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Compressors,wherefullcompression(uptothefinalpressure)occursinone
process,arecalledonestagecompressors.Ontheotherhand,compressors,where
fullcompressionoccursinseveralcompressionprocessesaccompaniedbyinter-
mediatecooling,arecalledmulti-stagecompressors.
1.3.DESIGNSOLUTIONS
Pistoncompressorsaredividedon:
–one-stageandmulti-stage-dependingonthenumberofstagesofcompression,
–one-sidedortwo-sidedaction-dependingonifthepistoncompressesthegas
usingjustoneownsideortwosidesareemployed,
–airorwatercooling,
–assistedwithguidingdeviceorwithoutguidingdevice-dependsonifthecrank
mechanismhasguideroritdoesn’t.
Insmallandmiddle-sizecompressorstheverticalandV-typearrangementsof
thecylindersareused.Inthemiddle-sizeandbig-sizelow-speedcompressors,an
angle-typearrangement(intheformofletterL),aswellashorizontalarrangement,
isused.
Ifcylindershaveanair-coolingsystem,theirbodiesareprovidedwithcooling
finswhileoneendofthecrankshafthascoolingfanresponsibleforforcedairde-
liverytothepassagesbetweentwoneighborfins.
Cylindersofthepistoncompressorsprovidedwiththewater-coolingsystem
havespecialwaterjacketswhereforcedcirculationofcoolingwateroccurs.Men-
tionedjacketsarethepartsofthemainwatercoolingsystemsmountedinthecom-
pressors.
Anadvantageofair-cooledcompressorsoverwater-cooledistheabsenceof
coolingjacketthatmakespossiblethemtoworkintheconditionswheretheam-
bienttemperatureisbelow273K(0ºC).Thedisadvantageofsuchcompressorsis
lesscoolingrate(highervalueofthepolytropicindexinthecompressionprocess)
incomparisonwithwater-cooledcompressors.
Cross-sectionoftheone-stagecompressorwithone-sidedaction,air-cooled,
withverticalcylinderarrangementispresentedinFig.1.1.Asitcanbeseen
fromFig.1.1thecompressorhasnoguidingdeviceatthecrankmechanism
andisdrivenbyelectricmotorthroughthebeltdrive.Thebeltpulleywithteeth
actsasafan.
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