Multistage Dry Vacuum Pump Thermal Expansion Control
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Solution Overview
Problem
Conventional vacuum pumps face challenges in achieving high vacuum levels due to thermal expansion differences between the cylinder body and rotor, leading to adhesive sticking and increased maintenance costs, as they require multiple pumps in series to manage overheating and compression ratios.
Innovation Solution
A multistage dry vacuum pump design where a gas passage surrounds the outer cylinder, with a cooling water jacket circulating around it, communicating with the exhaust space to cool both the cylinder body and rotor, maintaining similar thermal expansion conditions and optimizing gap sizes for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cooling water passage is formed at the outer wall of the pump body cylinder to cool the cylinder body, then the cylinder body is cooled effectively, but the rotor is heated and thermally expanded due to direct heat transfer from compression, causing thermal expansion differences and adhesive sticking
Solution Approach 1:
The cooling system is segmented into two independent paths: an outer cooling water passage for cooling the cylinder body, and an inner gas passage for cooling the rotor through circulated gas. This segmentation allows independent temperature control of each component, preventing thermal expansion differences while maintaining reliable operation.
Solution Approach 2:
The gas circulated through the gas passage acts as an intermediary cooling medium for the rotor. Instead of directly cooling the rotor with water (which would cause thermal expansion differences), the system uses the gas as a mediator to transfer heat away from the rotor, maintaining similar thermal conditions between the rotor and cylinder body.
2Reliability
If larger gaps are formed between the rotor and cylinder body to accommodate thermal expansion differences, then adhesive sticking is prevented, but vacuum level deteriorates and exhaust speed decreases
Solution Approach 1:
The system changes the temperature parameter of both the rotor and cylinder body to be similar through independent cooling control. By maintaining similar temperatures, the thermal expansion difference is minimized, allowing the use of smaller gaps that improve exhaust speed while still preventing adhesive sticking through active cooling management.
3Manufacturing precision
If two or three-stage pumps are connected in series to achieve high vacuum degree, then the desired vacuum level is reached, but the passage length increases and maintenance costs significantly increase
Solution Approach 1:
The patent merges multiple pump stages into a single integrated pump body with multiple cylinders arranged in series. This combining approach achieves the high vacuum degree of multi-pump systems while reducing the number of separate pump units, shortening gas passages, and lowering maintenance costs through unified structure and single-unit operation.
4Device complexity
If a single multistage pump structure is used instead of multiple pumps in series, then passage length is reduced and maintenance cost decreases, but thermal expansion differences cause overheating and adhesive sticking
Solution Approach 1:
The cooling system is segmented into two independent paths: an outer cooling water passage for cooling the cylinder body, and an inner gas passage for cooling the rotor through circulated gas. This segmentation allows independent temperature control of each component, preventing thermal expansion differences while maintaining reliable operation.
Solution Approach 2:
The gas circulated through the gas passage acts as an intermediary cooling medium for the rotor. Instead of directly cooling the rotor with water (which would cause thermal expansion differences), the system uses the gas as a mediator to transfer heat away from the rotor, maintaining similar thermal conditions between the rotor and cylinder body.
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 allows for the attainment of high vacuum levels with a smaller pump size and reduced maintenance costs by ensuring similar thermal expansion conditions between the rotor and cylinder, enhancing exhaust speed and stability while minimizing thermal expansion gaps.
Implementation Method 1
cooling water is forced to circulate around an outer wall of the gas passage, and the gas passage communicates with an exhaust space of the cylinder, so the gas cooled in the gas passage is cooled together with the cylinder body and a rotor
Implementation Method 2
a cooling water jacket for circulating cooling water is formed close to the outer side of the gas passage in a shape like surrounding the gas passage
Implementation Method 3
a high temperate heat generating during a compress process in which a rotor intakes and exhausts into the interior of a cylinder
Data Source
AI summary
The multistage dry vacuum pump is disclosed, in which it is possible to prevent a pump from being adhesively stuck, which problem occurs due to a difference in thermal expansions between a cylinder body and a rotor, by making thermal expansion conditions between a cylinder body and a rotor of a pump similar by concurrently cooling the cylinder body and the rotor of the pump. The gas passage for transferring gas compressed by each cylinder is provided at each cylinder body in a shape of surrounding an outer side of each cylinder, and a cooling water jacket for circulating cooling water is provided close to an outer side of the gas passage, and a communication passage is formed at a gas passage contacting with the cooling water jacket and is connected with an exhaust space of the cylinder.