Closed Impeller Manufacturing With Selective Channel Surface Finishing
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Solution Overview
Problem
Conventional subtractive techniques cannot achieve the ideal geometry for closed impellers, leading to inefficiencies and surface roughness issues that compromise fatigue lifetime and isentropic efficiency, especially at low specific speeds and high rotational speeds.
Innovation Solution
A multi-step method involving additive manufacturing followed by post-processing and machining to create closed impellers with smooth surfaces, using extra material to facilitate machining and ensure smooth transitions between areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If additive manufacturing is used to create closed impellers, then complex channel geometries can be achieved, but surface roughness increases and fatigue lifetime decreases
Solution Approach 1:
The channel surface is divided into two distinct zones: a first zone with smooth surface finish and a second zone with rougher surface finish. This segmentation allows different surface treatment methods to be applied to different areas, optimizing both fatigue resistance in critical zones and geometric complexity in non-critical zones.
Solution Approach 2:
Different surface qualities are applied to different locations on the impeller. The first area (critical for fatigue) receives smooth surface treatment while the second area (less critical) retains the as-printed rougher surface. This local differentiation resolves the contradiction by providing high surface quality where needed while maintaining manufacturing efficiency elsewhere.
2Manufacturing precision
If conventional subtractive techniques are used to machine impellers, then smooth surfaces are achieved, but complex channel geometries cannot be produced
Solution Approach 1:
The invention merges additive manufacturing and subtractive machining techniques into a hybrid process. Additive manufacturing creates the complex closed impeller geometry, while selective subtractive machining refines the surface in critical areas. This combination achieves both geometric complexity and surface smoothness that neither method could achieve alone.
Solution Approach 2:
The complex impeller geometry is first created using additive manufacturing as a preliminary step, establishing the closed design with intricate channel structures. Subsequently, selective machining is performed on specific areas to achieve the required surface finish. This preliminary action allows the complex shape to be achieved before applying surface refinement where necessary.
3Loss of energy
If closed impeller design is used, then isentropic efficiency increases, but manufacturing complexity increases
Solution Approach 1:
Instead of applying complex surface treatment to the entire impeller, the invention uses partial action by treating only the first area (critical zones) with smooth surface finish. The second area retains the as-printed surface. This partial treatment reduces manufacturing complexity while maintaining the efficiency benefits in critical areas.
Data Source
AI summary
A method for manufacturing an impeller, in particular, for a turbomachine, said impeller comprising vanes forming channels in the impeller, the method comprising the following steps: a) forming a raw impeller part by means of additive manufacturing; b) removing), from the raw impeller part, at an inner surface of at least one channel, material in a first area and in a second area of the inner surface, by means of post-processing, to obtain an intermediate impeller part; and c) removing, from the intermediate impeller part in the first area, material by means of machining.