How Does An Air Compressor Work?

The basic idea of an air compressor is, a machine compresses and pumps air inside a tank and releases the compressed air when needed.

But if it were that easy, you wouldn’t be looking it up, would you?

There are several types of air compressors in the market, and each of them is mechanically different. So, the working process will also be different.

Here, we have listed and described all of the types of compressors with their mechanical functions. Some additional topics have also been added, which are inevitable to understand how an air compressor works.

What Is an Air Compressor?

Yes, it is necessary to define an air compressor so that you don’t confuse it with inflators or deflators.

In an air compressor, you have a tank and a motor. The motor is powered by electricity and sucks in the air when it is turned on. This air is sent to the tank.

The heavily built tank holds the air that can be more than ten or twenty times the atmospheric pressure. Some motors can create a greater maximum pressure. The condensed air stores potential energy that can be used with pneumatic tools.

Type of Air Compressors

Air compressors can be divided into two types based on displacement.

  • Positive air Displacement Compressors
  • Dynamic air Displacement Compressors

Displacement refers to the capability of the air compressor’s pump. Which basically means how much air can be displaced per minute. We will have a better understanding of them as you read through the article.


How Does An Air Compressor Work What Are Positive Displacement Compressors, And How Do They Work?

This air compressor captures a certain volume of air according to its capability in the compression chambers. Then it compresses the air by physically reducing the volume of the chamber. Lastly, it delivers the compressed air into a tank as potential energy to be used with your tools.

There are many types of positive displacement air compressors. The below three are the most prominent-

  • Piston type air compressors
  • Rotary screw air compressors
  • Rotary vane air compressors

Here you will have full disclosure of their working mechanisms.

Piston type air compressors

These are a lot like combustion engines. In the compressor cylinder, there is a piston connected to a wrist pin and crankshaft. They power the cylinder to reciprocate. The head of the cylinder has a suction valve/loader valve and a discharge valve/unloader valve.

As the crankshaft rotates, the piston comes down and sucks the air in from the suction valve. When the piston goes up to finish the stroke, it compresses the sucked air. Then the compressed air discharges from the discharge valve/unloader valve. The compressor works by repeating this process.

Piston compressors are of two types.

  • Single-stage
  • Multiple-stage

The main difference between the two air power machines is that multiple-stage has multiple pistons that can create more kinetic energy. That also means that the typical two-stage air compressors come under the single-stage piston air compressor.

Single-stage compressors have less horsepower than multiple-stage compressors. But the single-stage is enough for home garages air compressors.

Rotary screw air compressors

These are mostly used with industrial air tools. They are great for jackhammers and impact wrenches.

To create a flow of air, it uses two rotors. One rotor has helical lobes, which is the main rotor, and the secondary has helical grooves.

The air enters the compressor through the inlet valve. After that, the screw turns in a rotary motion, and then the pressure is created by reducing air volume.

Some rotary screw compressors consist of only one screw. Those oil-free rotary screw compressors are not industrial air compressors. If you want a large energy flow and greater production, then you have to use two screws.

Rotary vane compressors

Vane rotary compressors work like other air compressors but with a slight difference of course. Most of them are oil-lubricated.

Do you know what is lubricate and what’s the difference between lubricated and non-lubricated oil compressor systems? We will discuss this in a bit.

So, as I was saying, the vane air compressors have rotors with radial and movable blades. It uses centrifugal force by rotation to press the vane against the stator walls. Air is more drawn when the distance between rotors and stators increases.

The volume of air is compressed in different compressor pockets; because of that, the volume decreases at the time of rotation. When it passes the outlet port, the air is free.

Dynamic Displacement Air Compressors

These air compressor types increase the velocity of the air and restrict the airflow at the same time, which causes the air compression. Point to be noted that there is no physical compression like in the positive displacement air compressors.

There are two types of these compressors-

  • Axial flow air compressor
  • Centrifugal air compressor

These compressors have very complicated designs. I will try my best to make them as easy as possible for you.

Axial flow air compressor

These compressors look a lot like jet engines. They have a broader opening to let air in, and the chamber narrows down inside. There is also a shaft where the fans are mounted that also increases in volume inside. The shaft can also be called the rotor or the axial.

When the fan blades move, it pushes the air inside. As there is less space inside, the volume of the air decreases and the air pressure increases. That is the basic idea for axial compressors.

In this process, the air also heats up rapidly. So, there could be some cooling methods to keep the temperature down while it is in operation. Although they are used with industrial power tools, you will also find small versions of them that can be used at home.

Centrifugal Air Compressors

In a centrifugal compressor, there are three basic components. They are-

  • Impeller
  • Diffuser
  • Volute casing

The impeller is a circular disc. It has curved blades that rotate with it. When it rotates at high speeds, air enters the blades from the center of the disc and exits from the edges. The velocity of the air increases rapidly in the disc due to centrifugal force.

This radially moving high-velocity air is slowed down by the diffuser. It slows them down by increasing the flow area, in turn increasing the pressure. The volute-shaped casing collects this slow-moving high-pressure air and stores it in the air storage tank.

There is a lot more in this compressor. But this is the basic principle.

What is Lubricated Air Compressor?

To keep the machine maintained and to ensure that it works swiftly, you need to use oil. It doesn’t damage the device but keeps the mechanism maintained.

It helps to reduce the heat of the compressor, which is a must; otherwise, the heat can mess up your compressor. So, make sure you maintain your machine.

Difference between Lubricated and Non-Lubricated Oil Compressors

Oil-lubricated compressors need to be oiled regularly for maintenance. Air needs to be filtered as well. Make sure you do it from time to time; otherwise, the heat will mess up the machine.

Non-lubricated oil compressors are free from using oil for lubrication. You don’t have to oil them at all. But they need major repair and don’t last long. Because they generate heat faster and are not good for heavy-duty tasks.

So, I would suggest buying lubricated oil compressors for your betterment, especially for industrial applications even though you might have to go through the trouble of lubrication. Because oil-free compressors can be very bad no matter what power sources you are using.

Final words

This article was just to show you the variety of compressors and their basic mechanical principles. There is a lot more science in each of the compressor types. But that is a topic for another day.