Burner construction

A fuel burner comprising means forming a burning chamber of cylindrical shape and defining a burner axis therein, said chamber having an inlet opening at one end and including a peripheral cylindrical wall extending from one end to the other and displaced from said axis by a predetermined radial dimension means forming a vortex box disposed in coupled relation to said inlet opening for introducing combustion air into said body and along said axis, having a back wall spaced away from said inlet opening and having a plurality of internal vanes arranged in a circle surrounding said axis and radially tilted thereto for imparting spiral flow to air passing through and along the axis of said burner, port means coupling said vortex box to said chamber and having a radial dimension from the axis which is less than the radial dimension of said burner wall, said coupling means and burner wall being constructed and arranged to form an expansion step for combustion air flowing therebetween, so that a flow pattern through the burner is established in which combustion air is introduced through said inlet in an axial direction to produce a swirling air flow about said axis and along a generally cylindrical annular combustion zone, the combustion air moving forwardly and outwardly as it passes past the step and through said zone, a portion thereof recirculating by moving in a rearward direction along the axis of the burner and towards the inlet opening and vortex box to produce a secondary flow in opposition to the general flow of combustion air therethrough to thereby establish a stagnant air region at the inlet to said burner which region remains relatively constant with respect to the overall flow rate of combustion air therethrough, pilot injector means comprising a nozzle mounted to discharge fuel immediately adjacent to said back wall for injecting a limited quantity of liquid fuel into said stagnant region and directed along the axis of said chamber, said fuel being ignited therein to form a stable pilot flame for said burner, main fuel injector means for injecting finely divided liquid fuel generally along said burner axis and into the region of said combustion zone, a plurality of nozzles disposed along an annular ring surrounding said pilot injector means and having outlet orifices located substantially proximate to said back wall, said injector means being constructed and arranged to limit the injection to a region bounded by a cylindrical surface surrounding said stagnant zone and extending radially therefrom to said main fuel injector means and a conical surface intersecting the main fuel injector means and passing adjacent said port means.