Inter-Shaft Bearing Support With Rupture Decoupling for Rotor Instability
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Solution Overview
Problem
In aircraft engines, a vane rupture due to debris ingestion can cause significant vibration and radial movements in the low pressure rotor, leading to potential engine shutdown or destruction as unbalance is transmitted to the high pressure rotor through inter-shaft bearings.
Innovation Solution
A mechanical decoupler support system with a rigid body and a damper body is integrated between the shafts, allowing for decoupling of radial movements between the low and high pressure shafts upon abnormal loads, maintaining engine operation by mitigating instability through a brittle material rupture mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid support connects the bearing to the high pressure shaft, then the support maintains rigidity during normal operation, but it transmits radial movements and loads from the low pressure shaft to the high pressure shaft during accidents
Solution Approach 1:
The support is segmented into a rigid body portion and a separable coupling mechanism. The rigid body maintains structural integrity during normal operation, while the coupling mechanism allows controlled separation upon detecting abnormal radial movements, preventing damage transmission to the high pressure shaft
Solution Approach 2:
The system incorporates a pre-configured rupture mechanism with a defined load threshold that activates before catastrophic failure can occur. This beforehand cushioning allows the rigid body to rupture controllably under extreme conditions, absorbing the harmful effects before they can propagate to the high pressure shaft
2Object-affected harmful factors
If a conventional dampener support is used to reduce radial movements, then damping is provided, but the support rigidity is compromised causing instabilities during normal operation
Solution Approach 1:
The support system transitions from a static rigid structure to a dynamic system that adapts its characteristics based on operating conditions. During normal operation, the rigid body provides stable support. During accidents with excessive radial movements, the system dynamically changes state through controlled rupture, allowing the low pressure shaft to move independently while the high pressure shaft remains stable
3Object-affected harmful factors
If the rigid body is designed to rupture at a load threshold, then damage transmission is limited, but the device complexity increases
Solution Approach 1:
The rupture mechanism is extracted as a distinct functional element within the support structure. The rigid body is designed with a specific geometric feature (such as a notched section or reduced thickness zone) that concentrates stress and ensures predictable rupture at a defined load threshold, simplifying the overall design while achieving damage limitation
Solution Approach 2:
The rigid body is designed as a sacrificial element that is intentionally made vulnerable to rupture under extreme conditions. This disposable component protects more critical elements (the high pressure shaft and bearing) by failing first, absorbing the harmful effects through controlled rupture
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 limits damage transmission from the damaged rotor, allowing the engine to operate in a degraded mode, reducing accident risk by decoupling radial movements and damping instabilities, thus preventing engine shutdown.
Implementation Method 1
the rigid body being able to be ruptured at a load threshold to be transmitted between the abutting faces
Implementation Method 2
a damper body housed in a cavity of the support delimited by the abutting faces
Data Source
AI summary
An inter-shaft bearing is supported by a support including a solid rigid body which is non-deformable during normal operation, but which can break in the event of an excessive stress, such as a blade failure. A damper included in the support limits the movements between the two shafts and prevents excessive instability.