Characterization of flow-blurring atomization with Smoothed Particle Hydrodynamics (SPH)

Abstract

The liquid atomization process relies on the disturbance of the liquid surface by various forces. In the case of “flow-blurring” (FB) atomization, this is achieved by inducing flow instabilities near the liquid channel exit. In this study, we analyze the underlying dynamics of these coherent turbulent structures and their role in the primary atomization within the FB regime. For that purpose, Smoothed Particles Hydrodynamics (SPH) simulations have been conducted using alternative FB nozzle geometries at different operating conditions. An in-house developed visualization and data exploration platform (postAtom) was used to capture the time-resolved Lagrangian coherent structures ($\mathrm{LCSs}$) via the finite-time Lyapunov exponent ($\mathrm{FTLE}$) fields. Simulations were conducted at different gas/liquid momentum ratios at the nozzle exit by changing the mass flow rate of the gas phase and/or changing the position of the liquid injector. The effect of outer chamber design on the atomization performance is further assessed. The results indicate that the design of the mixing chamber can trigger an oscillatory behavior at the nozzle exit, which has a direct impact on the evolution of the micro-ligaments and the consecutive primary atomization. Comparisons between different operating points further reveal that FB atomization may not be achieved if the gas momentum is below a certain threshold value.