Open Rotor Design for Centrifugal Flow Machines
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Solution Overview
Problem
Traditional centrifugal pump impeller structures face issues such as high friction losses, limited cross-sectional flow area, and unreliable axial force balancing, leading to inefficiencies and maintenance challenges, particularly with the use of slide ring seals which can become dry and clogged with solids.
Innovation Solution
A fully open rotor design is introduced, eliminating shrouds and support discs, with a novel working vane geometry that ensures equal pressures across the rotor, allowing for efficient fluid circulation and flushing of the sealing chamber, reducing the need for balancing holes and enabling the use of smaller bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a closed impeller with shrouds is used, then axial force balancing is achieved, but friction losses increase and cross-sectional flow area is reduced
Solution Approach 1:
The patent removes the shrouds (rear and front) from the impeller design, extracting the components that caused high friction losses and reduced flow area. The working vanes are supported only by the hub, eliminating the shroud structures that created harmful friction and flow restrictions while maintaining axial force balancing through the balancing holes in the hub.
Solution Approach 2:
The impeller is segmented into discrete working vanes supported by the hub, rather than a continuous shrouded structure. The balancing function is segmented into separate balancing holes in the hub, allowing independent optimization of flow paths and force balancing without the constraints of a closed shroud design.
2Force
If a closed impeller with shrouds is used, then axial force balancing is achieved, but cross-sectional flow area is limited
Solution Approach 1:
The shroud structures that occupied significant cross-sectional flow area are completely removed. The working vanes are mounted directly on the hub without enclosing shrouds, maximizing the open flow area available for fluid passage while maintaining axial force balancing through the hub's balancing holes.
3Force
If balancing holes are provided through the rear shroud, then axial force is balanced, but the sealing chamber becomes contaminated with solids
Solution Approach 1:
The balancing holes are moved from the rear shroud to the hub, extracting them from the sealing chamber environment. This allows axial force balancing to be achieved in the hub rather than through the sealing chamber, preventing solid contamination of the sealing area while maintaining effective force balancing.
Solution Approach 2:
The hub acts as an intermediary structure that provides axial force balancing through its balancing holes, separating the balancing function from the sealing chamber. This intermediary approach allows force balancing without direct contamination of the sealing environment by solids in the liquid.
4Loss of energy
If a fully open rotor design is used, then friction losses are reduced and efficiency is improved, but axial force balancing becomes challenging
Solution Approach 1:
The hub serves as an intermediary structure that provides axial force balancing for the open rotor design. The balancing holes in the hub create pressure equalization without requiring closed shrouds, enabling the open rotor configuration to maintain force balancing while reducing friction losses.
Solution Approach 2:
The shroud structures that caused high friction losses are removed, creating a fully open rotor design. The axial force balancing function is extracted and relocated to the hub through balancing holes, allowing the open configuration to maintain force balancing capability without the harmful friction of closed shrouds.
5Ease of manufacture
If traditional impeller structures are used, then manufacturing is possible, but the efficiency ratio is decreased due to complex structures and balancing arrangements
Solution Approach 1:
Complex shroud structures and additional balancing arrangements are removed, simplifying the impeller design to working vanes mounted on a hub. This extraction of unnecessary components reduces manufacturing complexity while improving the efficiency ratio by eliminating the efficiency penalty associated with traditional closed impeller structures.
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 design enhances efficiency by reducing friction losses, improves axial force balancing, and ensures long-lasting, trouble-free operation of the shaft sealing, while being cost-effective and easier to manufacture.
Implementation Method 1
design which ensures equal pressures across the rotor
Implementation Method 2
enhances efficiency by reducing friction losses
Data Source
Figure 1~2
Figure 3a~3c
Figure 4~7
AI summary
The present invention relates to a novel rotor structure for a centrifugal flow machine. The rotor (10) of the invention has newly designed working vanes (14) that are attached to the hub (12) of the rotor without any support disc or shroud. Additionally, the novel vane (14) has means for efficiently flushing the sealing Chamber behind the rotor (10).