Fan Axial Containment via Speed Sensor Gap
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Solution Overview
Problem
In gas turbine engines, a failure of the fan thrust bearing can cause the fan shaft and geared architecture to move forward, potentially leading to engine damage as there is no effective containment mechanism to prevent this movement.
Innovation Solution
A gas turbine engine design that includes a compartment housing the fan thrust bearing assembly with a speed sensor and pickup system, where the sensor gap is strategically smaller than other gaps, allowing the speed sensor to detect the fan shaft's forward movement and trigger a shutdown, ensuring the fan and geared architecture remain contained within the compartment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan thrust bearing assembly fails, then the fan shaft and geared architecture move forward, but this causes potential engine damage due to lack of containment
Solution Approach 1:
The speed sensor pickup and sensor are positioned to create a sensor gap that is smaller than the thrust bearing assembly gap. This preliminary arrangement ensures that the sensor contacts the pickup before the fan shaft can move forward enough to cause damage, creating a preventive barrier against the harmful effect of uncontained movement
Solution Approach 2:
The speed sensor provides continuous feedback on the axial position of the fan shaft through the sensor pickup. When the fan shaft moves forward due to thrust bearing failure, the sensor detects this movement by losing contact with the pickup, providing real-time feedback that triggers the containment response
2Reliability
If a containment mechanism is added to prevent fan shaft movement, then reliability improves, but device complexity increases
Solution Approach 1:
The speed sensor system serves dual purposes: it monitors fan shaft position for normal operation and simultaneously acts as the containment detection mechanism. The existing speed sensor is repurposed to detect thrust bearing failure, eliminating the need for a separate containment sensor system and reducing overall device complexity
Solution Approach 2:
The speed sensor assembly performs multiple functions: it monitors rotational speed during normal operation and detects axial displacement of the fan shaft during thrust bearing failure. This multi-functionality allows a single component to provide both operational monitoring and safety containment detection
Data Source
AI summary
A gas turbine engine (20) and method for containing a fan inside an engine after a fan thrust bearing assembly failure. The engine (20) may comprise a fan (42), a housing (100) including a compartment (102), a fan shaft (104) inside the compartment (102) and comprising a bowl (108), a support structure (110) inside the compartment (102), a speed sensor pickup (114) mounted on the outer surface (120) of the bowl (108), a speed sensor (112) mounted on the support structure (110), and a fan thrust bearing assembly (41) disposed forward of the bowl (108). The fan thrust bearing assembly (41) including a bearing (126). The speed sensor (112) and the sensor pickup (114) define a defining a sensor gap (116). The bearing (126) and the outer surface (120) defining a fan thrust bearing gap (130), wherein the sensor gap (116) is less than the fan thrust bearing gap.