Bridged Stage Piece Design for Multistage Pump Flow and Casting
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Solution Overview
Problem
Conventional multistage pumps face issues with flow disturbances due to stage pieces in the middle of the flow path and difficulties in casting thin cross-sectional bridging posts, often requiring costly weld fabrication to avoid cracking.
Innovation Solution
A two-post bridged stage piece design that mimics the hydraulic contour of the flow passage, allowing for efficient casting and reducing energy loss by better guiding flow into the downstream impeller, while being thicker to prevent cracking and eliminate the need for weld fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional thin cross-section bridging posts are used, then the stage piece can be cast, but the posts are difficult to cast without crack propagation
Solution Approach 1:
The patent changes the geometric parameters of the bridging posts by increasing the cross-sectional thickness from conventional thin sections to substantially thicker sections. This parameter change allows the posts to be cast without crack propagation while maintaining structural integrity and reliability.
2Strength
If conventional four-post design is used, then structural support is provided, but flow disturbance occurs in the middle of the flow path
Solution Approach 1:
The patent extracts two of the four conventional bridging posts from the design, retaining only two posts that are positioned to minimize flow disturbance. This reduction in the number of posts eliminates the flow disturbance problem while maintaining sufficient structural support through the strategically positioned remaining posts.
Solution Approach 2:
The patent employs an asymmetric two-post design rather than a symmetric four-post configuration. The two posts are positioned at specific locations that mimic the hydraulic contour of the flow passage, creating an asymmetric arrangement that better guides flow into the downstream impeller while providing necessary structural support.
3Reliability
If thicker bridging posts are used, then cracking is prevented during casting, but the posts may interfere with flow path
Solution Approach 1:
The patent applies local quality by making the bridging posts substantially thicker at specific critical sections where cracking is most likely to occur during casting. The increased thickness is localized to areas requiring enhanced crack resistance, while the overall post geometry is designed to minimize flow interference. The posts are shaped to mimic the hydraulic contour of the flow passage, ensuring that the thicker sections are positioned where they provide maximum structural benefit with minimum flow disturbance.
Data Source
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AI summary
A stage piece for a multistage pump includes a first ring, a second ring, and a post. The connects the first ring to the second ring and has a first radial end and a second radial end and a first side and a second side connecting the first and second ends. The first and second sides are arcuate and extend toward each other such that the first radial end is longer that the second radial end.