Tube firing burner

The combination of, a heat-insulating wall having inner and outer sides and having an opening extending between said sides, a radiant tube projecting inwardly from the inner side of said wall and having an outer portion disposed within the full length of said opening, and a burner for firing said tube and having a tubular body secured to the outer side of said wall and located in substantially coaxial relation with said tube, a fuel delivery pipe extending into said body from the outer end portion thereof, means for supplying a flow of fuel through said pipe, means for supplying a flow of combustion air into said body from the outer end portion thereof, means for shaping said air into a tubular stream adjacent the discharge end of said delivery pipe, a metallic combustion sleeve coaxial with said delivery pipe and positioned to receive the flow of fuel and the tubular stream of air, said combustion sleeve extending through the full length of said opening and being telescoped within and spaced radially inwardly from the outer end portion of said tube, said combustion sleeve having an inner end extending inwardly beyond the inner side of said wall so as to discharge the fuel/air mixture into said tube beyond said wall, and an abrupt restriction within said sleeve adjacent the inner end thereof and beyond the inner side of said wall to create turbulence within the fuel/air mixture discharged from said sleeve.