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Centrifugal compressors - function, differences & areas of application

Construction and function of centrifugal compressors

A centrifugal compressor is similar in function to a centrifugal fan and usually consists of a housing with guide vanes, a shaft and an impeller with blades. The impeller is used to accelerate the gas from the inside to the outside and transfer energy to it according to the laws of fluid mechanics.

In contrast to positive displacement compressors such as piston or screw compressors, a centrifugal compressor first accelerates the air or gas and then generates a pressure increase in the diffuser, converting the velocity energy into pressure energy. Centrifugal compressors work continuously and require sufficiently high speeds to generate pressure. They can have either oil-free or oil-lubricated bearings and are also used in exhaust gas turbochargers or gas turbine aircraft engines, for example.

Difference between centrifugal compressors and axial compressors

A basic distinction is made between centrifugal compressors and axial compressors in turbo compressors. This distinguishes them:

Radial compressor

Centrifugal compressors are working machines with a compact design. They are characterized by the fact that the gas to be compressed flows axially into the impeller and is then deflected radially outwards. There are single-stage and multi-stage centrifugal compressors in which the flow is diverted after each stage. Part of the mechanical energy supplied is converted into heat, which is why the gas or air is often cooled down between the stages. Centrifugal compressors are capable of generating high pressures and are therefore used in areas with high pressure requirements.

Axial compressor

In axial compressors (single-stage or multi-stage), on the other hand, the gas to be compressed flows through the compressor parallel to the shaft. Axial compressors are often used in pipelines or in jet engines. Compared to centrifugal compressors, they can handle larger flow rates, are often lighter, cheaper and more efficient. Axial compressors are therefore mainly used in applications with a high volume flow, but have a low pressure ratio per stage.

Axial-radial combination compressor

There is also a combination of axial and centrifugal compressors: the so-called axial- centrifugal combination compressor. This compressor combines the advantages of both types of compressor, as the large volume flow is first pre-compressed in the axial compressor and then brought to the desired high pressure in the centrifugal compressor. The use of diagonal compressors enables optimum use of both properties, high performance and offers flexibility with regard to the required pressure and volume flow requirements.

Centrifugal compressors are used in a wide range of industries and sectors where pressure and volume flow requirements need to be met. From the automotive industry to power generation and aerospace, turbo compressors play an important role in providing compressed air and increasing pressures in various process gas systems.

For example, they are used in combination with turbines as turbochargers in cars. This works as follows: The turbine is driven by the exhaust gases and supplies the energy for the compressor. The compressor in turn sucks in the gases axially and accelerates them at high speed. The medium then leaves the compressor wheel radially and enters the diffuser, where the speed is reduced and both the pressure and temperature are increased.

Other areas of application for the radial compressor are

Extraction systems, heat pumps and cooling systems Drying applications Waste water treatment Conveyor technology Food and packaging industry Air supply cabinets for printing presses and finishing machines practically in all process gas plants in the chemical and petrochemical industries Refineries