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Can centrifugal air compressors use frequency conversion control?

Can centrifugal air compressors use frequency conversion control?

  • 2022-06-20

The principle of centrifugal air compressor:

Centrifugal air compressors are speed compressors. The impeller drives the gas to rotate at a high speed, so that the gas generates centrifugal force. Due to the diffused flow of the gas in the impeller, the flow rate and pressure of the gas after passing through the impeller are improved. Continuous production out compressed air.


Centrifugal air compressors rely on changes in kinetic energy to increase the pressure of the gas. When the rotor with blades (that is, the working wheel) rotates, the blades drive the gas to rotate, transfer work to the gas, and make the gas obtain kinetic energy. After entering the stator part, the energy pressure head is converted into the required pressure due to the speed of the diffuser action of the stator, the speed is reduced, and the pressure is increased. .


Why can't or isn't necessary?

Frequency conversion control is very effective for screw compressors. Through pressure feedback, frequency conversion adjusts the speed . The screw type "changes in speed independent of the discharge pressure", while the centrifugal type is "the discharge pressure changes with the change of the speed". That is, as the speed of the centrifuge decreases, its pressure also decreases. Therefore, when a certain level of pressure is required at the tail end, the capacity regulation of centrifugal compressors cannot use variable frequency control.


The capacity adjustment method of the centrifugal air compressor mainly depends on controlling the opening size of the intake guide vanes to control the intake air volume, and measures for venting or backflow. The adjustable range of the centrifuge itself is generally about 70%-100%. Even if the frequency conversion control is used, it cannot be less than the minimum flow rate of the compressor (or because the back pressure of the compressor is higher than its maximum discharge pressure), otherwise, it is easy to produce "" Surge".


Surge is extremely harmful to centrifuges and cannot be eliminated from the design of the machine so far. The way to prevent "surge" is to increase the flow. Therefore, even if the frequency conversion adjustment is used, the adjustable range is still about 70%-100%.


Magnetic levitation frequency conversion centrifugal air compressor


At present, the latest magnetic levitation frequency conversion centrifugal air compressor, the adjustment range is still 70%-100%. The use of magnetic levitation is convenient for frequency conversion and speed regulation on the body mechanism.


The main purpose of frequency conversion of magnetic levitation centrifuge:

1 . reduce wasted power (when emptying) (2.5% power consumption)

2 .solve the problem of not being able to load quickly. Solving these two problems is equivalent to the full-load regulation of the magnetic levitation frequency conversion centrifugal centrifuge.

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