Gas Velocity Distribution for a Confined-type Gas Atomization Nozzle
Gas flow characteristics for a confined-type gas atomization nozzle have been studied to design properly the fine powder atomization nozzle through increasing the gas jet speed in the pulverizing region. Before flowing downward vertically, discrete gas jets spouted from the atomization nozzle converge around the geometrical focus, where the vertical gas velocity in the center portion reaches a saturation. The gas velocity distributions on the horizontal plane are influenced by apex angle and protrusion length. When the apex angle is less than 50°, the effect of protrusion length on the velocity distribution is relatively small. Whereas, in case of larger apex angle than 65°, the protrusion gives interference of suppressing the gas flow under the condition that sufficient suction pressure is formed at the melt orifice. The gas velocity distribution around the geometrical focus is not affected by changing the impinging gas pressure at the same mass flow rate. In order to increase the gas velocity in the pulverizing region, adjacent arrangement of gas jets to the melt delivery tube tip is important because of much reduced energy loss.