An overview of some most used compressors
Criteria for the selection of a compressor is firstly the required system pressure and volume flow. Further decision criterias are the quality of the compressed air (oil-free, humidity level), distribution of compressed air (centralized or decentralized supply).
You can distinguish roughly between displacement compressors and flow compressor.
Positive Displacement compressors compress a closed volume of air to the desired pressure. The pressure generated by displacement compressors can be regarded as high, while the flow rate is rather small.
Flow compressors utilize a motor, which accelerates the air via an impeller. Over a subsequent extension tube and pipe junction the speed and static pressure can build up. The volume flows produced hereby can be very large (up to 50000 m3 / min), but the pressure generated is rather small. Flow compressors are mainly installed in air conditioning systems.
Pistons compress the intake air, which are driven itself via a crank. Self opening and closing valves ensure suction of the intake air as well as the displacing of the now compressed air.
The diaphragm compressor belongs to the family of the piston compressors. Here the suction chamber is sealed from the piston by means of a diaphragm.
As an advantage the compressed air in the compression chamber does not come in contact with the lubricated piston and thus can be kept free of oil. The diaphragm compressor has its weak point here in its membrane itself, since the elasticity is limited.so the suction area is sealed from the piston by a membrane.
Sliding vane compressor
Advantage here is in the pulsation-free flow (as opposed to piston compressors). Therefor a compressed air reservoir may be optional. In addition, these compressors are quiet and relatively insensitive to dirt.In an eccentrically mounted rotor movable slides are mounted, which are pressed by the centrifugal force against the housing wall. Due to the eccentric mounting of the rotor, the air in the chambers between the rotor and slider is compressed.
The pressure, which can be achieved with this compressor, is about 9 bar an flow upto 18 m3/min.