US3291189A - Gas burner - Google Patents

Description

Dec. 13, 1966 o, H. SCHADE, JR

GAS BURNER Filed March 9, 1965 www@ INVENToRs 0770 Icy/4,05 A6,

United States Patent O 3,291,189 GAS BURNER Otto H. Schade, Jr., North Caldwell, NJ., assignor to Radio Corporation of America, a corporation of Delaware Filed Mar. 9, 1965, Ser. No. 438,235 5 Claims. (Cl. 158-116) This invention relates to gas burners.

In certain applications in which gas burners are used, such as in the provision of heat for thermoelectric generators, it is desirable that the burners be simple in design and operation, require no moving parts, and that they be relatively noiseless, efcient, and safe over long periods of time with little or no attention.

One of the main problems associated with prior art burners is the difficulty of providing a burner ame which is highly stable and unfluctuating over extended periods of time and which retains its stability at varous fuelconsumption or ring rates `of the burner. By a stable and unuctuating ame is meant a flame which burns the gas fuel `smoothly and without turbulence and whose dame-front (i.e., the inner cone of the flame) remains at a fixed location in the burner regardless of the burner firing rate. Turbulent combustion causes undesirable noise, and variations in the location of the flame-front cause non-uniform and inefficient heating of the load or element heated by the burner.

A further problem associated with prior art burners is the difficulty of avoiding disturbances or turbulence in the flow of gas fuel in the pipe lines leading to the burner head where the fuel is consumed. The pipes have natural resonant frequencies, and such fuel flow disturbances excite the pipes into resonance, thereby producing loud and highly objectionable noises.

It is an object of this invention to provide an improved and novel gas burner.

It is a further object of this invention to provide a simple and inexpensive gas burner having the aforementioned desired properties and having a flame which is highly stable and noiseless over extended periods of time and over a wide range of firing rates, and wherein a uniform and laminar iiow of fuel to the burner head is achieved.

The general type of gas burner to which the present improvements relate comprise in general, a burner head at which the gas fuel is burnt, a fuel injector for supplying a gas-air mixture to the burner head, and a heat absorbing and dissipating element associated with the burner head for absorbing heat from the burner ame and uniformly and eihciently transferring the heat to the burner load.

Features of the novel burner relate to the provision of a gridwork of high thermal conductivity material providing a plurality of ports through the burner head, the provision of heat transferring and heat insulating means for maintaining the gridwork at a relatively low temperature, and the provision of baffle means for providing a uniform and laminar flow of fuel through the pipe lines leading to the burner head and through the burner head gridwork.

Additional features of the invention and advantages of the burner of this invention are described in greater detail hereinafter.

In the drawings:

FIG. 1 is a longitudinal section of a burner shown in connection with a thermoelectric converter, the converter and the burner together comprising a thermoelectric generator; and

FIG. 2 is a graph illustrating the effects of novel bafe means on the ow of gas fuel through parts of the burner shown in FIG. l.

rerice With reference to FIG. 1, a thermoelectric generator 6 is shown comprising a thermoelectric converter 8 and a burner 10. Converter 8, which is the load of the burner 10, comprises a cylindrical tubular member 12 closed at each end by insulating discs 18 and 20. Further details of the thermoelectric converter 8 are not given since such converters are known in the art and form no part of the present invention. It is noted, however, that for maximum eficiency of operation of the thermoelectric generator, the inside wall of tubular member 12 should be uniformly heated. To this end, it is desirable that the heat distributing characteristic of the burner 10 be substantially invariant with time and with adjustments in the fuel consumption settings of the burner.

Burner 10 comprises, in general, a burner head 24, a heat absorbing and dissipating element 26 mounted on the head 24, and a tubular fuel injector 28 of, e.g., Venturi-type secured to head 24. Element 26 and burner head 24 extend into the converter 8 through an aperture in the disc 20, as shown. Mounting means for the burner 10 and the converter 8 are not shown.

Burner head 24 comprises a tubular member 30 of heat and oxidation resistant material, such as stainless steel, having a relatively thin (eg. 10-20 mils) outwardly extending annular ange 34 which has an upturned axially extending lip at its periphery. Because of the thinness of ange 34, and the low thermal conductivity of stainless steel (0.2 watt/cm. C.), the flange has a low heat transferring capacity.

Received within tubular member 30, and adjacent to one end 36 thereof, is a honeycomb or gridwork 40 formed from a material having a high thermal conductivity, in the order of 1.5-4.0 watts/cm. C. Copper, which has a thermal conductivity of 3.8 watts/cm. C. is preferable. To prevent oxidation of the copper gridwork, the copper is preferably coated with a material such as nickel. Gridwork 40 provides a plurality of axially extending tubes or ports 42 through which the gas fuel passes prior to its combustion. Combustion of the fuel occurs at the outlet end 44 of ports 42. As described hereinafter, the flame-front is anchored to the outlet end 44 of the gridwork. That is, the flame-front neither moves away from the gridwork nor inwardly thereof, thereby providing a highly stable flame.

