Recirculating burner

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Region of clean,

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Percent

Excess

CONSTANT SMOKENO 3O COLOR TRANSiTION

REGION OF SMOKY, REGION OF CLEAN YELLOW-FLAME BLUE - FLAME, COMBUSTON QUIET COMBUSTION

Percent recirculation

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inlet at the interface of the first passage and the vapor

RECIRCULATING BURNER izing chamber outlet, positioned to direct air under BACKGROUND OF THE INVENTION pressure through the first passage and combustion chamber inlet into the combustion chamber, the sec

This invention relates to recirculating liquid fuel ond passage, the vaporizing chamber, and the first passage together defining a recirculation path for hot

It is known to use recirculated hot combustion gases combustion gases from the combustion chamber back to vaporize liquid fuel, such as oil, for blue-flame, to the combustion chamber inlet, the path having suffi smoke-free, and quiet combustion. It has been said that cient width to provide in conjunction with the air inlet the percent recirculation should be at least 50%, for 10 enough recirculation to maintain blue-flame combus maintaining blue-flame combustion, but that the per tion, the hot gases being drawn by suction created by cent recirculation necessary increases with the percent the air inlet into the vaporizing chamber, and the va excess air used. American Petroleum Institute Publica porized fuel and hot gases being drawn by the same tion 1723-A, January, 1965, pp. 2-4, esp. FIG. 1. suction into the first passage, where they are mixed "Blue-flame combustion', as the term is used hereinaf 15 with air entering from the air inlet to provide a combus ter, will refer to the "Region of clean, blue-flame, quiet tible mixture, the mixture entering the combustion combustion' labeled on FIG. 1 of this API publication, chamber through the combustion chamber inlet for reprinted herein as FIG: 1. Reichhelm et al. U.S. Pat. burning in the combustion chamber. In a preferred No. 3,705,784 and Reichhelm U.S. Pat. No. 3,361,183 embodiment the combustion chamber is cylindrical, teach introducing liquid oil into the flow of recirculated 20 the first passage enters the combustion chamber tan hot gases, the driving force for recirculation being pro gentially thereto, through the combustion chamber vided by suction owing to ejector action by incoming inlet, the second passage connects tangentially with the air, although the former patent specifies recirculation combustion chamber, the vaporizing chamber is cylin of only a small portion of the gases. Von Linde U.S. drical, the second passage enters the vaporizing cham Pat. No. 3,174,526 teaches spraying atomized liquid 25 ber tangentially through the vaporizing chamber inlet, fuel into recirculated hot combustion gases in a pre the fuel inlet atomizer is directed into the cylindrical chamber slightly upstream of the sites for mixing with vaporizing chamber along the axis thereof, and the air air and burning. Thermal Research & Engineering inlet and fuel inlet atomizer include nozzles. Corp. of Conshohocken, Pennsylvania, offers an inter Other advantages and features of the invention will nally recirculating burner utilizing tangential entry of 30 be apparent from the description and drawings herein inlet air to create a vortex to draw back the hot com of a preferred embodiment thereof. bustion gases (Bulletin No. 143, pp. 6-7). Complete vaporization of the oil is desired to attain blue-flame BRIEF DESCRIPTION OF THE DRAWINGS combustion. FIG. 1 is a graph showing oil burner operating char SUMMARY OF THE INVENTION acteristics as a function of percent recirculation and percent excess air.

