US 3090420 A
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May 21, 1963 E. sAcco 3,090,420
BURNER FOR LIQUID FUELS Filed Dec. 19, 1960 INVENTOR.
ERNESTO SACCO United States Patent Ofiice 3,090,420 Patented May 21, 1963 3,090,420 BURNER FOR LIQUID FUELS Ernesto Sacco, Via Ghilini 32, Alessandria, Italy Filed Dec. 19, 196i), Ser. No. 76,686 Claims priority, application Italy Jan. 20, 1960 2 Claims. (ill. 158-36) Burners for liquid fuels are well known, which use particular pumps to atomize the liquid fuel and make it suitable for the combustion; in other types the combustion is preceded by the mixing of the fuel with a certain amount of compressed air.
In any burner attempts are made to reach the best conditions to get the highest efiiciency in the combustion by suitably varying the shapes of the various parts and the temperature or pressure of the fuel and the comburent.
The present invention has for its object to provide a burner having particular devices in the fuel injection assembly suitable to improve the burner efficiency.
The burner for liquid fuels according to this invention is characterized in that the liquid fuel is heated in the fuel injection assembly before being mixed with compressed air to reach the most suitable temperature for combustion.
The burner for liquid fuels according to this invention is further characterized in that the heating of the fuel is accomplished by means of an electric resistance wound in a spiral around a pipe of refractory material which surrounds the fuel piping.
The burner for liquid fuels according to this invention, is also characterized in that the fuel conduit, in the portion where it is surrounded by the refractory material with electric resistance, passes through the last portion of the compressed air conduit to the mixer, so that the electric resistance, besides heating the fuel, may heat the air too, in such a way that it favours the subsequent mixing, helps avoid any dangerous deposit of unburnt fuel on the bottom of the boiler or the like, and betters the dissociation of the small parts of hydrogen contained in the air, with a remarkable increase in the thermal result.
The burner for liquid fuels according to this invention, is also characterized in that the necessary turbulence within the mixer is obtained by a circular ring distributor of air, with various bores in its circumference, such bores being placed tangentially to it, so as to oblige the air to a rotatory motion.
The burner for liquid fuels according to this invention, is finally characterized in that the amount of fuel, coming out of the burner is regulated by means of a stiff rod passing through the last portion of the conduit, said rod having a longitudinal motion which may be regulated by a handle actuating a screw die system connected to an end of the rod; the other end being shaped in such a way as to be able to partially or totally interrupt the feeding of the fuel into the mixer.
An embodiment of the burner according to this invention is shown schematically and by way of example only. in the accompanying drawings in which:
FIG. 1 is a perspective view of the longitudinal section of the last portion of the ducts, for the comburent air and fuel, forming chambers of the ignition assembly;
FIG. 2 is an enlarged fragmentary longitudinal section of the mixture and turbulence chambers taken on line 22 of FIG. 3; and
FIG. 3 is a section taken on line 33 of FIG. 2 and looking in the direction of the arrows.
With reference to the drawings, 9 denotes the collection chamber of the compressed air which from said chamber passes on through conduit 10 to the annular distributor integral with atomizer 19 which is fastened,
by means of a stop nut 11, to a threaded element 30, which is screwed on conduit 10 and locked by a backnut 23. A shaft 15 acts on the opening of a frustoconical element 31 arranged on the end of a fuel duct 21. Numeral 32 denotes the tangential bores of the annular distributor 22 and 14 a pipe of a refractory material carrying an electric resistance wound as a double spiral 26 and 26', joined at end 33 and connected to the electric plug pin 34 and 34' at the other end respectively.
The liquid fuel, heated in a known manner, is introduced under pressure also in a known manner, into conduit 21; around said conduit is arranged the electric resistance wound on a double spiral 26 and 26'. Said two spirals are coaxial and wound with equal turns but out of phase by half a pitch, so that the turns of one fall between the turns of the other; said spirals are welded together at the ends 33 directed towards the mixer and are passed through by the electric current coming in at the plug 34 and out from the plug 34', said two plugs being located at the accessible end of the conduit. The electric resistance heats further the fuel passing inwardly until it reaches the critical temperature, with the consequent forming of gas which passes out, from the frustoconical element 31 screwed on the end of duct 21, to a degree controlled by adjustment of the stiff, control shaft 15.
