Small turbine molecular pump
Turbomolecular pump is a kind of high vacuum acquisition equipment, which is used to provide a clean high vacuum environment. It has been widely used in electronic industry, optical engineering, surface science and other fields. Small turbomolecular pumps, with their advantages of small size, light weight and low power consumption, are often used in equipment or instruments that require vacuum without emphasis on pumping speed, such as vacuum acquisition equipment as mass spectrometer and leak detector.
Turbine molecular pump takes impeller group as its pumping actuator. The impeller group consists of alternately arranged dynamic and static impellers. When the impeller rotates at high speed, its speed is close to the molecular thermal speed, while the static impeller remains stationary.
Molecular pumps are mainly classified:
1. Traction Molecular Pump: A molecular pump that collides with a high-speed rotating rotor to obtain kinetic energy and is driven to the pump outlet.
2. Turbine Molecular Pump: the use of high-speed rotating blades and stationary vanes cooperate to achieve the pumping of molecular pumps.
3. Compound molecular pump: It can maintain high pumping performance in high pressure area. A spiral traction molecular pump is equipped on the high pressure side of the original turbomolecular pump, and the pump units of the two pumps are connected in series.
Performance and characteristics of small turbine molecular pumps:
The ratio of pump exhaust pressure to intake pressure is called compression ratio. The compression ratio is related not only to the series and rotational speed of the pump, but also to the type of gas. A high molecular weight gas has a high compression ratio. The compression ratio for nitrogen (or air) is 108-109; for hydrogen, 102-104; for gas with large molecular weight, such as oil vapor, it is greater than 1010. The pump has a limit pressure of 10-9 Pa, operating pressure range of 10-1-10-8 Pa, and pumping rate of tens to thousands of litres per second (1 liter = 10-3 m 3).
Turbomolecular pumps have to operate in the state of molecular flow (the average free path of gas molecules is much larger than the maximum size of the duct cross-section flow) to demonstrate its superiority, so it is required to have a working pressure of 1-10-2 Pa of the first stage vacuum pump. The molecular pump itself is driven directly by an intermediate frequency motor with a rotational speed of 10000~60000 R / s.