The invention provides a safe, clean, simple, sturdy, FIG. 2 is a side view, in cross section, of one embodi compact, easy-to-assemble and install, convenient-to ment of the invention; and use, and versatile recirculating liquid fuel burner capa FIG. 3 is a view through 3-3 of FIG. 2. ble of producing blue-flame, smoke-free, and quiet 40 combustion. DESCRIPTION OF THE PREFERRED The burner can also easily burn gaseous fuels, such as EMBODIMENT natural gas. There are few parts making up the burner . There is shown in FIG. 2 burner 10, comprising hous apparatus. Vaporization of the liquid fuel is complete, ing 12, which contains cylindrical combustion chamber unwanted condensation of the fuel along the burner 45 14, cylindrical vaporizing chamber 16, and passages 18 walls is prevented, and combustion is thereby made and 20, passage 18 interconnecting the inlet of com more efficient. Start-up is efficient, without waste of bustion chamber 14 with the outlet of vaporizing cham oil, and does not require complex or cumbersome start ber 16 and passage 20 interconnecting combustion ing equipment. High flame temperatures can be chamber 14 toward its outlet with the inlet of vaporiz achieved for a variety of industrial applications, such as 50 ing chamber 16. Passage 18 enters combustion cham forging and glass melting. ber 14 tangentially thereto, and passage 20 leaves com The invention features a burner for burning a vapor bustion chamber 14 from the side opposite to that at izable liquid-fuel comprising a housing, a combustion which passage 18 enters it (FIG. 3), and enters vaporiz chamber in the housing; the combustion chamber hav ing chamber 16 tangentially thereto. Air inlet 22 having ing an inlet and an outlet, a vaporizing chamber in the 55 ejector nozzle 22a is positioned to enter vaporizing housing, the vaporizing chamber having an inlet and an chamber 16 adjacent the outlet thereof and tangen outlet, a first passage interconnecting the combustion tially thereto, directing air under pressure into passage chamber inlet with the vaporizing chamber outlet, the 18, passage 18 serving as a mixing chamber, as will be first passage serving as a mixing chamber, a second explained hereinafter. Oil inlet 24 having nozzle 24a is passage interconnecting the combustion chamber 60 positioned along the axis of vaporizing chamber 16 toward the combustion chamber outlet with the vapor adjacent the tangential entry of passage 20. Housing 12 izing chamber inlet, for carrying hot combustion gases comprises burner section 13 and recirculation section from the combustion chamber into the vaporizing 15, the sections being composed, respectively, of inner chamber, a vaporizable liquid fuel inlet atomizer con refractories 13a and 15a of 3000' F. heat-resistant nected to the vaporizing chamber and positioned to 65 concrete and outer metal piping 13b and 15b. Sections direct atomized liquid fuel into the vaporizing cham 13 and 15 are held together by bolts (not shown) be ber, the atomizer being effective to support vaporiza tween flanges 30, the two sections together completing tion of the fuel before the same touches a wall, an air passages 18 and 20. Burner 10 is mounted on a furnace, 4 boiler or other heating receptacle by means of flange produce a combustible mixture. Combustion is charac 32 surrounding and spaced inward from the combus terized by a blue flame, and is quiet and smoke-free. tion chamber outlet 34. Outlet 34 is inserted into a hole Fuel consumption is variable. One simply adjusts the in the furnace wall (not shown), and flange 32 is bolted amount of spray through nozzle 24a and air through to the furnace wall through flange holes 32a. Industrial nozzle 22a to obtain, the desired rate of consumption spark plug 26 positioned opposite and slightly down within the permitted range. Fuel and air inputs can be stream of the entrance of passage 18 into combustion stoichiometric, though excess air can be used. w chamber 14 provides ignition at start-up. Section 15 In full operation as above described, passages 18 and can be demounted from section 13 by removal of bolts 20 and vaporizing chamber 16 are all wide enough to from flanges 30, if prolonged use of gaseous fuel is 10 provide, in conjunction with air inlet 22, a percent desired, making section 15 unnecessary. The upper half recirculation sufficient to maintain blue-flame combus of passage 20 is then blocked by a cover bolted to tion, which, with no excess input air, would be at least upper flange 30, and air and gaseous fuel enter through 50% under standard conditions, i.e., 1 atmosphere of the upper half of passage 18 for use of the burner in the pressure and 70 F., where percent recirculation R, is gas mode. 15 defined as follows:

Passage 20 carries hot burned gases from chamber 14 down to chamber 16. Oil inlet 24 carries liquid oil from R = standard cfm of recirculated combustion products X 00 an oil source into nozzle 24a. Nozzle 24a atomizes the standard cfm of stoichiometric input air liquid fuel into a fine spray in the form of a cone. Hot gases from passage 20 enter vaporizing chamber 16, 20 and swirl about the cone of spray to evaporate the fuel The inner width of these parts, which together define oil before its particles touch a wall. the recirculation path, is large enough to lower the Air inlet nozzle 22a drives air under pressure into pressure large drop caused by nozzle 22a and sustain this amount of recirculation flow.

passage 18, creating a suction in passage 18, which suction serves to draw the gaseous contents of vaporiz 25 The concept of introducing the fuel at the inlet end of ing chamber 16 through passage 18 into combustion upon the vaporizing chamber, and into a gas stream acted chamber 14. In combustion chamber 14, cylindrical J. Syska, by a vortex generator, was that solely of Andrew projection 28 extending inwardly along the axis of cy whose patent application is entitled "Recircu lating lindrical chamber 14 acts as a flameholder for burning 610,250. Burner', and was filed Sept. 4, 1975, Ser. No.

