Partial-Shroud Impeller Structure for Blade Rub Control
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Solution Overview
Problem
Compressor impeller blades often experience unwanted rubbing and abrasion due to insufficient clearance with the casing, leading to damage and performance loss, which is addressed by incorporating a partial shroud to control performance without compromising efficiency.
Innovation Solution
A hybrid shroud impeller design featuring a partial shroud integrated with the rotor blades, allowing for controlled clearance and optimized performance by integrating a partial shroud with the blades and splitter blades, forming a flow path from the inlet to a bleed feature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between impeller and casing is increased to avoid blade contact, then blade damage is reduced, but performance optimization is compromised
Solution Approach 1:
The shroud is segmented into a partial shroud structure that covers only a portion of the blade tip circumference, rather than a complete circular shroud. This segmentation allows the design to maintain protective coverage where needed while leaving other areas open for performance optimization, resolving the contradiction between damage prevention and performance.
Solution Approach 2:
The partial shroud provides localized protection at specific critical areas of the blade tips where contact risk is highest, rather than uniformly increasing clearance across the entire impeller. This local quality approach maintains performance in non-critical areas while providing reliability where needed.
2Reliability
If a complete shroud is added to protect blade tips, then blade damage is reduced, but weight increases
Solution Approach 1:
The shroud structure is divided into a partial coverage configuration, providing protection only where blade tip contact is most likely to occur. This segmentation reduces the total material required compared to a complete circular shroud, thereby reducing weight while maintaining essential protective function.
3Productivity
If clearance is reduced to optimize performance, then performance improves, but blade rubbing and abrasion increase
Solution Approach 1:
The partial shroud acts as an intermediary protective element between the blade tips and the casing. It provides a physical barrier that prevents direct contact and rubbing between blades and casing, while allowing the clearance to be optimized for performance. The shroud absorbs the harmful contact effects.
4Reliability
If abradable materials are used in blade tips or casing, then blade contact damage is reduced, but material susceptibility to high temperature failure increases
Solution Approach 1:
The partial shroud is designed as a sacrificial protective element that can be replaced if damaged, rather than relying on expensive heat-resistant abradable materials. This approach provides contact protection without the temperature susceptibility of abradable materials, using a simpler, more temperature-resistant structure.
Data Source
AI summary
A hybrid shroud impeller including a hub having a first and a second axial end; the hub including an outer surface formed radially opposite a hub bore; a full blade extending radially from the outer surface; a splitter blade extending radially from the outer surface adjacent to the full blade; a bleed feature formed in a casing; a partial shroud integrally formed with a portion of the full blade and the splitter blade opposite the outer surface of the hub; a flow path formed between the outer surface of the hub, a shroud inner surface of the partial shroud and a blade surface of each of the full blade and the splitter blade; and the flow path extending from an inlet proximate the first axial end and an outlet proximate the second axial end; the partial shroud extends from the inlet to the bleed feature.