Fan Platform Locking Bolt for Low Hub Ratio
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Solution Overview
Problem
Existing turbomachine fan designs face challenges in achieving a low hub ratio while ensuring easy attachment of inter-blade platforms to the fan disc without degrading the flow path, particularly due to significant clearance requirements and potential air flow disruptions from bulky attachments or poor surface control.
Innovation Solution
The design incorporates a fan disc with a yoke and inter-blade platforms featuring a base, tab, and lock configuration, where the lock's pin engages with orifices in the tab and yoke to securely attach the platform, allowing for a low hub ratio without increasing clearance or degrading flow quality, using composite materials for the base and tab and metallic materials for the lock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the platform is resumed upstream with a bulky attachment to allow resumption of centrifugal forces, then the hub ratio decreases, but the device complexity and flow path quality deteriorate
Solution Approach 1:
The attachment structure is segmented into separate functional elements: a lock component with a pin, a tab on the platform, and corresponding orifices in the yoke. This segmentation allows each element to perform its specific function without requiring a bulky integrated attachment structure, thereby reducing device complexity while maintaining structural integrity and flow path quality.
2Area of stationary object
If the hub ratio is reduced by reducing the distance between platform surface and fan disc, then the aerodynamic efficiency improves, but the clearance for axial assembly increases
Solution Approach 1:
The locking mechanism utilizes the radial dimension through the pin engaging with orifices in the radial direction, rather than requiring additional axial clearance. This dimensional shift allows the platform to be securely attached with minimal axial distance from the fan disc, enabling reduced hub ratio while maintaining adequate assembly clearance.
3Reliability
If a pin-based locking mechanism is used to attach the platform, then the attachment reliability improves, but the device complexity increases
Solution Approach 1:
The locking function is merged into the lock component itself, where the pin is an integral part of the lock rather than a separate element. The lock combines the pin, the bearing surface against the tab, and the engagement features into a single component that attaches to the platform and engages with the yoke orifices, thereby ensuring reliable attachment without significantly increasing device complexity.
Data Source
AI summary
A fan includes: a fan disc; an inter-blade platform including a base and a radial tab, a second orifice being formed in the tab of the platform; and a lock having a downstream edge configured to bear against the tab of the platform. The one among the downstream edge and the yoke of the fan disc includes a pin, the other includes a first orifice, the pin being configured to enter the first orifice and the second orifice so as to block the platform relative to the fan disc.