Air Compressors – Working Principle and Types


Over the years, air compressors have evolved to become a high-utility workhorse device in many industries. Whether it is supplying dependable power to any manufacturing and automotive unit or providing fresh, contaminant-free pressurized air to food & beverage or chemical industries, the need for a high-quality and efficient air compressor has progressively grown.

Essentially, an air compressor is a device that converts power, such as that coming from an electrical motor, diesel engine, gasoline, etc. into potential energy stored as pressurized air. Today, there are plenty of different air compressor types available on the market. Each type is differently designed, resulting in varying operational efficiencies, costs, and performance levels. 

You can find air compressors in a wide range of situations, from small gas stations to big-sized manufacturing plants. Besides, these devices are also finding a way into workshops, garages, and basements for jobs like inflating pool toys and powering tools like drills, nail guns, etc. 

Air compressors are evidence of human innovation. It is crucial to understand how these devices work so you can easily select the right air compressor for your needs. 

Air Compressor – Working Principle

Air compressors work by forcing air into a vessel and then pressurizing it. The air is made to enter a container through an opening that helps to build pressure. The compressed air can be then used as energy upon its release. 

Air compressors are powered by an engine that converts electrical energy into kinetic energy. The device works in a similar way to a combustion engine, using a piston, valve, crankshaft, head, and a connecting rod. 

Different Types of Air Compressors 

There are two different methods of achieving air compression: positive displacement and dynamic compression. The outcomes of both are very similar but there is a considerable difference in the process. 

In positive displacement compressors, the air is forced to enter a chamber where the volume is decreased to compress the air. The most common types include the following:

  • Piston compressors (Reciprocating)
  • Rotary screw compressors (Single Rotor)
  • Scroll compressors (Double Rotor)

Dynamic compressors, on the other hand, work at constant pressure instead of flow. The most common types include:

  • Centrifugal compressors
  • Axial compressors

1. Positive Displacement Compressors



These compressors have a cavity that enables a volume of air or gas into the machine at atmospheric pressure. This cavity then becomes smaller, shrinking the volume of air and at the same time, growing its pressure. 

In piston compressors, a piston moves up the cylinder, which reduces the space in the cavity. This increases the air pressure so it can easily fit into the smaller cavity. Piston compressors can incorporate various stages of compression to get the needed pressure, making them highly suitable for high-pressure applications. 

A double rotor compressor includes a chamber in which the air is trapped between the male and female rotor profiles. As these rotors rotate, the air gets pushed into smaller spaces, thus building pressure. In these compressors, the air is typically sealed with oil or special Teflon coatings. 

In a scroll compressor, one spiral-shaped rotor swings against another spiral that is fixed. As these spirals rotate against each other, the cavity trapping the air between them becomes smaller and smaller. This results in a decrease in the air volume and a simultaneous increase in the pressure. 


2. Dynamic Compressors


Also known as Turbocompressor, a dynamic compressor works at a constant pressure. These devices generate power by rushing air with quickly revolving blades and then limiting the air to create pressure. The kinetic energy produced is stored in the form of static energy within the compressor. 

Centrifugal air compressors slow down the incoming air using a diffuser to build up potential energy. Owing to their multiple-phase compression process, these compressors can easily produce high amounts of energy in a relatively small machine. They are commonly used in chemical and petrochemical industries, glass or steel manufacturing plants, power generation units, etc. 

Axial compressors, on the other hand, are rarely used in construction projects. Instead, they find applications in high-speed engines on planes and ships. 

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