Asymmetric Washer Counterbore Assembly for Smooth Turbomachine Surfaces
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Solution Overview
Problem
The existing assembly methods for turbomachines create asperities on aerodynamic surfaces due to the use of screw-type fasteners within counterbores, leading to difficulties in sealing and potential detachment during operation.
Innovation Solution
A washer with asymmetry about the screwing axis is used to accommodate the fastening screw, featuring a second aerodynamic surface that extends in continuity with the first surface, minimizing disturbances and ensuring proper positioning to smooth out asperities, and can be designed as a single part or with specific shapes to fit various counterbore geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If screw-type fasteners are used within counterbores to attach stator vanes to the fan casing, then secure attachment is achieved, but asperities are created on the aerodynamic surface leading to sealing difficulties and potential detachment
Solution Approach 1:
A washer is introduced as an intermediary element between the screw head and the aerodynamic surface. The washer fills the counterbore completely, with its first surface supporting the screw head and its second surface forming a smooth continuation of the aerodynamic vein, thereby eliminating asperities while maintaining secure attachment
Solution Approach 2:
The washer is divided into distinct functional zones: a first surface for mechanical support of the screw head, a body portion filling the counterbore volume, and a second surface forming the aerodynamic seal. This segmentation allows each zone to optimize its specific function while working together as a unified solution
2Reliability
If a cap is used to seal the counterbore, then sealing may be achieved, but the outer wall of the vein is strongly conical making sealing difficult and the cap may become detached during operation
Solution Approach 1:
The sealing function is merged with the fastening washer itself. The washer simultaneously provides mechanical support for the screw head and forms the aerodynamic seal by having its second surface extend in continuity with the first aerodynamic surface, eliminating the need for separate sealing components
Solution Approach 2:
The washer exhibits different properties at different locations: the first surface and body portion provide mechanical support and structural function, while the second surface is specifically designed with aerodynamic smoothness to provide sealing. This local differentiation of properties allows the single component to fulfill multiple functions effectively
Data Source
AI summary
The invention concerns a part of a turbomachine, including an element having a first aerodynamic surface including a counterbore at the bottom of which is provided a mounting hole of a fastening screw of the part, and a washer configured to be accommodate into the counterbore and intended to serve as a support for a head of the fastening screw, wherein the washer has an asymmetry of revolution about a screwing axis and is engaged by shape complementarity in the counterbore, and in that the washer includes a second aerodynamic surface extending in the continuity of the first surface.