초록 ▼

A swirl-type internal flame recirculation burner as used to fire asphalt plant aggregate dryers, air heaters and calcining kilns and method includes an atomizer assembly for swirling primary air in two concentric streams with the inner stream swirling more rapidly than the outer stream. Fuel oil is

A swirl-type internal flame recirculation burner as used to fire asphalt plant aggregate dryers, air heaters and calcining kilns and method includes an atomizer assembly for swirling primary air in two concentric streams with the inner stream swirling more rapidly than the outer stream. Fuel oil is blast atomized in a continuous sheet into the inner stream without prefilming and then is shear atomized as the inner and outer streams violently intermix. The burning and swirling fuel and primary air mixture recirculates upstream along the burner axis. Secondary air is swirled in the same direction as the primary air and surrounds the primary air stream to promote further mixing and internal recirculation. A metal frustro-conical flame holder surrounds the burner head to stabilize and shape the recirculation flame and shield low-burn flames from tertiary air. The swirl of the secondary air is also adjusted to shape the flame. The burner may also be fired on gas or a combination of gas and oil.

대표청구항 ▼

1. A burner including an axial fuel pipe; a fuel atomizer at the downstream end of the pipe; a primary air pipe coaxial with the fuel pipe, surrounding the fuel pipe and extending upstream from the fuel atomizer; a secondary air pipe coaxial with the fuel pipe, surrounding the primary air pipe

