Abstract: Methods and apparatus particularly useful for atomizing a heavy highly viscous liquid into fine droplets (such as petroleum distillate resid to droplets on the order of 100 thousandths of a millimeter), with the aid of at least one auxiliary gas. This employs in a nozzle head an array of a plurality of primary channels and at least two secondary channels associated with each said primary channel. The primary channels each have an inlet end connected to a high pressure source of liquid, and have an outlet end defining an atomization orifice. The secondary channels each have an inlet end being connected to at least one source of auxiliary gas and an outlet end. The outlets of the secondary channels each intersect with a commonly associated primary channel at the same or different locations upstream of the respective atomization orifice at angles of less than 90.degree., typically 45.degree. or less. Liquid is passed through a plurality of primary channels thereby forming a liquid core stream.