Mounted on the other end 46 of tubular member 30, as, eg., by means of a screw thread, is the injector 28. Injector 28 extends into tubular member 30 and into tightly abutting and good thermal contact with the gridwork 40. Injector 28 is made from a high thermal conductivity material, such as aluminum, which has -a thermal conductivity of 2.0 watts/ cm. C. The wall of injector 28 is thicker than required for reasons of strength, having a thickness of about 1A inch, and has a large heat dissipating area in comparison with that of burner head 24. Injector 28 is -cooled by the ambient atmosphere and by the flow of the gas fuel therethrough, as described hereinafter. Injector 28 serves as a heat sink for burner head 24 and maintains the gridwork 40 at a relatively low temperature during operation of the burner.

The tubular injector 28 includes a section 52 of gradually increasing diameter, which serves as a nozzle, and a straight sided, open end cylindrical section 54 through which a source 56 of combustible gas, such as propane, extends. The gas is preferably pressurized at around l0- 15 p.s.i.g. As the gas passes upwardly through the nozzle section 52, it entrains or entraps air which enters the injector 28 through the open end of the cylindrical section 54. By proper design of the nozzle section 52, in accordance with known principles, sucient quantities of air may be entrained with the gas to provide complete combustion of the gas without the addition of further air at the point of combustion. The use of the Venturi-type injector 28 thus obviates the need for moving parts, such as blowers and the like, for providing a lproper mixture of air and gas for complete combustion of the gas. The burner head may be thus used in confined areas, such as in the enclosed 'thermoelectric converter 8 shown in FIG. l.. Ports 60 or provided through the insulating disc 18 to permit exhausting-v of the products of combustion of the fuel.

To obtain uniform, turbulent-free and stable combustion kof the fuel at the outlet end 44 of gridwork 40, the ow of the air-gas mixture through each of the gridwork ports 42 should be substantially equal in amount, constant, and laminar. This is partially accomplished by the gridwork, and enhanced by the provision of a pair of baflles .64 and 66 mounted on the inside wall of injector 28 adjacent to and coaxial with the inlet end 68 of the gridwork 40.. Baiiie 64 is a tubular member of gradually increasing diameter in the direction of fuel iiow, and baille 66 has a generally tear-drop shape, with the pointed end thereof closest to the burner head 24. The batlie 66 positioned within the inlet of the baffle 64 shapes the fuel stream into a rst annulus, 4and baffle 64 splits the first annulus into two further annuli. In general, the

'- impingement of the flame against element 26. Such impingement would produce a hot band just above the burner head and cause unequal heating of the burner load. Conversely, too large a diameter of the lower portion of element 26 produces a cold band. With burner head diameters in the range of 0.75 to 3.0 inches, the lower baflies 64 and 66 are shaped to provide two annular fuel streams of equal cross-sectional area at the gridwork end of the batiies. Dividing the fuel flow into separate streams provides more uniform and laminar How of the fuel to the gridwork 40.

The effect of baffles 64 and 66 is illustrated in the graph of FIG. 2, wherein the ordinate is normalized fuel Velocity (V), and the abscissa is radial distance from the center line of the injector 28 to the wall thereof, the line C in FIG. 2 representing the injector center line. Curve 70 in FIG. 2 shows the measured velocity distribution or velocity profile of the fuel ow at the inlet end 68 of gridwork 40 in the absence of bai- lies 64 and 66. The parabolic shape of curve 70 indicates that the rate of fuel liow to the gridwork 40 varies across the face of the gridwork.

Curve 72 shows the velocity distribution of the fuel ow resulting from the use of the tear-drop baffle 66 alone. Curve 72 shows a considerable spreading and iiattening of the velocity distribution as compared to the velocity distribution shown by curve 70, and signifies that a considerable improvement in equality of fuel ow across the face of the gridwork and to the various ports 42 has occurred.

Curve 74 shows the velocity distribution of the fuel flow resulting from the use of both of the baies 64 and 66, and shows a further improvement in uniformity and equality of fuel flow.

It is found that providing a uniform and equal ow of fuel to the gridwork ports prevents cross-currents and other flow disturbances thereby providing a more stable and noiseless flame.

Mounted on flange 34 of burner head 24 is the heat absorbing and dissipating element 26. The purpose of element 26 is to extract the heat energy from the burner flame in a small space and to transfer the heat in an efiicient and uniform manner to the burner load.

