Structural characteristics of composite molecular pump

Composite molecular pump is a series combination of molecular pump and traction molecular pump, set the advantages of the two pumps in one. Pump in a wide range of pressure ((10-6 ~ 1Pa) has a larger pumping speed and higher compression ratio, greatly improving the pump outlet pressure.Australian company Alcatle produced a static pressure bearing and Dynamic seal of the composite molecular pump, can be completely oil-free, and without the first stage pump to the atmosphere directly to the exhaust.
Complex molecular pump in many forms, according to the structure points, there are two main: one is the turbine blades and disc traction pumps in series combination; the other is the turbine blades and drum traction pump series combination. Turbine stage is mainly used to increase pump pumping speed, generally used to help improve the pumping speed of the blade shape, level in l0 level or less. Traction level is mainly used to increase the compression ratio of the pump, increase the pump outlet pressure.
Traction level is in the flat disk flat plate according to a certain law out of a number of profile groove, and then a few pieces of disk connected in series form, Archimedes spiral line, logarithmic spiral, circle Arc and so on. When pumping, the gas molecules are "dragged" by high-speed rotating discs to flow along the grooves in a directional flow from the inside to the outside and the reciprocating return from the outside to the inside, so as to achieve the purpose of pumping air.
Cylinder traction level is in the cylindrical rotor or stator cylindrical surface to open a certain cross-sectional shape of the groove, such as rectangular, circular arc, triangular and other shapes of multi-head spiral groove. Because the simple traction type groove line is open on the outer surface of the rotor cylinder or the inner surface of the pump body, the momentum transfer of the gas molecules can be fully utilized by the linear velocity of the cylindrical outer circle to improve the pumping effect of the pump. In the design and manufacture, you can achieve a better pumping effect by changing the angle between helical groove channel and suction direction (helix angle).
In the design of the composite molecular pump, must deal with the turbo-class and traction level between the match and convergence relationship. As the turbine stage has a larger pumping area, pumping speed is large, while the traction groove groove pumping area smaller, at the junction of the two structures, the turbine blades compressed gas molecules flow suddenly changed so that The movement of gas molecules in the joints from the disorder into disorder, to make reflux increased, decreased suction capacity. Therefore, the design should be at the turbine level and traction level transition plus transitional structure, in order to improve the pumping performance of the pump.
With the continuous improvement of the composite molecular pump, its application fields are more and more widely used. In some pumping systems, it can replace the diffusion pump, shorten the pumping time of the system, and obtain a clean vacuum environment without oil pollution.

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