Dynamic Compressor: Working Principle, Types and Applications

Compressors are most commonly used to compress compressible fluids. The dynamic compressor is the most famous type of air compressor. It uses an impeller and a diffuser to compress the air or gas. This article mainly explains the dynamic compressor working, types, and its applications.

What is a Dynamic Compressor?

The dynamic compressor is a rotary continuous-flow machine in which a rotating element accelerates the air as it enters the element, transforming the velocity head into pressure, partially in the rotating element and partially in stationary diffusers or blades.

This type of compressor contains an impeller that has multiple blades. The impeller is connected to an electric motor or generator. It gets power from the motor.

In dynamic compressors, when the impeller blades rotate, they suck air into the impeller cavity and increase the velocity of the air. After discharging through the impeller, the air enters the diffuser where the velocity of the air is converted into pressure energy.

Mostly, these compressors act as turbochargers with a radial or axial gas flow pattern. Dynamic compressors are mainly designed for high gas flow rates.

Dynamic Compressor

Dynamic displacement compressors work at constant pressure, while positive displacement compressors work at a constant gas flow rate. A positive displacement compressor compresses gas using a reciprocating element such as a piston or plunger, while the dynamic displacement compressor uses an impeller and a diffuser for air compression.

Compared to positive displacement compressors, dynamic compressors are more reliable. They are more reliable because there are no alternative components that are subject to repeated loads during use. These compressors are easy to design. Dynamic compressors are usually used in large applications.

Dynamic Compressor Working Principle

dynamic compressor working

The dynamic displacement compressor working principle is based on thermodynamics principles. This compressor contains an impeller. The impeller gets power from an electric motor. When the impeller starts rotating, the air is sucked from the environment into the compression chamber.

When the air passes through the impeller blades, the impeller blades provide kinetic energy to the air and increase its speed. 

This compressor also contains a diffuser. After passing through the impeller blades, the air enters the diffuser. The diffuser converts the speed of the air into pressure energy. After that, the air is discharged through the outlet of the dynamic compressor and stored in a storage tank.

Types of Dynamic Compressors

Dynamic compressors have the following types:

  • Centrifugal compressor 
  • Axial compressor 
  • Turbo compressor

1) Centrifugal Compressors

Centrifugal compressor is one of the most famous types of dynamic compressor. This compressor performs a compression process by applying an inertial force (turning, deceleration, and acceleration) to the gas through a rotating impeller.

In this compressor, the air draws into the impeller center and then accelerates centrifugally toward its circumference. When the diffuser compresses the air, it scrolls there. In the diffuser, the speed of the air reduces, and the pressure increases. In these compressors, the compression process usually completes in 2 or 3 phases.

centrifugal compressors

The centrifugal compressor has more load efficiency than other oil-free compressors. However, the performance of these compressors significantly changes according to the conditions of the compressor inlet such as high humidity, low air pressure, and heat.

Read More: Centrifugal Compressor Types and Working

2) Axial Flow Compressor

Axial flow compressors can handle large flow rates of air. It has relatively small housing. The pressure range of these compressors is low to moderate.

The axial compressor uses a series of blades that look like jet engines to force air into smaller areas. These types of dynamic compressors don’t commonly utilize in industries. Generally, the axial compressor is lighter and smaller than the centrifugal compressor. These compressors typically run faster than centrifugal compressors.

axial compressors

Mostly, axial compressors are used for large and constant gas flow at relatively moderate pressures, for example, in a ventilation system. Its high speed makes it ideal for connecting a gas turbine to generate electricity and propel aircraft. Therefore, these compressors are designed for high reliability, high efficiency, and high capacity purposes.

The axial compressors are most commonly used for different applications including blast furnaces, wind tunnels, wastewater treatment, and air separation. Nowadays these compressors are usually used in Aeroplanes.

3) Turbo-Expander Compressors

A turboexpander is also known as an expansion turbine. An axial or centrifugal turbine expands gas under high pressure to generate work to drive the compressor.


As shown in the figure, the term “turboexpander” is commonly used to define an expander/compressor as a unit. Mostly, it consists of two main parts. The radial compressor (booster) and the radial intake expansion are integrated with one component. The wheel connects to a single axle. The expansion turbine is the engine, and the compressor is the powered unit.

In a natural gas upgrading plant, the purpose of the turbo-expand purpose is to effectively perform two different but complementary functions in a single machine. Its principal function is to generate cooling in the process of gas flow efficiently.

Components of Dynamic Compressor

The dynamic compressor has the following main parts:

  • Inlet
  • Impeller 
  • Volute casing 
  • Radial diffuser

dynamic compressor parts

1) Inlet

The inlet of the dynamic compressor is a simple pipe. However, the operating range of the compressor can also expand by setting the charge line to a lower mass flow rate. Also, the intake guide vane installs in water for pre-swirling.

2) Impeller

The rotating impeller blades gradually transfer kinetic energy to the working fluid. The impeller output speed can reach supersonic speeds. So, the type of compressor impeller depends on the angle of the outlet blades.

3) Volute Casing

It collects the flow by rotating it circumferentially and directing it to the outlet pipe of the compressor. The flow velocity in the flow path is further reduced, and the static pressure increases.

The volute can take on various geometric shapes. The ideal process for a compressor is uniform entropy compression without heat exchange with the environment.

4) Radial diffuser

The diffuser transforms the kinetic energy of the working fluid into pressure energy. This is achieved by gradually decreasing the flow rate and increasing the cross-sectional area. Depending on the application, the diffuser can be without a leaf or with a leaf.

Advantages and Disadvantages of Dynamic Displacement Compressors

Advantages of Dynamic Compressors

  1. The dynamic compressor is more reliable than the positive displacement compressors.
  2. It has the ability to work with various water flows.
  3. These compressors are most commonly used for large-scale applications.
  4. they are easy to design.
  5. These have a low weight.
  6. It requires less maintenance.
  7. It is oil-free in nature.

Disadvantages of Dynamic Compressors

  1. Dynamic compressors are less efficient than positive displacement compressors.
  2. Dynamic displacement compressors do not compress gas by decreasing the volume, which is the most common method.
  3. These compressors use one or more rotating elements to accelerate the air and then reduce its velocity.
  4. Choke, stall, and Surge issues.
  5. Not suitable for very high compression.
  6. Sensitive to changes in gas composition.

Applications of Dynamic Compressor

  1. The dynamic compressor is used in refrigeration applications.
  2. These are used for gas injection.
  3. These compressors also use for compression in gas powerplants.
  4.  Dynamic displacement compressors are also used in Aero-plane.
  5. They are also used for pipeline compression.

Read More

What are the types of the dynamic compressors?

Dynamic compressors have the following types:

  • Centrifugal compressor
  • Axial compressor
  • Turbo compressor

What are the applications of the dynamic compressor?

  • Used in refrigeration applications.
  • These are used for gas injection.
  • These compressors also use for compression in gas powerplants.
  •  Dynamic displacement compressors are also used in Aero-plane.
  • They are also used for pipeline compression.

What are the parts of the dynamic compressor?

  • Impeller
  • Inlet
  • Outlet
  • Diffuser
Read More

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