Manual

4|Descriptionoffunction BÜCHILabortechnikAG
18/46 UltrasonicController
Fig.4:Nozzledesign(schematic)
1 Electricalconnector 2 Rearhorn
3 Temperaturesensor 4 Activeelectrode
5 Atomizingsurface 6 Piezoelectrictransducer
7 Groundelectrode 8 Housing
9 Groundlug
Discshapedceramicpiezoelectrictransducersconverthighfrequencyelectrical
energyfromapowergeneratorintovibratorymechanicalenergyatthesame
frequency.
Thetransducersaresandwichedbetween2titaniumcylinders,whichactto
concentrateandamplifythevibration,maximizingitattheatomizingsurface.Ti
taniumisusedbecauseofitsgoodacousticalcharacteristics,corrosionresis
tanceandhighstrength.
Theliquidisdeliveredtotheatomizingsurfacethroughalargediameterfeed
tubethatrunsthelengthofthenozzle.Thelargeliquidfeedorificeassuresfree
domfromclogging.
4.2.1.1 Nozzle,powersettings
Theultrasonicatomizationprocessishighlydependentonthepowerdelivered
tothenozzle.Bestresultsareachievedwithinarelativelynarrowinputpower
range.Belowacriticalpowerlevel,referredtoasthe“stallpoint”,thereisinsuf
ficientenergytoproduceatomization.Thepowerrangeinwhichatomization
proceedsnormallyisgenerallyconfinedtoanarrowregion,approximately0.5–
1.5Wattabovethestallpoint.Atpowerlevelsabovethisrange,theliquidislit
erally“rippedapart”bytheexcessenergyprovided,causinglargechunksof
materialtobeexpelled,ratherthanthecharacteristicsoftsprayoffinedrops.
Thisconditionisknownascavitation.
Theactualpoweratwhichthestallpointoccursisdependentonseveralfac
tors:
• Nozzletype(mechanicalandelectricalcharacteristics,size)
• Liquidcharacteristics(e.g.viscosity,solidscontent)
• Flowrate
• Sizeoftheatomizingsurface