Blisk Partial Root Cut for Blade Replacement
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Solution Overview
Problem
In turbomachinery, damaged blades on integrally bladed rotor disks (blisks) are difficult and costly to repair, as the entire blisk often becomes useless if a single blade is damaged, due to the need for extensive welding and machining processes.
Innovation Solution
A blisk design with partially cut dovetail roots allows for easy removal of damaged blades by completing a cut or breaking them off, and the resulting slot can securely accommodate a replacement blade with a matching dovetail root, using methods like EDM machining or friction damping elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blades are formed into the disk as a single piece (blisk), then manufacturing cost is reduced and structural integrity is improved, but repairability of damaged blades deteriorates
Solution Approach 1:
The blade root is segmented into a retained portion (integrally formed with the disk) and a removable portion (containing the cutting plane). This allows the blade to be functionally divided into permanent and replaceable components, enabling individual blade replacement while maintaining the overall blisk structure.
Solution Approach 2:
The removable portion of the blade root is extracted as a separate, replaceable component. By providing a cutting plane that extends into the blade root, the damaged portion can be separated and removed from the disk, allowing replacement without replacing the entire blisk.
2Reliability
If extensive welding and machining is performed to repair a damaged blade, then the blade can be restored, but repair time and cost increase significantly
Solution Approach 1:
The cutting plane is pre-formed during manufacturing, creating a prepared interface for future blade replacement. This preliminary action eliminates the need for extensive machining during repair, allowing quick removal of damaged blades and installation of replacements.
Solution Approach 2:
Instead of repairing the damaged blade in place through welding and machining, the approach is inverted: the blade is designed to be removable and replaceable. This reverses the traditional repair paradigm from restoration to replacement, significantly reducing repair time and cost.
3Ease of repair
If a complete slot is formed in the disk for blade replacement, then blade removal is simplified, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of forming complete slots throughout the disk, the cutting plane is implemented locally at specific blade root locations. This localized approach provides the necessary blade removal capability only where needed, minimizing additional manufacturing complexity while maintaining repairability.
Solution Approach 2:
Rather than forming complete circular slots around each blade, only a partial cutting plane extending into the blade root is created. This partial action is sufficient to enable blade removal when needed, without the excessive complexity and cost of complete slot formation.
Data Source
AI summary
An integrally bladed rotor disk, commonly referred to as an IBR or a blisk, includes partial cuts in the rotor disk extending from the rotor disk surface and along side the blades to form a partial root portion below each blade. A damaged blade can be removed from the rotor disk by breaking off the partial root portion from the disk or additionally cutting the disk to join the two cuts forming the partial root portion of the damaged blade. A replacement blade having a root already formed on the blade can then be inserted into the remaining slot of the rotor disk and secured to the rotor disk by any known means. The partial formed root of the blade can be in the shape of a dove tail root or a fir tree root.