EFFECT OF NOZZLE GEOMETRY AND POSITION ON GAS ATOMIZATION

Gas atomization is widely practised far the production of rapidly soli dified powder and spray deposits. The most common operating modes in g as atomization are the gravity or free fall and the aspirating or clos ed couple modes. In this study static pressure measurements at the tip of the delivery tube were made in a closed atomizer for different tub e tip designs using a double Coanda nozzle arrangement. These measurem ents coupled with gas and melt visualization using CO, and water were used to identify delivery tube/gas nozzle positions that would subsequ ently yield successful atomization. Gas atomization of zinc was then c arried out and visualization of the melt spray revealed that an aspira ting mode can be achieved at a ratio of gas aspirating to melt gravity force of 0.16 N. Furthermore, the aspirating mode of atomization is s hown to yield a narrower size distribution than the gravity mode at th e same gas/metal ratio. Thus, controlled atomizer performance may be a chieved by the proper placement of the delivery tube for a given gas n ozzle.