Centrifugal Pump Sawtooth Seal for Leakage and Seizing Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Centrifugal pumps, particularly borehole pumps, face volume flow losses and unstable operating behavior due to seizing between metallic impellers and wear rings, especially when handling fluids with solids, which reduces hydraulic efficiency.
Innovation Solution
The design incorporates an axially extending sawtooth with a rake angle greater than 0° on the suction side for the race and/or wear ring, creating a 'Tesla valve-like' structure that deflects volume flow back to the pressure side, reducing volume flow losses and maintaining stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a flat sealing surface is used between the impeller ring and wear ring, then the sealing gap can be kept small to reduce leakage, but seizing occurs between metallic components especially when solids are present in the fluid
Solution Approach 1:
The invention applies a sawtooth profile with curved tooth flanks to the sealing surfaces of the impeller ring and/or wear ring. This curved geometry replaces the conventional flat sealing surface, creating a non-contact labyrinth seal that prevents seizing while maintaining small effective sealing gaps. The curved tooth flanks guide the fluid flow and prevent direct metallic contact between rotating and stationary components.
Solution Approach 2:
The sealing surface is segmented into multiple sawtooth profiles instead of a single flat surface. This segmentation creates multiple small steps that collectively form an effective sealing barrier, reducing the leakage area while maintaining reliability. The segmented structure prevents seizing by distributing the sealing function across multiple discrete features rather than a single continuous contact surface.
2Reliability
If labyrinthine seals are used between the impeller ring and wear ring, then seizing is prevented, but the pressure drop between them becomes low resulting in reduced hydraulic efficiency
Solution Approach 1:
The sawtooth profile features asymmetric tooth geometry with a rake angle between 10° and 45° relative to the radial direction. This asymmetry creates directional flow resistance that is higher in the reverse flow direction (from pressure side to suction side) than in the forward direction. The asymmetric design prevents seizing like a labyrinth seal while maintaining higher pressure drop and thus better hydraulic efficiency compared to conventional symmetric labyrinthine seals.
Solution Approach 2:
The invention changes the geometric parameters of the sealing structure by introducing a sawtooth profile with specific rake angles (10°-45°) and tooth heights (0.5-2.0 mm). These parameter changes optimize the balance between preventing seizing and maintaining hydraulic efficiency. The specific parameter ranges are chosen to create sufficient flow resistance while avoiding excessive pressure drop that would reduce pump performance.
3Productivity
If multiple impellers are arranged axially in series to achieve high hydraulic efficiency, then pumping performance is improved, but radial forces increase causing shaft deflection and potential contact between impeller and wear ring
Solution Approach 1:
The sawtooth profile acts as a cushioning feature that prevents direct contact between the impeller ring and wear ring even when shaft deflection occurs. The non-contact labyrinth seal design with tooth flanks provides a buffer zone that absorbs radial displacements caused by shaft deflection, preventing seizing and maintaining reliable operation throughout the pump's service life.
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 effectively reduces volume flow losses and enhances hydraulic efficiency by deflecting flow back to the pressure side, minimizing contact and shaft deflection, and is particularly beneficial for borehole pumps with multiple impellers connected in series.
Implementation Method 1
at least one axially extending sawtooth with a suction-side oriented rake angle α > 0° is formed on the impeller ring and/or the split ring facing the sealing gap... increases the flow resistance from the pressure side to the suction side... a flow of volume through the sealing gap occurs during normal operation of the centrifugal pump from the pressure side to the suction side. This flow of volume reduces the hydraulic efficiency of the centrifugal pump, as described previously. By providing at least one sawtooth with a suction-side oriented rake angle α > 0°, the flow of volume originating from the pressure side is at least partially redirected back towards the pressure side.
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to a centrifugal pump, in particular a borehole pump, with an impeller (3) having a suction-side oriented running ring (6) radially limiting the impeller (3) and a gap ring (7) radially enclosing the running ring (6) in such a way that an axially extending sealing gap (8) is formed between the gap ring (7) and the running ring (6), wherein at least one axially extending saw tooth (9) with a suction-side oriented rake angle α > 0° is formed on the running ring (6) facing the sealing gap (8).