US2703609A

US2703609A - Gas burner

Info

Publication number: US2703609A
Application number: US202352A
Authority: US
Inventors: Jr James Bain; Jr George E Ott
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1950-12-22
Filing date: 1950-12-22
Publication date: 1955-03-08
Anticipated expiration: 1972-03-08

Description

March 8, 1955 AIN, JR, ET AL 2,703,609

GAS BURNER Filed Dec. 22, 1950 lnven tovsz James Bain J11, Geowlgp e E. O lrl: J11,

Their. A t tor neg.

United States Patent '0 GAS BURNER JamesBain, :Jr., ,Waldoboro, Maine, and George E. Ott, Jr., Willoughhy Ohio, .assignors to General Electric Company, a corporation of New York Application-December 22, 1950, Serial No. 202,352

3 Claims. (Cl. 158116) This invention relates generally to gas burners and more particularly to industrial type burners capable of meeting ,stringentrequirements as to the intensity and steadiness of its flame jets. Burners of this type are extensively used in ;the manufacture of glass and ceramic wares, including electric lamps.

The gas burners considered herein are particularly adaptedfio be mounted in banks for heating glass parts carried on .a suitable conveyorsystem or on a rotating turret, as ,in the manufacture of electric lamps. Each burner ,is required to produce one or more pencil-like jets of flame of predetermined length and intensity. The combustible gas used maybe either natural or manufactured fuel gas containing a suitable mixture of volatile hydrocarbons, andthe combustion-supporting gas may be either airor oxygen. In'general, the combustible gas and the combustion-supporting gas are mixed together and .the .mixture issues as a narrow stream through suitable orifices in the face-of the burner. Combustion takesplace throughout the body of the jets, and, in order to prevent theflame from traveling back into the mixing chamber or orifice tube of the burner, the velocity of the mixed gases at the orifice is made greater than the speed of propagation of combustion in the gas. At a point slightly forward of the orifice, the velocity of the gas drops to a value equal to the velocity of propagation of combustion, andthatcondition'determinesthe point of rearward cutofl of .the flame. The flame or jet is thus in a state of dynamic equilibrium and has a tendency towards .unsteadiness. In other words, the .main flame has atendency to shorten and lengthen erratically, to flicker, and I also possiblyto go out. In order to stabilize the main flame, a pilot flame is generally provided, and it may serve additionally to preheat the gases issuing from the orifice for the main flame.

In some of the prior art burner constructions, the gas jets for the main flames issue through narrow tubular orifices in the body of the burner. The main jet orifices are surrounded by a stack of fine mesh screens which serve to mix the gas for the pilot flame and to retard its flow. The pilot flame burns as a relatively thin sheet in contact with the outer screen of the stack and imparts to it a considerable amount of its heat. The stack, being in thermal contact with the tubular orifice, serves to heat up the gases for the main flame and increases the velocity of propagation of combustion through it. This factor in turn may be utilized to increase the velocity of the gas through the orifice and the length of the pencillike jet of flame.

One of the most diflicult problems encountered in the design of a gas burner of the type outlined above is that of achieving steadiness of the main flames in order that the objects required to be heated will be maintained at an even temperature. Even where a pilot flame is provided, there still remains a noticeable tendency for the main flame to waver from side to side and to flicker, which condition is very objectionable.

The object of this invention is to provide a new and improved type of gas burner by means of which a main jet of flame may be maintained without flickering or wavering.

Another object of this invention is to provide a new and improved construction in a gas burner in connection with an auxiliary flame utilized for piloting the main flames.

In accordance with the invention, the gases for the pilot flame in a burner are mixed and retarded by allowing them to diffuse through a core comprising a porous mass of powdered sintered metal. In a preferred embodiment, the core may consist of a mixture of copper and iron having a porosity of approximately It is shaped 2 to provide alaminar flow of gasyforthe ,pilotflame ,surrounding the main flame in .order to prevent flickering and oscillation. The :pilot flameis disposed nearthe base of the main flame, ,andserves additionally .to preheat the gases issuing from Ithe orifice -tub.es. for'the .mainI-flame.

For further objects and advantages and for ,a better understanding of the invention, attention .is zllOW directed to the following description,andaccompanying drawing. The features of the invention believed :to .be .novel will be more particularly pointed-out ,in the appended claims.

,In the drawing:

Fig. .1 is..a. CI'OSSrSCCtiOIlfll view of ,-an industrial typegas burner embodying .the invention.

Figs. 2 and 3 are plansectionalandend viewsrespectively of the same burner.

Referring to Figs. .1 .and 2, the burnercomprisesa body or casing 1.,defininga,mixingchamber [which .is provided with a ball'head .Zadaptedtobe held.in.a.,suitable socket for mounting purposes. .A.mixture .of :combustible gases is admitted .into the casing .throughthe opening 3 which communicates with a corresponding passage in the cooperatingsocket. Theactualburner element is shown generally at 4 and is press fitted .intoa threaded sleeve 5 which .is screwed into ,thecas'ing and locked in place by=meansof athreaded nut 6.

