Coupling method for internal nozzle flow and the spray formation for viscous liquids

Abstract

Understanding the disturbances introduced by cavitation inside spray nozzles is important, when simulating the spray formation of highly viscous liquids. In this paper, a new model for cavitation-induced primary break-up is proposed, which is able to map the influence of cavitating nozzle flow on spray formation. Detailed experimental and numerical investigations of the viscous nozzle flow have been performed in order to develop an improved primary break-up model [1]. The proposed model describes the transition from the flow inside the nozzle, modelled using a homogeneous equilibrium model (HEM) method, to the first primary droplets modelled using a Eulerian–Lagrangian method. Thus, providing the boundary conditions for the calculation of the secondary break-up and spray formation. The nozzle exit is divided into a definite number of patches. Liquid momentum and vapor volume fraction from each patch are used to initialize the primary droplets. The model has been implemented in the open-source CFD software package OpenFOAM and validation has been done using high-speed shadow graphic imaging. The simulated spray tip penetration and spray cone angle at the near-nozzle region show a good agreement with the experiment results.