Air-Core–Liquid-Ring (ACLR) Atomization Part II: Influence of Process Parameters on the Stability of Internal Liquid Film Thickness and Resulting Spray Droplet Sizes

Abstract

Air-core–liquid-ring (ACLR) atomization presents a specific type of internal mixing pneumatic atomization. It can be used for disintegration of high viscous feed liquids into small droplets at relatively low gas consumptions. However, the specific principle of ACLR atomization is still under research and no guidelines for process and atomizer design are available. Regarding literature on pre-filming atomizers, it can be hypothesized for ACLR atomization that the liquid film thickness inside the exit orifice of the atomizer, as well as the resulting spray droplet sizes decrease with increasing air-to-liquid ratio (ALR) and decreasing feed viscosity. In this study, the time dependent liquid film thickness inside the exit orifice of the atomizer was predicted by means of computational fluid dynamics (CFD) analysis. Results were compared to high speed video images and correlated to measured spray droplet sizes. In conclusion, the hypothesis could be validated by simulation and experimental data, however, at high viscosity and low ALR, periodic gas core breakups were detected in optical measurements. These breakups could not be predicted in CFD simulations, as the simplification of an incompressible gas phase was applied in order to reduce computational costs and time. Nevertheless, the presented methods show good potential for improvement of atomizer geometry and process design as well as for further investigation of the ACLR atomization principle.

Spraying of Viscous Liquids: Influence of Fluid-Mixing Mechanism on the Performance of Internal-Mixing Twin-Fluid Atomizers

“…The second method, the FFT (Fast Fourier Transform) analysis, was used to identify the periodic behavior of the spray pulsations and to indirectly gain information about the two-phase flow in the atomizer mixing chamber. Similar analysis was, for the numerical simulation results, used in [37].…”

Special Issue on Performance Measurement and Optimization for Sustainable Production Processes Improvement

“…Wittner et al [19,20] focused on the air-core-liquid-ring atomization and Chan and Kuo [21] investigated the wheat germ drying performance. Holgado [22] used system engineering approach to performance-based maintenance services design.…”

Experimental Analysis and CFD Modelling of the Flow Conditions inside an Air-Core-Liquid-Ring Atomizer

“…While there are some computational studies of pneumatic internal-mixing models, most of them modelled only waterair mixtures or did very limited experimental validation of the model [5,6]. Only Wittner et al [7] focused on the ACLR nozzle design. However, they assumed a constant density for the gas phase, instead of using a compressible gas model, which can increase simulation error [5].…”