| Melt flow rate is considered to be an important process variable in gas atomization because it greatly affects the droplet sizes, microstructures and mechanical properties of the final products. It is, however, difficult to predict the melt flow rate accuratly because it is also influenced by the aspiration pressure under the melt orifice in confined type gas atomization. It seems to be impossible to measure the orifice pressure directly during gas atomization. Hence upto now the orifice pressure has been measured statically with the pressure gage connected to the upper side of melt orifice without flow. But it is different from the real atomizing conditions, in which melt flows through the orifice. In this study, the dynamic orifice pressure was calculated by measuring the flow-out time of the melt. The dynamic aspiration effect varies with the protrusion height of melt nozzle, increases with the increasing gas jet velocity and decreases as melt flow rate increases. |
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