In general, the heat absorbing and dissipating element may comprise a tubular structure of heat resistant material such as an alloy comprising iron, cobalt, and nickel, known as Inconel, an alloy comprising nickel and chrome, known as Nichrome, or the like. (These Ialloys may also be used for the burner head 24.) As shown in FIG. l, the element 26 is mounted in surrounding relation with the outlet end 44 of the burner head gridwork 40. The burner head flame burns Wholly within element 26, and the products of combustion from the burner ame pass outwardly from the heat dissipating element and through the exhaust ports 60. Element 26 may be a foraminous member, an open-ended, solid Wall cylinder, or the like, to permit exhausting of the products of combustion. The heat dissipating element is heated diameter of element 26 is preferably larger than the burner head by about 0.25 to 0.75 inch.

The upper portion of element 26 may have Various shapes depending upon the burner load. For the converter load 8 shown in FIG. 1, for example, element 26 has a frustro-conical shape decreasing in diameter in the upward direction. The wall of element 26 is formed from one or more layers of metal screens having meshes in the order of 40 to 200 meshes per inch.

The element 26 shown in FIG. 1 provides uniform heating of the inside of tubular member 12. This occurs because whereas the smaller yarea upper portions of element 26 radiate smaller `amounts of heat than the larger area lower portions of element 26, the hot exhaust gases from the burner ame heat the upper portions of member 12 to `a greater extent than the lower portions thereof. That is, only the exhaust gases passing through the wall of the lower portion of element 26 heat the lower portion of member l2, whereas these exhaust lgases plus the exhaust gases from the upper portions of element 26 ow past and heat the upper portions of member 12.

Heat radi-ant elements having shapes and forms other than that of the element 26 may `also 'be used, depending upon the size of the burner, the character of the load, and the heating characteristics desired.

Element 26 is mounted on the thin flange 34, and is thus in relatively poor thermal conductivity relation with burner head 24. Also, the upward ow of gases prevents transfer of heat from element 26 to burner head 24 by convection. Thus, relatively little heat is transferred to the burner head 24 from element 26.

In summary, the burner described herein provides a highly stable, and noiseless flame over a large range of gas-air fuel flow rates. Stable combustion provides uniform heating of the load, hence high efficiency. In operation of the burners, it is found that the flame front is anchored to the outlet end 44 of the burner head ports 42. That is, for extended periods of time and for various fuel settings, the position of the ame front is fixed and unliuctuating. This is accomplished in several ways. First, by maintaining the burner gridwork 40 at a low temperature by means of the high thermal conductivity material of which the gridwork is formed, by the good thermal conductivity relation between the gridwork and the heat dissipating injector 28, and by the poor heat transfer relation between the burner head and the heat dissipating element 26 mounted thereon, as described, dash-back of the ame is prevented. That is, should the burner 'ame tend to consume the fuel faster than it emerges from the -gridwork 40 and thus tend to recede inwardly of the gridwork, the cool gridwork wal-ls quickly cool the fuel gases below the ignition point of the fuel and prevent combustion of the fuel within the gridwork. Propane-fired burners herein described have been made with 'burner head diameters up to 3 inchesin diameter operating at iring rates from 50,000 B.t.u. -per hour to flame extinction with no'flame ashback into the burner head. The avoidance of ashback is an important safety feature of burners intended for long periods of unattended use.

Additionally, the provision of baie means such as the bailles 64 and `66, provides a uniform and equal rate f fuel flow to the various gridwork lports. This contributes not only to a highly stable llame-front, but to the avoidance of oscillations of the pipe lines leading to and from the burner head.

What is claimed is:

1. A `gas 'burner comprising a burner head including a gridwork providing a plurality of ports therethrough, said gridwork having 'a high thermal conductivity, a fuel injector having a fuel path therethrough leading to said gridwork, `said fuel injector having a large heat dissipating capacity in comparison with said ygridwork and being engaged with s aid gridwork in good thermal conductivity relation therewith, a heat absorbing and dissipating element mounted on the other side of said burner head in spaced and surrounding relation with said gridwork and infpoor'fheat transfer relation therewith, and'baille means disposed on the injector side of said burner in the path of said fuel for providing a uniform and equal rate of fuel ilow to each of said ports.

2. A gas burner comprising a burner head, said head including .a tubular support member, -a mounting flange of low thermal conductivity extending from said support member, and a `gridwork of high thermal conductivity material mounted within said support member `and providing a plurality of ports extending longitudinally through said support member, said ports having inlet and outlet ends, a tubular heat dissipating element mounted on said flange in surrounding and spaced relation with the outlet ends of said gridwork ports and adjacent to one end of said support member, :a tubular fuel injector of high thermal conductivity material coupled to the other end of said support member and engaged in good thermal conductivity relation with said gridwork, a gas fuel source extending into said injector for passing fuel through said injector land through said other end of said support member, and baille means disposed on the injector side of said support member in the path of said fuel for providing a uniform `and equal rate of fuel ilow to each of said ports.

