1. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop L. TATOULIAN, J-P. BORRA Laboratoire de Physique des Gaz et des Plasmas, UMR 8578, Ecole Supélec, Plateau de Moulon, 91192 Gif-Sur-Yvette Cedex, France. Effect of nozzle geometry on operating ranges (V,Q) in cone-jet mode of EHD Atomisation

2. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop Goals and means Experimental set-up Operating ranges (V,Q) for given geometry & conductivity Droplet properties Influence of nozzle geometry on (V,Q) operating ranges Conclusions and applications OUTLINE

3. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop GOALS Control the size distribution of droplets by nozzle geometry: –Operating ranges (Voltage (V)-liquid flow rate (Q)) of EHDA in cone-jet mode, for a given nozzle geometry –Influence of nozzle geometry on operating ranges (V,Q) MEANS Nozzle (Dout = [1.8-8] mm; Din = [0.4-1.3] mm) Liquid pump (Q = [0-100] mL/h) DC high voltage supply (V = [0-15] kV) Diagnostics (visual, electric & granulometric) GOALS and MEANS

4. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop Electro-Hydro-Dynamic Atomisation : Physical principle Neutral droplet Hydrodynamic and gravity pressures Without Electric Field Capilary pressure Viscous stress NOZZLE mm  d ~ mm

5. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop Experimental SET-UP Production system Investigation technique DC High voltage supply Oscilloscope Liquid pump HV probe SPRAY NOZZLE PLANE R=10Mohm Phase Doppler Anemometry (PDA) Laser beam Size measurement Measuring volume

6. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop Succession of EHDA spraying modes  Vcone-jet V Vmin Cone-jet mode 7 kV Vmax 12.5 kV dripping, µdripping, intermitent cone-jet. Multi Cone-jet Mode 5 ml/h & Dout = 2 mm

7. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop CONE-JET MODE (V,Q) operating ranges Q fixed V fixed Unstable modes Unstable modes Vincreases Q increases VARICOSE (axysimetric) KINK (asymetric) Monodispersity dN dLogdp 0.1 1 10 dp Particle diameter (µm) dN / dLog dp Polydispersity 0.1 1 10 KINKVARICOSE

8. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop Outer nozzle diameter FOR CONE JET MODE - higher Vmin and Qmin - larger (V,Q) ranges IN CONE JET MODE - No dependance of  Q(VARICOSE) - Dependance of  Q(KINK) r1r1 2mm3.1mm 8mm Dout V,Q fixed r 1 ; r 2 Scone Charge density & as outer diameter increases with outer diameter r2r2

9. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop Inner nozzle diameter 1) - Vmin sligthly increases - Qmin slightly decreases - No dependance of (V,Q) ranges 2) Possible obstruction of nozzle tip 3) Stabilisation of liquid jet as inner diameter decreases r 1.3mm0.4mm V,Q fixed rDin

10. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop Nozzle geometry: a way to control the droplet size ? VARICOSE KINK Dout = 8mm Dout = 3.1mm Dout = 2mm 1) Dp = f (Qliq n ) 2) A Qliq fixe, Dp # f(D out) 3)  Q (VARIOSE) =>  d var. 4)  Q(KINK) =>  d kink with Dout # f( Dout) Qmax varicose = 9 ml/h Dp theoretical ~ Q liq 1/3

11. CNRS/L.P.G.P./Equipe DECHARGE ELECTRIQUE ET ENVIRONNEMENT 5 th Electrohydrodynamics International Workshop CONCLUSIONS –For a given conductivity, cone-jet mode exists only within an appropriate (V,Q) operating ranges –Outer nozzle diameter increases (V,Q) ranges –  Q(varicose) independant of nozzle geometry –  Q(kink) is larger as outer diameter increases APPLICATIONS –Thin film Deposition at Atmospheric Pressure in air –Powder Production CONCLUSIONS AND PERSPECTIVES