Turbomolecular Pump Vane Design for High Flow Rate
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Solution Overview
Problem
Existing turbomolecular pump designs using two-dimensional cross sectional vane models fail to adequately address high flow rate and high back pressure demands due to limitations in simulating three-dimensional molecular movement and reverse flow considerations.
Innovation Solution
The turbomolecular pump incorporates vane stages with specific dimensionless number ratios (Xo(R)>Xo(S) and Xi(R)<Xi(S)) and additional adjustments to optimize vane shapes, particularly at the outer and inner circumferential portions, to enhance evacuation performance by reducing reverse flow and increasing gas flow area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-dimensional cross sectional vane model is used for design, then the design process is simplified and manufacturing is easier, but the evacuation performance in high flow rate region is insufficient
Solution Approach 1:
The patent transitions from a two-dimensional cross-sectional vane model to a three-dimensional vane design that accounts for radial variations in the dimensionless number X. By introducing radial positioning and varying X values at different radial distances from the rotation shaft, the design captures three-dimensional molecular flow effects while maintaining a systematic design approach, thereby improving evacuation performance without excessive manufacturing complexity.
2Device complexity
If the dimensionless number X is kept constant or changes linearly across all stages, then the design is simpler, but it cannot adequately address high back pressure demands
Solution Approach 1:
The patent applies local quality by varying the dimensionless number X according to the specific functional requirements of different vane stages. Intermediate flow region stages use larger X values to handle higher molecular densities, while outlet side stages use smaller X values to efficiently manage molecules at lower pressures. This localized optimization ensures each stage is tuned for its specific operating conditions, improving overall reliability under high back pressure.
Solution Approach 2:
The patent systematically changes the parameter X (dimensionless number) across different vane stages and radial positions to optimize performance. By defining specific X value ranges for different operational regions and adjusting them according to molecular flow conditions, the design adapts to varying pressure and flow rate requirements, thereby enhancing evacuation performance under high back pressure conditions.
3Device complexity
If rotor vanes and stator vanes are designed with the same principles, then the design process is more uniform, but reverse flow effects are not properly considered
Solution Approach 1:
The patent introduces asymmetry in the vane design by differentiating between rotor vane and stator vane configurations. Rotor vanes are designed with specific X values optimized for moving molecules forward, while stator vanes use different X values to effectively redirect and contain reverse-flowing molecules. This asymmetric design allows each component to address its specific functional role, with stator vanes specifically optimized to minimize reverse flow 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 design significantly enhances evacuation performance, especially in high flow rate regions, by optimizing the dimensionless number X considering three-dimensional movement and reverse flow effects, leading to improved gas flow and reduced reverse flow.
Implementation Method 1
analysis according to the prior art theory and design method used in such a two dimensional cross sectional vane model is executed while only taking into consideration the movement of molecules within the cross section
Implementation Method 2
the rotor vanes and the stator vanes are considered as being equivalent, and vane design is performed for both of them with the same design principle
Data Source
AI summary
In a turbomolecular pump, in connection with a dimensionless number X that is the ratio of an inter-vane distance S to a chord length C for moving vane blades of rotor impeller (4B) and stationary vane blades of stator impeller (2B), with dimensionless numbers at the outer circumferential portion and the inner circumferential portion of a first vane stage being termed Xo(R) and Xi(R) and dimensionless numbers at the outer circumferential portion and the inner circumferential portion of a second vane stage being termed Xo(S) and Xi(S), and with respect to vane stages that are adjacent along the direction of the rotational shaft, at least one vane stage is provided that satisfies a first relational equation “Xo(R)>Xo(S)” and a second relational equation “Xi(R)<Xi(S)”. As a result it is possible to enhance the evacuation performance, in particular the evacuation performance in the high flow rate region, as compared to a prior art turbomolecular pump in which the vane design has been performed according to a two-dimensional cross sectional vane model.