Centrifugal Fan Impeller Shroud Segmentation for Welding and Airflow
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Solution Overview
Problem
Centrifugal fan impellers with staircase-shaped blade and shroud welds often experience reduced blowing performance and increased blowing noise due to airflow obstruction near the shroud.
Innovation Solution
The centrifugal fan impeller features a curved shroud plate portion with flat plate-like sections that oppose the blade axial end portions, allowing for robust welding at chord length direction centers, reducing the area required for welding, and incorporating leading edge recessed and trailing edge raised portions to prevent airflow disruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If staircase shapes are formed in the blades and shroud for welding, then the blades and shroud can be welded to each other, but the airflow in the vicinity of the shroud is obstructed, leading to reduced blowing performance and increased blowing noise
Solution Approach 1:
The shroud is divided into a curved plate portion and a flat plate portion, with the flat plate portion specifically positioned to oppose the blade axial end portions. This segmentation allows the welding to be concentrated on the flat plate portion while the curved plate portion maintains smooth airflow, thus resolving the contradiction between welding strength and blowing performance
Solution Approach 2:
Different portions of the shroud are given different geometries: the curved plate portion has a curved surface optimized for airflow, while the flat plate portion has a flat surface optimized for welding. This local differentiation allows each portion to fulfill its specific function without compromising the other, addressing both welding strength and blowing performance requirements
2Reliability
If staircase shapes are formed in the blades and shroud for welding, then the blades and shroud can be welded to each other, but the blowing noise increases due to airflow obstruction
Solution Approach 1:
The shroud is segmented into curved and flat plate portions, confining the staircase welding structure to only the flat plate portion. This segmentation prevents the welding structure from extending into the airflow path, thereby reducing blowing noise while maintaining welding strength
Solution Approach 2:
The flat plate portion is specifically designed with a flat surface to facilitate welding, while the curved plate portion maintains a smooth curved surface that does not obstruct airflow. This local quality differentiation ensures that welding is achieved where needed without generating harmful noise in the airflow path
3Ease of manufacture
If flat plate portions are formed on the shroud for welding, then the welding area is reduced and welding is simplified, but gaps may form due to strain during molding
Solution Approach 1:
Leading edge recessed portions and trailing edge raised portions are pre-formed on the flat plate portion of the shroud before welding. These preliminary features compensate for expected gaps caused by molding strain, ensuring that the final welded joint achieves the required quality despite the simplified flat plate design
Data Source
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AI summary
A shroud (80) has: a curved plate-like shroud curved plate portion (81); and flat plate-like shroud flat plate portions (82) corresponding to just parts of sections of the shroud (80) that oppose shroud-side blade axial end portions (72). In the blade axial end portions (72) are formed blade flat surfaces (72a) that follow the shroud flat plate portions (82) and blade curved surfaces (72b, 72c) that follow the shroud curved plate portion (81). Welded portions (8b) resulting from the blade flat surfaces (72a) and the shroud flat plate portions (82) being welded to each other are formed between the blade axial end portions (72) and the shroud (80).