Evaluation of the spray characteristics of a single droplet with imaging techniques

S. VULGARAKIS MINOV1&2, F. COINTAULT1, D. NUYTTENS2, J. VANGEYTE2, J. PIETERS3, B.HIJAZI1&2

AGROSUP DIJONINSTITUT NATIONAL SUPÉRIEUR DES SCIENCES AGRONOMIQUES DE L’ALIMENTATION ET DE L’ENVIRONNEMENT

Département Agronomie Agroéquipements Elevage & Environnement (D2A2E) 26 Bd Dr Petitjean - BP 87999 - 21079 Dijon cedex - France

+33 (0)380772348 - +33 (0)380772551 – Site Web : http://www.agrosupdijon.fr

1) AgroSup Dijon – UP GAP – 26, Bd Dr Petitjean – BP 87999 – 21079 Dijon cedex – France2) Institute for Agricultural and Fisheries Research (ILVO) - Technology and Food Science Unit, Agricultural Engineering Research Group – Burg. Van Gansberghelaan 115 – 9820 Merelbeke – Belgium 3) Department of Biosystems Engineering – Faculty of Bioscience Engineering- Ghent University – Coupure Links 653-9000 Gent - Belgium

Improvement of existing techniques Development of accurate spray quantification techniques.

MotivationPesticides Sprayers Nozzles Application accuracy and efficiency of

plant protection productsMaximization of spray efficiency and

minimizing residues and off target losses

Material and methodsImage acquisition system

Droplet generator setup: 1-Droplet generator with piezoelectric element, 2-HS camera & lens, 3-Light source, 4-PC, 5-Pressure supplier, 6- Signal amplifier, 7- Pulse generator, 8- Liquid tank.

Droplet generator

Droplet generator: 1- Glass nozzle,2-Piezoelectric element, 3-Clamp, 4-Tubes.

Glass nozzleOrifice

diameter (µm)

Measured orifice

diameter (µm)

Nozzle 1 200 263 ± 0.000

Nozzle 2 150 123 ± 0.000

Nozzle 3 100 90 ± 0.000

Nozzle 4 50 65 ± 0.000

T

Droplet on demand mode

± Vp-p

± ta

± tp

An example of a driving rectangular pulse used to generate droplets where: ta is absorption time, tp is pulsation time and Vp-p is the amplitude of the pulse voltage.

Tracking single droplet

ta (ms) 0.01 - 5tp (ms) 0.01 - 50Vp (V) ± 4.5 Nozzle

opening (µm)

65 , 90 , 123 & 263

AmplifierDroplet

generator

Tested parameters

Algorithm description

False

Select frames for video

Pass droplets with circularity between 0.7 and 1

Convert the frames into binary

Noise remove

Label the droplet

Calculation of the droplet area and circularity

True

Droplet diameter and velocity

Results and discussions

Nozzle orifice opening (µm)

Droplet diameter range (µm)

Droplet velocity range (m/s)

65 134 ÷ 214 0.095 ÷ 0.805

90 242 ÷ 309 0.261 ÷ 1.250

123 312 ÷ 416 0.080 ÷ 0.684

263 389 ÷ 461 0.335 ÷ 0.772

On demand droplets produce in a repeatable way of size 134 - 461 µm with droplet ejection

velocity from 0.080 – 1.250 m/s.

0.01 0.2 0.3 0.4 0.5 0.6 0.7 0.7 0.8 0.9 0.9 2 5

100

200

300

400

500

0,01

0,1

0,8

1

10

50

ta (ms)

Dro

plet

dia

met

er (µ

m)

tp (ms)

Image background

Nozzle

Droplet

Binary image Droplet label Droplet center location

Droplet velocity

Results showed dependence between the droplet initial

characteristics and the pulse width and voltage amplitude.

FOV: 10.5 mm x 8.4mm.Camera settings: 1000 fps at 6 µs exp.time.

1 pixel = 8.227 µm

The pulse width parameters for single

droplet generation differ for every nozzle.

The smaller the nozzle orifice the harder the droplet

generation due to surface tension at nozzle exit.

The goal is to evaluate the droplet spray

characteristics with a droplet generator and

imaging technique.