Segmented Radial Control Shaft for Turbine Hub Maintenance
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Solution Overview
Problem
The existing mechanisms for controlling the pitch of fan blades in turbojet engines with contrarotating propellers face challenges due to limited access to the hubs, particularly in pusher configurations, where the radial control shafts need to be inserted through small diameters, making it difficult to maintain and assemble the control systems efficiently.
Innovation Solution
A radial control shaft designed as two independent portions, an external and an internal portion, allowing the external portion to be mounted outside the airflow passage and the internal portion to be mounted inside the hub, coupled together to adjust the pitch of the fan blades, reducing the need for large hub diameters and simplifying maintenance by preventing oil leakage and allowing external access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the hub diameter is reduced to improve propulsive efficiency, then propulsive efficiency is improved, but access to the hub for assembling and maintaining control shafts becomes limited
Solution Approach 1:
The control shaft is divided into two independent portions: an external portion accessible from outside the hub and an internal portion mounted inside the hub. This segmentation allows the external portion to be assembled and maintained without requiring access to the hub interior, thereby resolving the contradiction between reduced hub diameter and ease of operation.
2Loss of energy
If the hub diameter is reduced, then propulsive efficiency is improved, but the ability to insert and maintain control shafts becomes difficult
Solution Approach 1:
By segmenting the control shaft into external and internal portions, the external portion can be removed and maintained independently from the hub assembly. This eliminates the need to disassemble hub components for control shaft maintenance, resolving the contradiction between reduced hub diameter and ease of repair.
Solution Approach 2:
The external portion of the control shaft is extracted from the hub assembly, allowing it to be maintained separately. This extraction enables maintenance operations on the control shaft without requiring access to or disassembly of the hub interior, thereby improving ease of repair while maintaining reduced hub diameter.
3Strength
If a single-piece control shaft is used, then structural integrity is maintained, but assembly requires access to the hub interior which is limited in small diameter hubs
Solution Approach 1:
The control shaft is segmented into two portions that are coupled together. The coupling mechanism maintains structural integrity while allowing the external portion to be assembled from outside the hub, resolving the contradiction between structural integrity and ease of manufacture.
Solution Approach 2:
The internal portion of the control shaft is positioned inside the hub while the external portion extends outward, creating a nested arrangement. This nesting allows the control shaft to function as a single integrated component while enabling separate assembly of the external portion from outside the hub, improving ease of manufacture.
Data Source
AI summary
A radial control shaft for a device for controlling the pitch of fan blades of a turbine engine having an unducted fan, is disclosed. The shaft includes an external portion that is designed to be mounted in the control device from its outside and to be coupled to at least one fan blade in order to adjust its pitch, and an internal portion, independent of the external portion, that is designed to be mounted from the inside of the control device, to be connected to a load transfer bearing in order to pivot the shaft about a radial axis, and to close an oil enclosure in which the bearing is housed, the external and internal portions of the shaft being coupled to each other. A method of mounting such a shaft and a control device including such a shaft are also disclosed.