1. A burner including an axial fuel pipe; a fuel atomizer at the downstream end of the pipe; a primary air pipe coaxial with the fuel pipe, surrounding the fuel pipe and extending upstream from the fuel atomizer; a secondary air pipe coaxial with the fuel pipe, surrounding the primary air pipe and extending upstream from the atomizer; said secondary air pipe having an exit portion extending parallel to the axis of said fuel pipe; means for swirling primary air in a first direction; said means for swirling primary air including means adjacent said fuel atomizer defining two separate concentric swirl passages dividing the primary air into two flow masses, the first of said primary swirl passages configured to accelerate the flow of a first primary air mass therethrough in a swirling motion, the second of said primary swirl passages configured to impart a slower swirling motion to a second primary air mass flowing therethrough such that said second air mass flows faster axially than said first air massto thereby provide strong sheer atomization of fuel near said fuel atomizer upon engagement of the respective swirling air masses; the inner one of said separate concentric primary swirl passages having an exit portion diverging away from said atomizer and the outer of said primary swirl passages having an exit portion extending parallel to the axis of said fuel pipe; means for swirling secondary air in said first direction, said secondary air swirling means being adjustable to provide a varying degree of swirl in said secondary air; and a damper assembly joining the primary and secondary air pipes including an outer duct connected to said primary and secondary air pipes at an angle such that primary and secondary air respectively are directed with a minimum pressure drop to each respective primary and secondary swirling means, the duct having an upstream mouth adapted to be connected to a souce of combustion air, an interior wall dividing the duct into a primary air passage and a secondary air passage, both passages communicating with the upstream duct mouth, the primary air passage communicating with the primary air pipe, the secondary air passage communicating with the secondary air pipe, a first damper within the primary air passage to control the flow of primary air therethrough, a second damper within the secondary air passage to control the flow of secondary air therethrough. 2. A burner as in claim 1 wherein the primary air pipe includes a larger diameter upstream section, a smaller diameter downstream section and a radially inward step joining said sections a distance upstream from the atomizer; and the secondary air pipe includes a larger diameter section, a smaller diameter section and a radially inward step joining said sections located downstream of the step in the primary air pipe. 3. A burner as in claim 2 including a gas pipe coaxial with the fuel pipe located between the primary and secondary air pipes, as inlet means joining the upstream end of the gas pipe and extending outwardly of the burner away from the damper assembly, said gas pipe including a radially inwardly extending step located between the radially inwardly extending steps in said primary and secondary air pipes. 4. A burner as in claim 2 including a plurality of secondary air swirl vanes located in the space between the steps in the primary and secondary air pipes and a gang ring operatively connected to said secondary air swirl vanes whereby movement of said ring simultaneously moves the vanes to vary the degree of swirl imparted to secondary air. 5. A burner as in claim 1 wherein said duct is rectangular in cross section, said interior wall extends between opposite sides of the duct to define rectangular primary and secondary air passages and the primary air passage is located on the side of the duct nearest said fuel pipe axis. 6. A burner as in claim 5 wherein the side of the duct farthest from said fuel pipe axis is oriented at approximately 135° to said axis and the side of the duct nearest said axis is oriented at an angle of approximately 45° to said axis. 7. A burner as in claim 1 including a frusto-conical flame holder and air deflector mounted on said secondary air pipe adjacent the downstream end thereof and extending downstream beyond the burner head, said flame holder and air deflector having a close fit with the secondary air pipe to limit the flow of air therebetween. 8. A burner as in claim 7 wherein the flame holder is axially adjustable and extends outwardly at an angle of approximately 25°. 9. A burner as in claim 1 wherein the angular change in direction of primary air flow between said primary air passage of said primary air pipe is not more than 45°. 10. A burner as in claim 9 wherein the angular change in direction of secondary air flow between said secondary air passage and said secondary air pipe is not more than 45°. 11. A swirl type burner comprising an axial atomizer having first swirl generating means for swirling an inner flow of primary air in a first direction, an oil delivery passage opening into the swirled first flow of air, second swirl generating means located outwardly and surrounding the first swirl generating means for swirling a second flow of primary air in said first direction, the downstream mouths of said first and second means being located adjacent to each other so that the swirled first and second flows are free to intermingle following discharge from the mouths to thereby provide strong sheer atomization of fuel near said atomizer; the mouth of said first swirl generating means having a portion diverging away from said atomizer and the mouth of said second swirl generating means having a portion extending parallel to the axis of said atomizer; outer swirl generating means surrounding said atomizer for swirling in said first direction a third flow of air comprising secondary air; said outer swirl generating means having a exit portion extending parallel to the axis of said atomizer; means for directing combustion air with a minimum loss in pressure to each of the first and second swirl generating means and to the outer swirl generating means; a gas delivery system including a gas pipe having an annular gas outlet located between the atomizer and the outer swirl generating means so that said system delivers gas between the swirling inner flows of primary air and the outer flow of secondary air, each of said atomizer, outer swirl generating means and gas delivery system having downstream ends defining a burner head; and a frustro-conical member surrounding the burner head and secured to the outer swirl generating means, said frusto-conical member including an outer air deflector surface extending from the outer swirl generating means a distance radially outwardly and axially downstream past the burner head for deflecting downstream flowing air from the burner heed and an inner surface for shaping the flame on the burner head. 12. A burner as in claim 11 where the swirl number for the first swirl generating means is about 1.55, the swirl number for the second swirl generating means is about 0.96 and the swirl number for the outer swirl generating means is apprximately between 0.4 and 1.4 and the burner flame is of the internal recirculation type. 13. A burner as in claim 12 wherein the outer swirl generating means includes a set of adjustable radial swirl vanes and means ganging said vanes together for simultaneous movement to vary the swirl number of the outer swirl generating means. 14. A burner as in claim 13 including dampers controlling the flow of air to each of said swirl generating means, said dampers have opened and closed positions, said closed positions permitting sufficient air flow to the swirl means to maintain an internal recirculation gas flame at low burn. 15. A burner including an axial fuel pipe; a fuel atomizer at the downstream end of said fuel pipe; a primary air pipe coaxial with and surrounding said fuel pipe and extending upstream from said atomizer; a secondary air pipe coaxial with said fuel pipe, surrounding said primary air pipe and extending upstream from said atomizer; means adjacent to said atomizer for swirling primary air including means defining a first swirl passage and a second swirl passage, said first and second swirl passages being oriented concentrically relative to each other, each of said first and second swirl passages being configured to accelerate the primary air flowing respectively therethrough in a swirling motion in the same direction and at a different degree of swirl and in an axial direction at a different flow rate than the other said swirl passage, thereby to promote strong sheet atomization of fuel near said atomizer; the inner one of said primary swirl passages having an exit portion diverging away from said atomizer and the outer of said primary swirl passages having an exit portion extending parallel to the axis of said fuel pipe; means for swirling secondary air in the same direction as the swirling primary air flows, said secondary air swirling means being adjustable to provide a varying degree of swirl in said secondary air; said secondary airpipe having an exit portion extending parallel to the axis of said fuel pipe; and means for directing combustion air with a minimum loss in pressure to the respective primary and secondary swirling means. 16. A swirl type burner as in claim 15, wherein said secondary pipe includes an annular first diameter passage extending to the burner head, an annular second flow passage having a diameter larger than said first passage and extending upstream from the upstream end of the first passage; a radially inward stop joining the downstream end of the annular second flow passage with the upstream end of the annular first diameter passage, said step including an outer annular wall joining the outer walls of said passages and an inner annular wall joining the inner walls of said passages; and a swirl vane assembly at said step including a plurality of radial vanes positioned between said walls, each vane including a shaft rotatably extending through a bore in the outer step wall, said shafts being arranged in a circle on said wall, a pin extending from the outer end of each shaft, an annular adjustment ring surface thereof adjacent to each shaft, a link rotatably seated in each bore, each link having a cross bore with the pin from the adjacent shaft slideably extending through said cross bore, and adjustment ring lock means for freeing said annular adjustment ring for limited rotational movement to move all of said links relative to said shafts and thereby simultaneously rotate said radial vanes to vary the swirl of the flow and for locking the ring and vanes in a desired position. 17. A burner as in claim 16 wherein said inner wall includes an outwardly extending annular portion cooperating with said outer wall to define a radially inward flow path at the step, said vanes being positioned within said radially inward flow path. 18. A burner as in claim 16 wherein each of said vanes includes a portion extending from the shaft radially inwardly to substantially fill the space between said walls and a portion extending radially outwardly of the shaft to substantially fill the space therefrom to the outer wall of the second flow passage. 19. A burner as in claim 18 wherein said vanes are adjustable between 30° and 65° to a radial line extending from the axis of the individual pins to the burner axis. 20. A burner as in claim 16 wherein the swirl number for the assembly is between about 0.4 and 1.4.