INTERNAL AND NEAR-NOZZLE TRANSIENT FLOW OF A SPILL-RETURN ATOMIZER

Abstract

The present study investigates, numerically, the spill-return atomizer's (SRa) internal flow features within a 3D geometry by the use of a commercial code, ANSYS FLUENT. Experimental measurements, from the literature, are used to validate the numerical results of spray-cone angle (SCA), discharge coefficient (CD), and mass flow rates. The unsteady flow is solved as two-phase flow using the volume of fluid (VOF) method. The turbulence is captured using the K-ω shear-stress transport (SST) turbulence model. The geo-reconstruct scheme is used to capture the gas-liquid interface. An adaptive mesh refinement (AMR) is applied to refine the regions featuring high gradients in space. The simulations manage to capture the overall flow characteristics of a SRa with the formation of an air core and a thin liquid film in the exit region of the swirl chamber. Profiles of axial and tangential mean velocities are obtained. Furthermore, pressure measurements are conducted and pictures of the air core, velocity, and pressure field are taken for qualitative analysis. The tangential velocity profile resembles a Rankine vortex. The results show that air cores behave differently (size and shape) when changing the spill to feed ratio (SFR) due to a significant rise in the velocity profiles inside the swirl chamber, which directly affect the SRa performances, such as SCA and breakup process. The results show an important influence of the SFR variation on the gas-liquid volume fraction. A brief overview at the end is devoted to creation of the liquid spray cone outside of the injector, as well as the liquid sheet breakup process.