Turbomachine Disc Shim Notch Mounting for Thermal Stress Reduction
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Solution Overview
Problem
Existing shims for protecting turbine blades in turbomachines face issues such as axial displacement, mechanical strength limitations due to thermal stresses, and difficulty in maintaining mechanical integrity, leading to premature wear and increased maintenance needs.
Innovation Solution
A shim is positioned in a notch between two teeth of the disc, rather than on the blade root, with a base extending axially along the entire length of the notch and axial holding elements that increase the shim's strength and reduce thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shim is mounted on the blade root with folded tongues, then the shim can be retained in position, but the mechanical strength is insufficient to withstand thermal stresses and axial displacements occur
Solution Approach 1:
The shim is extracted from the blade root mounting and repositioned to the disc notch. This removes the shim from the high thermal stress environment of the blade root while maintaining its protective function on the blade through reduced contact area. The holding elements remain on the disc rather than being attached to the blade root.
Solution Approach 2:
The mounting location transitions from a one-dimensional blade root surface to a two-dimensional disc notch structure. This dimensional change provides a larger structural framework for the holding elements and distributes thermal stresses across the disc rather than concentrating them on the shim and blade root interface.
2Object-affected harmful factors
If the shim is mounted on the blade root, then wear protection is provided, but thermal stresses from blade expansion/contraction cause deterioration and damage
Solution Approach 1:
The shim contact with the blade is localized to specific areas through the notched configuration and holding element positioning. This localizes the wear protection function to critical zones while minimizing the shim's exposure to thermal stresses across its entire structure.
Solution Approach 2:
The disc notch structure serves as an intermediary mounting platform between the blade and the shim. This intermediary structure absorbs and distributes thermal stresses, preventing direct transmission of thermal cycles from the blade to the shim that would cause deterioration.
3Object-affected harmful factors
If the shim is positioned on the blade root, then direct wear protection is achieved, but axial displacement and disengagement occur under operational stresses
Solution Approach 1:
The shim function is merged with the disc structure through the notch integration. The holding elements are formed as integral parts of the disc-notch-shim assembly rather than separate components, creating a unified structure that resists axial displacement through the combined mechanical strength of the disc and shim.
Data Source
AI summary
An assembly includes a disk of a moving gear of a turbomachine comprising an axis of rotation and teeth. The teeth each include a first lateral surface on one side and a second lateral surface on the other side. Slots are formed between the teeth and each include a bottom surface that connects the first lateral surface of one tooth to the second lateral surface of an adjacent tooth. A first radial surface and a second radial surface are formed on either side of the disk and delimit the slots and teeth. A shim is mounted in a slot and includes an outer surface that partly covers the first and second radial surfaces, a base in contact with the bottom surface, a first lateral arm and a second lateral arm which are connected to one another by the base.