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Researchonamplitudeandfrequencycharacteristicsofresonance
ofequipmentoperatinginwater
XUHongquan,ZHOUYe,LIAOCuilin,CAODengfeng,ZOUZhichao
(ChinaInstituteofWaterResourcesandHydropowerResearch,Beijing 100038,China)
Abstract:Intheoperationofequipmentsubmergedinwatersuchashydraulicmachinery,faultssuchasequip
mentdamagecausedbyseverevibrationareoftenencountered ,whicharemostlyconsideredtobecausedbyreso
nance.Dimensionlesstreatmentiscarriedoutforsteady - statevibrationsolutionsofthefreevibrationandforcedvi
brationequationsofthesimpleharmonicvibrationsystemwithsingledegreeoffreedfirstly.Thentheresonancefre
quencyratioandresonanceamplituderatiowithdifferentdampingratiosarecalculatedanditisfoundthatthereisa
one - to - onecorrespondingmonotonicallyvaryingrelationbetweenthreeratios.Areverseestimationmethodispro
posedandthatistomeasurethefreevibrationfrequencyofequipmentinwaterandairrespectively ,assumethe
freevibrationfrequencyinairisthenaturalfrequency ,andthendeterminethedampingratioandresonanceampli
tuderatioinwater.Theresearchusesthehammeringmethodtomeasurethefreevibrationfrequencyofthemodel
Francisturbinerunnerinwaterandair.Itisfoundthatthefreevibrationfrequencyinwaterislowerthanthatinair ,
andtheratioofthefirst - orderfreevibrationfrequencyinwatertothatinairisabout0.758~0.872.Ifthisvalueis
assumedtobethefreevibrationfrequencyratioinwater ,thecorrespondingdampingratioinwatercanbecalculat
edtobe0.652~0.490,andtheamplificationratiooftheresonanceamplitudeisabout1.01~1.17.Inthisstudy,
therealresonancetestofthecantileverbeamsfixedinthemiddlewasalsocarriedoutinairandwater.Obvious
resonanceoccursnearthecalculatednaturalfrequencyofthecantileverbeamduringvibrationtest.Duringthevi
brationtestinwater ,itwasalsofoundthattheresonancefrequencywassignificantlylowerthanthatintheair.The
ratioofresonanceamplitudeinthewaterobtainedbythereversemethodwaslessthan2 ,andthemagnificationof
resonanceamplitudeinthewatertotheinitialvibrationamplitudeintheairwasalsoverysmall.Itfurtherindicates
thattheamplificationofresonancetoexcitationamplitudeisverylimited.
Keywords:turbinerunner;cantileverbeam;resonance;freevibration;naturalfrequency;damping;vibrationam
plitude
(责任编辑:王 婧)
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