ID 260

Simulation Study of a Two-fluid, Electrostatic Nozzle

 

Abstract:

Spray drying converts liquids into dried particles with certain desirable qualities. The novel use of electrostatic injection techniques in spray dry applications has shown improvements in the overall efficiency of the process. Early data suggests significant savings in energy required to atomize the fluid and produce desired solid particles, through reduced heat and compressed air requirements. This work empirically investigates the parameters that influence the spray produced by a two-fluid, electrostatic nozzle. The simulation is focused on the primary atomization and near field spray characteristics. The validation metrics used are acquired via Phase Doppler Interferometry (PDI) and Laser Sheet Imaging (LSI) to characterize the spray performance. Prediction of spray performance was executed using Computational Fluid Dynamics (CFD) simulations, as it related to spray technology. The computational model and simulations were conducted using the ANSYS Fluent modeling software package. A Volume of Fluid (VOF) model was employed along with a two equation turbulence model. The near nozzle region spray sheet and associated perturbances were well predicted with a very fine mesh. Away from this region, the smaller packets of liquid are converted into LaGrangian parcels using Fluent’s built-in VOF-to-DPM transitional model. The use of dynamic mesh refinement and coarsening helps in keeping the total computational elements within a uniform range. This approach saves CPU time by allowing coarser mesh in the far region. Further post-processing tools are used to analyze the resulting size distribution at several different cross sectional planes downstream of the nozzle. The computational model’s agreement, and disagreement, with the experimentally acquired results provides insight for optimizing electrostatic injections in spray-dry applications.