Helical Impeller Polishing for Blisk Surface Roughness
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Solution Overview
Problem
Current methods for polishing centrifugal impellers in turbomachines are inefficient, particularly in achieving the required surface roughness criterion Ra of 0.6 µm, as they are either labor-intensive, dependent on operator skill, or fail to effectively polish complex shapes due to stagnation of abrasive particles.
Innovation Solution
A polishing method involving a helical movement of the impeller, synchronized with rotation and translation, replicating the air flow trajectory between blades, and a device with drive means to implement this movement, ensuring the polishing agent moves in a helical path matching the impeller's pitch, allowing for efficient surface finishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual polishing using abrasive belts is used, then complex shapes can be polished, but the process is very time-consuming and labor-intensive
Solution Approach 1:
The patent replaces manual mechanical polishing with an automated system using abrasive particles suspended in a fluid medium. The impeller is rotated and translated through the abrasive-laden fluid, allowing automated surface treatment without manual intervention, thus reducing labor time while maintaining the ability to polish complex geometries.
Solution Approach 2:
The patent uses a fluid medium (liquid or gas) carrying abrasive particles to perform the polishing action. The impeller is immersed in or exposed to this fluid stream, allowing the abrasive-laden fluid to contact and polish all surfaces including complex geometries, significantly reducing manual labor time.
2Productivity
If conventional polishing machines are used, then polishing can be automated, but they cannot polish parts of complex shapes due to stagnation of abrasive particles
Solution Approach 1:
The patent employs dynamic movement of the impeller through combination of rotation around its axis and translation along the axis. This dual movement prevents stagnation of abrasive particles by continuously changing the contact points and flow patterns, ensuring all surfaces including complex geometries are effectively polished while maintaining automation.
Solution Approach 2:
The patent adds a translational movement dimension to the conventional rotational polishing. By moving the impeller both rotationally and translationally through the abrasive fluid, the system accesses all surfaces of complex geometries that would be unreachable with simple rotation, eliminating stagnation zones.
3Productivity
If polishing by abrasive particles with cover enclosure is used, then automation is achieved, but the desired roughness criterion Ra is not achieved due to particle stagnation
Solution Approach 1:
The patent uses simultaneous rotation and translation of the impeller to create dynamic abrasive particle flow patterns. This prevents particle stagnation by continuously renewing the contact between fresh abrasive particles and the impeller surfaces, ensuring consistent Ra values are achieved across all surfaces including complex geometries.
Solution Approach 2:
The patent employs periodic reciprocating translation of the impeller in combination with continuous rotation. This periodic back-and-forth movement ensures that all surfaces are repeatedly exposed to fresh abrasive particles, preventing stagnation and achieving uniform surface roughness control throughout the complex geometry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method and device combination enables efficient polishing of complex shapes, achieving the desired surface roughness while being simple, robust, and reducing labor costs, with improved aerodynamic performance by mimicking the air flow trajectory, thus enhancing the turbomachine's efficiency.
Implementation Method 1
move the impeller, or more generally the disc provided with a blade comprising blades defining air veins formed of a portion of helix, according to a helical movement whose pitch is close to the pitch of the helix
Implementation Method 2
polishing by means of abrasive particles... place in this volume of the abrasive particles, then to rotate the impeller around its axis arranged horizontally. Rotation and gravity cause particles to move across the surface to be polished
Implementation Method 3
Rotation and gravity cause particles to move across the surface to be polished
Data Source
Figure 1
Figure 2~3
AI summary
Device for polishing centrifugal impellers (2) for a turbomachine compressor, comprising a tank (8) intended to be filled with a polishing agent, an impeller support (10) able to turn the impeller (2) about its axis and move it along its axis so that all points of the impeller (2) are moved in a helical path the pitch of which is similar to that of the helix from which the overall shape of the airstreams of the impeller, delimited by the impeller blades, is derived.