泵站中水泵的选型问题-外文翻译

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1、ThepumpinpumpingstationselectionproblemRotarypumpsThesearebuiltinmanydifferentdesignsandareextremelypopularinmodernfluid-powersystem.Themostcommonrotary-pumpdesignsusedtodayarespur-gear,generated-rotary,sliding-vane,andscrewpump,eachtypehasadvantagesthatmakeit

2、themostsuitableforagivenapplication.Spur-gearpumps.thesepumpshavetwomatinggearsareturnedinacloselyfittedcasing.Rotationofonegear,thedrivercausesthesecond,orfollowergear,toturn.thedrivingshaftisusuallyconnectedtotheuppergearofthepump.Whenthepumpisfirststarted,r

3、otationofgearsforcesairoutthecasingandintothedischargepipe.thisremovalofairfromthepumpcasingproducesapartialvacuumonthepumpinlet,herethefluidistrappedbetweentheteethoftheupperandlowergearsandthepumpcasing.continuedrotationofthegearsforcesthefluidoutofthepumpdi

4、scharge.Pressureriseinaspur-gearpumpisproducedbythesqueezingactiononthefluidaditisexpelledfrombetweenthemeshinggearteethandcasing,.avacuumisformedinthecavitybetweentheteethadunmesh,causingmorefluidtobedrawnintothepump,aspur-gearpumpisaconstant-displacementunit

5、,itsdischargeisconstantatagivenshaftspeed.theonlywaythequantityoffluiddischargebyaspur-gearpumpoftypeinfigurecanberegulatedisbyvaryingtheshaftspeed.moderngearpumpsusedinfluid-powersystemsdeveloppressuresuptoabout3000psi.Figureshowsthetypicalcharacteristiccurve

6、sofaspur-gearrotarypump.Thesecurvesshowthecapacityandpowerinputforaspur-gearpumpatvariousspeeds.Atanygivenspeedthecapacitycharacteristicisnearlyaflatlinetheslightdecreaseincapacitywithriseindischargepressureiscausedbyincreasedleakageacrossthegearsfromthedischa

7、rgetothesuctionsideofthepump.leakageingearpumpsissometimestermedslip.Slipalsoincreasewitharisepumpdischargepressure.thecurveshowingtherelationbetweenpumpdischargepressureandpumpcapacityisoftentermedthehead-capacityorHQcurve.therelationbetweenpowerinputandpumpc

8、apacityisthepower-capacityorPQcurve.Powerinputtoasqur-gearpumpincreaseswithboththeoperatingspeedanddischargepressure.asthespeedofagearpumpisincreased.Itsdischargerateingallonspermi