Centrifugal Pump Front Shroud Grooves for Gas-Liquid Flow
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Solution Overview
Problem
Centrifugal pumps experience a significant decline in performance and often 'breakdown' when handling gas-liquid two-phase flows, especially at higher gas content levels due to gas accumulation and instability issues, with existing solutions providing limited improvements and requiring additional components like inducers.
Innovation Solution
The introduction of macroscopic grooves on the surface of the front shroud directed towards the impeller blades, which enhance secondary flow and mixing, delaying gas accumulation by creating intensified vortices and turbulence, thereby improving the handling of higher gas contents without the need for additional components like inducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tip clearance gap is increased to improve gas handling capability, then resistance to gas accumulation improves, but pump stability deteriorates due to severe instabilities and surging
Solution Approach 1:
The front shroud surface is segmented into multiple macroscopic grooves that divide the flow path into distinct channels. This segmentation creates multiple localized secondary flow regions that collectively enhance gas-liquid mixing while maintaining overall flow stability, preventing the severe instabilities associated with increased tip clearance gap alone.
Solution Approach 2:
Macroscopic grooves are strategically positioned at specific locations on the front shroud where gas accumulation is most problematic. The grooves create localized turbulence and secondary flow zones precisely where needed to disrupt gas pockets, while maintaining stable flow in other regions of the pump.
2Reliability
If an inducer is added to improve two-phase mixing, then pump performance improves, but device complexity increases due to additional components
Solution Approach 1:
The front shroud is given a dual function: it maintains its structural role while simultaneously serving as a mixing enhancement device through the integrated macroscopic grooves. This eliminates the need for a separate inducer component, as the grooved shroud performs the mixing function that would otherwise require an additional axial impeller.
Solution Approach 2:
The mixing function is merged into the existing front shroud structure by adding macroscopic grooves to its surface. This integration combines the structural support function of the shroud with the flow mixing function, creating a multi-functional component that reduces overall device complexity.
3Reliability
If rotational speed is increased to improve two-phase mixing, then mixing capability improves, but energy consumption increases
Solution Approach 1:
The macroscopic grooves on the front shroud create curved flow paths that generate secondary flows and vortices. These curved geometries promote natural mixing through centrifugal forces and flow separation phenomena, achieving effective two-phase mixing without requiring excessive rotational speed and the associated high energy consumption.
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
The macroscopic grooves on the front shroud significantly improve two-phase mixing and reduce gas accumulation, leading to enhanced performance and efficiency in transporting gas-liquid two-phase flows, even at high gas content levels, by creating strong secondary flows and vortices, thus making the handling of higher gas amounts more economical and stable.
Implementation Method 1
The macroscopic grooves of the present invention are characterized by having dimensions such as depth and width in the order of millimeter. It was observed that providing such macroscopic grooves on the front shroud increases the strength of secondary flow and improves two-phase mixing. The mixing effect of the secondary flow in the tip clearance gap across the impeller blades is maximized by creating intensified vortices
Implementation Method 2
The mixing effect of the secondary flow in the tip clearance gap across the impeller blades is maximized by creating intensified vortices, thereby delaying and reducing gas accumulation
Implementation Method 3
Centrifugal pumps are well known devices for energy conversion where rotational energy of an impeller is transferred to the fluid that is to be transported
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The present invention relates to a centrifugal pump (1) with semi-open impeller (2) having a back plate (3), a number of blades (4) provided onto the back plate (3), and a front shroud (5, 7) arranged upstream of the impeller (2) at a defined distance above the blades (4), wherein onto the face of the front shroud (5, 6) directed towards the blades (4) a number of macroscopic grooves (5, 7) is provided for improved mixing and transport of gas-liquid two-phase flows.