The vocabulary of compressors: dynamic and volumetric compression

Now let’s start a new article that will lead us to know the most important terms in the field of compression and compressors. In this article, we will deal in particular with the basic principles of air or gas compression, which are essentially two: volumetric compression and dynamic compression. 

Volumetric compression encompasses all the alternative type compressors, rotary and orbital: piston compressors, scroll compressors, screw compressors, cam compressors and vane compressors. Instead, the axial and radial turbocompressors can be included into the category of the dynamic compression system. 

The difference between the two types of compression: volumetric compression vs. dynamic compression

In volumetric compression, the air or gas is drawn into multiple compression chambers sealed on the inlet side. With the entry of air or gas, the volume of the chambers decreases gradually generating the compression of the elements; when the desired compression value is reached, the valves that allow air or gas to be discharged into the outlet system are activated. 

In dynamic compression, air or gas is instead sucked in by the blades of an impeller rotary compression system that increases its speed progressively. Once high speed is reached, the elements are discharged from the diffuser which has the task of transforming the kinetic energy into static pressure. The compression ratio is given by the absolute pressure between inlet and outlet sides of air or gas. 

A practical example that can explain the functioning of the volumetric compressor is the bicycle pump: the air is sucked into a cylinder (the pump) and compressed by a piston, hence piston compression. Piston compressors work in the exact same way as a bicycle pump – the piston in this case is represented by a connecting rod and a rotating driveshaft. 

TO FIND OUT MORE: The piston compressor

In the dynamic compressor, it’s the pressure that increases while gas or air flow inside it, that rules the system. The components are “moved” by the driving force of the impeller and are pushed at maximum speed until the diffuser slows them down, producing static pressure. The difference between axial or radial dynamic compressors, on the other hand, lies in the direction that is adopted for the flow of air or gas. Finally, unlike volumetric compressors, in dynamic compression a small pressure variation determines a bigger variation in the flowrate. 

This feature helps us to better understand the macro difference between turbo compressors (dynamic compressors) and volumetric compressors: 

• the first type is made of compressors with variable flow and pressure, and is used to reach high levels of airflow.
• the second one has continual flow and variable pressure, and is suitable for providing high pressure ratios even at low speed. 

Riem Italy specializes in the sale and distribution of volumetric compressors (piston compressors, screw compressors etc.) and turbo compressors. We can design solutions for medium and large plants since we have many units around the world. 

If you want to know more about Riem Italy’s volumetric and dynamic compression products, take a look at our services: Riem Italy services