Centrifugal Pump Tongue Flow Passages for Low-Flow Stability
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Solution Overview
Problem
Centrifugal pumps experience performance instabilities and reduced efficiency at low flow rates due to stall and turbulence in the discharge passage, leading to decreased kinetic energy and overall performance, particularly in volute and diffuser type pumps.
Innovation Solution
Incorporating flow passages in the tongue of the centrifugal pump, which direct fluid from the inner to the outer surface, providing additional kinetic energy to the boundary layers and reducing stall, thereby stabilizing the pump head curve and improving performance at low flows without affecting operation at the best efficiency point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump operates at low flow rates, then the discharge passage experiences stall and turbulence, but the kinetic energy and overall performance decrease
Solution Approach 1:
The patent applies local quality by introducing flow passages specifically in the tongue region where stall and turbulence occur at low flows. The flow passages are strategically positioned to affect only the boundary layer flow in the discharge passage entrance, leaving the rest of the pump operation unchanged. This localized intervention stabilizes the flow without affecting overall pump performance at best efficiency point.
Solution Approach 2:
The flow passages act as an intermediary mechanism between the high-pressure region near the impeller and the discharge passage. They introduce a controlled flow that mediates the unstable boundary layer flow at low flow rates, preventing stall and turbulence while maintaining the pump's normal operation at best efficiency point.
2Device complexity
If conventional pump designs are used, then the structure remains simple, but performance instabilities occur at low flow rates
Solution Approach 1:
The tongue is segmented by introducing multiple flow passages through it. This segmentation allows the tongue to perform dual functions: maintaining its structural role in separating discharge passages and simultaneously acting as a flow control element that stabilizes boundary layer flow. The segmentation is minimal, requiring only drilling or machining passages through the existing tongue structure.
3Loss of energy
If the pump is sized and optimized for best efficiency point operation, then efficiency is maximized, but performance becomes sensitive to deviations from BEP
Solution Approach 1:
The flow passages perform preliminary action by pre-conditioning the boundary layer flow before it enters the discharge passage. At low flow rates, the flow passages introduce a stabilizing flow that prevents stall and turbulence in advance, allowing the pump to operate stably across a wider range without losing efficiency at the best efficiency point.
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 flow passages in the tongue enhance kinetic energy delivery to the boundary layers, reducing instabilities and improving overall pump performance at low flows without major constructional changes, thus maintaining efficiency and reducing costs.
Implementation Method 1
The tongue comprises at least one flow passage, which extends from the inner surface through the tongue to the outer surface
Implementation Method 2
providing additional kinetic energy to the boundary layers and reducing stall
Implementation Method 3
Centrifugal pumps have at least one impeller and a pump shaft for rotating the impeller
Data Source
AI summary
A centrifugal pump includes a pump casing having a central axis defining an axial direction, a pump chamber, an impeller arranged within the pump chamber and rotatable about the axial direction, a discharge passage for discharging the fluid from the pump chamber, and a tongue for guiding the fluid to the discharge passage. The tongue includes an inner surface facing the central axis, an outer surface facing away from the central axis, and a leading edge joining the inner surface and the outer surface. The tongue includes a flow passage extending from the inner surface through the tongue to the outer surface.