Types of Air Compressors and How to Choose

Types of Air Compressors

There are many types of air compressors.

1. According to the working principle, it can be divided into three categories: volumetric, dynamic and thermal compressors.

2. According to the lubrication method, it can be divided into oil-free air compressor and oil-lubricated air compressor.

3. According to performance, it can be divided into: low noise, variable frequency, explosion-proof and other air compressors.

4. According to the use, it can be divided into: refrigerator compressor, air conditioning compressor, refrigeration compressor, oil field compressor, natural gas filling station, rock drill, pneumatic tools, vehicle braking, door and window opening and closing, textile machinery For tire inflation, plastic machinery compressors, mining compressors, marine compressors, medical compressors, and sandblasting and painting.

5. According to the type, it can be divided into: fixed type, mobile type and closed type.

Positive displacement compressor - A compressor that directly relies on changing the volume of the gas to increase the pressure of the gas.

Piston compressor is a positive displacement compressor whose compression element is a piston that reciprocates in the cylinder.

Rotary compressor - is a positive displacement compressor in which compression is achieved by forced movement of rotating elements.

Sliding vane compressor - It is a rotary variable displacement compressor in which the axial sliding vanes slide radially on the eccentric rotor of the same cylindrical cylinder. The air trapped between the slides is compressed and discharged.

Liquid-piston compressor - is a rotary positive displacement compressor in which water or other liquid acts as a piston to compress the gas and then expel the gas.

Roots double-rotor compressor - a rotary positive displacement compressor in which two Roots rotors mesh with each other to intercept the gas and send it from the air inlet to the exhaust port. There is no internal compression.

Screw compressor is a rotary positive displacement compressor in which two rotors with spiral gears mesh with each other, causing the volume of the meshing area of the two rotors to change from large to small, thereby compressing and discharging the gas.

Velocity compressor - is a rotary continuous air flow compressor in which high-speed rotating blades accelerate the gas passing through it, thereby converting velocity energy into pressure. This conversion occurs partly on rotating blades and partly on stationary diffuser or recirculator baffles.

Centrifugal compressor - A speed compressor in which one or more rotating impellers accelerate the gas. The main air flow is radial.

Axial Compressor - A velocity-type compressor in which the gas is accelerated by a rotor equipped with blades. The main air flow is axial.

Mixed flow compressor - also a speed compressor. The shape of its rotor combines some characteristics of both centrifugal and axial flow.

Jet compressor - uses a high-speed jet of gas or steam to take away the inhaled gas, and then converts the velocity of the mixed gas into pressure on the diffuser.

Permanent magnet variable frequency compressor - Since the variable frequency screw air compressor takes advantage of the stepless speed regulation feature of the frequency converter, it can start smoothly through the controller or the PID regulator inside the frequency converter; it is suitable for occasions with large fluctuations in gas consumption. , and can quickly adjust the response.

Unipolar compression screw air compressor - the head is a screw air compressor composed of a pair of male and female rotors. This model is a widely used screw air compressor.

Bipolar compression screw air compressor - the machine head is composed of two pairs of yin and yang rotors. After the first-level compression, the gas enters the second-level compression. The compression ratio is high, and the power is one gear lower than that of the first-level compression air compressor.

How to Choose:

Determine work stress

When preparing to purchase an air compressor, you must first determine the working pressure required at the air end, add a margin of 1-2 bar, and then select the pressure of the air compressor. Of course, the size of the pipeline diameter and the number of turning points are also factors that affect the pressure loss. The larger the pipeline diameter and the fewer turning points, the smaller the pressure loss; conversely, the greater the pressure loss.

Therefore, when the distance between the air compressor and each gas-end pipeline is too far, the diameter of the main pipeline should be appropriately enlarged. If the environmental conditions meet the installation requirements of the air compressor and the working conditions permit, it can be installed close to the gas end.

Volume flow selection

1. When selecting the volume flow rate of an air compressor, you should first understand the volume flow rate of all gas equipment and multiply the total flow rate by 1.2;

2. When a new project is launched, the model can be selected based on the flow value provided by the design institute;

3. Learn about the volumetric flow parameters of the gas equipment from the gas equipment supplier for selection;

4. When renovating an air compressor station, you can refer to the original parameter values and actual gas consumption for selection;

Appropriate selection is beneficial to both the user and the air compressor equipment. Selection that is too large is wasteful, and selection that is too small may cause the air compressor to be in a loaded state for a long time or not use enough air or the pressure cannot be pumped up.

The relationship between the three

When the power remains unchanged, when the rotational speed changes, the volumetric flow rate and working pressure also change accordingly; for example: a 22KW air compressor, the working pressure is determined to be 7bar during manufacture, calculated according to the technical curve of the compressor host Rotation speed, exhaust volume is 3.8 m3/min; when the working pressure is determined to be 8bar, the rotation speed must be reduced, at this time, the exhaust volume is 3.6 m3/min; because, as the rotation speed decreases, the exhaust volume also decreases accordingly, and so on analogy.

The power selection is based on the condition that the working pressure and volumetric flow rate are met, and the power supply capacity can meet the power of the matching drive motor.

Therefore, the steps for selecting an air compressor are: first determine the working pressure, then determine the corresponding volume flow rate, and finally the power supply capacity.