Flywheel Mitigates Rotor Shaft Bowing in Aircraft Engines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aircraft gas turbine engines face issues with rotor shaft bowing due to uneven cooling, leading to thermal deformation and potential damage during engine restart, especially in scenarios where power for rotor straightening methods is not available, causing delays and increased costs.
Innovation Solution
A system that transfers rotational energy from the rotor shaft to a flywheel, using transmissions and generators to store and redistribute energy, thereby reducing or preventing thermal bowing of the rotor shaft, and also powers aircraft systems during peak electrical loading, reducing fuel consumption and eliminating the need for auxiliary power units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If tighter cold build clearances are implemented to reduce air leakage and improve fuel consumption, then fuel efficiency is improved, but rotor shaft bowing causes more severe rubbing against the engine casing
Solution Approach 1:
The flywheel stores rotational energy during engine operation and automatically releases it during shutdown to rotate the rotor shaft and straighten thermal bowing before restart, preventing rubbing issues proactively without requiring manual intervention or external power sources
Solution Approach 2:
The system uses the engine's own operational energy to charge the flywheel, which then autonomously performs the rotor straightening function during shutdown without requiring external power sources like APU or ground equipment, making the system self-sufficient
2Object-affected harmful factors
If rotor shaft rotation is performed using Engine Turning Motor (ETM) or auxiliary power to straighten the bow, then rotor shaft bowing is mitigated, but power availability issues cause delays and increased operational costs
Solution Approach 1:
The flywheel system is self-powered, using energy captured during engine operation to automatically straighten the rotor shaft during shutdown without requiring external power sources, eliminating waiting times and dependency on ground equipment availability
Solution Approach 2:
The flywheel continuously captures rotational energy during engine operation and immediately utilizes it during shutdown, creating an uninterrupted protective action that eliminates idle waiting time associated with external power source availability
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 system effectively mitigates rotor shaft bowing, reduces fuel consumption, and simplifies ground logistics by using stored energy to power aircraft systems, minimizing delays and operational costs.
Implementation Method 1
rotating the shaft (1) so that the shaft cools uniformly, returns to thermal equilibrium, and straightens, and/or (2) so that centrifugal forces straighten the bow
Implementation Method 2
the upper portion 120 of the HP compressor's (engine's rotor) 108 rotor shaft 122 becomes hotter than the lower portion 124 of the rotor shaft 122 and causes uneven cooling and thermal deformation of the engine rotor shaft 122 (i.e., rotor bowing)
Data Source
AI summary
A mechanical flywheel used to power an aircraft system. In one example, the flywheel is used to rotate a rotor shaft in the aircraft's engine and prevent bowing of the rotor shaft caused by a thermal gradient. In another example, the mechanical flywheel provides electrical power at peak demand times. In yet another example, the flywheel is used as a load source or sink by the engine's control system so as to aid engine operability and engine acceleration rates during abnormal flight conditions.