Operation in the start-up and full-running modes will My most preferred embodiment makes use of a vor now be described. In start-up, oil in atomized form is tex generator at the recirculation chamber inlet, as admitted into burner 10 through nozzle 24a, and is disclosed in said Syska application, hereby incorpo drawn by the suction from air passing from nozzle 22a rated herein by reference.

Other embodiments are within the following claims.

into passage 18, where the atomized oil is mixed with 35 What the incoming air, to provide a combustible mixture. is claimed is:

The mixture enters combustion chamber 14 tangen comprising: 1. A burner for burning a vaporizable liquid fuel tially thereto, and is ignited by spark plug 26. Combus a housing, tion occurs in chamber 14, with projection 28 provid ing flameholding. Burning is in the form of a swirl of 40 a combustion chamber in said housing, said combus burning gases, and passage 20 is arranged tangentially tion chamber having an inlet and an outlet, at the opposite side of chamber 14 from passage 18 so a vaporizing chamber in said housing, said vaporizing that passage 20 will receive a portion of the swirling chamber having an inlet and an outlet, gases and convey them downward to chamber 16. a first passage interconnecting said combustion In full operation, part of the swirling gaseous prod 45 chamber inlet with said vaporizing chamber outlet, ucts of combustion leaves burner 10 through outlet 34, said first passage serving as a mixing chamber, but part is drawn into passage 20 by the suction created a second passage interconnecting said combustion by air nozzle 22a, nozzle 22a and passage 18 together chamber toward said combustion chamber outlet acting as a jet ejector pump. The tangential connection with said vaporizing chamber inlet, for carrying hot of passages 18 and 20 into chamber 14 on opposite 50 combustion gases from said combustion chamber sides of the axis of chamber 14 is designed, in conjunc into said vaporizing chamber, tion with the swirling mode of combustion, to provide a vaporizable liquid fuel inlet atomizer connected to minimum pressure drop path for the recirculating gases said vaporizing chamber and positioned to direct exiting chamber 14 through passage 20. The recirculat atomized liquid fuel into said vaporizing chamber, ing gases are further drawn tangentially into vaporizing 55 for vaporization therein of said fuel by said hot chamber 16, where they swirl down the chamber in the combustion gases, said atomizer being effective to direction of air inlet 22. Oil is injected in atomized form support vaporization of said fuel before the same into the stream of hot gases, the heat from which vapor touches a wall, izes the atomized oil before it has an opportunity to an air inlet at the interface of said first passage and condense on the vaporizing chamber wall. Chamber 16 60 said vaporizing chamber outlet, positioned to di is kept below the temperature required to crack the rect air under pressure through said first passage hydrocarbon fuel (usually 900 F.) because the heat and combustion chamber inlet into said combus required to vaporize the liquid fuel comes from the hot tion chamber, gases, leaving them cooler, though chamber 16 stays said second passage, said vaporizing chamber, and above the fuel vaporization temperature (usually 600 65 said first passage together defining a recirculation F.). The suction described above draws the hot gases path for hot combustion gases from said combus and vaporized oil from vaporizing chamber 16 into tion chamber back to said combustion chamber passage 18, where they are mixed with incoming air to inlet, said path having sufficient width to provide in

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S 6 conjunction with said air inlet enough recirculation said combustion chamber being cylindrical, said first to maintain blue-flame combustion, passage entering said combustion chamber tangen said hot combustion gases being drawn by suction tially thereto through said combustion chamber inlet, said second passage connecting tangentially created by said air inlet into said vaporizing cham with said combustion chamber, said vaporizing ber and said vaporized fuel and hot gases being chamber being cylindrical, said second passage drawn by said suction into said first passage, where entering said vaporizing chamber tangentially they are mixed with air entering from said air inlet through said vaporizing chamber inlet, and said to provide a combustible mixture, said mixture O fuel inlet atomizer being directed into said cylindri entering said combustion chamber through said cal vaporizing chamber along the axis thereof. 2. The burner of claim 1 wherein said air inlet and combustion chamber inlet for burning in said com said fuel inlet atomizer include nozzles bustion chamber, and ck k k