Turbomachine Fan Module Shear Bolt Decoupling
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Solution Overview
Problem
In aircraft turbomachines equipped with electric machines, extreme events like blade breakage can cause rotor-stator contact, leading to friction and potential engine fires or fan disk blocking due to unbalance and eccentricity, which existing technologies fail to adequately mitigate.
Innovation Solution
A fan module with a rotor of an electric machine is designed, where the support is fixed to the disk via fuse screws that break when a predetermined torque threshold is exceeded, decoupling the rotor from the fan disk and preventing rotor-stator contact by magnetization force, thus avoiding fire and blocking risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor of the electric machine is firmly attached to the fan disk, then the rotor is securely held during normal operation, but during extreme events like blade breakage, the unbalance force causes rotor-stator contact leading to fire risk and fan disk blocking
Solution Approach 1:
The attachment system transitions from static (firm attachment) to dynamic (breakable connection). The fusible screws are designed to maintain attachment during normal operation but break under extreme unbalance forces, allowing the rotor to decouple and become a fixed stator part, thereby preventing rotor-stator contact and associated hazards
Solution Approach 2:
The attachment mechanism is segmented into replaceable fusible screws rather than a monolithic rigid connection. This segmentation allows the connection to be selectively broken (screws snap) under specific conditions while maintaining integrity during normal operation, enabling the rotor to be decoupled from the fan disk when needed
2Reliability
If shear screws are used to attach the rotor support to the fan disk, then the rotor can be decoupled during extreme events, but the device complexity increases due to the special screw design and installation requirements
Solution Approach 1:
The fusible screws are designed as disposable safety components with a predetermined limited lifespan or strength threshold. They are intentionally made to break under extreme conditions, serving as a sacrificial element that protects more critical components. This approach simplifies the overall safety system by using a simple, replaceable component rather than a complex active sensing and actuation 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
The solution effectively decouples the electric rotor from the fan disk during extreme events, preventing rotor-stator contact and associated risks of fire and blocking, while ensuring resistance in nominal operations.
Implementation Method 1
the support is fixed to the disc by means of shear screws which are configured to break when a torsional torque transmitted by the disc to the support exceeds a predetermined threshold
Implementation Method 2
The electric rotor will therefore no longer be driven in rotation by the fan disc and will become a fixed stator part thanks to the magnetic force which exists between it and its stator
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a fan module (100) for an aircraft turbomachine (10), comprising: - a fan (14) comprising a disc (32a) carrying fan blades (30), - a rotor (62a) of an electric machine (62), this rotor (62a) having an annular general shape and being mounted coaxially downstream of the fan (14), - an annular support (90) for the rotor (62a) with a downstream end (90b) fixed to said rotor (62a) and with an upstream and (90a) fixed to the fan disc (32). According to the invention, the support (90) is fixed to the disc (32a) by way of shear bolts (99) which are configured to break when a torque transmitted by the disc (32a) to the support (90) exceeds a predetermined threshold. The invention also relates to an aircraft turbomachine comprising such a module (100). Figure for the abstract: Figure 2