Published: 19/11/2022
Types of Air Compressors and What They Are Used For
There are four main types of air compressor: rotary screw and reciprocating (piston) compressors, which are positive displacement machines that compress air by reducing its volume; and axial and centrifugal compressors, which are dynamic machines that use rapidly rotating blades to accelerate air and convert kinetic energy into pressure. Rotary screw and piston compressors cover most industrial and workshop needs, while dynamic compressors serve very high-volume applications such as turbines and large plants.
What is an air compressor?
An air compressor is a machine that draws in air, compresses it, and turns it into a source of power for air tools and equipment. The compressed air can then be used straight away or stored in a receiver tank until it’s required.
While every air compressor compresses air to create pressurised energy, the way it does this depends on the type of compressor. Some compressors use pistons to compress air in short bursts. Other types rely on rotating screws or vanes to deliver a continuous supply of compressed air. Depending on the type of compressor you choose, the method of compression can affect everything from airflow and pressure output to energy efficiency and noise levels.
The four main types of air compressors
Air compressors are generally divided into two main categories based on the way they compress air: positive displacement compressors and dynamic compressors.
Positive displacement compressors (such as rotary screw and reciprocating models) work by trapping a specific amount of air in a chamber and reducing its volume. As the space becomes smaller, the air pressure increases.
Dynamic compressors (including centrifugal and axial types) use rotating blades to accelerate the air. This movement increases the air’s velocity, which is then converted into pressure energy.
| Compressor Type | Category | How It Compresses Air | Best For |
|---|---|---|---|
| Rotary screw | Positive displacement | Two counter-rotating screws trap and squeeze air | Continuous industrial use, workshops, food packaging |
| Reciprocating (piston) | Positive displacement | Pistons draw in and compress air in a cylinder | High-pressure, intermittent use; garages, agriculture |
| Axial | Dynamic | Air flows parallel to the axis through rotating blades | Jet engines, gas turbines, large plants |
| Centrifugal | Dynamic | Air is slowed through a diffuser to build pressure | Chemical/steel plants, turbochargers, HVAC |
Positive displacement air compressors
Positive displacement compressors work by pulling air into a chamber and then reducing the available space to compress it. As the air is squeezed, its pressure increases. This creates stored energy that can be used to operate tools and equipment.
The two main types of positive displacement compressors are rotary screw and reciprocating compressors. Although they both compress air, they use different designs to achieve this. This makes each type better suited to specific applications and working environments.
Reciprocating (Piston) Air Compressors
A reciprocating air compressor uses pistons that move back and forth inside a cylinder to draw in and compress air. As the piston moves, it reduces the space available for the air. In turn, this increases the air pressure. Once the air reaches the required pressure, it’s sent to a storage tank so it’s ready for use. These machines been widely used across many industries for over 200 years, thanks to their reliability and durability.
Key benefits of reciprocating compressors:
- High pressure and power output
- Energy efficiency for the majority of operations
- Low maintenance costs
- Cheap and readily available parts
- Long lifespan
Disadvantages
- Loud operation: The internal pistons are loud. Therefore, many businesses place them in a soundproofed room.
To explore the range of reciprocating air compressors, take a look at our blog: The types of reciprocating air compressors explained. This will be a useful guide to helping you choose the best reciprocating compressor for your needs.
Dynamic Air Compressors
Dynamic compressors are designed for applications that require a continuous supply of large volumes of air. Instead of compressing air in a chamber, they use high-speed rotating blades to increase the air’s velocity. The airflow is then slowed and converted from kinetic energy into pressure.
These compressors are typically used in large-scale applications, including power generation and industrial plants where high airflow rates are essential.
Axial Air Compressors
Axial compressors are built for applications that need a continuous supply of high-volume airflow. They move air through the compressor in a straight line along the direction of the rotating shaft. This gradually increases its pressure as it passes through multiple stages of rotating blades.
Because they can handle large amounts of air despite being super compact, axial compressors are commonly used in large gas turbines, including aircraft jet engines.
Centrifugal Air Compressors
Centrifugal compressors use a fast-spinning impeller to accelerate incoming air. The air then moves through a diffuser, where it slows down and the energy from its movement is converted into pressure.
Their multi-stage design allows them to deliver large volumes of compressed air from a compact unit. Some models can produce up to around 1,000 horsepower. Oiil-free options are available for applications where contaminant-free air is essential.
Compared with rotary screw and reciprocating compressors, centrifugal compressors have fewer moving parts. This can mean less maintenance and servicing.
Key benefits of centrifugal compressors:
- Continuous high-pressure airflow
- Energy efficient operation
- Lower operating costs
- High capacity performance
Some of the most common applications of centrifugal compressors include chemical plants, steel manufacturing and auxiliary power units.
Which Type of Air Compressor Do I Need?
The type of air compressor you require all depends on the end use. Other factors include how frequently you use it and the volume of compressed air you require.
For continuous, all-day industrial operations, a rotary screw compressor is usually the best option. These compressors are designed to provide an efficient supply of compressed air for high demanding environments.
For applications that only require occasional use (such as small workshops and garages), a reciprocating (piston) compressor is often the ideal choice. They are super compact and well suited to tasks where compressed air is needed intermittently rather than continuously. And for large-scale operations hat require high volumes of air, go for dynamic compressors such as axial and centrifugal models.
Not sure which compressor type is best for your application? Air Supply Ltd is here to help you find the most suitable solution for your requirements. We specialise in supplying, maintaining, and repairing industrial air compressors across the North East and throughout the UK. Contact us today for expert advice.
Frequently Asked Questions
What are the four main types of air compressor?
The four main compressor types are:
- Rotary screw compressors
- Piston compressors
- Axial compressors
- Centrifugal air compressors.
Rotary screw and piston compressors are positive displacement machines used in most industrial and workshop settings. Axial and centrifugal compressors are dynamic machines used for very high-volume applications like turbines and large plants.
What is the difference between positive displacement and dynamic compressors?
The main difference between positive displacement and dynamic compressors is the way they increase air pressure.
Positive displacement compressors (such as rotary screw and reciprocating compressors) work by trapping a fixed amount of air inside a chamber and reducing its volume. As the space gets smaller, the air pressure increases.
Dynamic compressors (axial and centrifugal compressors) work differently by using rotating blades to accelerate the airflow. The moving air is then slowed down, converting its kinetic energy into pressure.
Which type of air compressor is best for a workshop or garage?
A reciprocating compressor is the most appropriate choice for workshops and garages. It provides the high air pressure required for powering air tools and general maintenance work. Plus, it keeps maintenance costs affordable.
If, however, your workshop requires a steady flow of compressed air through the day, a rotaru screw compressor would be a more worthwhile option. It’s designed for constant operation, thanks to its 100% duty cycle.
Which air compressor type is quietest?
Rotary screw air compressors are among the quietest types of compressors available. This is because they operate using two interlocking helical rotors instead of pistons, which are known to create loud knocking noises and excessive vibrations.