Abstract：The primary breakup mechanism was investigated by numerical simulation combined with the formation theory of tornado. The effect of air/liquid mass flow rate and gas flow field form including rotational and irrotational flow on the primary atomization were discussed. The results show that using the swirling flow field form is benefits to the formation of a thin melt sheet at the nozzle tip with a higher effective using rate of gas. The primary breakup model which forms a miniature “fountain” at the nozzle tip abruptly shifts to melt sheet breakup model when the critical flow rate is 0.003 8 kg/s.

Keywords: primary atomization; swirling flow field; melt sheet; numerical simulation