Experimental study of liquid-jet atomization using LDV and DTV: study-case on an agricultural nozzle

Autor: Felis, F., Anselmet, Fabien, Tomas, S., Vallet, A., Amielh, M., Tinet, C.
Přispěvatelé: Information – Technologies – Analyse Environnementale – Procédés Agricoles (UMR ITAP), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Gestion de l'Eau, Acteurs, Usages (UMR G-EAU), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-AgroParisTech-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), Irstea Publications, Migration
Jazyk: angličtina
Rok vydání: 2016
Předmět:
Zdroj: CFTL 2016 : 15e Congrès Francophone de Techniques Laser
CFTL 2016 : 15e Congrès Francophone de Techniques Laser, Sep 2016, Toulouse, France. pp.8
Popis: [Departement_IRSTEA]Eaux [TR1_IRSTEA]GEUSI; International audience; A typical water round-nozzle jet for agricultural applications is presented in this study. The dispersion of water for irrigation purposes or pesticides is a key aspect to study to both reduce consumption and/or air pollution. LDV (Laser Doppler Velocimetry) and DTV (Droplet Tracking Velocimetry) optical techniques are used to gather statistical information from both the liquid and the gas phases of the spray. This information is later used to evaluate the performance of a mixture-fluid RANS turbulence model applied to a typical case-scenario. Previous experimental studies have been carried out in real agricultural nozzles using real conditions. Results obtained using these configurations have always introduced several biases and could not be applied to a more generalized numerical RANS model case. More specifically, DTV measurements in a 4.37 mmwater cannon showed a strong anisotropy factor of the principal Reynolds' Stresses on the dispersed liquid phase, these results are a clear departure from those obtained in more dispersed flows like fuel injectors. A simplified test scenario was constructed to remove some constraints and to provide a more controlled environment for the optical measurement techniques. Instead of the original 4.37 mmdiameter water cannon, a smaller round dn=1.2 mm nozzle was constructed in PMMA/Glass to provide visual access to the internal flow, where the actual injector is the circular glass tube of length Ln=50dn, so the flow turbulence at the exit of the nozzle was completely developed. Gravity effects on the liquid dispersion were attenuated by placing the injector in an up-down direction, making the flow statistically axisymmetric. Operating conditions were chosen to place the liquid jet in a turbulent atomization regime. LDV measurements were carried out first along the liquid core vertical axis, the results give a rough estimation of the liquid axial-velocity component from x/dn=0 to 800. On the vicinity, radial air profiles were obtained using small (~1 µm) olive oil tracers to capture the gas phase. From the Doppler-burst threshold between the liquid and oil particles, a distinction between phases was achieved. On the dispersed zone, DTV measurements were carried out to determine several radial profiles between x/dn=100 and 800, special attention to the depth-of-field (DOF) estimation was taken in order to obtain a less biased droplet's size-velocity correlation. Preliminary results showed a strong anisotropy factor (u'2/v'2~10-20) for both liquid and gas phase measurements, even in the external region far from the liquid core. The strong density ratio (water/air), flow's directionality and production of turbulent kinetic energy may be the cause of a poor atomization and weak mixing between the two fluids. These hypotheses are yet to be clarified later in the study, notably on the ability of a RANS model to predict this behavior.
Databáze: OpenAIRE
Externí odkaz: