With the development of vacuum application, there are many kinds of Roots vacuum pump. The pumping speed of Roots vacuum pump has changed from a few liters per second to hundreds of thousands and millions of liters per second. According to the working principle of Roots vacuum pump, roots vacuum pump can be basically divided into two types, namely gas capture pump and gas transfer pump. With the vacuum technology in the field of production and scientific research, the pressure range of its application is becoming wider and wider. Most vacuum pumps need to be composed of several roots vacuum pumps to pump together to meet the requirements of the production and scientific research process. Because the working pressure range involved in the vacuum application department is very wide, it is impossible to complete any kind of Roots vacuum pump It is suitable for all working pressure ranges. Different types of Roots vacuum pumps can only be used according to different working pressure ranges and different working requirements.
In order to use conveniently and meet the needs of various vacuum processes, various roots vacuum pumps are sometimes combined according to their performance requirements and applied in the form of units. The commonly used roots vacuum pumps include dry screw vacuum pump, water ring pump, reciprocating pump, slide valve pump, rotary vane pump, roots pump and diffusion pump. These pumps are the essential main pumps in the application of vacuum technology in various industries of national economy. In recent years, with the continuous and high-speed development of China’s economy, the downstream application industry related to roots vacuum pump keeps a rapid growth momentum. At the same time, under the joint pull of the continuous expansion of the application field of Roots vacuum pump and other factors, the roots vacuum pump industry in China has achieved sustained, stable and rapid development.
Roots vacuum pump is a mechanical vacuum pump with a pair of soled rotors rotating synchronously and at high speed. This pump can’t be aspirated alone. The front stage needs to be equipped with oil seal, water ring, etc. to directly exhaust the atmosphere. Its structure and working principle are similar to roots blower. When it works, its suction port is connected with the main pump of the evacuated vessel or vacuum system. There is no contact between the rotor and the rotor or between the rotor and the pump shell, and the clearance is generally 0.1-0.8mm; oil lubrication is not required. The rotor profile includes circular arc, involute, cycloid, etc. Involute rotor pump has high volume utilization ratio and easy to ensure machining accuracy, so the rotor profile is mostly involute. The rotating speed of Roots vacuum pump can be as high as 3450 ~ 4100 rpm; the pumping rate is 30 ~ 10000 L / S (1 L = 10-3 m3); the limit vacuum: single stage is 6.5 × 10-2 PA, double stage is 1 × 10-3 PA.
The limit vacuum of Roots vacuum pump depends not only on the structure and manufacturing accuracy of the pump itself, but also on the limit vacuum of the front stage pump. In order to improve the limit vacuum of the pump, roots pump can be used in series. The working principle of roots pump is similar to that of Roots blower. Due to the continuous rotation of the rotor, the extracted gas is drawn into the space V0 between the rotor and the pump shell from the air inlet, and then discharged through the exhaust port. As the V0 space is totally closed after suction, the gas in the pump cavity is not compressed and expanded.
However, when the top of the rotor turns the edge of the exhaust port and the space V0 is connected with the exhaust side, because of the high gas pressure at the exhaust side, a part of the gas flows back into the space V0, which makes the gas pressure suddenly increase. As the rotor continues to rotate, the gas exits the pump. In the cavity of roots pump, two “8” shaped rotors are vertically installed on a pair of parallel shafts, and a pair of gear belts with a transmission ratio of 1 move in reverse synchronous rotation with each other. There is a certain gap between the rotors, between the rotors and the inner wall of the pump casing, which can realize high-speed operation.