A vacuum pump for a turbine molecule
The turbo molecular pump is the use of high-speed rotating impeller the momentum transfer to the gas molecules, the vacuum pump flow gas generated in the direction of.
Turbo molecular pump has the advantages of quick start, anti radiation, anti air impact, no gas storage and desorption, no oil mist pollution or small pollution, and so on, which can achieve clean ultra-high vacuum. Turbo molecular pumps are widely used in high vacuum manufacturing processes, such as high energy accelerators, controlled thermonuclear reactors, heavy particle accelerators and vacuum coating.
Structure and composition
The turbo molecular pump is mainly composed of the pump body, the rotor blade (dynamic impeller), the static impeller and the driving system.
There are two vertical and horizontal.
The linear velocity of the outer edge moving impeller is heated by the gas molecules (usually 150-400 M / s). The compression ratio of one impeller is very small, and the turbine molecular pump is made up of more than 10 impellers and impellers. The impeller and the static impeller are arranged alternately. The geometric size of the dynamic and static impeller is basically the same, but the angle of the blade is opposite. The picture on the right shows a whole rotor of 20 moving impellers. A static impeller is installed between the two moving impellers. The outer edge of the impeller is fixed by the ring, and the clearance between the impeller and the impeller is kept at about 1 millimeters. The impeller can rotate freely between the impellers.
The ratio of the pump exhaust pressure and the intake pressure is called the compression ratio. The compression ratio is related to the pump level and speed, and is also related to the gas type. High molecular weight gas has a high compression ratio. The compression ratio for nitrogen (or air) is 108 to 109; hydrogen is from 102 to 104; for larger molecular weight gases, such as oil steam greater than 1010.
The ultimate pressure of the pump is 10-9Pa, the working pressure range is 10-1 ~ 10-8Pa, and the pump speed is 10 ~ thousands liters per second (1L = 10-3m3).
Turbo molecular pump must prove its superiority in molecular flow state (the average free path of gas molecules is much larger than the maximum volume of pipe section), so a working pressure of 1 to 10-2 Pa vacuum pump should be needed.
The speed of the molecular pump itself is 10000 ~ 60000 rev / min if the motor is driven directly by the motor.
Large pumping speed, no oil, quick start.
Scope of work: low vacuum ~, high vacuum, atmosphere ~ super high vacuum.
The ultimate vacuum: 10-6 / 10-10torr.
Disadvantages: vibration, high cost, vulnerable to attack