Pump Sealing Bore Segmentation for Leakage Reduction
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Solution Overview
Problem
Multi-stage pumps, such as vacuum and compressor pumps, face issues with leakage due to manufacturing tolerances, which require a balance between adequate running-clearance and preventing rotor-stator contact, leading to inefficiencies and performance degradation.
Innovation Solution
The design incorporates a reduced-size bore with semi-circular portions offset by manufacturing tolerances, maintaining adequate running-clearance while minimizing leakage by matching the radius of the bore to the rotor's external radius and utilizing a discontinuous aperture configuration with tangentially extending portions, reducing fluid leakage between the rotor and stator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger bore is provided to accommodate manufacturing tolerances and prevent rotor-stator contact, then reliability is improved, but leakage increases
Solution Approach 1:
The bore is segmented into two distinct portions: a first portion extending from the first face with a first radius, and a second portion extending from the second face with a second radius. This segmentation allows each portion to be optimized for different functions - the first portion prevents rotor-stator contact while the second portion minimizes leakage, resolving the contradiction between reliability and energy loss.
2Loss of energy
If a reduced-size bore is provided to minimize leakage, then energy efficiency is improved, but the risk of rotor-stator contact increases due to manufacturing tolerances
Solution Approach 1:
Different portions of the bore have different local qualities - the first portion has a larger radius (first radius) to prevent rotor-stator contact, while the second portion has a smaller radius (second radius) to minimize leakage. This local differentiation allows the system to simultaneously achieve both reliability and energy efficiency.
3Adaptability or versatility
If the bore radius is increased to accommodate location tolerances of stator faces, then manufacturing adaptability is improved, but leakage increases
Solution Approach 1:
The bore is divided into two portions with different radii. The first portion extends from the first face with a first radius that accommodates location tolerances of the first face, while the second portion extends from the second face with a second radius that minimizes leakage. This segmentation allows the design to be adaptable to manufacturing variations without sacrificing energy efficiency.
Solution Approach 2:
The solution addresses the two-dimensional tolerance problem by introducing a dimensional variation along the bore length. The radius changes from the first radius at the first face to the second radius at the second face, using the longitudinal dimension to resolve the conflict between tolerance accommodation and leakage prevention.
Data Source
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Figure 3
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AI summary
A pump assembly and method are disclosed. The pump comprises: a first housing part defining a first portion of a bore extending within the first housing part and shaped to receive a rotor; and a second housing part defining a second portion of the bore extending within the second housing part and shaped to receive the rotor, the first housing part having a first face abutable against an opposing second face of the second housing part to position the first portion of the bore with the second portion of the bore to receive the rotor, the first portion of the bore having a first circular cross-section portion centred along the first face and the second portion of the bore having a second circular cross-section portion centred, within the second housing part, at a distance from the second face. In this way, a reduced-size bore can be provided which reduces leakage while also providing for adequate running-clearance between the rotor and the bore.