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1、10NoiseandVibrationsAsexplainedinChap.5,theflowattheimpelleroutletisnon-uniform.Thedif-fuservanesorvolutecutwatersarethusapproachedbyanunsteadyflow.Theflowatthestatorvanesactsbackonthevelocityfieldintheimpeller.Therelatedphe-nomenaarecalled“rotor/statorinteraction”(RSI).Asaconsequenc
2、eoftheRSI,hydraulicexcitationforcesaregenerated.Thesegiverisetopressurepulsations,mechanicalvibrationsandalternatingstressesinvariouspumpcomponents.Thevibrationstransmittedtothefoundationsspreadassolid-bornenoisethroughoutthebuilding.Thepressurepulsationsexcitethepumpcasingtovibratio
3、ns.Theyalsotravelasfluid-bornenoisethroughthepipingsystem,wheretheygeneratevi-brationsofthepipewalls.Thevibratingwallsandstructuresradiateair-bornenoise.Astheimportanceofalltheseeffectsincreaseswiththecircumferentialspeedoftheimpeller,vibrationproblemsareencounteredparticularlyinhigh
4、-pressurepumpapplications.Whetherthevibrationsandthenoiseofapumparefeltasdis-turbing,largelydependsonitsdesignandapplication.Evenverysmallpumps,forexample,centralheatingcirculationpumps,maybesubjecttostringentrequirementsconcerningthelimitationofnoise.Inmanyapplicationsthepumpsarebui
5、ltandtestedtostandardsandspecifica-tionsdefiningthemaximumallowablevibrationamplitudes(processpumpsandalmostalllargepumps).Thischapterfocusesinthefirstplaceonthehydrody-namicaspectsofvibrationexcitation,aswellasonthebasicphysicalmechanismsinvolved,inordertohelpwiththeanalysisofvibrat
6、ionproblems.Theinteractionbetweenhydraulicexcitationandmechanicalvibrationsisdiscussedtoo,butthetheoryofmechanicalvibrationsisbeyondthescopeofthistext.Thereisawealthofspecificliteratureonvibrationswhichshouldbeconsultedforcalculationandanalysismethods,mechanicalvibrations,testingmeth
7、odsanddatatreatment,e.g.[10.16,10.23,10.28].10.1UnsteadyflowattheimpelleroutletThevelocitydistributionattheimpelleroutletispitch-wisenon-uniformasare-sultoftheworktransmittedbythebladetothefluidandduetosecondaryflows.AccordingtoChap.5.2,thequalitativedistributionoftherelativevelocity
8、showsamaximu
