Low-Specific-Speed Pump Sealing for Inter-Stage Leakage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multi-stage centrifugal pumps, particularly those with low specific speed, face inefficiencies due to high liquid leakage across inter-stage seals, especially under high-pressure conditions, where existing sealing technologies like brush seals and compliant plate seals in turbines are not effective.
Innovation Solution
The implementation of a sealing arrangement using compliant plate members with a specific configuration, including slits and radially inwardly oriented rings, to form a labyrinth seal between the stationary and rotary components, enhancing the sealing efficiency by reducing leakage and maintaining axial stiffness even under high pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of stages is reduced to decrease device complexity, then the pressure drop across inter-stage seals increases, but sealing efficiency deteriorates and liquid leakage increases
Solution Approach 1:
The patent changes the geometric parameters of the sealing rings, specifically optimizing the gap width and axial length ratios. By adjusting these parameters, the sealing rings achieve effective sealing with reduced pressure drop across each seal, allowing fewer stages while maintaining sealing efficiency.
Solution Approach 2:
The patent applies different sealing ring designs at different locations. The sealing rings have varying gap widths and axial lengths tailored to specific positions in the pump, optimizing local sealing performance to compensate for the reduced number of stages.
2Loss of energy
If inter-stage sealing rings with small gaps are used to reduce liquid leakage, then friction losses increase and temperature rise occurs
Solution Approach 1:
The patent optimizes the gap width parameter of the sealing rings to achieve an optimal balance. The gaps are sized to minimize liquid leakage while controlling frictional heating, preventing excessive temperature rise in the processed fluid.
Solution Approach 2:
The patent addresses the leakage-friction trade-off by introducing axial length as an additional dimension for control. By adjusting the axial length of sealing rings independently of gap width, the patent achieves effective sealing without excessive friction, managing both leakage and temperature effects.
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 configuration significantly improves the sealing efficiency of multi-stage centrifugal pumps with low specific speed, allowing for a reduced number of stages while maintaining high overall pump efficiency, by minimizing leakage and maintaining sealing functionality under high pressure conditions.
Implementation Method 1
compliant plate members attached in facing relation at root ends to the respective stationary component and forming a sealing ring between the stationary component and the respective rotary component
Implementation Method 2
sealing efficiency by reducing leakage and maintaining axial stiffness even under high pressure differences
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A centrifugal pump is described, comprising: a casing 3; a rotary shaft 9 arranged for rotation in the casing; a plurality of pump stages 15, 17, each pump stage comprising an impeller 15 secured on said rotary shaft 9 and arranged for rotation in a respective impeller chamber 17 formed in the casing 3. The pump further comprises a plurality of sealing members for reducing leakage between a rotary component and a respective stationary component. At least one of the sealing members 27,29 comprises an arrangement of compliant plate members attached in facing relation at root ends to the respective stationary component and forming a sealing ring between the stationary component and the respective rotary component. Moreover, at least some pump stages have a specific speed of 25 or less.