Turbomolecular Pump Rotor Blade S-Shape Profile
Solution Overview
Problem
Conventional turbomolecular pumps with flat plate blades suffer from low bending rigidity, leading to potential collisions between rotor and stator blades due to air inrush, causing stress on the hub and reducing pumping performance, especially in the viscous flow region.
Innovation Solution
The design incorporates rotor blades with a curved S-shape or inversed S-shape cross-sectional profile, where the upstream portion is curved convexly backward and the downstream portion is curved convexly forward, increasing bending rigidity without increasing hub stress, and optimizing blade angles for enhanced pumping performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If flat plate blades are used, then the structure is simple and easy to manufacture, but the bending rigidity is low causing blade collision and hub stress
Solution Approach 1:
The blade cross-section is designed with curved surfaces instead of flat plates. Specifically, the pressure surface has a first curvature radius and the suction surface has a second curvature radius, creating an airfoil-like cross-sectional shape that significantly increases bending rigidity while maintaining manufacturing feasibility through standard blade manufacturing processes.
2Strength
If rotor blades are thickened to prevent collision, then bending rigidity increases, but stress on the hub inner circumference increases
Solution Approach 1:
The curvature radii are optimized locally at different positions along the blade span. The first curvature radius at the pressure surface and the second curvature radius at the suction surface are specifically designed to achieve adequate bending rigidity in the blade while controlling the root thickness to minimize hub stress. This localized optimization allows the blade to have sufficient strength without uniformly thickening the entire blade structure.
3Productivity
If conventional blade designs are used, then manufacturing is straightforward, but pumping speed in viscous flow region is insufficient
Solution Approach 1:
The blade profile parameters including curvature radii, blade angles, and cross-sectional shape are optimized to enhance pumping performance in the viscous flow region. The specific curvature radii and airfoil-like cross-section create more effective gas flow patterns that increase pumping speed without requiring complex manufacturing processes, as these parameters can be achieved through conventional blade manufacturing with precise control.
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 prevents collisions, enhances bending rigidity, and increases pumping speed in the viscous flow region, improving overall pumping performance by maintaining lower hub stress and efficient gas flow.
Implementation Method 1
it is possible to prevent collision between the adjacent rotor and stator blades due to air inrush, which may enter into the rotor, by increasing the high bending rigidity of the blades
Implementation Method 2
A turbomolecular pump has a pumping section that includes multi stages of rotor blades having a shape similar to those of an axial flow compressor, and multi stages of stator blades alternatively arranged with the rotor blades
Data Source
AI summary
An object is to provide a turbomolecular pump with rotor and stator blades alternatively arranged that can prevent collision between the adjacent rotor and stator blades due to air inrush, which may take place due to vacuum break in a system operation, prevent excessive centrifugal force to a hub portion of a rotor, and further enhance pumping performance. A blade cross sectional profile taken along the circumferential direction of each of the rotor blades of a rotor blade stage has an upstream portion curved convexly backward in a rotational direction of the rotor and a downstream portion curved convexly forward in the rotational direction of the rotor, thereby forming the blade cross sectional profile into an S-shape or inversed S-shape.