Department of Mechanical Engineering, Polytechnic School, University of São Paulo, Brazil
Cavitation characteristics in Hollow-Jet valves and possible solutions were investigated in the present work. Three-dimensional numerical simulations – CFD (Computational Fluid Dynamics) were carried out in an unsteady state, considering homogenous multiphase flow, to identify the phenomenon in these components. Different turbulence and cavitation models were assessed to reach the best compromise of models. The results confirmed the occurrence of cavities with a mixture of vapor and liquid at the valve tip. The cavities are followed by a vortex generation near the same region. These vortices are the result of a high-velocity gradients, especially in the shear region of the discharge pipe wall, and they are followed by the detachment of the cavities from the valve tip. The methods and models were validated by a reproduction attempt of the results from a similar work on literature. Solutions to avoid or reduce cavitation were proposed and analyzed. Refurbishment and protective coatings against cavitation were particularly described, to envisage an economical solution to reuse the valves, avoiding their disposal or replacement.