What are the differences between Roots fans and screw blowers?

Roots fan and screw fan have a great difference, the two similar places are the same as the blower, there are positive pressure and negative 

pressure classification, in order to facilitate everyone to understand the difference between the two fans

1. Different origins

Roots fan origin and the United States, screw fan origin and Germany.

The screw fan was first proposed by the German H.Krigar in 1878, and it was not until 1934 that the Swedish Royal Institute of Technology 

A.Lysholm laid the technology and began to be applied in industry.

2, rotor difference

At present, the most popular design on the market is the involute design, and the rotor of the screw fan is the rotor linear design.

3. Different pressure ranges

The more widely used single-stage Roots blower pressure range is 9.8 to 98kpa, and the two-stage Roots blower pressure range is 98kpa to

 198kpa. Screw fan pressure range 0.3~1.2Bar

4. It works differently

In the process of running and conveying air, the cavity between the rotor does not change the volume, and the pressure comes from forcing

 a large amount of air into a relatively small external cavity, such as: pipelines or gas storage tanks, the density of the air in the external cavity 

continues to increase, resulting in pressure, usually called "external compression".

The working principle of the screw blower is somewhat different from that of the Roots blower, the air is also sucked in and then discharged, 

when inhaling, the cavity between the screw and the screw is the largest, when the gas is discharged, the cavity volume will become very small, 

that is to say, in the rotation process, it is equivalent to the 2m? Is the gas compressed to 1m? At the same time, the pressure is increased to 

1bar, that is, the pressure increase is not from the external pipe network, but from the change of the internal cavity of the compressor.