An air compressor is basically a device that uses a mechanical pump to take air from the atmosphere, compress it and store it. This compressed air can then be used at any desired pressure.Factories and businesses use compressors to drive machinery and air tools. The application we are most familiar with is to put air in our vehicle tires.
An air compressor can be a very handy tool to have at home. It will take care of all your inflating needs and can be used for cleaning purposes and of course to run air tools like nailers and spray guns.Serving uses in individual tool-kits and industrial production sets alike, air compressors are useful for powering paint sprayers, finish nailers and impact wrenches. Power and versatility are an air compressor’s chief benefits, but every product contains a slew of options for diverse projects.
They are two main types of air compressors.
1) Reciprocating Compressor:
This device is very similar to a piston engine. But instead of burning air-fuel mixture, this device takes in uncompressed air in the suction stroke, compresses it during the compression stroke, and lets out compressed air at a higher pressure and temperature during the exhaust stroke. The compressed air is then stored in a pressure reservoir and can be used when needed. This type provides intermittent pressure supply.
2) Centrifugal type:
This is an indirect type of compressor. It involves an impeller housed in an involute casing. The air enters this compressor from the centre and is forced rapidly inside the casing. The cross-section area of the housing decreases as the air goes from the inlet to outlet. The compression takes place due to the sudden drop in speed the air experiences once leaving the compressor housing. The pressure output of this type is generally less than the reciprocating type. But the output is continuous.
Working Of An Air Compressor
The Reciprocating compressor works more or less like an IC engine. It has only two strokes though and also that it is a power consuming device, unlike the IC engine which is power generating.
During the intake stroke, the piston moves from the TDC to the BDC. The vacuum created by the suction opens the intake valve on the compressor and socks air into the compression chamber. Once the piston reaches the BDC, the valve closes and the compression stroke starts (from BDC to TDC). In due course, the discharge valve on the other side opens up and the compressed air gets released. Depending on whether it is a single stage or a multistage compression, there can either be an intercooler or it may not be present.
One of the drawbacks of the Reciprocating compressor is that the air supply is intermittent. That is, at the end user your airflow is not continuous. Also, the volume of air that can be handled is limited. As your requirement increases, your compressor size keeps going up.
The next generation of air compressor is the screw compressor. Here the machine consists of a part called the aired, which is the heart of the device. It contains two lobes cut in a particular profile along which the air flows. The airend is generally crowned with an intake valve. The shaft of the airend is coupled to a prime mover (an engine or an electric motor).
The prime mover rotates the lobes which create a vacuum in the airend case. This gives a pulse to the intake valve which opens according to the amount of vacuum created and sucks in air. The air then traverses along the lobes and gets discharged either to a storage tank or for end use. Screw compressors provide a more consistent flow of air than their Reciprocating counterparts and are considered more reliable.
Centrifugal air compressor functions just like a pump. It has a casing which contains a blade profile coupled to a prime mover. Centrifugal compressors generally are used in those applications where the air flow required is huge.