Pin-Based Fastening for Turbomachine Fan Inter-Blade Platforms
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Solution Overview
Problem
In small-diameter turbomachine engines, the use of inter-blade platforms is hindered by the bulkiness of nut and bolt fastening systems, which makes it difficult to manipulate the required tools within the limited space, leading to constraints on engine design and increased mechanical stresses on fan blades.
Innovation Solution
A pin-based fastening system that extends axially along the entire platform, allowing for secure attachment of inter-blade platforms to the disk without the need for specific tools, using radial lugs and orifices, and optionally supported by annular endplates for alignment and immobilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nut and bolt fastening systems are used to attach inter-blade platforms to the disk, then the platforms can be securely fastened, but the fastening systems become too bulky to manipulate within the limited space of small-diameter engines
Solution Approach 1:
The invention extracts the fastening function from the bulky nut and bolt system and implements it through a simpler pin inserted into an orifice. The pin extends axially through the platform and disk, providing secure fastening without requiring the complex manipulation of nuts and bolts in confined spaces.
Solution Approach 2:
The pin acts as an intermediary element that simplifies the fastening operation. Instead of manipulating multiple components (nuts, bolts, washers), a single pin is inserted through a pre-defined orifice, serving as a mediator between the platform and disk to achieve secure attachment.
2Device complexity
If blades are formed in one piece with integrated platforms, then the structure is simpler, but the blade roots become heavier and subject to considerable mechanical stresses
Solution Approach 1:
The invention segments the platform from the blade, allowing them to be manufactured and optimized independently. The platform is attached to the disk separately via pins, while the blade roots can be designed with reduced weight and stress concentration, eliminating the need for heavy integrated structures.
3Device complexity
If blades are formed in one piece with integrated platforms, then the structure is simpler, but the mechanical stresses at the blade roots increase significantly
Solution Approach 1:
By segmenting the platform from the blade and attaching it separately to the disk, the invention eliminates stress concentration at the blade root interface. The platform carries its own attachment loads through the pin fastening system, preventing stress transmission to the blade roots.
4Ease of operation
If a single pin is used to fasten the platform, then the fastening process is simplified and tools are not required, but additional components (endplates) may be needed for alignment and immobilization
Solution Approach 1:
The orifice is pre-defined in the platform, and the pin is designed with a head that automatically provides alignment when inserted. The upstream endplate is positioned beforehand to bear against the pin head, ensuring correct positioning and alignment before the pin is fully inserted and secured.
Data Source
AI summary
A turbomachine fan including blades mounted in slots at the periphery of a rotor disk, and inter-blade platforms having radial lugs for fastening to corresponding lugs of the disk is disclosed. Each platform is fastened to the disk by a pin inserted into orifices in the lugs of the platform and into corresponding orifices in the lugs of the disk.