3. A `gas burner comprising a burner head, said head including a tubular support member, an annular flange havin-g a low thermal conductivity extending outwardly of said support member and ladjacent to one end thereof, and Ia gridwork of high thermal conductivity material mounted within said support member and providing a plurality of longitudinally extending ports through said support' member, said ports having inlet and outlet ends, a tubular foraminous heat dissipating element mounted on said annular flange in surrounding and spaced relation with the outlet ends of said gridwork ports, a tubular fuel injector of high thermal conductivity material coupled to the other end of said support member, said injector having -a large heat dissipating area in comparison with said burner head, one end of said fuel injector lbeing in good thermal conductivity relation with said gridwork, the other end of said injector being open to the atmosphere, a gas fuel source extending into said injector through said open end thereof for passing fuel through said injector and through said support member, and baflle means `adjacent to said inlet ends of said `gridwork ports and in the path of said fuel, said baille means com- 6 prising a teardrop shaped baille coaxial with said gridwork and a tubular member of `gradually increasing diameter in the direction of fuel ilow disposed coaxially around said teardrop shaped baille.

4. A gas burner comprising a burner head, said head including a tubular support member, lan annular flange of low thermal conductivity extending outwardly of said support member -adjacent to one end thereof, and a gridwork of high thermal conductivity material mounted within said support member and providing a plurality of longitudinally extending ports through said support member, said ports having inlet and outlet ends, a frustroconical heat radiant element formed from a metal mesh, the larger diameter end of said element being mounted on said annular flange in surrounding and spaced relation with the outlet ends of said gridwork ports, `a tubular fuel injector of high thermal conductivity material coupled to the other end of said support member, one end of said fuel injector being in good thermal conductivity relation to said gridwork, the other end of said injector being open to the atmosphere, a `gas fuel source extending into said injector through said open end thereof for passing ya stream of fuel through said injector and into said support member, and baille -means mounted adjacent to said inlet ends of said ports and in the path of said fuel, said baille means subdividing said fuel stream into separate streams having approximately equal crosssectional areas.

5. A gas burner comprising a burner head, said head including a tubular support member, an annular flange of low thermal conductivity extending outwardly of said support member adjacent to one end thereof, and a gridwork of high thermal conductivity material mounted within said support member and providing a plurality of longitudinally extending ports through said support member, said ports having inlet and outlet ends, a frustroconical heat radiant element formed from a metal mesh, the larger diameter end of said element being mounted on said annular ilange in surrounding and spaced relation with the outlet ends of said gridwork ports, a tubular fuel injector of high thermal conductivity material coupled to the other end of said support member, one end of said fuel injector `being engaged in good thermal conductivity lrelation to said gridwork, the other end of said injector being open to the atmosphere, a gas fuel source extending into said injector through said open end thereof for passing fuel through said injector land into said support member, and baille means mounted adjacent to said inlet ends of said ports and in the path of said fuel, said baflle means comprising .a teardrop shaped baille coaxial with said -gridwork and a tubular member of gradually increasing diameter in the direction of fuel flow disposed coaxially around said teardrop shaped baille.

References Cited by the Examiner UNITED STATES PATENTS 499,731 6/1893 Hartmann et al. 158-114 745,872 12/1903 Machlet 158-112 1,494,499 5/ 1924 ODowd 126-92 X 2,518,544 8/1950 Anthes 158-114 X JAMES W. WESTHAVER, Primary Examiner.

Claims (1)

1. A GAS BURNER COMPRISING A BURNER HEAD INCLUDING A GRIDWORK PROVIDING A PLURALITY OF PORTS THERETHROUGH, SAID GRIDWORK HAVING A HIGH THERMAL CONDUCTIVITY, A FUEL INJECTOR HAVING A FUEL PATH THERETHROUGH LEADING TO SAID GRIDWORK, SAID FURL INJECTOR HAVING A LARGE HEAT DISSIPATING CAPACITY IN COMPARISON WITH SAID GRIDWORK AND BEING ENGAGED WITH SAID GRIDWORK IN GOOD THERMAL CONDUCTIVITY RELATION THEREWITH, A HEAT ABSORBING AND DISSIPATING ELEMENT MOUNTED ON THE OTHER SIDE OF SAID BURNER HEAD IN SPACED AND SURROUNDING RELATON WITH SAID GRIDWORK AND IN POOR HEAT TRANSFER RELATION THEREWITH, AND BAFFLE MEANS DISPOSED ON THE INJECTOR SIDE OF SAID BURNER IN THE PATH OF SAID FUEL FOR PROVIDING A UNIFORM AND EQUAL RATE OF FUEL FLOW TO EACH OF SAID PORTS.

Images