The compressed air in chamber 9 passes on to conduit 10 reduced to a thin cylindrical film which is heated by contact with the electric resistance 2626' as well as by radiation and then reaches distributor 22. From said distributor, through the tangential bores 32, it enters the mixing chamber inside part 22 where it is rotated at a high speed and mixed with the vaporized fuel, and forms an atomized mixture which exits out of the burner through the bore 19.
Said mixture, being at a high temperature, on entering the combustion chamber, in which too there is a high temperature, burns quickly and completely, avoiding the formation of unburnt residues.
During the period of ignition of the burner, that is when the temperature of the combustion chamber is low, the mixture on entering the said combustion chamber cools for the difference in temperature; said cooling, however, owing to the speed at which the mixture burns, is not sufiicient to bring the mixture below the ignition temperature, so that it burns without forming unburnt residues.
The comburent air has a certain degree of humidity which allows a dissociation between hydrogen and oxy gen, which are then recombined in the later combustion inside the flame, increasing the heat value of the flame and promoting a complete combustion of the fuel; said increase in the heat value of the flame being obtained at the expense of the heating electric energy supplied through resistance 26, 26'.
The electric energy supplied may be calculated to pro duce a strong heat since the air passing at a high speed through the duct 10 prevents the resistance from reaching unduly high temperatures prejudicial to its life.
The usual cleaning of the atomizer and other parts, may be accomplished in the following way: the stop nut 11 is loosened or removed, the atomizer-mixture chamber group is taken out, and then all the passage bores may be cleaned.
On reassembling the above device, it is necessary to take care that the frustoconical surface of the element 31 fits perfectly the inner opening of the combustion cham her, so that the air coming from the conduit 10 may be compelled to enter the mixture chamber only through the suitable bores of the ring distributor.
When the surface of the element 31 does not fit per- 3 fectly the opening of said chamber, it is necessary to loosen the backnut 23, to rotate the element 30 on which it is threaded, making the said element displace for the distance necessary for the above fitting, and then the backnut 23 and the stop nut 11 may be locked again.
Although for describing reasons the present invention has been described and illustrated according to what is above stated, many modifications and changes may be made in embodying the invention, as for instance by replacing the stiff rod 15 and the handle 8 with suitable shut-oft valves on the air and fuel pipings for a better regulation. All these and other changes however, have to be considered as based on the main ideas of the invention as summarized in the following claims.
What I claim is:
1. A liquid fuel injecting assembly comprising an inner fuel duct surrounded by an outer gas duct coaxial therewith in their last portion before a combustion chamber of a burner, a tube of refractory material between said ducts and adherent to the fuel duct, said tube having an outer diameter slightly smaller than the inner diameter of the air duct, so as to leave an annular space of small thickness for the passage of gas, said tube having an electric resistance coiled on its outer surface arranged to heat the gas within the gas duct to a high temperature directly by conduction and radiation and simultaneously to increase the temperature of the liquid fuel by conduction through the Wall of said fuel duct so that the fuel passes to a vapor phase, an annular chamber at the end of the gas duct surrounding a mixing chamber at the end of said fuel duct, small radial channels provided in the walls of said mixing chamber to permit entry of gas under pressure from said annular chamber,
means for regulating the entry of fuel from said fuel duct to the mixing chamber, and a discharge bore in said mixing chamber having a relatively small diameter to impart a high speed to the mixture of gas and fuel discharged into an adjacent combustion chamber.
2. A liquid fuel injection assembly according to claim 1 wherein said electric resistance comprises two sets of spirals exactly equal but out of phase by half a pitch so that the turns of one are arranged between the turns of the other, the spiral ends being close to said mixing chamber at the discharge end of the assembly and welded to each other, and the other ends of said spirals being connected to electric plug in pins provided at an intermediate zone of said gas duct.
References Cited in the file of this patent UNITED STATES PATENTS 482,508 Harvey Sept. 13, 1892 1,537,687 Morris May 12, 1925 1,779,849 Lusk Oct. 28, 1930 2,225,869 Janitschek Dec. 24, 1940 2,306,831 Proctor Dec. 29, 1942 2,355,693 Aldrich Aug. 15, 1944 2,424,440 Duffy July 22, 1947 2,507,464 De Andrade So May 9, 1950 2,556,047 Stanley June 5, 1951 2,825,398 Clarke Mar. 4, 1958 FOREIGN PATENTS 469,059 Great Britain July 19, 1937 250,416 Italy Oct. 5, 1926