ID 143

Drop Characteristics of two gelled fluids at High Generalized Herschel–Bulkley Extended Jet Reynolds Numbers using Impinging Jets

 

Abstract:

The current study investigates the drop characteristics of sprays produced by the like-on-like jet impingement of two non-Newtonian, shear-thinning, Herschel–Bulkley fluids. The two fluids used in this work were water-based, gelled solutions of 1.0 wt.-% agar and 1.0 wt.-% kappa carrageenan. A rotational rheometer and a capillary viscometer were used to measure the strain-rate dependency of viscosity and the Herschel–Bulkley Extended (HBE) rheological model was used to characterize the shear-thinning behavior. A contact angle goniometer was used to measure the gel-air surface tension for the two solutions. A generalized HBE jet Reynolds number Rej,gen-HBE was used to characterize the drop size and drop velocity, which were measured using Phase Doppler Anemometry (PDA). PDA measurements were obtained at high Rej,gen-HBE, which allowed for the formation of spherical drops within the spray. PDA optical configuration enabled a drop size measurement range of approximately 2.3 to 116.2 μm and 50,000 drops were measured at each test condition to ensure statistical significance. The arithmetic mean diameter (D10), Sauter mean diameter (D32), and mass median diameter (MMD) were used as representative diameters to characterize the drop size. The mean axial drop velocity Uz-mean along with its root-mean square Uz-rms were used to characterize the drop velocity. The polydisperse nature of the spray was characterized using number, surface area, and volume probability density functions (pdfs). Drop characteristics were compared to those of DI water and differences in the spray characteristics were ascribed to viscous effects and molecular differences of the two gelled solutions.