaft, enabling the fan to rotate at an optimized lower speed while maintaining structural integrity and operational reliability
2Strength
If the reduction device and turbine shaft are made stronger to withstand high torsional torque, then shaft breakage is prevented, but the weight and cost of components increase due to over-dimensioning
Solution Approach 1:
A torque limiting device is integrated into the reduction device to prevent excessive torsional torque from being transmitted to the turbine shaft and reduction device components. This device includes a torque limiting mechanism that activates when a predetermined torque threshold is exceeded, thereby protecting the components from breakage while allowing them to be designed with optimal rather than excessive strength
Solution Approach 2:
The torque limiting device changes the torque transmission parameter dynamically by engaging a friction element or clutch mechanism when a predetermined torque is exceeded. This allows the system to operate efficiently under normal conditions while automatically limiting torque during abnormal conditions, preventing component failure without requiring over-dimensioned parts
3Productivity
If the fan blades are made larger to improve aerodynamic performance, then the fan efficiency increases, but the risk of blade loss and foreign object ingestion increases, leading to higher torsional torque
Solution Approach 1:
The torque limiting device is positioned beforehand in the power transmission path to cushion against excessive torsional torque that may result from fan blade loss or foreign object ingestion. This protective mechanism activates before damage can propagate to the turbine shaft and reduction device, maintaining system reliability even when aerodynamic performance is enhanced with larger fan blades
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
The solution effectively limits torsional torque, preventing shaft breakages and maintaining fan operation, reducing the risk of aerodynamic drag and allowing for lighter design of turbomachine components by avoiding over-dimensioning, while ensuring safe operation and reduced drag even after uncoupling.
Implementation Method 1
a fuse connecting element which is interposed between the reduction device and the turbine shaft and which is able to be broken when it is subject to a so called uncoupling resistant torque exerted by the device for reducing speed on the turbine shaft
Data Source
AI summary
A turbomachine includes a fan shaft driven by a turbine shaft via a device for reducing a speed of rotation. The turbomachine includes an uncoupling device interposed between the reduction device and the turbine shaft. The uncoupling device is configured to uncouple the reduction device and the turbine shaft in response to the exceeding of a determined resistant torque exerted by the reduction device on the turbine shaft.