The burner element 4 comprises .a core .5-which.consists of a porous sintered mass:of powdered metal, ,pervious to the diffusion of gas therethrough. Preferably, .the powdered metal consists of a copper and .iron mixture, the former providing. excellent conduction .and the ,latter rigidity. However, .it will be understood thatanytype of suitable heatconducting-materialmaybe used.for the core, including stainlesssteel ,Where an oxygen-rich flame is required. We have found that the,po,rosity.of,the;mass is preferably .in the rangeof 55% 10.60%. ,It will be understood of course ,that. a lesser porosity :may be.utilized where fuel gasissuppliedtothe burner underthig her pressures than areusually encountered.commercially. .In order to restrict .the flow of ,gas through the .core to a direction generally longitudinal with respect .to .the orifice tube,.the core Ssurroundsanorificetubefi through which the gas mixture escapesinajet for eonstituting the :main .flame, The core :5 .surroundedby a close fitting nonporous casing 7 which may be bonded to the core material; the core, along with the casing, curves inwards at its forward end towards the axis of the main jet orifice tube 6. The shape of the casing 7 surrounding the core 5 may be seen from Figs. 1 and 2, and it is adapted for a core including three orifice tubes as shown in Fig. 3. It will be understood however, that Where a single orifice tube is used, the casing 7 may have a uniform annular end configuration.

The shape of the porous body 5 as limited by the nonporous casing 7 assures a laminar flow of the gases for the pilot flame, as indicated by the stream lines at 8. As a result, the pilot flame shown at 9 emerges parallel to the gases of the main flame indicated at 10, and the pilot flame stabilizes the main flame without causing it to flicker. We have found that if the pilot flame gases are allowed to flow in a nonparallel fashion with respect to the main flame, eddy currents and turbulence develop and varying forces are exerted against the main flame. The end result is oscillation and flickering of the tip of the main flame 10. However, by causing the pilot gases to issue in parallelism with the main flame gases as achieved by the burner construction illustrated, turbulence is eliminated and steadiness of the main flame tip is achieved. g

We have also found that the pilot flame should be as near to the main flame as possible in order to eliminate cold spots near its base. Since one of the purposes of the pilot flame is to preheat gases passing through the orifice tube for the main flame, the pilot will be all the more effective inasmuch as it is in direct contact with the orifice tube. For the same reason it is desirable that the core material have a high heat conductivity in order to increase the preheating of the gases for the main flame in the orifice tube. It is also desirable that the pilot flame be symmetrical with the main flame so that the force exerted by it on one side of the main flame will be opposed by an equal force on the other side. Nonob- 3 servance of this feature results in the pilot exerting a greater force on one side than on the other and results in flickering and oscillation of the tip of the main flame.

The requirements of a burner for steadiness and efficiency of combustion in the main flame are met in the burner construction in accordance with the invention. The pilot flame 9 is located right at the base of the main flame 10 and practically in immediate contact with it. Moreover, the gases for the pilot flame emerge substantially parallel to those for the main flame and symmetrically all around it so that the flickering and oscillation of the flame tip is substantially eliminated.

In a preferred construction of a burner element 4 in accordance with the invention, the core 5 is molded directly about the orifice tube 6 and the whole sintered together as a unit. We have found this procedure preferable to attempting to drill a hole through the core body because the porosity of the core is so high that the bore of any hole drilled in it is rough and results in a ragged fire. After sintering, the assembly of the core with the orifice tube 6 may be sprayed with aluminum metal in order to form the nonporous casing 7. It will be understood that previous to spraying, the ends perpendicular to the orifice tube are covered in order to prevent the aluminum from being sprayed onto them. Besides sealing, the aluminum coating provides extra rigidity to the powdered metal and the excess thereof may be ground off to achieve a press fit of the burner element 4 within the sleeve 5. It will be understood however that other more conventional constructions may be used, and that the porous core may be provided as an annular ring which is merely placed around an orifice and surrounded by a suitable casing.

While a certain specific embodiment has been shown and described, it will of course be understood that various modifications may be made without departing from the invention. Thus, the shape of the casing 7 will be modified in accordance with the number of orifice tubes provided in the core body. Likewise, the porosity of the core 5 will be varied to suit the pressure of the gas supplied to the burner and also in accordance with the intensity of pilot flame required. The appended claims are intended to cover any such modifications coming within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A gas burner comprising means defining a mixing chamber, a porous core of powdered sintered metal having a rearward face exposed to the interior of said chamber, an orifice tube through said core for a main flame and extending from a forward face to and terminating at a rearward face of said core, means for supplying a gas mixture to said chamber, and an impervious casing fitted closely to and surrounding said core except its rearward and forward faces, said core being tapered towards the axis of said orifice tube in the direction of said forward face for achieving a laminar flow of gas through said core to produce a pilot flame.

2. A gas burner comprising means defining a mixing chamber, a core of porous heat conducting material having a rearward face exposed to the interior of said chamber and having an orifice formed therethrough from said forward face to and terminating at the rearward face thereof, means to render impervious to the gas mixture the surface of said core defining said orifice as well as the outer surface of said core so as to restrict the gas flow through said core to a direction longitudinally of and around said orifice, whereby the gas mixture from said chamber diffuses through said core for a pilot flame at its front face and the gas mixture issues from-said mixing chamber through said orifice for a main flame.

3. A gas burner comprising a socket having a gas inlet and an open ended chamber adapted to receive a combustible gas mixture for discharge to a combustion surface, and a burner element fitted in the open end of the chamber and comprising a porous core of powdered sintered metal pervious to said gas mixture, an orifice tube through said core and leading from the forward face to and terminating at the rearward face thereof for conducting a jet of gas for a main flame, and an impervious coating of sprayed metal on the exterior surface of said core between said faces, said core and said casing being gradually tapered toward the axis of said orifice tube in the direction of said forward face for achieving a laminar flow of gas through said core to produce a steady pilot flame at said forward face.

References Cited in the file of this patent UNITED STATES PATENTS 1,495,164 Coberly May 27, 1924 2,227,899 Grubb Jan. 7, 1941 2,528,738 Calkins Nov. 7, 1950