Editing Centrifugal compressor (section)

== Turbomachinery similarities ==
Centrifugal compressors are similar in many ways to other [[turbomachinery]] and are compared and contrasted as follows:

=== Similarities to axial compressor ===
[[File:Turboprop T-53.jpg|thumb|upright= 1.35|Cutaway showing an axi-centrifugal compressor gas turbine]]
Centrifugal compressors are similar to [[axial compressor]]s in that they are rotating airfoil-based compressors. Both are shown in the adjacent photograph of an engine with 5 stages of axial compressors and one stage of a centrifugal compressor.<ref name="Lakshminarayana"/> The first part of the centrifugal impeller looks very similar to an axial compressor. This first part of the centrifugal impeller is also termed an ''inducer''. Centrifugal compressors differ from axials as they use a significant change in radius from inlet to exit of the impeller to produce a much greater pressure rise in a single stage (e.g. 8<ref>=The Development Of Jet And Turbine Aero Engines 4th edition, Bill Gunston 2006, {{ISBN|0 7509 4477 3}}, p.217</ref> in the [[Pratt & Whitney Canada PW200]] series of helicopter engines) than does an axial stage. The 1940s-era German [[Heinkel HeS 011]] experimental engine was the first aviation turbojet to have a compressor stage with radial flow-turning part-way between none for an axial and 90 degrees for a centrifugal. It is known as a mixed/diagonal-flow compressor. A diagonal stage is used in the [[Pratt & Whitney Canada PW600]] series of small turbofans.

=== Centrifugal fan ===

[[File:CentrifugalCompressor.jpg|thumb|upright=1.3|A low speed, low-pressure centrifugal compressor or [[centrifugal fan]], with upward discharging cone used to diffuse the air velocity]]
Centrifugal compressors are also similar to [[centrifugal fan]]s of the style shown in the neighboring figure as they both increase the energy of the flow through the increasing radius.<ref name="Shepherd"/> In contrast to centrifugal fans, compressors operate at higher speeds to generate greater pressure rises. In many cases, the engineering methods used to design a centrifugal fan are the same as those to design a centrifugal compressor, so they can look very similar.

For purposes of generalization and definition, it can be said that centrifugal compressors often have density increases greater than 5 percent. Also, they often experience relative fluid velocities above [[Mach number]] 0.3<ref name="API673">{{cite book|last=API|title=Std 673-2002 Centrifugal Fans for Petroleum, Chemical and Gas Industry Services|date=July 2002|publisher=API|location=New York|url=http://global.ihs.com/doc_detail.cfm?item_s_key=00392744/}}{{Dead link|date=July 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> when the working fluid is air or nitrogen. In contrast, fans or blowers are often considered to have density increases of less than five percent and peak relative fluid velocities below Mach 0.3.

=== Squirrel-cage fan ===
[[File:CentrifugalFan.png|thumb|upright=1.3|A low-speed, low-pressure blower used for HVAC ventilation]]
Squirrel-cage fans are primarily used for ventilation. The flow field within this type of fan has internal recirculations. In comparison, a centrifugal fan is uniform circumferentially.

=== Centrifugal pump ===
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| caption1=A 3D-solids model of a type of [[centrifugal pump]]
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| caption2=Cut-away of a [[centrifugal pump]]
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Centrifugal compressors are also similar to [[Centrifugal pump|centrifugal pumps]]<ref name="Shepherd"/> of the style shown in the adjacent figures. The key difference between such compressors and pumps is that the compressor working fluid is a gas (compressible) and the pump working fluid is liquid (incompressible). Again, the engineering methods used to design a centrifugal pump are the same as those to design a centrifugal compressor. Yet, there is one important difference: the need to deal with [[cavitation]] in pumps.

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=== Radial turbine ===

Centrifugal compressors also look very similar to their turbomachinery counterpart the [[radial turbine]] as shown in the figure. While a compressor transfers energy into a flow to raise its pressure, a turbine operates in reverse, by extracting energy from a flow, thus reducing its pressure.{{citation needed|date=December 2021}} In other words, power is input to compressors and output from turbines.

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