Abstract: A forced-draft burner including a cylindrical blast tube and an inner tube concentric with the blast tube defining an annular space therebetween for the flow of combustion air, the inlet end of the inner tube having a 90.degree. bend for securement to a side wall of the burner and the outer end of the inner tube extending beyond the blast tube, said inner tube outer end being closed and having peripheral openings to form a nozzle, vanes fixed on the inner tube within the annular space for imparting a preliminary swirl to combustion air, and a spinner blade mounted on the inner tube planar with the end of the blast tube to impart additional rotary swirl to the combustion air prior to the introduction of fuel thereto, said spinner blade having a circumference less than the diameter of the blast tube to define an annular space adjacent the blast tube. The inner tube, internal vanes and spinner blade can be axially adjusted within the blast tube or removed for servicing or replacement as an integral unit.

Abstract: A forced draught fuel burner for use with gas or oil fuel and adapted to operate without swirl is disclosed in which a first inner cylindrical tube substantially concentric with and spaced from a blast tube defines an outer annular space having baffle means positioned within the outer annular space at the outlet ends of the pair of tubes, said baffle means having a substantially perpiheral circular opening of uniform cross-section for discharge of secondary combustion air, a second inner cylindrical tube having means for mounting said second inner tube substantially concentrically within said first inner tube for axial reciprocal travel therein, said second inner cylindrical tube having an inlet end and an outlet end and said second inner tube defining an inner annular space with said first inner tube, a diffuser ring having an outside diameter smaller than the diameter of the first inner cylindrical tube defining a narrow circular slot of uniform cross-section at the periphery of the inner annular space and