PURPOSE: To obtain a burner assembly for bringing about a complete combustion of fuel by moving first air through and around blades to impart a rotation to the air to agitate a stream of fuel mixture.

CONSTITUTION: Liquid fuels are supplied from a tank 15 and injected into a fuel gun 25. Compressed air is supplied from an air compressor source 18 and a pipe 19 to fuel. A window box 20 is provided, and the air is supplied to the burner assembly and into a furnace via a fan 21. The air of a first volume is supplied into a housing 26 via a leg 34 and exhausted from an end 29 out of the furnace. A swirler 28 has a cylindrical hub 35 and a plurality of blades 36, and axial air of a remarkable amount passing the housing 26 flows around the swirler. A diameter of the swirler 28 is increased to an inner diameter of the housing 26 to enhance a control of a flame pattern and to increase a combustion efficiency.