Investigation of three-phase nozzle flow (water- sand -air) in an innovative sand-blasting system

The study presented herewith was mainly focused on the numerical analysis of air-sand-water three-phase turbulent flow through converging-diverging nozzle. For this purpose dispersed flow of air-sand-water by various air inlet pressures, ambient air inlet temperature, sand particles and water droplets by different mass flow rates and temperature were considered. This study puts emphasis on sand blasting nozzle which is employed in Farrow abrasive system. Two-way turbulence coupling between particles/droplets and air flow as well as interference between the incident stream of particles and rebounded from the wall were applied in the numerical model. In addition, the shock wave which is produced in supersonic flow at diverging part of nozzle was considered. In order to capture the turbulent flow features accurately, Standard, RNG and Realizable k- models as well as Spalart-Allmaras and Reynolds Stress turbulence models were tested. Meanwhile, Eulerian Model and Discrete Phase Model were employed for simulating of multi-phase flow through the nozzle. Eventually, Realizable k-ε Discrete Phase model was utilized in the present study. Since there is not any experimental or analytical result on three-phase flow through the nozzle, for validation of model, the same turbulent and multi-phase models were utilized on air-water two-phase flow. The obtained results were in good agreement with the experimental data. According to the results of three-phase flow simulation, the averaged exhaust momentum of sand particles had inverse proportion with water mass flow rate. The increasing of air inlet pressure had significant effect on mean exhaust velocity of sand particles. Moreover, the air exhaust velocity had direct proportion with inlet temperature of water droplets and sand particles. This investigation may be used in further studies related to the optimisation of sand blasting nozzle in different working conditions.