Axial Compressor vs Centrifugal Compressor: Working Principle & Applications

Both axial and centrifugal compressors, also referred to as turbo compressors operate by the velocity of gas and convert the energy to pressure.

A dynamic compressor works at a constant pressure, unlike a displacement compressor which works with a constant flow. Dynamic compressor performance is affected by external conditions like ambient air temperature, for example and this can vary the outlet capacity.

This article will explore the major differences between axial and centrifugal compressors.

As the name suggests, axial compressors are known for their axial flow.

In axial compressors, the gas or air passes along the shaft of the compressor through stationary and rotating blades. It increases the velocity of the air gradually while the stationary blades convert the kinetic energy to pressure.

Axial compressors are smaller in size and lighter in weight, compared to centrifugal compressors and normally operate at higher speeds.

Common applications for axial compressors are found in gas turbines electricity generation or for the propulsion of air crafts. 

Axial flow compressors are comprised of multiple stages of stationary and rotating blades. The air is drawn in parallel to the axis of the rotation. It is then compressed at every stage.

These compressors are very high-speed and gas flows into the intake ports and pushes the gas through the compressional space via stationary stators rotating rotor blades.

In the axial-flow compressors, the flow enters the compressors in an axial direction, as the name suggests. The flow then exits from the gas turbine. In axial compressors, it works by accelerating the fluid and diffusing it so that the pressure increases.

The industrial gas turbine has low pressure ratio and firing temperatures. The compressors compress the working fluid by accelerating the fluid and diffusing it so that the pressure increases. 

Axial compressors have the following applications:

• Blast furnace air
• Air separation plants
• High-speed ship engines
• In small scale power statins
• Land-based gas turbines
• Aircraft turbojet engines

DOWNLOAD: Step By Step Guide To Select A Centrifugal Compressor

Centrifugal compressors have a rotating impeller disk. This impeller disk sucks the air into the center of the disk through an inlet, adjusted at a 90-degree angle to eye of the disk’s center.

The disk comes with impeller vanes which is why it looks like a pie. Around the impeller disk is a diffuser vane volute casing. The air enters the eye of the impeller disk and gets redirected outward because of the inertia of rotation and the impeller vanes.

The low-pressure air gets to the edge of the disc to enter the casing through the diffuser. Eventually, the diffuser and the casing slow down the air, increasing the pressure. Centrifugal compressor can be 1 stage for low pressure applications and at the same time in 2 or 3 stages with intercoolers (stainless-steel) for medium pressure air where pressure ratios per stage is keep lower to have better efficiency. A high-speed gearbox is integrated with the compressor stages to rate the impellers on high-speed pinions.
This technology is preferred for process industries or plants with large constant air demands. 

Radial / Centrifugal compressors have the following applications:

• Glass factories
• Aluminum smelters
• Air separation plants
• Textile plants
• Wastewater treatment
• Chemical process
• Small turbofan engines
• Gas compression in oil platforms

• Axial flow compressors do not change the gas direction while centrifugal compressors do.
• Axial compressors are generally smaller and lighter than centrifugal compressors.
• Centrifugal compressors are easy to fix and maintain. They come as Plug & Play units delivered from factory.
• Centrifugal compressors are comparatively less expensive.
• Axial compressors used for moderate pressure applications while Centrifugal compressors are higher pressures for process/ utilities/ factories.

Let’s break down the advantages and disadvantages of both compressors one by one. 

• It has a high peak efficiency
• It has a small frontal area
• The increased number of stages with negligible losses leads to increase in pressure

• The manufacturing of axial compressors is difficult
• These compressors are expensive
• These compressors are sensitive to disruptions in flow
• These compressors are sensitive to the aerodynamic stall and angle of attack

• It is highly reliable and low maintenance
• These compressors are energy-efficient
• The compressors are insensitive to flow disruptions
• It is a wide range of rotational speed
• These compressors are oil-free in nature
• It does not have many rubbing parts

• These compressors are sensitive to changes in gas composition
• It requires sophisticated vibration mounting
• These compressors face choking, stalling, and surging

We hope that this article was helpful in getting a deeper understanding of the differences of centrifugal and axial compressors.

Atlas Copco provides robust axial and centrifugal compressor solutions that are capable of handling pressures up to 205 bar and volume flows up to 560,000 m3/h.

For more information on the axial and centrifugal compressors,  get in touch with our technical experts.