The composition and calculation of the eccentric arc rotor profile of Roots oil pump and why the speed cannot be too high

[1]

The composition and value calculation of the eccentric arc rotor profile of Roots oil pump

The Roots LC Roots pump has been widely used in petrochemical, mining, building materials, underwater engineering, etc. In recent years, the application of Roots units has increased sharply, playing an important role in the development of the national economy that cannot be ignored.

. The Roots rotor is the core component of the Roots oil pump, which directly affects the performance of the machine. At present, Roots rotors mainly have involute profiles with large arc tooth tips and circular envelope profiles. When selecting the rotor profile, the following factors of the rotor are mainly considered:

① The volume utilization coefficient should be as large as possible, that is, the area occupied by the rotor under the same working parameters should be smaller

② Roots rotors should have good symmetry, good rotor meshing, smooth operation, no noise, and good interchangeability

③ The rotor should have sufficient strength and not break

④ Easy to manufacture with high precision

⑤ Good air tightness, no leakage or gas leakage, and the rotor rotation time gap should not change too much

At present, the main types of involute blade profiles used in China are large circular tooth tips, with low area utilization coefficient, poor air tightness, and large changes in meshing clearance. This article studies the profile of eccentric circular arc rotors in order to overcome these shortcomings

The difference between eccentric arc rotor profile and arc rotor profile is that the center of the former's arc deviates from the axis of symmetry, while the center of the latter's arc is on the axis of symmetry. So eccentric circular arc rotors will appear thinner than circular arc rotors

[2] Why can't the speed of Roots pumps be too high?

Although the higher the speed of most mechanical equipment, the higher its efficiency will also be, this does not apply to all mechanical equipment.

. Just like the speed cannot be too high, once the speed is too high, it will not only fail to improve work efficiency, but also cause some problems with the Roots pump. So why can't the speed of the device be too high

1. The suction and exhaust of the Roots pump during operation are achieved through the action of the air valve. If the speed is too high, it will cause the action of the air valve to fail to keep up, which is prone to lagging phenomenon, resulting in increased volume loss and actually not conducive to the improvement of vacuum degree.

. At the same time, it can also cause severe impact on the pump valve, exacerbating equipment wear and tear

2. The equipment itself will vibrate, and as the speed increases, the vibration of its various parts will also increase, causing adverse effects

Another situation is that due to the high rotational speed, the stroke becomes shorter at the pumping rate. However, when installing an air valve, the cylinder diameter cannot be too small, otherwise it will cause an increase in clearance volume, a shorter compression line and expansion line, which is not conducive to improving the vacuum degree. For vacuum, the equipment should use low speed and long stroke

4. After the speed increases, the balancing effect of the Roots pump in the balance channel will become less obvious, and it will not be able to balance the gas in time, nor can it reduce the impact of the clearance volume, thereby affecting the vacuum degree

Therefore, overall, the speed of the Roots pump cannot be too high or too low. Only by keeping its speed within a reasonable range can its working efficiency be maintained in a good state. So when operating and using this device, everyone should also pay more attention to the issue of its speed. Once abnormal phenomena occur, they should be adjusted in a timely manner to avoid causing adverse conditions