Basic knowledge of air compressor
Air compressor is the main gas supply, which is the original motive (usually motor) of the mechanical energy converted into gas pressure to the device, is the occurrence of compressed air pressure device.
Many types of air compressors, according to the principle can be divided into displacement compressors, reciprocating compressors, centrifugal compressors, positive displacement compressor works by the volume of compressed gas, so that unit volume density of gas molecules to increase the pressure of compressed air; centrifugal compressor works to increase the velocity of gas molecules, the gas molecules with the gas kinetic energy into pressure energy, thereby raising the pressure of compressed air. Reciprocating compressors (also called piston compressor) works directly compressed gas, when gas pressure reaches a certain post-discharge.

Now commonly used in air compressor with piston air compressors, screw air compressor, (screw air compressor is divided into twin-screw air compressors and single screw air compressor), centrifugal compressors and sliding Chip air compressors, scroll air compressor. Here is the definition of the various compressors. Like Cam type, and diffusion pumps, diaphragm compressors which are not included, because they use a special and relatively small size.

Displacement compressors - depend directly on changes in gas volume to increase the gas pressure in the compressor.
Reciprocating compressors - the displacement compressors, the compression element is a piston in the cylinder for reciprocating motion.
Rotary Compressor - the displacement compressors, compressed by the rotational movement component of the mandatory implementation.
Vane compressors - rotary variable capacitance compressor is, in the same axial vane eccentric rotor cylinder for cylinder radial sliding. Interception in the air vane is compressed between the discharge.
Liquid - piston compressor - is rotary positive displacement compressor, in which water or other liquid as a piston to compress gas, then the gas emissions.
Roots dual rotor compressor - is a rotary positive displacement compressor, in which the two roots rotor meshing with each other to the gas stopped and taken from the intake vents. No internal compression.
Screw compressor - is rotary displacement compressor, in which two of the rotor with a helical gear meshing with each other, so the gas compressed and discharged.
Speed compressor - is a continuous flow rotary compressor, in which high speed rotating blades to the gas to accelerate through it, so the speed can translate into pressure. Part of this transformation occurred in the rotating blade, the part in the fixed diffuser or baffle on the return channel.
Centrifugal compressor - is the speed compressor, in which one or more rotating impellers (blades usually the side) so that gas to accelerate. The main flow is radial.
Axial compressor - is the speed compressor, in which the gas accelerated by the rotor blades installed. The main flow is axial.
Mixed-flow compressor - the compressor is a speed type, the shape of its rotor combines centrifugal and axial flow between some of the features.
Jet compressors - high-speed jet of gas or steam inhalation of the gas flow away, and then mixed in the diffuser will be translated into the speed of gas pressure.
By the motor direct drive compressors, the crankshaft can rotate to drive the piston rod to produce reciprocating motion, causing the cylinder volume changes. As the cylinder pressure changes, through the intake valve to the air through the air filter (muffler) into the cylinder, the compression stroke, due to the reduced cylinder volume, the role of compressed air through the exhaust valve through the exhaust pipe, one-way valve (check valve) into the gas tank, when the exhaust pressure when the rated pressure of 0.7MPa pressure switch control by the automatic shutdown. When the pressure of tank is down to 0.5 - 0.6MPa, the pressure switch automatically starts.
The main basis for selection of air compressors is according to the pneumatic system pressure and flow of work.
Work pressure gas source should be higher than the maximum working air pressure system about 20% higher, because to consider gas pipeline along the loss and partial loss. If the demand of working pressure is too low, then could use pressure reducing valve to supply. Air compressor discharge pressure into the rated voltage (0.7 ~ 1.0MPa), medium pressure (1.0 ~ 10MPa), high pressure (10 ~ 100MPa) and high pressure (100MPa or more) can be selected according to actual demand. Commonly use of pressure normally 0.7-1.25.
First, the characteristics required by air compressor, choose the type of air compressor. Then according to the work required pneumatic system pressure and flow are two parameters to determine the compressor's output pressure pc and inhalation flow rate qc, the final selected models of air compressors.
(1) air compressor output pressure pc
pc = p + p
pc: air compressor output pressure
p: pneumatic actuators the maximum working pressure
p: total pressure loss of pneumatic systems.
In general, the other p = 0.15 ~ 0.2MPa.
(2) inhalation of air compressor flow qc
No gas cylinders, qb = qmax
Set cylinders, qb = qsa
qb: air traffic system
qmax: maximum air consumption pneumatic system
qsa: pneumatic system, the average air consumption
Compressor suction flow rate, qc = kqb
qc: compressor suction flow
k: correction factor. Major consideration pneumatic components, fittings, etc. of the leakage, the estimation error of air consumption pneumatic system, pneumatic devices multiple non-concurrent use efficiency and increase the possibility of new factors such as pneumatic devices. General k = 1.5 ~ 2.0.
(3) air compressor power P
p = (n +1) * k * p1 * qc * (pc/p1 )^{[( k-1) / [(n +1) * k] -1) / (k-1) * 0.06