Integral Axial Thrust Bearings in Multistage Centrifugal Pumps
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Solution Overview
Problem
Multistage centrifugal pumps face issues with unbalanced thrust forces due to operating outside a narrow equilibrium point, leading to excessive up-thrust or down-thrust, which complicates manufacturing and wear over time, especially with large thrust bearings that require accurate shimming and balancing.
Innovation Solution
The integration of an axial load and bearing system within the pump, comprising diffuser bushings and impeller bearings, allows independent axial movement of impellers and shafts, providing a balanced force to up-thrust and down-thrust forces, reducing the need for separate thrust bearings and enabling operation over a wider range of flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If large thrust bearings are used to control aggregated thrust load, then thrust force control is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent divides the thrust bearing system into multiple smaller bearings distributed across different stages (first stage thrust bearing, second stage thrust bearing, third stage thrust bearing) rather than using a single large thrust bearing. Each stage has its own thrust bearing that handles local thrust forces, segmenting the overall thrust control function into manageable portions that are easier to manufacture and maintain.
Solution Approach 2:
The patent transitions from centralized thrust control (single large bearing) to distributed thrust control across multiple dimensions/stages. By placing thrust bearings at different axial positions corresponding to different impeller stages, the system manages thrust forces in a distributed manner across the axial dimension, reducing the complexity of any single bearing while maintaining overall thrust control.
2Force
If large thrust bearings are used, then thrust force control is improved, but manufacturing precision requirements increase due to shimming and balancing needs
Solution Approach 1:
By segmenting the thrust bearing system into multiple smaller bearings, each bearing handles a portion of the total thrust load. This reduces the precision requirements for each individual bearing compared to a single large bearing that would need to handle the entire aggregated thrust load, making manufacturing and assembly more feasible.
Solution Approach 2:
Each thrust bearing is designed to handle the specific thrust forces generated by its corresponding impeller stage. The local quality of each bearing can be optimized for its specific location and load conditions, rather than requiring uniform high precision across a single large bearing that must accommodate varying thrust conditions across all stages.
3Force
If narrow operating range is used to balance up-thrust and down-thrust, then thrust force balance is improved, but productivity decreases
Solution Approach 1:
The segmentation of thrust control into multiple stage-specific bearings allows each bearing to independently manage thrust forces at its location. This enables the pump to operate across a wider range of flow rates because the distributed bearing system can accommodate varying thrust conditions at different stages without requiring the entire system to operate at a single equilibrium point.
Solution Approach 2:
The thrust bearing system is designed to dynamically adapt to varying operating conditions. Each thrust bearing can respond to the specific thrust forces generated by its corresponding impeller stage, allowing the system to maintain thrust balance across a broader operating range rather than being constrained to a fixed narrow equilibrium point.
Data Source
AI summary
A multistage centrifugal pump includes a housing, a rotatable shaft and first and second turbomachinery stages. The first turbomachinery stage includes a first diffuser connected to the housing, a first impeller connected to the rotatable shaft. The second turbomachinery stage includes a second diffuser connected to the housing and a second impeller connected to the rotatable shaft. The multistage centrifugal pump further includes an integral axial load and bearing system that includes at least one diffuser bushing and at least one impeller bearing. The integral axial load and bearing system permits the independent axial movement of the first and second impellers. The integral axial load and bearing system also provides an opposite force to up-thrust and down-thrust produced by the first and second turbomachinery stages.