Avoidance of moulding defects in injection moulded metal matrix composites: F.Ahmed, M.J.Bevis. (Wolfson Centre, Brunel University, Uxbridge, UK.)

Abstract

Atomization of high viscosity liquids for industrial processes requires the design of more efficient atomizers. In this work, the operation of an air-assisted atomizer, based on a Venturi-vortex system, was examined atomizing liquids with increasing viscosity. In this atomizer prototype, air was injected tangentially in a central convergent chamber and discharged axially suctioning liquid from a coaxial compartment through an annular slit. This atomizer is characterized by the generation of a high velocity swirling airstream and the use of large internal liquid passages. The resulting sprays were experimentally analyzed by means of a phase-Doppler Anemometer. The droplet diameter and two velocity components were measured at different axial stations and radial locations along the spray. Operating with low liquid flow rates, a good atomization quality was achieved generating sprays with a significant fraction of small droplets. Drops with diameters up to 50 μm were considered, which constitute 99% of the total number of measured droplets. Sauter mean diameters below 30 μm were obtained even when pure glycerine was atomized. Air/liquid mass flow rate ratios above 7.5 were handled. The effects of varying the air injection pressure and the conical chamber geometry were also investigated. A drop of the atomizer efficiency was noted when a shorter convergent chamber was used.