What is the difference between centrifugal and axial compressor?

Answer 1

*Axial compressors are rotating, aerofoil based compressors in which the working fluid principally flows parallel to the axis of rotation. This is in contrast with centrifugal, axi-centrifugal and mixed-flow compressors where the air may enter axially but will have a significant radial component on exit.

*Axial flow compressors produce a continuous flow of compressed gas, and have the benefits of high efficiencies and large mass flow capacity, particularly in relation to their cross-section. They do, however, require several rows of aerofoils to achieve large pressure rises making them complex and expensive relative to other designs (e.g. centrifugal compressor).

*Centrifugal fan/blowers are more suited to continuous-duty applications such as ventilation fans, air movers, cooling units, and other uses that require high volume with little or no pressure increase. In contrast, multi-stage reciprocating compressors often achieve discharge pressures of 8,000 to 10,000 psi (59 MPa to 69MPa). One example of an application of centrifugal compressors is their use in re-injecting natural gas back into oil fields to increase oil production.

Centrifugal compressors are often used in small gas turbine engines like APUs (auxiliary power units) and smaller aircraft gas turbines.

A significant reason for this is that with current technology, the equivalent flow axial compressor will be less efficient due primarily to a combination of rotor and variable stator tip-clearance losses.

There are few single stage centrifugal compressors capable of pressure-ratios over 10:1, due to stress considerations which severely limit the compressor's safety, durability and life expectancy.

*Compressor section location depends on the type of compressor. In the centrifugal-flow engine the compressor is between the accessory section and the combustion section; in the axial-flow engine the compressor is between the air inlet duct and the combustion section.

*Centrifugal-flow compressors have the following advantages:

* High pressure rise per stage.

* Efficiency over wide rotational speed range.

* Simplicity of manufacture with resulting low cost.

* Low weight.

* Low starting power requirements.

They have the following disadvantages:

* Large frontal area for given airflow.

* Impracticality if more than two stages because of losses in turns between stages.

**Axial-flow compressors have the following advantages:

* High peak efficiency.

* Small frontal area forgiven airflow.

* Straight-through flow, allowing high ram efficiency.

* Increased pressure rise due to increased number of stages with negligible losses.

They have the following disadvantages:

* Good efficiency over narrow rotational speed range.

* Difficulty of manufacture and high cost.

* Relatively high weight.

* High starting power requirements (this has been partially overcome by split compressors).

Answer 2

Centrifugal compressors use centrifugal force to increase the velocity of the air which is then converted to pressure, while axial compressors use rotating blades to accelerate and compress air in the axial direction. Centrifugal compressors are more compact and simpler in design, but axial compressors are more efficient and better suited for high flow rate applications.